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Physics LibreTexts

Model Glossary (start)

  • Page ID
    30755
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    accuracy
    the degree to which a measured value agrees with correct value for that measurement
    approximation
    an estimated value based on prior experience and reasoning
    classical physics
    physics that was developed from the Renaissance to the end of the 19th century
    conversion factor
    a ratio expressing how many of one unit are equal to another unit
    derived units
    units that can be calculated using algebraic combinations of the fundamental units
    English units
    system of measurement used in the United States; includes units of measurement such as feet, gallons, and pounds
    fundamental units
    units that can only be expressed relative to the procedure used to measure them
    kilogram
    the SI unit for mass, abbreviated (kg)
    law
    a description, using concise language or a mathematical formula, a generalized pattern in nature that is supported by scientific evidence and repeated experiments
    meter
    the SI unit for length, abbreviated (m)
    method of adding percents
    the percent uncertainty in a quantity calculated by multiplication or division is the sum of the percent uncertainties in the items used to make the calculation
    metric system
    a system in which values can be calculated in factors of 10
    model
    representation of something that is often too difficult (or impossible) to display directly
    modern physics
    the study of relativity, quantum mechanics, or both
    order of magnitude
    refers to the size of a quantity as it relates to a power of 10
    percent uncertainty
    the ratio of the uncertainty of a measurement to the measured value, expressed as a percentage
    physical quantity
    a characteristic or property of an object that can be measured or calculated from other measurements
    physics
    the science concerned with describing the interactions of energy, matter, space, and time; it is especially interested in what fundamental mechanisms underlie every phenomenon
    precision
    the degree to which repeated measurements agree with each other
    quantum mechanics
    the study of objects smaller than can be seen with a microscope
    relativity
    the study of objects moving at speeds greater than about 1% of the speed of light, or of objects being affected by a strong gravitational field
    scientific method
    a method that typically begins with an observation and question that the scientist will research; next, the scientist typically performs some research about the topic and then devises a hypothesis; then, the scientist will test the hypothesis by performing an experiment; finally, the scientist analyzes the results of the experiment and draws a conclusion
    second
    the SI unit for time, abbreviated (s)
    SI units
    the international system of units that scientists in most countries have agreed to use; includes units such as meters, liters, and grams
    significant figures
    express the precision of a measuring tool used to measure a value
    theory
    an explanation for patterns in nature that is supported by scientific evidence and verified multiple times by various groups of researchers
    uncertainty
    a quantitative measure of how much your measured values deviate from a standard or expected value
    units
    a standard used for expressing and comparing measurements
    acceleration
    the rate of change in velocity; the change in velocity over time
    acceleration due to gravity
    acceleration of an object as a result of gravity
    average acceleration
    the change in velocity divided by the time over which it changes
    average speed
    distance traveled divided by time during which motion occurs
    average velocity
    displacement divided by time over which displacement occurs
    deceleration
    acceleration in the direction opposite to velocity; acceleration that results in a decrease in velocity
    dependent variable
    the variable that is being measured; usually plotted along the ysize 12{y} {}-axis
    displacement
    the change in position of an object
    distance
    the magnitude of displacement between two positions
    distance traveled
    the total length of the path traveled between two positions
    elapsed time
    the difference between the ending time and beginning time
    free-fall
    the state of movement that results from gravitational force only
    independent variable
    the variable that the dependent variable is measured with respect to; usually plotted along the xsize 12{x} {}-axis
    instantaneous acceleration
    acceleration at a specific point in time
    instantaneous speed
    magnitude of the instantaneous velocity
    instantaneous velocity
    velocity at a specific instant, or the average velocity over an infinitesimal time interval
    kinematics
    the study of motion without considering its causes
    model
    simplified description that contains only those elements necessary to describe the physics of a physical situation
    position
    the location of an object at a particular time
    scalar
    a quantity that is described by magnitude, but not direction
    slope
    the difference in ysize 12{y} {}-value (the rise) divided by the difference in xsize 12{x} {}-value (the run) of two points on a straight line
    time
    change, or the interval over which change occurs
    vector
    a quantity that is described by both magnitude and direction
    y-intercept
    the y-size 12{y} {}value when xsize 12{x} {}= 0, or when the graph crosses the ysize 12{y} {}-axis
    air resistance
    a frictional force that slows the motion of objects as they travel through the air; when solving basic physics problems, air resistance is assumed to be zero
    analytical method
    the method of determining the magnitude and direction of a resultant vector using the Pythagorean theorem and trigonometric identities
    classical relativity
    the study of relative velocities in situations where speeds are less than about 1% of the speed of light—that is, less than 3000 km/s
    commutative
    refers to the interchangeability of order in a function; vector addition is commutative because the order in which vectors are added together does not affect the final sum
    component (of a 2-d vector)
    a piece of a vector that points in either the vertical or the horizontal direction; every 2-d vector can be expressed as a sum of two vertical and horizontal vector components
    direction (of a vector)
    the orientation of a vector in space
    head (of a vector)
    the end point of a vector; the location of the tip of the vector’s arrowhead; also referred to as the “tip”
    head-to-tail method
    a method of adding vectors in which the tail of each vector is placed at the head of the previous vector
    kinematics
    the study of motion without regard to mass or force
    magnitude (of a vector)
    the length or size of a vector; magnitude is a scalar quantity
    motion
    displacement of an object as a function of time
    projectile
    an object that travels through the air and experiences only acceleration due to gravity
    projectile motion
    the motion of an object that is subject only to the acceleration of gravity
    range
    the maximum horizontal distance that a projectile travels
    relative velocity
    the velocity of an object as observed from a particular reference frame
    relativity
    the study of how different observers moving relative to each other measure the same phenomenon
    resultant
    the sum of two or more vectors
    resultant vector
    the vector sum of two or more vectors
    scalar
    a quantity with magnitude but no direction
    tail
    the start point of a vector; opposite to the head or tip of the arrow
    trajectory
    the path of a projectile through the air
    vector
    a quantity that has both magnitude and direction; an arrow used to represent quantities with both magnitude and direction
    vector addition
    the rules that apply to adding vectors together
    velocity
    speed in a given direction
    acceleration
    the rate at which an object’s velocity changes over a period of time
    carrier particle
    a fundamental particle of nature that is surrounded by a characteristic force field; photons are carrier particles of the electromagnetic force
    dynamics
    the study of how forces affect the motion of objects and systems
    external force
    a force acting on an object or system that originates outside of the object or system
    force
    a push or pull on an object with a specific magnitude and direction; can be represented by vectors; can be expressed as a multiple of a standard force
    force field
    a region in which a test particle will experience a force
    free-body diagram
    a sketch showing all of the external forces acting on an object or system; the system is represented by a dot, and the forces are represented by vectors extending outward from the dot
    free-fall
    a situation in which the only force acting on an object is the force due to gravity
    friction
    a force past each other of objects that are touching; examples include rough surfaces and air resistance
    inertia
    the tendency of an object to remain at rest or remain in motion
    inertial frame of reference
    a coordinate system that is not accelerating; all forces acting in an inertial frame of reference are real forces, as opposed to fictitious forces that are observed due to an accelerating frame of reference
    law of inertia
    see Newton’s first law of motion
    mass
    the quantity of matter in a substance; measured in kilograms
    net external force
    the vector sum of all external forces acting on an object or system; causes a mass to accelerate
    Newton’s first law of motion
    a body at rest remains at rest, or, if in motion, remains in motion at a constant velocity unless acted on by a net external force; also known as the law of inertia
    Newton’s second law of motion
    the net external force Fnetsize 12{F rSub { size 8{"net"} } } {} on an object with mass msize 12{m} {} is proportional to and in the same direction as the acceleration of the object, asize 12{a} {}, and inversely proportional to the mass; defined mathematically as a=Fnetmsize 12{a= { {F rSub { size 8{ ital "net"} } } over {m} } } {}
    Newton’s third law of motion
    whenever one body exerts a force on a second body, the first body experiences a force that is equal in magnitude and opposite in direction to the force that the first body exerts
    normal force
    the force that a surface applies to an object to support the weight of the object; acts perpendicular to the surface on which the object rests
    system
    defined by the boundaries of an object or collection of objects being observed; all forces originating from outside of the system are considered external forces
    tension
    the pulling force that acts along a medium, especially a stretched flexible connector, such as a rope or cable; when a rope supports the weight of an object, the force on the object due to the rope is called a tension force
    thrust
    a reaction force that pushes a body forward in response to a backward force; rockets, airplanes, and cars are pushed forward by a thrust reaction force
    tensile strength
    the breaking stress that will cause permanent deformation or fraction of a material
    angular velocity
    ωsize 12{ω} {}, the rate of change of the angle with which an object moves on a circular path
    arc length
    Δssize 12{Δs} {}, the distance traveled by an object along a circular path
    banked curve
    the curve in a road that is sloping in a manner that helps a vehicle negotiate the curve
    center of mass
    the point where the entire mass of an object can be thought to be concentrated
    centrifugal force
    a fictitious force that tends to throw an object off when the object is rotating in a non-inertial frame of reference
    centripetal acceleration
    the acceleration of an object moving in a circle, directed toward the center
    centripetal force
    any net force causing uniform circular motion
    Coriolis force
    the fictitious force causing the apparent deflection of moving objects when viewed in a rotating frame of reference
    fictitious force
    a force having no physical origin
    gravitational constant, G
    a proportionality factor used in the equation for Newton’s universal law of gravitation; it is a universal constant—that is, it is thought to be the same everywhere in the universe
    ideal angle
    the angle at which a car can turn safely on a steep curve, which is in proportion to the ideal speed
    ideal banking
    the sloping of a curve in a road, where the angle of the slope allows the vehicle to negotiate the curve at a certain speed without the aid of friction between the tires and the road; the net external force on the vehicle equals the horizontal centripetal force in the absence of friction
    ideal speed
    the maximum safe speed at which a vehicle can turn on a curve without the aid of friction between the tire and the road
    microgravity
    an environment in which the apparent net acceleration of a body is small compared with that produced by Earth at its surface
