Glossary
- Page ID
- 47005
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| (Eg. "Genetic, Hereditary, DNA ...") | (Eg. "Relating to genes or heredity") |  |
The infamous double helix | https://bio.libretexts.org/ | CC-BY-SA; Delmar Larsen |
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Word(s) |
Definition |
Image | Caption | Link | Source |
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| 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 |
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| 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) | ||||
| 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 | ||||
| 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 | ||||
| quantum mechanics |
the study of objects smaller than can be seen with a microscope |
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| 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 | ||||
| theory | an explanation for patterns in nature that is supported by scientific evidence and verified multiple times by various groups of researchers | ||||
| units | a standard used for expressing and comparing measurements | ||||
| kinematics | the study of motion without considering its causes | ||||
| position | the location of an object at a particular time | ||||
| 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 | ||||
| scalar | a quantity that is described by magnitude, but not direction | ||||
| vector | a quantity that is described by both magnitude and direction | ||||
| average speed | distance traveled divided by time during which motion occurs | ||||
| average velocity | displacement divided by time over which displacement occurs | ||||
| instantaneous velocity | velocity at a specific instant, or the average velocity over an infinitesimal time interval | ||||
| instantaneous speed | magnitude of the instantaneous velocity | ||||
| time | change, or the interval over which change occurs | ||||
| model | simplified description that contains only those elements necessary to describe the physics of a physical situation | ||||
| elapsed time | the difference between the ending time and beginning time | ||||
| acceleration | the rate of change in velocity; the change in velocity over time | ||||
| average acceleration | the change in velocity divided by the time over which it changes | ||||
| instantaneous acceleration | acceleration at a specific point in time | ||||
| free-fall | the state of movement that results from gravitational force only | ||||
| acceleration due to gravity | acceleration an object undergoes while in free-fall | ||||
| 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 | ||||
| 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 | ||||
| trajectory | the path of a projectile through the air | ||||
| centripetal acceleration | the acceleration of an object moving in a circle, directed toward the center | ||||
| ultracentrifuge | a centrifuge optimized for spinning a rotor at very high speeds | ||||
| uniform circular motion | an object moving in a circular path at constant speed | ||||
| dynamics | the study of how forces affect the motion of objects and systems | ||||
| 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 | ||||
| inertia | the tendency of an object to remain at rest or remain in motion | ||||
| law of inertia | see Newton’s first law of motion | ||||
| mass | the quantity of matter in a substance; measured in kilograms | ||||
| 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 | ||||
| free-fall | a situation in which the only force acting on an object is the force due to gravity | ||||
| external force | a force acting on an object or system that originates outside of the object or system | ||||
| net external force | the vector sum of all external forces acting on an object or system; causes a mass to accelerate | ||||
| 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 | ||||
| Newton’s second law of motion | The acceleration of a system is directly proportional to and in the same direction as the net external force acting on the system, and inversely proportional to its mass. | ||||
| system | the object or the group of objects under consideration | ||||
| weight | the force due to gravity; \(w=mg\) for objects on Earth | ||||
| Newton’s third law of motion | Whenever one body exerts a force on a second body, the first body experiences a force by the second body that is equal in magnitude and opposite in direction to the force that it itself exerts. | ||||
| thrust | a reaction force that pushes a body forward; rockets, airplanes, and cars are pushed forward by a thrust, a reaction force to propellants pushed backward | ||||
| 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 | ||||
| apparent weight | sensation of weight due to contact forces; usually the same as normal force | ||||
| 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 | ||||
| deformation | displacement from equilibrium | ||||
| spring constant | a constant related to the rigidity of a system: the larger the spring constant, the more rigid the system; the spring constant is represented by k | ||||
| restoring force | force acting in opposition to the force caused by a deformation | ||||
| friction | a force that opposes relative motion or attempts at motion between systems in contact | ||||
| kinetic friction | a force that opposes the motion of two systems that are in contact and moving relative to one another | ||||
| static friction | a force that opposes the motion of two systems that are in contact and are not moving relative to one another | ||||
| magnitude of static friction | \(f_{\mathrm{s}} \leq \mu_{\mathrm{s}} N\), where \(\mu_{\mathrm{s}}\) is the coefficient of static friction and \(N\) is the magnitude of the normal force | ||||
| magnitude of kinetic friction | \(f_{\mathrm{k}}=\mu_{\mathrm{k}} N\), where \(\mu_{\mathrm{k}}\) is the coefficient of kinetic friction | ||||