    Newton’s universal law of gravitation
    every particle in the universe attracts every other particle with a force along a line joining them; the force is directly proportional to the product of their masses and inversely proportional to the square of the distance between them
    non-inertial frame of reference
    an accelerated frame of reference
    pit
    a tiny indentation on the spiral track moulded into the top of the polycarbonate layer of CD
    radians
    a unit of angle measurement
    radius of curvature
    radius of a circular path
    rotation angle
    the ratio of the arc length to the radius of curvature on a circular path: Δθ=Δsrsize 12{Δθ= { {Δs} over {r} } } {}
    ultracentrifuge
    a centrifuge optimized for spinning a rotor at very high speeds
    uniform circular motion
    the motion of an object in a circular path at constant speed
    basal metabolic rate
    the total energy conversion rate of a person at rest
    chemical energy
    the energy in a substance stored in the bonds between atoms and molecules that can be released in a chemical reaction
    conservation of mechanical energy
    the rule that the sum of the kinetic energies and potential energies remains constant if only conservative forces act on and within a system
    conservative force
    a force that does the same work for any given initial and final configuration, regardless of the path followed
    efficiency
    a measure of the effectiveness of the input of energy to do work; useful energy or work divided by the total input of energy
    electrical energy
    the energy carried by a flow of charge
    energy
    the ability to do work
    fossil fuels
    oil, natural gas, and coal
    friction
    the force between surfaces that opposes one sliding on the other; friction changes mechanical energy into thermal energy
    gravitational potential energy
    the energy an object has due to its position in a gravitational field
    horsepower
    an older non-SI unit of power, with 1 hp=746 W
    joule
    SI unit of work and energy, equal to one newton-meter
    kilowatt-hour
    (kW⋅h)size 12{ \( "kW" cdot h \) } {} unit used primarily for electrical energy provided by electric utility companies
    kinetic energy
    the energy an object has by reason of its motion, equal to 12mv2size 12{ { {1} over {2} } ital "mv" rSup { size 8{2} } } {} for the translational (i.e., non-rotational) motion of an object of mass msize 12{m} {} moving at speed vsize 12{v} {}
    law of conservation of energy
    the general law that total energy is constant in any process; energy may change in form or be transferred from one system to another, but the total remains the same
    mechanical energy
    the sum of kinetic energy and potential energy
    metabolic rate
    the rate at which the body uses food energy to sustain life and to do different activities
    net work
    work done by the net force, or vector sum of all the forces, acting on an object
    nonconservative force
    a force whose work depends on the path followed between the given initial and final configurations
    nuclear energy
    energy released by changes within atomic nuclei, such as the fusion of two light nuclei or the fission of a heavy nucleus
    potential energy
    energy due to position, shape, or configuration
    potential energy of a spring
    the stored energy of a spring as a function of its displacement; when Hooke’s law applies, it is given by the expression 12kx2size 12{ { {1} over {2} } ital "kx" rSup { size 8{2} } } {} where xsize 12{x} {} is the distance the spring is compressed or extended and ksize 12{k} {} is the spring constant
    power
    the rate at which work is done
    radiant energy
    the energy carried by electromagnetic waves
    renewable forms of energy
    those sources that cannot be used up, such as water, wind, solar, and biomass
    thermal energy
    the energy within an object due to the random motion of its atoms and molecules that accounts for the object's temperature
    useful work
    work done on an external system
    watt
    (W) SI unit of power, with 1 W=1 J/s
    work
    the transfer of energy by a force that causes an object to be displaced; the product of the component of the force in the direction of the displacement and the magnitude of the displacement
    work-energy theorem
    the result, based on Newton’s laws, that the net work done on an object is equal to its change in kinetic energy
    change in momentum
    the difference between the final and initial momentum; the mass times the change in velocity
    conservation of momentum principle
    when the net external force is zero, the total momentum of the system is conserved or constant
    elastic collision
    a collision that also conserves internal kinetic energy
    impulse
    the average net external force times the time it acts; equal to the change in momentum
    inelastic collision
    a collision in which internal kinetic energy is not conserved
    internal kinetic energy
    the sum of the kinetic energies of the objects in a system
    isolated system
    a system in which the net external force is zero
    linear momentum
    the product of mass and velocity
    perfectly inelastic collision
    a collision in which the colliding objects stick together
    point masses
    structureless particles with no rotation or spin
    quark
    fundamental constituent of matter and an elementary particle
    second law of motion
    physical law that states that the net external force equals the change in momentum of a system divided by the time over which it changes
    center of gravity
    the point where the total weight of the body is assumed to be concentrated
    dynamic equilibrium
    a state of equilibrium in which the net external force and torque on a system moving with constant velocity are zero
    mechanical advantage
    the ratio of output to input forces for any simple machine
    neutral equilibrium
    a state of equilibrium that is independent of a system’s displacements from its original position
    perpendicular lever arm
    the shortest distance from the pivot point to the line along which F lies
    SI units of torque
    newton times meters, usually written as N·m
    stable equilibrium
    a system, when displaced, experiences a net force or torque in a direction opposite to the direction of the displacement
    static equilibrium
    a state of equilibrium in which the net external force and torque acting on a system is zero
    static equilibrium
    equilibrium in which the acceleration of the system is zero and accelerated rotation does not occur
    torque
    turning or twisting effectiveness of a force
    unstable equilibrium
    a system, when displaced, experiences a net force or torque in the same direction as the displacement from equilibrium
    angular acceleration
    the rate of change of angular velocity with time
    angular momentum
    the product of moment of inertia and angular velocity
    change in angular velocity
    the difference between final and initial values of angular velocity
    kinematics of rotational motion
    describes the relationships among rotation angle, angular velocity, angular acceleration, and time
    law of conservation of angular momentum
    angular momentum is conserved, i.e., the initial angular momentum is equal to the final angular momentum when no external torque is applied to the system
    moment of inertia
    mass times the square of perpendicular distance from the rotation axis; for a point mass, it is I=mr2size 12{I= ital "mr" rSup { size 8{2} } } {} and, because any object can be built up from a collection of point masses, this relationship is the basis for all other moments of inertia
    right-hand rule
    direction of angular velocity ω and angular momentum L in which the thumb of your right hand points when you curl your fingers in the direction of the disk’s rotation
    rotational inertia
    resistance to change of rotation. The more rotational inertia an object has, the harder it is to rotate
    rotational kinetic energy
    the kinetic energy due to the rotation of an object. This is part of its total kinetic energy
    tangential acceleration
    the acceleration in a direction tangent to the circle at the point of interest in circular motion
    torque
    the turning effectiveness of a force
    work-energy theorem
    if one or more external forces act upon a rigid object, causing its kinetic energy to change from KE1size 12{E rSub { size 8{k1} } } {} to KE2size 12{E rSub { size 8{k2} } } {}, then the work Wsize 12{W} {} done by the net force is equal to the change in kinetic energy
    absolute pressure
    the sum of gauge pressure and atmospheric pressure
    adhesive forces
    the attractive forces between molecules of different types
    Archimedes’ principle
    the buoyant force on an object equals the weight of the fluid it displaces
    buoyant force
    the net upward force on any object in any fluid
    capillary action
    the tendency of a fluid to be raised or lowered in a narrow tube
    cohesive forces
    the attractive forces between molecules of the same type
    contact angle
    the angle θsize 12{θ} {} between the tangent to the liquid surface and the surface
    density
    the mass per unit volume of a substance or object
    diastolic pressure
    the minimum blood pressure in the artery
    diastolic pressure
    minimum arterial blood pressure; indicator for the fluid balance
    fluids
    liquids and gases; a fluid is a state of matter that yields to shearing forces
    gauge pressure
    the pressure relative to atmospheric pressure
    glaucoma
    condition caused by the buildup of fluid pressure in the eye
    intraocular pressure
    fluid pressure in the eye
    micturition reflex
    stimulates the feeling of needing to urinate, triggered by bladder pressure
    Pascal’s Principle
    a change in pressure applied to an enclosed fluid is transmitted undiminished to all portions of the fluid and to the walls of its container
    pressure
    the force per unit area perpendicular to the force, over which the force acts
    pressure
    the weight of the fluid divided by the area supporting it
    specific gravity
    the ratio of the density of an object to a fluid (usually water)
    surface tension
    the cohesive forces between molecules which cause the surface of a liquid to contract to the smallest possible surface area
    systolic pressure
    the maximum blood pressure in the artery
    systolic pressure
    maximum arterial blood pressure; indicator for the blood flow
    active transport
    the process in which a living membrane expends energy to move substances across
    Bernoulli’s equation
    the equation resulting from applying conservation of energy to an incompressible frictionless fluid: P + 1/2pv2 + pgh = constant , through the fluid
    Bernoulli’s principle
    Bernoulli’s equation applied at constant depth: P1 + 1/2pv12 = P2 + 1/2pv22
    dialysis
    the transport of any molecule other than water through a semipermeable membrane from a region of high concentration to one of low concentration
    diffusion
    the movement of substances due to random thermal molecular motion
    flow rate
    abbreviated Q, it is the volume V that flows past a particular point during a time t, or Q = V/t
    fluid dynamics
    the physics of fluids in motion
    laminar
    a type of fluid flow in which layers do not mix
    liter
    a unit of volume, equal to 10−3 m3
    osmosis
    the transport of water through a semipermeable membrane from a region of high concentration to one of low concentration
    osmotic pressure
    the back pressure which stops the osmotic process if one solution is pure water
    Poiseuille’s law
    the rate of laminar flow of an incompressible fluid in a tube: Q = (P2P1)πr4/8ηl
    Poiseuille’s law for resistance
    the resistance to laminar flow of an incompressible fluid in a tube: R = 8ηl/πr4
    relative osmotic pressure
    the back pressure which stops the osmotic process if neither solution is pure water
    reverse dialysis
    the process that occurs when back pressure is sufficient to reverse the normal direction of dialysis through membranes
    reverse osmosis
    the process that occurs when back pressure is sufficient to reverse the normal direction of osmosis through membranes
    Reynolds number
    a dimensionless parameter that can reveal whether a particular flow is laminar or turbulent
    semipermeable
    a type of membrane that allows only certain small molecules to pass through
    terminal speed
    the speed at which the viscous drag of an object falling in a viscous fluid is equal to the other forces acting on the object (such as gravity), so that the acceleration of the object is zero
    turbulence
    fluid flow in which layers mix together via eddies and swirls
    viscosity
    the friction in a fluid, defined in terms of the friction between layers
    viscous drag
    a resistance force exerted on a moving object, with a nontrivial dependence on velocity
    absolute zero
    the lowest possible temperature; the temperature at which all molecular motion ceases
    Avogadro’s number
    NA , the number of molecules or atoms in one mole of a substance; NA=6.02×1023size 12{N rSub { size 8{A} } =6 "." "02" times "10" rSup { size 8{"23"} } } {} particles/mole