| 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 | ||||
| center of mass | the point where the entire mass of an object can be thought to be concentrated | ||||
| microgravity | an environment in which the acceleration of a body due to non-gravitational forces is small compared with that produced by Earth on 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 | ||||
| centripetal force | any net force causing uniform circular motion | ||||
| 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 | ||||
| banked curve | the curve in a road that is sloping in a manner that helps a vehicle negotiate the curve | ||||
| energy | the ability to do work | ||||
| 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 | ||||
| joule | SI unit of work and energy, equal to one newton-meter | ||||
| net work | work done by the net force, or vector sum of all the forces, acting on an object | ||||
| 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 | ||||
| kinetic energy | the energy an object has by reason of its motion, equal to \(\frac{1}{2} m v^{2}\) for the translational (i.e., non-rotational) motion of an object of mass \(m\) moving at speed \(v\) | ||||
| gravitational potential energy | energy associated with height of objects on the Earth | ||||
| conservative force | a force that is a function of position alone, with the result that the work done by the force depends only on the starting and ending points of a motion and not on the particular path taken | ||||
| potential energy | energy due to position, shape, or configuration | ||||
| 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 | ||||
| mechanical energy | the sum of kinetic energy and potential energy | ||||
| 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 | ||||
| electrical energy | the energy carried by a flow of charge | ||||
| chemical energy | the energy in a substance stored in the bonds between atoms and molecules that can be released in a chemical reaction | ||||
| radiant energy | the energy carried by electromagnetic waves | ||||
| nuclear energy | energy released by changes within atomic nuclei, such as the fusion of two light nuclei or the fission of a heavy nucleus | ||||
| thermal energy | the energy within an object due to the random motion of its atoms and molecules that accounts for the object's temperature | ||||
| deformation | displacement from equilibrium | ||||
| elastic potential energy | potential energy stored as a result of deformation of an elastic object, such as the stretching of a spring | ||||
| power | the rate at which work is done | ||||
| watt | (W) SI unit of power, with \(1 \mathrm{~W}=1 \mathrm{~J} / \mathrm{s}\) | ||||
| horsepower | an older non-SI unit of power, with \(1 \mathrm{~hp}=746 \mathrm{~W}\) | ||||
| kilowatt-hour | \((\mathrm{kW} \cdot \mathrm{h})\)unit used primarily for electrical energy provided by electric utility companies | ||||
| linear momentum | the product of mass and velocity | ||||
| 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 | ||||
| change in momentum | the difference between the final and initial momentum; the mass times the change in velocity | ||||
| impulse | the average net external force times the time it acts; equal to the change in momentum | ||||
| 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 total kinetic energy, in addition to the total momentum | ||||
| inelastic collision | a collision in which total kinetic energy is not conserved | ||||
| perfectly inelastic collision | a collision in which the colliding objects stick together | ||||
| oscillate | moving back and forth regularly between two points | ||||
| wave | a disturbance that moves from its source and carries energy | ||||
| period | time it takes to complete one oscillation | ||||
| periodic motion | motion that repeats itself at regular time intervals | ||||
| frequency | number of events per unit of time | ||||
| amplitude | the maximum displacement from the equilibrium position of an object oscillating around the equilibrium position | ||||
| 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 | ||||
| natural frequency | the frequency at which a simple harmonic oscillator oscillates if it is set in motion without a driving force | ||||
| damping force | a frictional force which converts the mechanical energy of the oscillatory motion into thermal energy | ||||
| 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 | ||||
| longitudinal wave | a wave in which the disturbance is parallel to the direction of propagation | ||||
| transverse wave | a wave in which the disturbance is perpendicular to the direction of propagation | ||||
| wave velocity | the speed at which the disturbance moves; also called wave speed, propagation velocity, or propagation speed | ||||
| wavelength | the distance between adjacent identical parts of a wave | ||||
| 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 | ||||
| destructive interference | when two identical waves arrive at the same point exactly out of phase; that is, precisely aligned crest to trough | ||||
| fundamental frequency | the lowest frequency of a periodic waveform | ||||
| nodes | the points where the string does not move; more generally, nodes are where the wave disturbance is zero in a standing wave | ||||
| overtones | multiples of the fundamental frequency of a sound | ||||
| superposition | the phenomenon that occurs when two or more waves arrive at the same point | ||||
| audible range | frequencies between 20 Hz and 20,000 Hz | ||||
| infrasound | sound waves below audible frequencies (less than 20 Hz) | ||||
| hearing | the perception of sound | ||||
| sound | a disturbance of matter that is transmitted from its source outward | ||||
| ultrasound | sound waves above audible frequencies (greater than 20,000 Hz) | ||||
| pitch | the perception of the frequency of a sound | ||||
| Doppler shift | the change in wave frequency due to relative motion of source and observer | ||||
| sonic boom | a constructive interference of sound created by an object moving faster than sound | ||||
| bow wake | V-shaped disturbance created when the wave source moves faster than the wave propagation speed | ||||
| angular acceleration | the rate of change of angular velocity with time | ||||
| angular velocity | the rate of change of angular position with time | ||||
| change in angular velocity | the difference between final and initial values of angular velocity | ||||
| radian | a unit of angular measure defined by the arc length covered by the angle divided by the radius of the circle that the arc length is part of; one full circle is \(2 \pi\) radians. | ||||
| 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 | ||||
| lever arm | the perpendicular distance between the center of rotation and the point at which force is being applied | ||||
| rotational inertia | resistance to change of angular velocity; also called moment of inertia; for a point mass, \(I=m r^{2}\) | ||||
| rotational kinetic energy | the kinetic energy due to the rotation of an object. This is part of its total kinetic energy | ||||
| angular momentum | the product of moment of inertia and angular velocity | ||||
| 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 | ||||
| precession | a type of motion that an object possessing angular momentum undergoes, as a torque perpendicular to the direction of angular momentum is applied, causing the direction of angular momentum to change; the circular wobbling motion traced by a slightly tilted circular top is an example | ||||
| right-hand rule | direction of angular velocity \(\omega\) 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 | ||||
| fluids | liquids and gases; a fluid is a state of matter that yields to shearing forces | ||||
| density | the mass per unit volume of a substance or object | ||||
| pressure | the force per unit area perpendicular to the force, over which the force acts | ||||
| pressure due to the weight of fluid | pressure at a depth below a fluid surface due to its weight; given by \(P=\rho g h\) | ||||
| 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 | ||||
| specific gravity | the ratio of the density of an object to a fluid (usually water) | ||||
| flow rate | abbreviated Q, it is the volume V that flows past a particular point during a time t, or Q = V/t | ||||
| liter | a unit of volume, equal to 10−3 m3 | ||||
| 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 | ||||
| temperature | the quantity measured by a thermometer | ||||
| Celsius scale | temperature scale in which the freezing point of water is 0ºC and the boiling point of water is 100ºC | ||||
| degree Celsius | unit on the Celsius temperature scale | ||||
| Fahrenheit scale | temperature scale in which the freezing point of water is 32ºF and the boiling point of water is 212ºF | ||||
| degree Fahrenheit | unit on the Fahrenheit temperature scale | ||||
| Kelvin scale | temperature scale in which 0 K is the lowest possible temperature, representing absolute zero | ||||
| absolute zero | the lowest possible temperature; the temperature at which all molecular motion ceases | ||||
| thermal equilibrium | the condition in which heat no longer flows between two objects that are in contact; the two objects have the same temperature | ||||
| 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 | ||||
| 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 | ||||
| Boltzmann constant | k , a physical constant that relates energy to temperature; k=1.38×10–23 J/K | ||||
| heat | the spontaneous transfer of energy due to a temperature difference | ||||
| kilocalorie | \(1 \text { kilocalorie }=1000 \text { calories }\) | ||||
| mechanical equivalent of heat | the work needed to produce the same effects as heat transfer | ||||
| conduction | heat transfer through stationary matter by physical contact | ||||
| convection | heat transfer by the macroscopic movement of fluid | ||||
| radiation | heat transfer which occurs when microwaves, infrared radiation, visible light, or other electromagnetic radiation is emitted or absorbed | ||||
| specific heat | the amount of heat necessary to change the temperature of 1.00 kg of a substance by 1.00 ºC | ||||
| heat of sublimation | the energy required to change a substance from the solid phase to the vapor phase | ||||
| 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 | ||||
| sublimation | the transition from the solid phase to the vapor phase | ||||
| 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 | ||||
| internal energy | the sum of the kinetic and potential energies of a system’s atoms and molecules | ||||
| human metabolism | conversion of food into heat transfer, work, and stored fat | ||||
| heat engine | a machine that uses heat transfer to do work | ||||
| isobaric process | constant-pressure process in which a gas does work | ||||
| isochoric process | a constant-volume process | ||||
| isothermal process | a constant-temperature process | ||||
| adiabatic process | a process in which no heat transfer takes place | ||||
| reversible process | a process in which both the heat engine system and the external environment theoretically can be returned to their original states | ||||
| irreversible process | a process which occurs in only one direction in nature; a process that cannot be exactly reversed | ||||
| 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 | ||||
| cyclical process | a process in which the path returns to its original state at the end of every cycle | ||||
| 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 | ||||
| Carnot cycle | a cyclical process that uses only reversible processes, the adiabatic and isothermal processes | ||||
| Carnot engine | a heat engine that uses a Carnot cycle | ||||