    Boltzmann constant
    k , a physical constant that relates energy to temperature; k=1.38×10–23J/K
    Celsius scale
    temperature scale in which the freezing point of water is 0ºCsize 12{0°C} {} and the boiling point of water is 100ºCsize 12{"100"°C} {}
    coefficient of linear expansion
    αsize 12{α} {}, the change in length, per unit length, per 1ºCsize 12{1°C} {} change in temperature; a constant used in the calculation of linear expansion; the coefficient of linear expansion depends on the material and to some degree on the temperature of the material
    coefficient of volume expansion
    βsize 12{β} {}, the change in volume, per unit volume, per 1ºCsize 12{1°C} {} change in temperature
    critical point
    the temperature above which a liquid cannot exist
    critical pressure
    the minimum pressure needed for a liquid to exist at the critical temperature
    critical temperature
    the temperature above which a liquid cannot exist
    Dalton’s law of partial pressures
    the physical law that states that the total pressure of a gas is the sum of partial pressures of the component gases
    degree Celsius
    unit on the Celsius temperature scale
    degree Fahrenheit
    unit on the Fahrenheit temperature scale
    dew point
    the temperature at which relative humidity is 100%; the temperature at which water starts to condense out of the air
    Fahrenheit scale
    temperature scale in which the freezing point of water is 32ºFsize 12{"32"°F} {} and the boiling point of water is 212ºFsize 12{"212"°F} {}
    ideal gas law
    the physical law that relates the pressure and volume of a gas to the number of gas molecules or number of moles of gas and the temperature of the gas
    Kelvin scale
    temperature scale in which 0 K is the lowest possible temperature, representing absolute zero
    mole
    the quantity of a substance whose mass (in grams) is equal to its molecular mass
    partial pressure
    the pressure a gas would create if it occupied the total volume of space available
    percent relative humidity
    the ratio of vapor density to saturation vapor density
    phase diagram
    a graph of pressure vs. temperature of a particular substance, showing at which pressures and temperatures the three phases of the substance occur
    PV diagram
    a graph of pressure vs. volume
    relative humidity
    the amount of water in the air relative to the maximum amount the air can hold
    saturation
    the condition of 100% relative humidity
    sublimation
    the phase change from solid to gas
    temperature
    the quantity measured by a thermometer
    thermal energy
    KE¯¯¯¯¯, the average translational kinetic energy of a molecule
    thermal equilibrium
    the condition in which heat no longer flows between two objects that are in contact; the two objects have the same temperature
    thermal expansion
    the change in size or volume of an object with change in temperature
    thermal stress
    stress caused by thermal expansion or contraction
    triple point
    the pressure and temperature at which a substance exists in equilibrium as a solid, liquid, and gas
    vapor
    a gas at a temperature below the boiling temperature
    vapor pressure
    the pressure at which a gas coexists with its solid or liquid phase
    zeroth law of thermodynamics
    law that states that if two objects are in thermal equilibrium, and a third object is in thermal equilibrium with one of those objects, it is also in thermal equilibrium with the other object
    conduction
    heat transfer through stationary matter by physical contact
    convection
    heat transfer by the macroscopic movement of fluid
    emissivity
    measure of how well an object radiates
    greenhouse effect
    warming of the Earth that is due to gases such as carbon dioxide and methane that absorb infrared radiation from the Earth’s surface and reradiate it in all directions, thus sending a fraction of it back toward the surface of the Earth
    heat
    the spontaneous transfer of energy due to a temperature difference
    heat of sublimation
    the energy required to change a substance from the solid phase to the vapor phase
    kilocalorie
    1kilocalorie=1000caloriessize 12{1`"kilocalorie=1000"`"calories"} {}
    latent heat coefficient
    a physical constant equal to the amount of heat transferred for every 1 kg of a substance during the change in phase of the substance
    mechanical equivalent of heat
    the work needed to produce the same effects as heat transfer
    net rate of heat transfer by radiation
    is Qnett=σeA(T42−T41)size 12{ { {Q rSub { size 8{"net"} } } over {t} } =σ`e`A` left (T rSub { size 8{2} } rSup { size 8{4} } - T rSub { size 8{1} } rSup { size 8{4} } right )} {}
    R factor
    the ratio of thickness to the conductivity of a material
    radiation
    heat transfer which occurs when microwaves, infrared radiation, visible light, or other electromagnetic radiation is emitted or absorbed
    radiation
    energy transferred by electromagnetic waves directly as a result of a temperature difference
    rate of conductive heat transfer
    rate of heat transfer from one material to another
    specific heat
    the amount of heat necessary to change the temperature of 1.00 kg of a substance by 1.00 ºC
    Stefan-Boltzmann law of radiation
    Qt=σeAT4,size 12{ { {Q} over {t} } =σ`e`A`T rSup { size 8{4} } ,} {} where σ is the Stefan-Boltzmann constant, A is the surface area of the object, Tsize 12{T} {} is the absolute temperature, and esize 12{e} {} is the emissivity
    sublimation
    the transition from the solid phase to the vapor phase
    thermal conductivity
    the property of a material’s ability to conduct heat
    adiabatic process
    a process in which no heat transfer takes place
    Carnot cycle
    a cyclical process that uses only reversible processes, the adiabatic and isothermal processes
    Carnot efficiency
    the maximum theoretical efficiency for a heat engine
    Carnot engine
    a heat engine that uses a Carnot cycle
    change in entropy
    the ratio of heat transfer to temperature Q/Tsize 12{Q/T} {}
    coefficient of performance
    for a heat pump, it is the ratio of heat transfer at the output (the hot reservoir) to the work supplied; for a refrigerator or air conditioner, it is the ratio of heat transfer from the cold reservoir to the work supplied
    cyclical process
    a process in which the path returns to its original state at the end of every cycle
    entropy
    a measurement of a system's disorder and its inability to do work in a system
    first law of thermodynamics
    states that the change in internal energy of a system equals the net heat transfer into the system minus the net work done by the system
    heat engine
    a machine that uses heat transfer to do work
    heat pump
    a machine that generates heat transfer from cold to hot
    human metabolism
    conversion of food into heat transfer, work, and stored fat
    internal energy
    the sum of the kinetic and potential energies of a system’s atoms and molecules
    irreversible process
    any process that depends on path direction
    isobaric process
    constant-pressure process in which a gas does work
    isochoric process
    a constant-volume process
    isothermal process
    a constant-temperature process
    macrostate
    an overall property of a system
    microstate
    each sequence within a larger macrostate
    Otto cycle
    a thermodynamic cycle, consisting of a pair of adiabatic processes and a pair of isochoric processes, that converts heat into work, e.g., the four-stroke engine cycle of intake, compression, ignition, and exhaust
    reversible process
    a process in which both the heat engine system and the external environment theoretically can be returned to their original states
    second law of thermodynamics
    heat transfer flows from a hotter to a cooler object, never the reverse, and some heat energy in any process is lost to available work in a cyclical process
    second law of thermodynamics stated in terms of entropy
    the total entropy of a system either increases or remains constant; it never decreases
    statistical analysis
    using statistics to examine data, such as counting microstates and macrostates
    amplitude
    the maximum displacement from the equilibrium position of an object oscillating around the equilibrium position
    antinode
    the location of maximum amplitude in standing waves
    beat frequency
    the frequency of the amplitude fluctuations of a wave
    constructive interference
    when two waves arrive at the same point exactly in phase; that is, the crests of the two waves are precisely aligned, as are the troughs
    critical damping
    the condition in which the damping of an oscillator causes it to return as quickly as possible to its equilibrium position without oscillating back and forth about this position
    deformation
    displacement from equilibrium
    destructive interference
    when two identical waves arrive at the same point exactly out of phase; that is, precisely aligned crest to trough
    elastic potential energy
    potential energy stored as a result of deformation of an elastic object, such as the stretching of a spring
    force constant
    a constant related to the rigidity of a system: the larger the force constant, the more rigid the system; the force constant is represented by k
    frequency
    number of events per unit of time
    fundamental frequency
    the lowest frequency of a periodic waveform
    intensity
    power per unit area
    longitudinal wave
    a wave in which the disturbance is parallel to the direction of propagation
    natural frequency
    the frequency at which a system would oscillate if there were no driving and no damping forces
    nodes
    the points where the string does not move; more generally, nodes are where the wave disturbance is zero in a standing wave
    oscillate
    moving back and forth regularly between two points
    over damping
    the condition in which damping of an oscillator causes it to return to equilibrium without oscillating; oscillator moves more slowly toward equilibrium than in the critically damped system
    overtones
    multiples of the fundamental frequency of a sound
    period
    time it takes to complete one oscillation
    periodic motion
    motion that repeats itself at regular time intervals
    resonance
    the phenomenon of driving a system with a frequency equal to the system's natural frequency
    resonate
    a system being driven at its natural frequency
    restoring force
    force acting in opposition to the force caused by a deformation
    simple harmonic motion
    the oscillatory motion in a system where the net force can be described by Hooke’s law
    simple harmonic oscillator
    a device that implements Hooke’s law, such as a mass that is attached to a spring, with the other end of the spring being connected to a rigid support such as a wall
    simple pendulum
    an object with a small mass suspended from a light wire or string
    superposition
    the phenomenon that occurs when two or more waves arrive at the same point
    transverse wave
    a wave in which the disturbance is perpendicular to the direction of propagation
    under damping
    the condition in which damping of an oscillator causes it to return to equilibrium with the amplitude gradually decreasing to zero; system returns to equilibrium faster but overshoots and crosses the equilibrium position one or more times
    wave
    a disturbance that moves from its source and carries energy
    wave velocity
    the speed at which the disturbance moves. Also called the propagation velocity or propagation speed
    wavelength
    the distance between adjacent identical parts of a wave
    acoustic impedance
    property of medium that makes the propagation of sound waves more difficult
    antinode
    point of maximum displacement
    bow wake
    V-shaped disturbance created when the wave source moves faster than the wave propagation speed
    Doppler effect
    an alteration in the observed frequency of a sound due to motion of either the source or the observer
    Doppler shift
    the actual change in frequency due to relative motion of source and observer
    Doppler-shifted ultrasound
    a medical technique to detect motion and determine velocity through the Doppler shift of an echo
    fundamental
    the lowest-frequency resonance
    harmonics
    the term used to refer collectively to the fundamental and its overtones
    hearing
    the perception of sound
    infrasound
    sounds below 20 Hz
    intensity
    the power per unit area carried by a wave
    intensity reflection coefficient
    a measure of the ratio of the intensity of the wave reflected off a boundary between two media relative to the intensity of the incident wave
    loudness
    the perception of sound intensity
    node
    point of zero displacement
    note
    basic unit of music with specific names, combined to generate tunes
    overtones
    all resonant frequencies higher than the fundamental
    phon
    the numerical unit of loudness
    pitch
    the perception of the frequency of a sound
    sonic boom
    a constructive interference of sound created by an object moving faster than sound