| Carnot efficiency | the maximum theoretical efficiency for a heat engine | ||||
| heat pump | a machine that generates heat transfer from cold to hot | ||||
| 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 | ||||
| entropy | a measurement of a system's disorder and its inability to do work in a system | ||||
| change in entropy | the ratio of heat transfer to temperature \(Q/T\) |
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| second law of thermodynamics stated in terms of entropy | the total entropy of a system either increases or remains constant; it never decreases | ||||
| macrostate | an overall property of a system | ||||
| microstate | each sequence within a larger macrostate | ||||
| statistical analysis | using statistics to examine data, such as counting microstates and macrostates | ||||
| static electricity | a buildup of electric charge on the surface of an object | ||||
| electromagnetic force | one of the four fundamental forces of nature; the electromagnetic force consists of static electricity, moving electricity and magnetism | ||||
| 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 | ||||
| law of conservation of charge | states that whenever a charge is created, an equal amount of charge with the opposite sign is created simultaneously | ||||
| electron | a particle orbiting the nucleus of an atom and carrying the smallest unit of negative charge | ||||
| 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 | ||||
| Coulomb’s law | the mathematical equation calculating the electrostatic force vector between two charged particles | ||||
| Coulomb force | another term for the electrostatic force | ||||
| electrostatic force | the amount and direction of attraction or repulsion between two charged bodies | ||||
| field | a map of the amount and direction of a force acting on other objects, extending out into space | ||||
| point charge | A charged particle, designated \(Q\), generating an electric field | ||||
| test charge | A particle (designated \(q\)) with either a positive or negative charge set down within an electric field generated by a point charge | ||||
| 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 | ||||
| vector | a quantity with both magnitude and direction | ||||
| vector addition | mathematical combination of two or more vectors, including their magnitudes, directions, and positions | ||||
| electric potential | potential energy per unit 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 | ||||
| electron volt | the energy given to a fundamental charge accelerated through a potential difference of one volt | ||||
| mechanical energy | sum of the kinetic energy and potential energy of a system; this sum is a constant | ||||
| conductor | an object with properties that allow charges to move about freely within it | ||||
| free charge | an electrical charge (either positive or negative) which can move about separately from its base molecule | ||||
| electrostatic equilibrium | an electrostatically balanced state in which all free electrical charges have stopped moving about | ||||
| polarized | a state in which the positive and negative charges within an object have collected in separate locations | ||||
| Faraday cage | a metal shield which prevents electric charge from penetrating its surface | ||||
| capacitor | an arrangement of conductors designed to store charge using voltage difference | ||||
| parallel-plate capacitor | an example of capacitor using arrangement of two parallel conducting plates placed near each other | ||||
| Van de Graaff generator | a machine that produces a large amount of excess charge, used for experiments with high voltage | ||||
| electrostatics | the study of electricity in electrostatic equilibrium | ||||
| photoconductor | a substance that is an insulator until it is exposed to light, when it becomes a conductor | ||||
| xerography | a dry copying process based on electrostatics | ||||
| grounded | connected to the ground with a conductor, so that charge flows freely to and from the Earth to the grounded object | ||||
| 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 | ||||
| ink-jet printer | small ink droplets sprayed with an electric charge are controlled by electrostatic plates to create images on paper | ||||
| electrostatic precipitators | filters that apply charges to particles in the air, then attract those charges to a filter, removing them from the airstream | ||||
| electric current | the rate at which charge flows, \(I=\Delta Q / \Delta t\) | ||||
| ampere | (amp) the SI unit for current; 1 A = 1 C/s | ||||
| Ohm’s law | an empirical relation stating that the current I is proportional to the potential difference V. It is often written as I = V/R, where R is the resistance | ||||
| resistance | the electric property that impedes current; for ohmic materials, it is the ratio of voltage to current, R = V/I | ||||
| ohm | the unit of resistance, given by \(1 ~\Omega=1 \mathrm{~V} / \mathrm{A}\) | ||||
| ohmic | a type of a material for which Ohm's law is valid | ||||
| simple circuit | a circuit with a single voltage source and a single resistor | ||||
| 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 | ||||
| series | a sequence of resistors or other components wired into a circuit one after the other | ||||
| resistor | a component that provides resistance to the current flowing through an electrical circuit | ||||
| resistance | causing a loss of electrical power in a circuit | ||||
| Ohm’s law | the relationship between current, voltage, and resistance within an electrical circuit: \(V=IR\) | ||||
| 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 | ||||
| current | the flow of charge through an electric circuit past a given point of measurement | ||||
| Joule’s law | the relationship between potential electrical power, voltage, and resistance in an electrical circuit, given by: \(P_{e}=I V\) | ||||
| 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 | ||||
| thermal hazard | a hazard in which electric current causes undesired thermal effects | ||||
| 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 | ||||
| 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 | ||||
| north magnetic pole | the end or the side of a magnet that is attracted toward Earth’s geographic north pole | ||||
| south magnetic pole | the end or the side of a magnet that is attracted toward Earth’s geographic south pole | ||||
| ferromagnetic | materials, such as iron, cobalt, nickel, and gadolinium, that exhibit strong magnetic effects | ||||
| magnetized | to be turned into a magnet; to be induced to be magnetic | ||||
| domains | regions within a material that behave like small bar magnets | ||||
| Curie temperature | the temperature above which a ferromagnetic material cannot be magnetized | ||||
| electromagnetism | the use of electrical currents to induce magnetism | ||||
| electromagnet | an object that is temporarily magnetic when an electrical current is passed through it | ||||
| magnetic monopoles | an isolated magnetic pole; a south pole without a north pole, or vice versa (no magnetic monopole has ever been observed) | ||||
| magnetic field | the representation of magnetic forces | ||||
| B-field | another term for magnetic field | ||||
| magnetic field lines | the pictorial representation of the strength and the direction of a magnetic field | ||||
| direction of magnetic field lines | the direction that the north end of a compass needle points | ||||
| 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 \(\mathbf{v}\) and the fingers point in the direction of the magnetic field \(\mathbf{B}\), 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 | ||||
| tesla | T, the SI unit of the magnetic field strength; \(1 \mathrm{~T}=\frac{1 \mathrm{~N}}{\mathrm{~A} \cdot \mathrm{m}}\) | ||||
| magnetic force | the force on a charge produced by its motion through a magnetic field | ||||
| gauss | G, the unit of the magnetic field strength; \(1 \mathrm{G}=10^{-4} \mathrm{~T}\) | ||||
| motor | loop of wire in a magnetic field; when current is passed through the loops, the magnetic field exerts force on the loops, which rotates a shaft; electrical energy is converted to mechanical work in the process | ||||
| meter | common application of magnetic force on a current-carrying loop that is very similar in construction to a motor; by design, the force is proportional to \(I\) and not \(\theta\), so the needle deflection is proportional to the current | ||||
| 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 | ||||
| magnetic field strength (magnitude) produced by a long straight current-carrying wire | defined as \(B=\frac{\mu_{0} I}{2 \pi r}\), where \(I\) is the current, \(r\) is the shortest distance to the wire, and \(\mu_{0}\) is the permeability of free space | ||||
| permeability of free space | the measure of the ability of a material, in this case free space, to support a magnetic field; the constant \(\mu_{0}=4 \pi \times 10^{-7} \mathrm{~T} \cdot \mathrm{m} / \mathrm{A}\) | ||||
| magnetic field strength at the center of a circular loop | defined as \(B=\frac{\mu_{0} I}{2 R}\) where \(R\) is the radius of the loop | ||||
| solenoid | a thin wire wound into a coil that produces a magnetic field when an electric current is passed through it | ||||
| magnetic field strength inside a solenoid | defined as \(B=\mu_{0} n I\) 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) | ||||
| Biot-Savart law | a physical law that describes the magnetic field generated by an electric current in terms of a specific equation | ||||
| 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 | ||||
| Maxwell’s equations | a set of four equations that describe electromagnetic phenomena | ||||
| induced current | the current created by a changing magnetic field through voltage induced over a conducting path | ||||
| magnetic flux | the amount of magnetic field going through a particular area, calculated with \(\Phi=B_{\perp} A\), where \(B_{\perp}\) is the magnetic field strength perpendicular to the area \(A\) | ||||
| electromagnetic induction | the process of inducing a voltage with a change in magnetic flux | ||||
| Faraday’s law of induction | the means of calculating the voltage in a coil due to changing magnetic flux, given by \(V=-N \frac{\Delta \Phi}{\Delta t}\) | ||||
| Lenz’s law | the minus sign in Faraday’s law, signifying that the voltage induced in a coil opposes the change in magnetic flux | ||||
| 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; \(\frac{V_{\mathrm{s}}}{V_{\mathrm{p}}}=\frac{N_{\mathrm{s}}}{N_{\mathrm{p}}}\) | ||||
| step-up transformer | a transformer that increases voltage | ||||
| step-down transformer | a transformer that decreases voltage | ||||
| direct current | (DC) the flow of electric charge in only one direction | ||||
| alternating current | (AC) the flow of electric charge that periodically reverses direction | ||||
| AC voltage | voltage that fluctuates sinusoidally with time. | ||||
| AC current | current that fluctuates sinusoidally with time. | ||||
| rms | a type of average taken for a time-varying quantity by squaring it, taking the mean of the square, and then taking the square-root of the mean. | ||||
| electromagnetic waves | radiation in the form of waves of electric and magnetic energy | ||||
| Maxwell’s equations | a set of four equations that comprise a complete, overarching theory of electromagnetism | ||||
| hertz | an SI unit denoting the frequency of an electromagnetic wave, in cycles per second | ||||
| speed of light | in a vacuum, such as space, the speed of light is a constant 3 x 108 m/s | ||||
| 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 | ||||
| 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 | ||||