    sound
    a disturbance of matter that is transmitted from its source outward
    sound intensity level
    a unitless quantity telling you the level of the sound relative to a fixed standard
    sound pressure level
    the ratio of the pressure amplitude to a reference pressure
    timbre
    number and relative intensity of multiple sound frequencies
    tone
    number and relative intensity of multiple sound frequencies
    ultrasound
    sounds above 20,000 Hz
    conductor
    a material that allows electrons to move separately from their atomic orbits
    conductor
    an object with properties that allow charges to move about freely within it
    Coulomb force
    another term for the electrostatic force
    Coulomb interaction
    the interaction between two charged particles generated by the Coulomb forces they exert on one another
    Coulomb’s law
    the mathematical equation calculating the electrostatic force vector between two charged particles
    dipole
    a molecule’s lack of symmetrical charge distribution, causing one side to be more positive and another to be more negative
    electric charge
    a physical property of an object that causes it to be attracted toward or repelled from another charged object; each charged object generates and is influenced by a force called an electromagnetic force
    electric field
    a three-dimensional map of the electric force extended out into space from a point charge
    electric field lines
    a series of lines drawn from a point charge representing the magnitude and direction of force exerted by that charge
    electromagnetic force
    one of the four fundamental forces of nature; the electromagnetic force consists of static electricity, moving electricity and magnetism
    electron
    a particle orbiting the nucleus of an atom and carrying the smallest unit of negative charge
    electrostatic equilibrium
    an electrostatically balanced state in which all free electrical charges have stopped moving about
    electrostatic force
    the amount and direction of attraction or repulsion between two charged bodies
    electrostatic precipitators
    filters that apply charges to particles in the air, then attract those charges to a filter, removing them from the airstream
    electrostatic repulsion
    the phenomenon of two objects with like charges repelling each other
    electrostatics
    the study of electric forces that are static or slow-moving
    Faraday cage
    a metal shield which prevents electric charge from penetrating its surface
    field
    a map of the amount and direction of a force acting on other objects, extending out into space
    free charge
    an electrical charge (either positive or negative) which can move about separately from its base molecule
    free electron
    an electron that is free to move away from its atomic orbit
    grounded
    when a conductor is connected to the Earth, allowing charge to freely flow to and from Earth’s unlimited reservoir
    grounded
    connected to the ground with a conductor, so that charge flows freely to and from the Earth to the grounded object
    induction
    the process by which an electrically charged object brought near a neutral object creates a charge in that object
    ink-jet printer
    small ink droplets sprayed with an electric charge are controlled by electrostatic plates to create images on paper
    insulator
    a material that holds electrons securely within their atomic orbits
    ionosphere
    a layer of charged particles located around 100 km above the surface of Earth, which is responsible for a range of phenomena including the electric field surrounding Earth
    laser printer
    uses a laser to create a photoconductive image on a drum, which attracts dry ink particles that are then rolled onto a sheet of paper to print a high-quality copy of the image
    law of conservation of charge
    states that whenever a charge is created, an equal amount of charge with the opposite sign is created simultaneously
    photoconductor
    a substance that is an insulator until it is exposed to light, when it becomes a conductor
    point charge
    A charged particle, designated Qsize 12{Q} {}, generating an electric field
    polar molecule
    a molecule with an asymmetrical distribution of positive and negative charge
    polarization
    slight shifting of positive and negative charges to opposite sides of an atom or molecule
    polarized
    a state in which the positive and negative charges within an object have collected in separate locations
    proton
    a particle in the nucleus of an atom and carrying a positive charge equal in magnitude and opposite in sign to the amount of negative charge carried by an electron
    screening
    the dilution or blocking of an electrostatic force on a charged object by the presence of other charges nearby
    static electricity
    a buildup of electric charge on the surface of an object
    test charge
    A particle (designated qsize 12{q} {}) with either a positive or negative charge set down within an electric field generated by a point charge
    Van de Graaff generator
    a machine that produces a large amount of excess charge, used for experiments with high voltage
    vector
    a quantity with both magnitude and direction
    vector addition
    mathematical combination of two or more vectors, including their magnitudes, directions, and positions
    xerography
    a dry copying process based on electrostatics
    capacitance
    amount of charge stored per unit volt
    capacitor
    a device that stores electric charge
    defibrillator
    a machine used to provide an electrical shock to a heart attack victim's heart in order to restore the heart's normal rhythmic pattern
    dielectric
    an insulating material
    dielectric strength
    the maximum electric field above which an insulating material begins to break down and conduct
    electric potential
    potential energy per unit charge
    electron volt
    the energy given to a fundamental charge accelerated through a potential difference of one volt
    equipotential line
    a line along which the electric potential is constant
    grounding
    fixing a conductor at zero volts by connecting it to the earth or ground
    mechanical energy
    sum of the kinetic energy and potential energy of a system; this sum is a constant
    parallel plate capacitor
    two identical conducting plates separated by a distance
    polar molecule
    a molecule with inherent separation of charge
    potential difference (or voltage)
    change in potential energy of a charge moved from one point to another, divided by the charge; units of potential difference are joules per coulomb, known as volt
    scalar
    physical quantity with magnitude but no direction
    vector
    physical quantity with both magnitude and direction
    AC current
    current that fluctuates sinusoidally with time, expressed as I = I0 sin 2πft, where I is the current at time t, I0 is the peak current, and f is the frequency in hertz
    AC voltage
    voltage that fluctuates sinusoidally with time, expressed as V = V0 sin 2πft, where V is the voltage at time t, V0 is the peak voltage, and f is the frequency in hertz
    alternating current
    (AC) the flow of electric charge that periodically reverses direction
    ampere
    (amp) the SI unit for current; 1 A = 1 C/s
    bioelectricity
    electrical effects in and created by biological systems
    direct current
    (DC) the flow of electric charge in only one direction
    drift velocity
    the average velocity at which free charges flow in response to an electric field
    electric current
    the rate at which charge flows, I = ΔQt
    electric power
    the rate at which electrical energy is supplied by a source or dissipated by a device; it is the product of current times voltage
    electrocardiogram (ECG)
    usually abbreviated ECG, a record of voltages created by depolarization and repolarization, especially in the heart
    microshock sensitive
    a condition in which a person’s skin resistance is bypassed, possibly by a medical procedure, rendering the person vulnerable to electrical shock at currents about 1/1000 the normally required level
    nerve conduction
    the transport of electrical signals by nerve cells
    ohm
    the unit of resistance, given by 1Ω = 1 V/A
    Ohm’s law
    an empirical relation stating that the current I is proportional to the potential difference V, ∝ V; it is often written as I = V/R, where R is the resistance
    ohmic
    a type of a material for which Ohm's law is valid
    resistance
    the electric property that impedes current; for ohmic materials, it is the ratio of voltage to current, R = V/I
    resistivity
    an intrinsic property of a material, independent of its shape or size, directly proportional to the resistance, denoted by ρ
    rms current
    the root mean square of the current, Irms=I0/2–√size 12{I rSub { size 8{"rms "} } = I rSub { size 8{0} } / sqrt {2} } {} , where I0 is the peak current, in an AC system
    rms voltage
    the root mean square of the voltage, Vrms=V0/2–√size 12{V rSub { size 8{"rms "} } = V rSub { size 8{0} } / sqrt {2} } {} , where V0 is the peak voltage, in an AC system
    semipermeable
    property of a membrane that allows only certain types of ions to cross it
    shock hazard
    when electric current passes through a person
    short circuit
    also known as a “short,” a low-resistance path between terminals of a voltage source
    simple circuit
    a circuit with a single voltage source and a single resistor
    temperature coefficient of resistivity
    an empirical quantity, denoted by α, which describes the change in resistance or resistivity of a material with temperature
    thermal hazard
    a hazard in which electric current causes undesired thermal effects
    ammeter
    an instrument that measures current
    analog meter
    a measuring instrument that gives a readout in the form of a needle movement over a marked gauge
    bridge device
    a device that forms a bridge between two branches of a circuit; some bridge devices are used to make null measurements in circuits
    capacitance
    the maximum amount of electric potential energy that can be stored (or separated) for a given electric potential
    capacitor
    an electrical component used to store energy by separating electric charge on two opposing plates
    conservation laws
    require that energy and charge be conserved in a system
    current
    the flow of charge through an electric circuit past a given point of measurement
    current sensitivity
    the maximum current that a galvanometer can read
    digital meter
    a measuring instrument that gives a readout in a digital form
    electromotive force (emf)
    the potential difference of a source of electricity when no current is flowing; measured in volts
    full-scale deflection
    the maximum deflection of a galvanometer needle, also known as current sensitivity; a galvanometer with a full-scale deflection of 50 μAsize 12{"50" mA} {} has a maximum deflection of its needle when 50 μAsize 12{"50" μA} {} flows through it
    galvanometer
    an analog measuring device, denoted by G, that measures current flow using a needle deflection caused by a magnetic field force acting upon a current-carrying wire
    internal resistance
    the amount of resistance within the voltage source
    Joule’s law
    the relationship between potential electrical power, voltage, and resistance in an electrical circuit, given by: Pe=IVsize 12{P rSub { size 8{e} } = ital "IV"} {}
    junction rule
    Kirchhoff’s first rule, which applies the conservation of charge to a junction; current is the flow of charge; thus, whatever charge flows into the junction must flow out; the rule can be stated I1=I2+I3size 12{I rSub { size 8{1} } =I rSub { size 8{2} } +I rSub { size 8{3} } } {}
    Kirchhoff’s rules
    a set of two rules, based on conservation of charge and energy, governing current and changes in potential in an electric circuit
    loop rule
    Kirchhoff’s second rule, which states that in a closed loop, whatever energy is supplied by emf must be transferred into other forms by devices in the loop, since there are no other ways in which energy can be transferred into or out of the circuit. Thus, the emf equals the sum of the IRsize 12{ ital "IR"} {} (voltage) drops in the loop and can be stated: emf=Ir+IR1+IR2size 12{"emf"= ital "Ir"+ ital "IR" rSub { size 8{1} } + ital "IR" rSub { size 8{2} } } {}
    null measurements
    methods of measuring current and voltage more accurately by balancing the circuit so that no current flows through the measurement device
    Ohm’s law
    the relationship between current, voltage, and resistance within an electrical circuit: V=IRsize 12{V= ital "IR"} {}
    ohmmeter
    an instrument that applies a voltage to a resistance, measures the current, calculates the resistance using Ohm’s law, and provides a readout of this calculated resistance
    parallel
    the wiring of resistors or other components in an electrical circuit such that each component receives an equal voltage from the power source; often pictured in a ladder-shaped diagram, with each component on a rung of the ladder
    potential difference
    the difference in electric potential between two points in an electric circuit, measured in volts
    potentiometer
    a null measurement device for measuring potentials (voltages)
    RC circuit
    a circuit that contains both a resistor and a capacitor
    resistance
    causing a loss of electrical power in a circuit
    resistor
    a component that provides resistance to the current flowing through an electrical circuit
    series
    a sequence of resistors or other components wired into a circuit one after the other
    shunt resistance
    a small resistance Rsize 12{R} {} placed in parallel with a galvanometer G to produce an ammeter; the larger the current to be measured, the smaller Rsize 12{R} {} must be; most of the current flowing through the meter is shunted through Rsize 12{R} {} to protect the galvanometer
    terminal voltage
    the voltage measured across the terminals of a source of potential difference
    voltage
    the electrical potential energy per unit charge; electric pressure created by a power source, such as a battery
    voltage drop
    the loss of electrical power as a current travels through a resistor, wire or other component
    voltmeter
    an instrument that measures voltage
    Wheatstone bridge
    a null measurement device for calculating resistance by balancing potential drops in a circuit
    Ampere’s law
    the physical law that states that the magnetic field around an electric current is proportional to the current; each segment of current produces a magnetic field like that of a long straight wire, and the total field of any shape current is the vector sum of the fields due to each segment
    B-field
    another term for magnetic field
    Biot-Savart law
    a physical law that describes the magnetic field generated by an electric current in terms of a specific equation
    Curie temperature
    the temperature above which a ferromagnetic material cannot be magnetized
    direction of magnetic field lines
    the direction that the north end of a compass needle points
    domains
    regions within a material that behave like small bar magnets
    electromagnet
    an object that is temporarily magnetic when an electrical current is passed through it
    electromagnetism
    the use of electrical currents to induce magnetism
    ferromagnetic
    materials, such as iron, cobalt, nickel, and gadolinium, that exhibit strong magnetic effects
    gauss
    G, the unit of the magnetic field strength; 1 G=10–4Tsize 12{"1 G"="10" rSup { size 8{ - 4} } `T} {}
    Hall effect
    the creation of voltage across a current-carrying conductor by a magnetic field
    Hall emf
    the electromotive force created by a current-carrying conductor by a magnetic field, ε=Blvsize 12{ε= ital "Blv"} {}
    Lorentz force
    the force on a charge moving in a magnetic field
    magnetic field
    the representation of magnetic forces
    magnetic field lines
    the pictorial representation of the strength and the direction of a magnetic field
    magnetic field strength (magnitude) produced by a long straight current-carrying wire
    defined as B=μ0I2πr, where I is the current, r is the shortest distance to the wire, and μ0 is the permeability of free space
    magnetic field strength at the center of a circular loop
    defined as B=μ0I2R where R is the radius of the loop
    magnetic field strength inside a solenoid
    defined as B=μ0nI where n is the number of loops per unit length of the solenoid (n=N/l, with N being the number of loops and l the length)
    magnetic force
    the force on a charge produced by its motion through a magnetic field; the Lorentz force
    magnetic monopoles
    an isolated magnetic pole; a south pole without a north pole, or vice versa (no magnetic monopole has ever been observed)
    magnetic resonance imaging (MRI)
    a medical imaging technique that uses magnetic fields create detailed images of internal tissues and organs
    magnetized
    to be turned into a magnet; to be induced to be magnetic
    magnetocardiogram (MCG)
    a recording of the heart’s magnetic field as it beats
    magnetoencephalogram (MEG)
    a measurement of the brain’s magnetic field
    Maxwell’s equations
    a set of four equations that describe electromagnetic phenomena
    meter
    common application of magnetic torque on a current-carrying loop that is very similar in construction to a motor; by design, the torque is proportional to I and not θ, so the needle deflection is proportional to the current
    motor
    loop of wire in a magnetic field; when current is passed through the loops, the magnetic field exerts torque on the loops, which rotates a shaft; electrical energy is converted to mechanical work in the process
    north magnetic pole
    the end or the side of a magnet that is attracted toward Earth’s geographic north pole
    nuclear magnetic resonance (NMR)
    a phenomenon in which an externally applied magnetic field interacts with the nuclei of certain atoms
    permeability of free space
    the measure of the ability of a material, in this case free space, to support a magnetic field; the constant μ0=4π×10−7T⋅m/A
    right hand rule 1 (RHR-1)
    the rule to determine the direction of the magnetic force on a positive moving charge: when the thumb of the right hand points in the direction of the charge’s velocity vsize 12{v} {} and the fingers point in the direction of the magnetic field Bsize 12{B} {}, then the force on the charge is perpendicular and away from the palm; the force on a negative charge is perpendicular and into the palm
    right hand rule 2 (RHR-2)
    a rule to determine the direction of the magnetic field induced by a current-carrying wire: Point the thumb of the right hand in the direction of current, and the fingers curl in the direction of the magnetic field loops
    solenoid
    a thin wire wound into a coil that produces a magnetic field when an electric current is passed through it
    south magnetic pole
    the end or the side of a magnet that is attracted toward Earth’s geographic south pole
    tesla
    T, the SI unit of the magnetic field strength; 1 T=1 NA⋅m
    back emf
    the emf generated by a running motor, because it consists of a coil turning in a magnetic field; it opposes the voltage powering the motor
    capacitive reactance
    the opposition of a capacitor to a change in current; calculated by XC=12πfCsize 12{X rSub { size 8{C} } = { {1} over {2π ital "fC"} } } {}
    characteristic time constant
    denoted by τsize 12{τ} {}, of a particular series RL circuit is calculated by τ=LRsize 12{τ= { {L} over {R} } } {}, where Lsize 12{L} {} is the inductance and R is the resistance
    eddy current
    a current loop in a conductor caused by motional emf
    electric generator
    a device for converting mechanical work into electric energy; it induces an emf by rotating a coil in a magnetic field
    electromagnetic induction
    the process of inducing an emf (voltage) with a change in magnetic flux
    emf induced in a generator coil
    emf=NABωsinωtsize 12{"emf"= ital "NAB"ω"sin"ωt} {}, where A is the area of an N-turn coil rotated at a constant angular velocity ω in a uniform magnetic field B, over a period of time t
    energy stored in an inductor
    self-explanatory; calculated by Eind=12LI2size 12{E rSub { size 8{"ind"} } = { {1} over {2} } ital "LI" rSup { size 8{2} } } {}
    Faraday’s law of induction
    the means of calculating the emf in a coil due to changing magnetic flux, given by emf=−NΔΦΔtsize 12{"emf"= - N { {ΔΦ} over {Δt} } } {}
    henry
    the unit of inductance; 1H=1Ω⋅ssize 12{1`H=1` %OMEGA cdot s} {}
    impedance
    the AC analogue to resistance in a DC circuit; it is the combined effect of resistance, inductive reactance, and capacitive reactance in the form Z=R2+(XL−XC)2−−−−−−−−−−−−−√size 12{Z= sqrt {R rSup { size 8{2} } + \( X rSub { size 8{L} } - X rSub { size 8{C} } \) rSup { size 8{2} } } } {}
    inductance
    a property of a device describing how efficient it is at inducing emf in another device
    induction
    (magnetic induction) the creation of emfs and hence currents by magnetic fields
    inductive reactance
    the opposition of an inductor to a change in current; calculated by XL=2πfLsize 12{X rSub { size 8{L} } =2π ital "fL"} {}
    inductor
    a device that exhibits significant self-inductance
    Lenz’s law
    the minus sign in Faraday’s law, signifying that the emf induced in a coil opposes the change in magnetic flux
    magnetic damping
    the drag produced by eddy currents
    magnetic flux
    the amount of magnetic field going through a particular area, calculated with Φ=BAcosθsize 12{Φ= ital "BA""cos"θ} {} where Bsize 12{B} {} is the magnetic field strength over an area Asize 12{A} {} at an angle θsize 12{θ} {} with the perpendicular to the area
    mutual inductance
    how effective a pair of devices are at inducing emfs in each other
    peak emf
    emf0=NABωsize 12{"emf" rSub { size 8{0} } = ital "NAB"ω} {}
    phase angle
    denoted by ϕsize 12{ϕ} {}, the amount by which the voltage and current are out of phase with each other in a circuit
    power factor
    the amount by which the power delivered in the circuit is less than the theoretical maximum of the circuit due to voltage and current being out of phase; calculated by cosϕsize 12{"cos"ϕ} {}
    resonant frequency
    the frequency at which the impedance in a circuit is at a minimum, and also the frequency at which the circuit would oscillate if not driven by a voltage source; calculated by f0=12πLC√size 12{f rSub { size 8{0} } = { {1} over {2π sqrt { ital "LC"} } } } {}
    self-inductance
    how effective a device is at inducing emf in itself
    shock hazard
    the term for electrical hazards due to current passing through a human
    step-down transformer
    a transformer that decreases voltage
    step-up transformer
    a transformer that increases voltage
    thermal hazard
    the term for electrical hazards due to overheating
    three-wire system
    the wiring system used at present for safety reasons, with live, neutral, and ground wires
    transformer
    a device that transforms voltages from one value to another using induction
    transformer equation
    the equation showing that the ratio of the secondary to primary voltages in a transformer equals the ratio of the number of loops in their coils; VsVp=NsNp
    amplitude
    the height, or magnitude, of an electromagnetic wave
    amplitude modulation (AM)
    a method for placing information on electromagnetic waves by modulating the amplitude of a carrier wave with an audio signal, resulting in a wave with constant frequency but varying amplitude
    carrier wave
    an electromagnetic wave that carries a signal by modulation of its amplitude or frequency
    electric field
    a vector quantity (E); the lines of electric force per unit charge, moving radially outward from a positive charge and in toward a negative charge
    electric field lines
    a pattern of imaginary lines that extend between an electric source and charged objects in the surrounding area, with arrows pointed away from positively charged objects and toward negatively charged objects. The more lines in the pattern, the stronger the electric field in that region
    electric field strength
    the magnitude of the electric field, denoted E-field
    electromagnetic spectrum
    the full range of wavelengths or frequencies of electromagnetic radiation
    electromagnetic waves
    radiation in the form of waves of electric and magnetic energy
    electromotive force (emf)
    energy produced per unit charge, drawn from a source that produces an electrical current
    extremely low frequency (ELF)
    electromagnetic radiation with wavelengths usually in the range of 0 to 300 Hz, but also about 1kHz
    frequency
    the number of complete wave cycles (up-down-up) passing a given point within one second (cycles/second)
    frequency modulation (FM)
    a method of placing information on electromagnetic waves by modulating the frequency of a carrier wave with an audio signal, producing a wave of constant amplitude but varying frequency
    gamma ray
    (γsize 12{g} {} ray); extremely high frequency electromagnetic radiation emitted by the nucleus of an atom, either from natural nuclear decay or induced nuclear processes in nuclear reactors and weapons. The lower end of the γ-ray frequency range overlaps the upper end of the X-ray range, but γsize 12{g} {} rays can have the highest frequency of any electromagnetic radiation
    hertz
    an SI unit denoting the frequency of an electromagnetic wave, in cycles per second
    infrared radiation (IR)
    a region of the electromagnetic spectrum with a frequency range that extends from just below the red region of the visible light spectrum up to the microwave region, or from 0.74μmsize 12{0 "." "74" μm} {} to 300μmsize 12{"300" μm} {}
    intensity
    the power of an electric or magnetic field per unit area, for example, Watts per square meter
    magnetic field
    a vector quantity (B); can be used to determine the magnetic force on a moving charged particle
    magnetic field lines
    a pattern of continuous, imaginary lines that emerge from and enter into opposite magnetic poles. The density of the lines indicates the magnitude of the magnetic field
    magnetic field strength
    the magnitude of the magnetic field, denoted B-field
    maximum field strength