| 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 strength | the magnitude of the electric field, denoted E-field | ||||
| magnetic field | a vector quantity (B); can be used to determine the magnetic force on a moving charged particle | ||||
| magnetic field strength | the magnitude of the magnetic field, denoted B-field | ||||
| transverse wave | a wave, such as an electromagnetic wave, which oscillates perpendicular to the axis along the line of travel | ||||
| standing wave | a wave that oscillates in place, with nodes where no motion happens | ||||
| wavelength | the distance from one peak to the next in a wave | ||||
| amplitude | the height, or magnitude, of an electromagnetic wave | ||||
| frequency | the number of complete wave cycles (up-down-up) passing a given point within one second (cycles/second) | ||||
| resonant | a system that displays enhanced oscillation when subjected to a periodic disturbance of the same frequency as its natural frequency | ||||
| oscillate | to fluctuate back and forth in a steady beat | ||||
| radiation pressure | pressure exerted by an electromagnetic wave on a surface | ||||
| solar sail | a spacecraft that utilizes radiation pressure due to solar radiation in its propulsion | ||||
| electromagnetic spectrum | the full range of wavelengths or frequencies of electromagnetic radiation | ||||
| 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 | ||||
| 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 | ||||
| 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 0.74 μm to 300 μm | ||||
| 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 | ||||
| visible light | the narrow segment of the electromagnetic spectrum to which the normal human eye responds | ||||
| X-ray | invisible, penetrating form of very high frequency electromagnetic radiation, overlapping both the ultraviolet range and the \(\gamma\)-ray range | ||||
| gamma ray | (\(\gamma\) 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 \(\gamma\) rays can have the highest frequency of any electromagnetic radiation | ||||
| 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 | ||||
| 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 | ||||
| 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 | ||||
| extremely low frequency (ELF) | electromagnetic radiation with wavelengths usually in the range of 0 to 300 Hz, but also about 1kHz | ||||
| carrier wave | an electromagnetic wave that carries a signal by modulation of its amplitude or frequency | ||||
| 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 | ||||
| TV | video and audio signals broadcast on electromagnetic waves | ||||
| very high frequency (VHF) | TV channels utilizing frequencies in the two ranges of 54 to 88 MHz and 174 to 222 MHz | ||||
| ultra-high frequency (UHF) | TV channels in an even higher frequency range than VHF, of 470 to 1000 MHz | ||||
| mirror | smooth surface that reflects light at specific angles, forming an image of the person or object in front of it | ||||
| law of reflection | angle of reflection equals the angle of incidence | ||||
| refraction | changing of a light ray’s direction when it passes through variations in matter | ||||
| index of refraction | for a material, the ratio of the speed of light in vacuum to that in the material | ||||
| dispersion | spreading of white light into its full spectrum of wavelengths | ||||
| 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 | ||||
| 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 | ||||
| diverging lens | a concave lens in which light rays that enter it parallel to its axis bend away (diverge) from its axis | ||||
| 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 | ||||
| focal length | distance from the center of a lens or curved mirror to its focal point | ||||
| magnification | ratio of image height to object height | ||||
| power | inverse of focal length | ||||
| real image | image that can be projected | ||||
| virtual image | image that cannot be projected | ||||
| 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 | ||||
| diverging mirror | a convex mirror in which light rays that strike it parallel to its axis bend away (diverge) from its axis | ||||
| law of reflection | angle of reflection equals the angle of incidence | ||||
| 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 | ||||
| direction of polarization | the direction parallel to the electric field for EM waves | ||||
| horizontally polarized | the oscillations are in a horizontal plane | ||||
| optically active | substances that rotate the plane of polarization of light passing through them | ||||
| polarization | the attribute that wave oscillations have a definite direction relative to the direction of propagation of the wave | ||||
| polarized | waves having the electric and magnetic field oscillations in a definite direction | ||||
| unpolarized | waves that are randomly polarized | ||||
| vertically polarized | the oscillations are in a vertical plane | ||||
| quantized | the fact that certain physical entities exist only with particular discrete values and not every conceivable value | ||||
| correspondence principle | in the classical limit (large, slow-moving objects), quantum mechanics becomes the same as classical physics | ||||
| quantum mechanics | the branch of physics that deals with small objects and with the quantization of various entities, especially energy | ||||
| blackbody | an ideal radiator, which emits thermal radiation ideally and absorbs all radiation incident on it at all wavelengths | ||||
| blackbody radiation | a thermal radiation, usually modeled for a blackbod | ||||
| ultraviolet catastrophe | failure of classical theory to correctly describe blackbody radiation at short wavelengths | ||||
| Planck’s constant | \(h=6.626 \times 10^{-34} \mathrm{~J} \cdot \mathrm{s} \) | ||||
| Planck law | first successful theoretical description of thermal radiation which used quantization of energy hypothesis | ||||