    the maximum amplitude an electromagnetic wave can reach, representing the maximum amount of electric force and/or magnetic flux that the wave can exert
    Maxwell’s equations
    a set of four equations that comprise a complete, overarching theory of electromagnetism
    microwaves
    electromagnetic waves with wavelengths in the range from 1 mm to 1 m; they can be produced by currents in macroscopic circuits and devices
    oscillate
    to fluctuate back and forth in a steady beat
    radar
    a common application of microwaves. Radar can determine the distance to objects as diverse as clouds and aircraft, as well as determine the speed of a car or the intensity of a rainstorm
    radio waves
    electromagnetic waves with wavelengths in the range from 1 mm to 100 km; they are produced by currents in wires and circuits and by astronomical phenomena
    resonant
    a system that displays enhanced oscillation when subjected to a periodic disturbance of the same frequency as its natural frequency
    RLC circuit
    an electric circuit that includes a resistor, capacitor and inductor
    speed of light
    in a vacuum, such as space, the speed of light is a constant 3 x 108 m/s
    standing wave
    a wave that oscillates in place, with nodes where no motion happens
    thermal agitation
    the thermal motion of atoms and molecules in any object at a temperature above absolute zero, which causes them to emit and absorb radiation
    transverse wave
    a wave, such as an electromagnetic wave, which oscillates perpendicular to the axis along the line of travel
    TV
    video and audio signals broadcast on electromagnetic waves
    ultra-high frequency (UHF)
    TV channels in an even higher frequency range than VHF, of 470 to 1000 MHz
    ultraviolet radiation (UV)
    electromagnetic radiation in the range extending upward in frequency from violet light and overlapping with the lowest X-ray frequencies, with wavelengths from 400 nm down to about 10 nm
    very high frequency (VHF)
    TV channels utilizing frequencies in the two ranges of 54 to 88 MHz and 174 to 222 MHz
    visible light
    the narrow segment of the electromagnetic spectrum to which the normal human eye responds
    wavelength
    the distance from one peak to the next in a wave
    X-ray
    invisible, penetrating form of very high frequency electromagnetic radiation, overlapping both the ultraviolet range and the γsize 12{g} {}-ray range
    converging lens
    a convex lens in which light rays that enter it parallel to its axis converge at a single point on the opposite side
    converging mirror
    a concave mirror in which light rays that strike it parallel to its axis converge at one or more points along the axis
    corner reflector
    an object consisting of two mutually perpendicular reflecting surfaces, so that the light that enters is reflected back exactly parallel to the direction from which it came
    critical angle
    incident angle that produces an angle of refraction of 90ºsize 12{"90"°} {}
    dispersion
    spreading of white light into its full spectrum of wavelengths
    diverging lens
    a concave lens in which light rays that enter it parallel to its axis bend away (diverge) from its axis
    diverging mirror
    a convex mirror in which light rays that strike it parallel to its axis bend away (diverge) from its axis
    fiber optics
    transmission of light down fibers of plastic or glass, applying the principle of total internal reflection
    focal length
    distance from the center of a lens or curved mirror to its focal point
    focal point
    for a converging lens or mirror, the point at which converging light rays cross; for a diverging lens or mirror, the point from which diverging light rays appear to originate
    geometric optics
    part of optics dealing with the ray aspect of light
    index of refraction
    for a material, the ratio of the speed of light in vacuum to that in the material
    law of reflection
    angle of reflection equals the angle of incidence
    law of reflection
    angle of reflection equals the angle of incidence
    magnification
    ratio of image height to object height
    mirror
    smooth surface that reflects light at specific angles, forming an image of the person or object in front of it
    power
    inverse of focal length
    rainbow
    dispersion of sunlight into a continuous distribution of colors according to wavelength, produced by the refraction and reflection of sunlight by water droplets in the sky
    ray
    straight line that originates at some point
    real image
    image that can be projected
    refraction
    changing of a light ray’s direction when it passes through variations in matter
    virtual image
    image that cannot be projected
    zircon
    natural gemstone with a large index of refraction
    aberration
    failure of rays to converge at one focus because of limitations or defects in a lens or mirror
    accommodation
    the ability of the eye to adjust its focal length is known as accommodation
    adaptive optics
    optical technology in which computers adjust the lenses and mirrors in a device to correct for image distortions
    angular magnification
    a ratio related to the focal lengths of the objective and eyepiece and given as M=−fofe
    astigmatism
    the result of an inability of the cornea to properly focus an image onto the retina
    color constancy
    a part of the visual perception system that allows people to perceive color in a variety of conditions and to see some consistency in the color
    compound microscope
    a microscope constructed from two convex lenses, the first serving as the ocular lens(close to the eye) and the second serving as the objective lens
    eyepiece
    the lens or combination of lenses in an optical instrument nearest to the eye of the observer
    far point
    the object point imaged by the eye onto the retina in an unaccommodated eye
    farsightedness
    another term for hyperopia, the condition of an eye where incoming rays of light reach the retina before they converge into a focused image
    hues
    identity of a color as it relates specifically to the spectrum
    hyperopia
    the condition of an eye where incoming rays of light reach the retina before they converge into a focused image
    laser vision correction
    a medical procedure used to correct astigmatism and eyesight deficiencies such as myopia and hyperopia
    myopia
    a visual defect in which distant objects appear blurred because their images are focused in front of the retina rather than being focused on the retina
    near point
    the point nearest the eye at which an object is accurately focused on the retina at full accommodation
    nearsightedness
    another term for myopia, a visual defect in which distant objects appear blurred because their images are focused in front of the retina rather than being focused on the retina
    numerical aperture
    a number or measure that expresses the ability of a lens to resolve fine detail in an object being observed. Derived by mathematical formula NA=nsinα,size 12{ ital "NA"=n"sin"α}where nsize 12{n} is the refractive index of the medium between the lens and the specimen and α=θ/2size 12{α= {θ} slash {2} }
    objective lens
    the lens nearest to the object being examined
    presbyopia
    a condition in which the lens of the eye becomes progressively unable to focus on objects close to the viewer
    retinex
    a theory proposed to explain color and brightness perception and constancies; is a combination of the words retina and cortex, which are the two areas responsible for the processing of visual information
    retinex theory of color vision
    the ability to perceive color in an ambient-colored environment
    rods and cones
    two types of photoreceptors in the human retina; rods are responsible for vision at low light levels, while cones are active at higher light levels
    simplified theory of color vision
    a theory that states that there are three primary colors, which correspond to the three types of cones
    axis of a polarizing filter
    the direction along which the filter passes the electric field of an EM wave
    birefringent
    crystals that split an unpolarized beam of light into two beams
    Brewster’s angle
    θb=tan−1(n2n1),size 12{θ rSub { size 8{b} } ="tan" rSup { size 8{ - 1} } left ( { {n rSub { size 8{2} } } over {n rSub { size 8{1} } } } right ),} {} where n2 is the index of refraction of the medium from which the light is reflected and n1 is the index of refraction of the medium in which the reflected light travels
    Brewster’s law
    tanθb=n2n1, where n1 is the medium in which the incident and reflected light travel and n2 is the index of refraction of the medium that forms the interface that reflects the light
    coherent
    waves are in phase or have a definite phase relationship
    confocal microscopes
    microscopes that use the extended focal region to obtain three-dimensional images rather than two-dimensional images
    constructive interference for a diffraction grating
    occurs when the condition dsinθ=mλ(form=0,1,–1,2,–2,…) is satisfied, where dsize 12{d} {} is the distance between slits in the grating, λsize 12{λ} {} is the wavelength of light, and msize 12{m} {} is the order of the maximum
    constructive interference for a double slit
    the path length difference must be an integral multiple of the wavelength
    contrast
    the difference in intensity between objects and the background on which they are observed
    destructive interference for a double slit
    the path length difference must be a half-integral multiple of the wavelength
    destructive interference for a single slit
    occurs when Dsinθ=mλ,(form=1,–1,2,–2,3,…)size 12{D`"sin"θ= ital "mλ",~m="1,"`"2,"`"3,"` dotslow } {}, where Dsize 12{D} {} is the slit width, λsize 12{λ} {} is the light’s wavelength, θsize 12{θ} {} is the angle relative to the original direction of the light, and msize 12{m} {} is the order of the minimum
    diffraction
    the bending of a wave around the edges of an opening or an obstacle
    diffraction grating
    a large number of evenly spaced parallel slits
    direction of polarization
    the direction parallel to the electric field for EM waves
    horizontally polarized
    the oscillations are in a horizontal plane
    Huygens’s principle
    every point on a wavefront is a source of wavelets that spread out in the forward direction at the same speed as the wave itself. The new wavefront is a line tangent to all of the wavelets
    incoherent
    waves have random phase relationships
    interference microscopes
    microscopes that enhance contrast between objects and background by superimposing a reference beam of light upon the light emerging from the sample
    optically active
    substances that rotate the plane of polarization of light passing through them
    order
    the integer msize 12{m} {} used in the equations for constructive and destructive interference for a double slit
    phase-contrast microscope
    microscope utilizing wave interference and differences in phases to enhance contrast
    polarization
    the attribute that wave oscillations have a definite direction relative to the direction of propagation of the wave
    polarization microscope
    microscope that enhances contrast by utilizing a wave characteristic of light, useful for objects that are optically active
    polarized
    waves having the electric and magnetic field oscillations in a definite direction
    Rayleigh criterion
    two images are just resolvable when the center of the diffraction pattern of one is directly over the first minimum of the diffraction pattern of the other
    reflected light that is completely polarized
    light reflected at the angle of reflection θbsize 12{θ rSub { size 8{b} } } {}, known as Brewster’s angle
    thin film interference
    interference between light reflected from different surfaces of a thin film
    ultraviolet (UV) microscopes
    microscopes constructed with special lenses that transmit UV rays and utilize photographic or electronic techniques to record images
    unpolarized
    waves that are randomly polarized
    vertically polarized
    the oscillations are in a vertical plane
    wavelength in a medium
    λn=λ/nsize 12{λ rSub { size 8{n} } =λ/n} {}, where λsize 12{λ} {} is the wavelength in vacuum, and nsize 12{n} {} is the index of refraction of the medium
    classical velocity addition
    the method of adding velocities when v<<csize 12{v"<<"c} {}; velocities add like regular numbers in one-dimensional motion: u=v+u', where v is the velocity between two observers, u is the velocity of an object relative to one observer, and u' is the velocity relative to the other observer
    first postulate of special relativity
    the idea that the laws of physics are the same and can be stated in their simplest form in all inertial frames of reference
    inertial frame of reference
    a reference frame in which a body at rest remains at rest and a body in motion moves at a constant speed in a straight line unless acted on by an outside force
    length contraction
    Lsize 12{L} {}, the shortening of the measured length of an object moving relative to the observer’s frame: L=L01−v2c2−−−−−√=L0γsize 12{ ital "L=L" rSub { size 8{0} } sqrt {1 - { {v rSup { size 8{2} } } over {c rSup { size 8{2} } } } } = { {L rSub { size 8{0} } } over {γ} } } {}
    Michelson-Morley experiment
    an investigation performed in 1887 that proved that the speed of light in a vacuum is the same in all frames of reference from which it is viewed
    proper length
    L0size 12{L rSub { size 8{0} } } {}; the distance between two points measured by an observer who is at rest relative to both of the points; Earth-bound observers measure proper length when measuring the distance between two points that are stationary relative to the Earth
    proper time
    Δt0. the time measured by an observer at rest relative to the event being observed: Δt=Δt01−v2c2√=γΔt0, where γ=11−v2c2√
    relativistic Doppler effects
    a change in wavelength of radiation that is moving relative to the observer; the wavelength of the radiation is longer (called a red shift) than that emitted by the source when the source moves away from the observer and shorter (called a blue shift) when the source moves toward the observer; the shifted wavelength is described by the equation λobs=λs1+uc1−uc−−−−√ where λobs is the observed wavelength, λs is the source wavelength, and u is the velocity of the source to the observer
    relativistic kinetic energy
    the kinetic energy of an object moving at relativistic speeds: KErel=(γ−1)mc2size 12{"KE" rSub { size 8{"rel"} } = left (γ - 1 right ) ital "mc" rSup { size 8{2} } } {}, where γ=11−v2c2√
    relativistic momentum
    psize 12{p} {}, the momentum of an object moving at relativistic velocity; p=γmusize 12{p= ital "γmu"} {}, where msize 12{m} {} is the rest mass of the object, usize 12{u} {} is its velocity relative to an observer, and the relativistic factor γ=11−u2c2√size 12{γ= { {1} over { sqrt {1 - { {u rSup { size 8{2} } } over {c rSup { size 8{2} } } } } } } } {}
    relativistic velocity addition
    the method of adding velocities of an object moving at a relativistic speed: u=v+u'1+vu'c2, where vsize 12{v} {} is the relative velocity between two observers, usize 12{u} {} is the velocity of an object relative to one observer, and u'size 12{u rSup { size 8{'} } } {} is the velocity relative to the other observer
    relativity
    the study of how different observers measure the same event
    rest energy
    the energy stored in an object at rest: E0=mc2
    rest mass
    the mass of an object as measured by a person at rest relative to the object
    second postulate of special relativity
    the idea that the speed of light csize 12{c} {} is a constant, independent of the source
    special relativity
    the theory that, in an inertial frame of reference, the motion of an object is relative to the frame from which it is viewed or measured
    time dilation
    the phenomenon of time passing slower to an observer who is moving relative to another observer
    total energy
    defined as E=γmc2, where γ=11−v2c2√
    twin paradox
    this asks why a twin traveling at a relativistic speed away and then back towards the Earth ages less than the Earth-bound twin. The premise to the paradox is faulty because the traveling twin is accelerating, and special relativity does not apply to accelerating frames of reference
    atomic spectra
    the electromagnetic emission from atoms and molecules
    binding energy
    also called the work function; the amount of energy necessary to eject an electron from a material
    blackbody
    an ideal radiator, which can radiate equally well at all wavelengths
    blackbody radiation
    the electromagnetic radiation from a blackbody
    bremsstrahlung
    German for braking radiation; produced when electrons are decelerated
    characteristic x rays
    x rays whose energy depends on the material they were produced in
    Compton effect
    the phenomenon whereby x rays scattered from materials have decreased energy
    correspondence principle
    in the classical limit (large, slow-moving objects), quantum mechanics becomes the same as classical physics
    de Broglie wavelength
    the wavelength possessed by a particle of matter, calculated by λ=h/psize 12{λ = h/p} {}
    gamma ray
    also γsize 12{γ} {}-ray; highest-energy photon in the EM spectrum
    Heisenberg’s uncertainty principle
    a fundamental limit to the precision with which pairs of quantities (momentum and position, and energy and time) can be measured
    infrared radiation
    photons with energies slightly less than red light
    ionizing radiation
    radiation that ionizes materials that absorb it
    microwaves
    photons with wavelengths on the order of a micron (μmsize 12{"μm"} {})
    particle-wave duality
    the property of behaving like either a particle or a wave; the term for the phenomenon that all particles have wave characteristics
    photoelectric effect
    the phenomenon whereby some materials eject electrons when light is shined on them
    photon
    a quantum, or particle, of electromagnetic radiation
    photon energy
    the amount of energy a photon has; E=hfsize 12{E = ital "hf"} {}
    photon momentum
    the amount of momentum a photon has, calculated by p=hλ=Ecsize 12{p = { {h} over {λ} } = { {E} over {c} } } {}
    Planck’s constant
    h=6.626×10–34J⋅ssize 12{h = 6 "." "626" times " 10" rSup { size 8{"–34"} } " J " cdot " s"} {}
    probability distribution
    the overall spatial distribution of probabilities to find a particle at a given location
    quantized
    the fact that certain physical entities exist only with particular discrete values and not every conceivable value
    quantum mechanics
    the branch of physics that deals with small objects and with the quantization of various entities, especially energy
    ultraviolet radiation
    UV; ionizing photons slightly more energetic than violet light
    uncertainty in energy
    lack of precision or lack of knowledge of precise results in measurements of energy
    uncertainty in momentum
    lack of precision or lack of knowledge of precise results in measurements of momentum
    uncertainty in position
    lack of precision or lack of knowledge of precise results in measurements of position
    uncertainty in time
    lack of precision or lack of knowledge of precise results in measurements of time
    visible light
    the range of photon energies the human eye can detect
    x ray
    EM photon between γsize 12{γ} {}-ray and UV in energy
    angular momentum quantum number
    a quantum number associated with the angular momentum of electrons
    atom
    basic unit of matter, which consists of a central, positively charged nucleus surrounded by negatively charged electrons
    atomic de-excitation
    process by which an atom transfers from an excited electronic state back to the ground state electronic configuration; often occurs by emission of a photon
    atomic excitation
    a state in which an atom or ion acquires the necessary energy to promote one or more of its electrons to electronic states higher in energy than their ground state
    atomic number
    the number of protons in the nucleus of an atom
    Bohr radius
    the mean radius of the orbit of an electron around the nucleus of a hydrogen atom in its ground state
    Brownian motion
    the continuous random movement of particles of matter suspended in a liquid or gas
    cathode-ray tube
    a vacuum tube containing a source of electrons and a screen to view images
    double-slit interference
    an experiment in which waves or particles from a single source impinge upon two slits so that the resulting interference pattern may be observed
    energies of hydrogen-like atoms
    Bohr formula for energies of electron states in hydrogen-like atoms: En=−Z2n2E0(n=1, 2, 3,…)
    energy-level diagram
    a diagram used to analyze the energy level of electrons in the orbits of an atom
    fine structure
    the splitting of spectral lines of the hydrogen spectrum when the spectral lines are examined at very high resolution
    fluorescence
    any process in which an atom or molecule, excited by a photon of a given energy, de-excites by emission of a lower-energy photon
    hologram
    means entire picture (from the Greek word holo, as in holistic), because the image produced is three dimensional
    holography
    the process of producing holograms
    hydrogen spectrum wavelengths
    the wavelengths of visible light from hydrogen; can be calculated by 1λ=R(1n2f−1n2i)size 12{ { {1} over {λ} } =R left ( { {1} over {n rSub { size 8{f} } rSup { size 8{2} } } } - { {1} over {n rSub { size 8{i} } rSup { size 8{2} } } } right )} {}
    hydrogen-like atom
    any atom with only a single electron
    intrinsic magnetic field
    the magnetic field generated due to the intrinsic spin of electrons
    intrinsic spin
    the internal or intrinsic angular momentum of electrons
    laser
    acronym for light amplification by stimulated emission of radiation
    magnitude of the intrinsic (internal) spin angular momentum
    given by S=s(s+1)−−−−−−−√h2π
    metastable
    a state whose lifetime is an order of magnitude longer than the most short-lived states
    orbital angular momentum
    an angular momentum that corresponds to the quantum analog of classical angular momentum
    orbital magnetic field
    the magnetic field generated due to the orbital motion of electrons
    Pauli exclusion principle
    a principle that states that no two electrons can have the same set of quantum numbers; that is, no two electrons can be in the same state
    phosphorescence
    the de-excitation of a metastable state
    planetary model of the atom
    the most familiar model or illustration of the structure of the atom
    population inversion
    the condition in which the majority of atoms in a sample are in a metastable state
    quantum numbers
    the values of quantized entities, such as energy and angular momentum
    Rydberg constant
    a physical constant related to the atomic spectra with an established value of 1.097×107m−1
    shell
    a probability cloud for electrons that has a single principal quantum number
    space quantization
    the fact that the orbital angular momentum can have only certain directions
    spin projection quantum number
    quantum number that can be used to calculate the intrinsic electron angular momentum along the z-axis
    spin quantum number
    the quantum number that parameterizes the intrinsic angular momentum (or spin angular momentum, or simply spin) of a given particle
    stimulated emission
    emission by atom or molecule in which an excited state is stimulated to decay, most readily caused by a photon of the same energy that is necessary to excite the state
    subshell
    the probability cloud for electrons that has a single angular momentum quantum number l
    x rays
    a form of electromagnetic radiation
    x-ray diffraction
    a technique that provides the detailed information about crystallographic structure of natural and manufactured materials
    z-component of spin angular momentum
    component of intrinsic electron spin along the z-axis
    z-component of the angular momentum
    component of orbital angular momentum of electron along the z-axis
    Zeeman effect
    the effect of external magnetic fields on spectral lines
    activity
    the rate of decay for radioactive nuclides
    alpha decay
    type of radioactive decay in which an atomic nucleus emits an alpha particle
    alpha rays
    one of the types of rays emitted from the nucleus of an atom
    antielectron
    another term for positron
    antimatter
    composed of antiparticles
    atomic mass
    the total mass of the protons, neutrons, and electrons in a single atom
    atomic number
    number of protons in a nucleus
    barrier penetration
    quantum mechanical effect whereby a particle has a nonzero probability to cross through a potential energy barrier despite not having sufficient energy to pass over the barrier; also called quantum mechanical tunneling
    becquerel
    SI unit for rate of decay of a radioactive material
    beta decay
    type of radioactive decay in which an atomic nucleus emits a beta particle
    beta rays
    one of the types of rays emitted from the nucleus of an atom
    binding energy
    the energy needed to separate nucleus into individual protons and neutrons
    binding energy per nucleon
    the binding energy calculated per nucleon; it reveals the details of the nuclear force—larger the BE/Asize 12{"BE"/A} {}, the more stable the nucleus
    carbon-14 dating
    a radioactive dating technique based on the radioactivity of carbon-14
    chart of the nuclides
    a table comprising stable and unstable nuclei
    curie
    the activity of 1g of 226Ra, equal to 3.70×1010Bqsize 12{3 "." "70" times "10" rSup { size 8{"10"} } " Bq"} {}
    daughter
    the nucleus obtained when parent nucleus decays and produces another nucleus following the rules and the conservation laws
    decay
    the process by which an atomic nucleus of an unstable atom loses mass and energy by emitting ionizing particles
    decay constant
    quantity that is inversely proportional to the half-life and that is used in equation for number of nuclei as a function of time
    decay equation
    the equation to find out how much of a radioactive material is left after a given period of time
    decay series
    process whereby subsequent nuclides decay until a stable nuclide is produced