| photoelectric effect | the phenomenon whereby some materials eject electrons when light is shined on them |
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| photon | a quantum, or particle, of electromagnetic radiation | ||||
| photon energy | the amount of energy a photon has; \(E=h f\) | ||||
| work function | the amount of energy necessary to eject an electron from a material; the binding energy in photoelectric effect | ||||
| de Broglie wavelength | the wavelength possessed by a particle of matter, calculated by \(\lambda=h / p\) | ||||
| 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 | ||||
| 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 | ||||
| probability wave | the description of wave characteristic of matter, as revealed by probability distribution experimentally | ||||
| probability distribution | the overall spatial distribution of probabilities to find a particle at a given location | ||||
| cathode-ray tube | a vacuum tube containing a source of electrons and a screen to view images | ||||
| planetary model of the atom | the most familiar model or illustration of the structure of the atom | ||||
| hydrogen spectrum wavelengths | the wavelengths of visible light from hydrogen; can be calculated by \(\frac{1}{\lambda}=R\left(\frac{1}{n_{\mathrm{f}}^{2}}-\frac{1}{n_{\mathrm{i}}^{2}}\right)\) | ||||
| Rydberg constant | a physical constant related to the atomic spectra with an established value of \(1.097 \times 10^{7} \mathrm{~m}^{-1}\) | ||||
| 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 | ||||
| energy-level diagram | a diagram used to analyze the energy level of electrons in the orbits 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 | ||||
| hydrogen-like atom | any atom with only a single electron | ||||
| energies of hydrogen-like atoms | Bohr formula for energies of electron states in hydrogen-like atoms: \(E_{n}=-\frac{Z^{2}}{n^{2}} E_{0}(n=1,2,3, \ldots)\) | ||||
| relativity | the study of how different observers measure the same event | ||||
| 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 | ||||
| Michelson-Morley experimentinertial 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 | ||||
| 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 | ||||
| second postulate of special relativity | the idea that the speed of light \(c\) is a constant, independent of the source | ||||
| 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 | ||||
| time dilation | the phenomenon of time passing slower to an observer who is moving relative to another observer | ||||
| twin paradox | \(\Delta t_{0} \). the time measured by an observer at rest relative to the event being observed: \(\Delta t=\frac{\Delta t_{0}}{\sqrt{1-\frac{v^{2}}{c^{2}}}}=\gamma \Delta t_{0} \), where \( \gamma=\frac{1}{\sqrt{1-\frac{v^{2}}{c^{2}}}}\) | ||||
| 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 | ||||
| proper length | \( L_{0}\); 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 | ||||
| length contractionrelativistic Doppler effects | \(L\), the shortening of the measured length of an object moving relative to the observer’s frame: \(L=L_{0} \sqrt{1-\frac{v^{2}}{c^{2}}}=\frac{L_{0}}{\gamma} \) | ||||
| classical velocity addition | the method of adding velocities when \(v<<c\); velocities add like regular numbers in one-dimensional motion: \(u = v+u^{\prime} \), where \(v\) is the velocity between two observers, \(u\) is the velocity of an object relative to one observer, and \(u^{\prime}\) is the velocity relative to the other observer |
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| relativistic velocity addition | the method of adding velocities of an object moving at a relativistic speed: \( \), where \(v\) is the relative velocity between two observers, \(u\) is the velocity of an object relative to one observer, and \(u^{\prime}\) is the velocity relative to the other observer | ||||
| 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 \[ \lambda_{\mathrm{obs}}=\lambda_{s} \sqrt{\frac{1+\frac{u}{c}}{1-\frac{u}{c}}} \nonumber\] where \(\lambda_{\mathrm{obs}}\)is the observed wavelength, \(\lambda_{s}\) is the source wavelength, and \(u\) is the velocity of the source to the observer |
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| relativistic momentum | \(p\), the momentum of an object moving at relativistic velocity; \(p=\gamma m u\), where \(m\) is the rest mass of the object, \(u\) is its velocity relative to an observer, and the relativistic factor \(\gamma=\frac{1}{\sqrt{1-\frac{u^{2}}{c^{2}}}}\) | ||||
| rest mass | the mass of an object as measured by a person at rest relative to the object | ||||
| total energy | defined as \(E = \gamma mc^2\), where \(\gamma = \frac{1}{\sqrt{1 - \frac{v^2}{c^2}}}\) | ||||
| rest energy | the energy stored in an object at rest: \(E_0 = mc^2\) | ||||
| relativistic kinetic energy | the kinetic energy of an object moving at relativistic speeds: \(KE_{rel} = (\gamma -1) mc^2\), where \(\gamma = \frac{1}{\sqrt{1 - \frac{v^2}{c^2}}}\) | ||||
| alpha ray | a component of nuclear radioactivity; consists of two protons and two neutrons | ||||
| beta ray | a component of nuclear radioactivity; consists of an electron | ||||
| gamma rayradioactivity | a component of nuclear radioactivity; consists of a high-energy photon | ||||
| ionizing radiation | a radiation that produces ionization; examples include alpha rays, beta rays, gamma rays, and X-rays | ||||
| nuclear radiation | radiation that originate in the nuclei of atoms; alpha, beta, and gamma rays are among most common forms; also see "radioactivity" | ||||
| radioactivity | the emission of rays from the nuclei of atoms | ||||
| radioactive | a substance or object that emits nuclear radiation | ||||
| range of radiation | the distance that the radiation can travel through a material | ||||