    electron capture
    the process in which a proton-rich nuclide absorbs an inner atomic electron and simultaneously emits a neutrino
    electron capture equation
    equation representing the electron capture
    electron’s antineutrino
    antiparticle of electron’s neutrino
    electron’s neutrino
    a subatomic elementary particle which has no net electric charge
    gamma decay
    type of radioactive decay in which an atomic nucleus emits a gamma particle
    gamma rays
    one of the types of rays emitted from the nucleus of an atom
    Geiger tube
    a very common radiation detector that usually gives an audio output
    half-life
    the time in which there is a 50% chance that a nucleus will decay
    ionizing radiation
    radiation (whether nuclear in origin or not) that produces ionization whether nuclear in origin or not
    isotopes
    nuclei having the same Zsize 12{Z} {} and different Nsize 12{Ns} {}s
    magic numbers
    a number that indicates a shell structure for the nucleus in which closed shells are more stable
    mass number
    number of nucleons in a nucleus
    neutrino
    an electrically neutral, weakly interacting elementary subatomic particle
    neutron
    a neutral particle that is found in a nucleus
    nuclear radiation
    rays that originate in the nuclei of atoms, the first examples of which were discovered by Becquerel
    nuclear reaction energy
    the energy created in a nuclear reaction
    nucleons
    the particles found inside nuclei
    nucleus
    a region consisting of protons and neutrons at the center of an atom
    nuclide
    a type of atom whose nucleus has specific numbers of protons and neutrons
    parent
    the original state of nucleus before decay
    photomultiplier
    a device that converts light into electrical signals
    positron
    the particle that results from positive beta decay; also known as an antielectron
    positron decay
    type of beta decay in which a proton is converted to a neutron, releasing a positron and a neutrino
    protons
    the positively charged nucleons found in a nucleus
    quantum mechanical tunneling
    quantum mechanical effect whereby a particle has a nonzero probability to cross through a potential energy barrier despite not having sufficient energy to pass over the barrier; also called barrier penetration
    radiation detector
    a device that is used to detect and track the radiation from a radioactive reaction
    radioactive
    a substance or object that emits nuclear radiation
    radioactive dating
    an application of radioactive decay in which the age of a material is determined by the amount of radioactivity of a particular type that occurs
    radioactivity
    the emission of rays from the nuclei of atoms
    radius of a nucleus
    the radius of a nucleus is r=r0A1/3size 12{r=r rSub { size 8{0} } A rSup { size 8{1/3} } } {}
    range of radiation
    the distance that the radiation can travel through a material
    rate of decay
    the number of radioactive events per unit time
    scintillators
    a radiation detection method that records light produced when radiation interacts with materials
    solid-state radiation detectors
    semiconductors fabricated to directly convert incident radiation into electrical current
    tunneling
    a quantum mechanical process of potential energy barrier penetration
    Anger camera
    a common medical imaging device that uses a scintillator connected to a series of photomultipliers
    break-even
    when fusion power produced equals the heating power input
    breeder reactors
    reactors that are designed specifically to make plutonium
    breeding
    reaction process that produces 239Pu
    critical mass
    minimum amount necessary for self-sustained fission of a given nuclide
    criticality
    condition in which a chain reaction easily becomes self-sustaining
    fission fragments
    a daughter nuclei
    food irradiation
    treatment of food with ionizing radiation
    free radicals
    ions with unstable oxygen- or hydrogen-containing molecules
    gamma camera
    another name for an Anger camera
    gray (Gy)
    the SI unit for radiation dose which is defined to be 1 Gy=1 J/kg=100 radsize 12{1`"Gy"=1`"J/kg"="100"`"rad"} {}
    high dose
    a dose greater than 1 Sv (100 rem)
    hormesis
    a term used to describe generally favorable biological responses to low exposures of toxins or radiation
    ignition
    when a fusion reaction produces enough energy to be self-sustaining after external energy input is cut off
    inertial confinement
    a technique that aims multiple lasers at tiny fuel pellets evaporating and crushing them to high density
    linear hypothesis
    assumption that risk is directly proportional to risk from high doses
    liquid drop model
    a model of nucleus (only to understand some of its features) in which nucleons in a nucleus act like atoms in a drop
    low dose
    a dose less than 100 mSv (10 rem)
    magnetic confinement
    a technique in which charged particles are trapped in a small region because of difficulty in crossing magnetic field lines
    moderate dose
    a dose from 0.1 Sv to 1 Sv (10 to 100 rem)
    neutron-induced fission
    fission that is initiated after the absorption of neutron
    nuclear fission
    reaction in which a nucleus splits
    nuclear fusion
    a reaction in which two nuclei are combined, or fused, to form a larger nucleus
    positron emission tomography (PET)
    tomography technique that uses β+size 12{β rSup { size 8{+{}} } } {} emitters and detects the two annihilation γsize 12{γ} {} rays, aiding in source localization
    proton-proton cycle
    the combined reactions 1H+1H→2H+e++ve, 1H+2H→3He+γ, and 3He+3He→4He+1H+1H
    quality factor
    same as relative biological effectiveness
    rad
    the ionizing energy deposited per kilogram of tissue
    radiolytic products
    compounds produced due to chemical reactions of free radicals
    radiopharmaceutical
    compound used for medical imaging
    radiotherapy
    the use of ionizing radiation to treat ailments
    relative biological effectiveness (RBE)
    a number that expresses the relative amount of damage that a fixed amount of ionizing radiation of a given type can inflict on biological tissues
    roentgen equivalent man (rem)
    a dose unit more closely related to effects in biological tissue
    shielding
    a technique to limit radiation exposure
    sievert
    the SI equivalent of the rem
    single-photon-emission computed tomography (SPECT)
    tomography performed with γsize 12{γ} {}-emitting radiopharmaceuticals
    supercriticality
    an exponential increase in fissions
    tagged
    process of attaching a radioactive substance to a chemical compound
    therapeutic ratio
    the ratio of abnormal cells killed to normal cells killed
    baryon number
    a conserved physical quantity that is zero for mesons and leptons and ±1size 12{ +- 1} {} for baryons and antibaryons, respectively
    baryons
    hadrons that always decay to another baryon
    boson
    particle with zero or an integer value of intrinsic spin
    bottom
    a quark flavor
    charm
    a quark flavor, which is the counterpart of the strange quark
    colliding beams
    head-on collisions between particles moving in opposite directions
    color
    a quark flavor
    conservation of total baryon number
    a general rule based on the observation that the total number of nucleons was always conserved in nuclear reactions and decays
    conservation of total electron family number
    a general rule stating that the total electron family number stays the same through an interaction
    conservation of total muon family number
    a general rule stating that the total muon family number stays the same through an interaction
    cyclotron
    accelerator that uses fixed-frequency alternating electric fields and fixed magnets to accelerate particles in a circular spiral path
    down
    the second-lightest of all quarks
    electron family number
    the number ±1size 12{ +- 1} {} that is assigned to all members of the electron family, or the number 0 that is assigned to all particles not in the electron family
    electroweak theory
    theory showing connections between EM and weak forces
    fermion
    particle with a half-integer value of intrinsic spin
    Feynman diagram
    a graph of time versus position that describes the exchange of virtual particles between subatomic particles
    flavors
    quark type
    fundamental particle
    particle with no substructure
    gauge boson
    particle that carries one of the four forces
    gluons
    exchange particles, analogous to the exchange of photons that gives rise to the electromagnetic force between two charged particles
    gluons
    eight proposed particles which carry the strong force
    grand unified theory
    theory that shows unification of the strong and electroweak forces
    hadrons
    particles that feel the strong nuclear force
    Higgs boson
    a massive particle that, if observed, would give validity to the theory that carrier particles are identical under certain circumstances
    leptons
    particles that do not feel the strong nuclear force
    linear accelerator
    accelerator that accelerates particles in a straight line
    meson
    particle whose mass is intermediate between the electron and nucleon masses
    meson
    hadrons that can decay to leptons and leave no hadrons
    muon family number
    the number ±1size 12{ +- 1} {} that is assigned to all members of the muon family, or the number 0 that is assigned to all particles not in the muon family
    particle physics
    the study of and the quest for those truly fundamental particles having no substructure
    pion
    particle exchanged between nucleons, transmitting the force between them
    quantum chromodynamics
    quark theory including color
    quantum chromodynamics
    the governing theory of connecting quantum number color to gluons
    quantum electrodynamics
    the theory of electromagnetism on the particle scale
    quark
    an elementary particle and a fundamental constituent of matter
    standard model
    combination of quantum chromodynamics and electroweak theory
    strange
    the third lightest of all quarks
    strangeness
    a physical quantity assigned to various particles based on decay systematics
    superstring theory
    a theory of everything based on vibrating strings some 10−35m in length
    synchrotron
    a version of a cyclotron in which the frequency of the alternating voltage and the magnetic field strength are increased as the beam particles are accelerated
    synchrotron radiation
    radiation caused by a magnetic field accelerating a charged particle perpendicular to its velocity
    tau family number
    the number ±1size 12{ +- 1} {} that is assigned to all members of the tau family, or the number 0 that is assigned to all particles not in the tau family
    theory of quark confinement
    explains how quarks can exist and yet never be isolated or directly observed
    top
    a quark flavor
    up
    the lightest of all quarks
    Van de Graaff
    early accelerator: simple, large-scale version of the electron gun
    virtual particles
    particles which cannot be directly observed but their effects can be directly observed
    stress
    ratio of force to area
    strain
    ratio of change in length to original length
    Stokes’ law
    Fs=6πrηvsize 12{F rSub { size 8{s} } =6πrηv} {}, where r is the radius of the object, η is the viscosity of the fluid, and v is the object’s velocity
    static friction
    a force that opposes the motion of two systems that are in contact and are not moving relative to one another
    shear deformation
    deformation perpendicular to the original length of an object
    magnitude of static friction
    fs≤μsNsize 12{f rSub { size 8{s} } <= μ rSub { size 8{s} } N} {}, where μs is the coefficient of static friction and N is the magnitude of the normal force
    magnitude of kinetic friction
    fk=μkNsize 12{f rSub { size 8{k} } =μ rSub { size 8{k} } N} {}, where μksize 12{μ rSub { size 8{K} } } {} is the coefficient of kinetic friction
    kinetic friction
    a force that opposes the motion of two systems that are in contact and moving relative to one another
    Hooke’s law
    proportional relationship between the force F on a material and the deformation ΔL it causes, F=kΔLsize 12{F=kΔL} {}
    friction
    a force that opposes relative motion or attempts at motion between systems in contact
    drag force
    FDsize 12{F rSub { size 8{D} } } {}, found to be proportional to the square of the speed of the object; mathematically FD∝v2size 12{F rSub { size 8{D} } prop `v rSup { size 8{2} } } FD=12CρAv2,size 12{F rSub { size 8{D} } = { {1} over {2} } Cρ ital "Av" rSup { size 8{2} } } where Csize 12{C} {} is the drag coefficient, Asize 12{A} {} is the area of the object facing the fluid, and ρsize 12{ρ} {} is the density of the fluid
    deformation
    change in shape due to the application of force
    weight
    the force wsize 12{w} {}due to gravity acting on an object of mass msize 12{m} {}; defined mathematically as: w=mgsize 12{w=mg} {}, where gsize 12{g} {} is the magnitude and direction of the acceleration due to gravity

    end

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