| Geiger tube | a very common radiation detector that usually gives an audio output | ||||
| photomultiplier | a device that converts light into electrical signals | ||||
| radiation detector | a device that is used to detect and track the radiation from a radioactive reaction | ||||
| 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 | ||||
| atomic mass | the total mass of the protons, neutrons, and electrons in a single atom | ||||
| atomic number | number of protons in a nucleus | ||||
| chart of the nuclides | a table comprising stable and unstable nuclei | ||||
| isotopes | nuclei having the same \(Z\) and different \(N\)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 | ||||
| neutron | a neutral particle that is found in a nucleus | ||||
| 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 | ||||
| protons | the positively charged nucleons found in a nucleus | ||||
| radius of a nucleus | the radius of a nucleus is \(r=r_{0} A^{1 / 3}\) | ||||
| parent | the original state of nucleus before decay | ||||
| daughter | the nucleus obtained when parent nucleus decays and produces another nucleus following the rules and the conservation laws | ||||
| positron | the particle that results from positive beta decay; also known as an antielectron | ||||
| decay | the process by which an atomic nucleus of an unstable atom loses mass and energy by emitting ionizing particles | ||||
| alpha decay | type of radioactive decay in which an atomic nucleus emits an alpha particle | ||||
| beta decay | type of radioactive decay in which an atomic nucleus emits a beta particle | ||||
| gamma decay | type of radioactive decay in which an atomic nucleus emits a gamma particle | ||||
| decay equation | the equation to find out how much of a radioactive material is left after a given period of time | ||||
| nuclear reaction energy | the energy created in a nuclear reaction | ||||
| neutrino | an electrically neutral, weakly interacting elementary subatomic particle | ||||
| electron’s antineutrino | antiparticle of electron’s neutrino | ||||
| positron decay | type of beta decay in which a proton is converted to a neutron, releasing a positron and a neutrino | ||||
| antielectron | decay series | ||||
| decay series | process whereby subsequent nuclides decay until a stable nuclide is produced | ||||
| electron’s neutrino | a subatomic elementary particle which has no net electric charge | ||||
| antimatter | composed of antiparticles | ||||
| 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 | ||||
| becquerel | half-life | ||||
| half-life | the time in which there is a 50% chance that a nucleus will decay | ||||
| 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 | ||||
| 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 | ||||
| carbon-14 dating | a radioactive dating technique based on the radioactivity of carbon-14 | ||||
| activity | the rate of decay for radioactive nuclides | ||||
| rate of decay | the number of radioactive events per unit time | ||||
| curie | the activity of 1g of \({ }^{226} \mathrm{Ra}\), equal to \(3.70 \times 10^{10} \mathrm{~Bq}\) | ||||
| Anger camera | a common medical imaging device that uses a scintillator connected to a series of photomultipliers | ||||
| gamma camera | another name for an Anger camera | ||||
| positron emission tomography (PET) | tomography technique that uses \(\beta^{+}\) emitters and detects the two annihilation \(\gamma\) rays, aiding in source localization | ||||
| radiopharmaceutical | compound used for medical imaging | ||||
| single-photon-emission computed tomography (SPECT) | tomography performed with \(\gamma\)-emitting radiopharmaceuticals | ||||
| tagged | process of attaching a radioactive substance to a chemical compound | ||||
| gray (Gy) | the SI unit for radiation dose which is defined to be \(1 \mathrm{~Gy}=1 \mathrm{~J} / \mathrm{kg}=100 \mathrm{~rad}\) | ||||
| linear hypothesis | assumption that risk is directly proportional to risk from high doses | ||||
| rad | the ionizing energy deposited per kilogram of tissue | ||||
| sievert | the SI equivalent of the rem | ||||
| 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 | ||||
| quality factor | same as relative biological effectiveness | ||||
| roentgen equivalent man (rem) | a dose unit more closely related to effects in biological tissue | ||||
| low dose | a dose less than 100 mSv (10 rem) | ||||
| moderate dose | a dose from 0.1 Sv to 1 Sv (10 to 100 rem) | ||||
| 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 | ||||
| shielding | a technique to limit radiation exposure | ||||
| break-even | when fusion power produced equals the heating power input | ||||
| 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 | ||||
| magnetic confinement | a technique in which charged particles are trapped in a small region because of difficulty in crossing magnetic field lines | ||||
| nuclear fusion | a reaction in which two nuclei are combined, or fused, to form a larger nucleus | ||||
| proton-proton cycle | the combined reactions \({ }^{1} \mathrm{H}+{ }^{1} \mathrm{H} \rightarrow{ }^{2} \mathrm{H}+e^{+}+v_{\mathrm{e}}\), \({ }^{1} \mathrm{H}+{ }^{2} \mathrm{H} \rightarrow{ }^{3} \mathrm{He}+\gamma\), and \({ }^{3} \mathrm{He}+{ }^{3} \mathrm{He} \rightarrow{ }^{4} \mathrm{He}+{ }^{1} \mathrm{H}+{ }^{1} \mathrm{H}\) | ||||
| breeder reactors | reactors that are designed specifically to make plutonium | ||||
| breeding | reaction process that produces 239Pu | ||||
| criticality | condition in which a chain reaction easily becomes self-sustaining | ||||
| critical mass | minimum amount necessary for self-sustained fission of a given nuclide | ||||
| fission fragments | a daughter nuclei | ||||
| 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 | ||||
| nuclear fission | reaction in which a nucleus splits | ||||
| neutron-induced fission | fission that is initiated after the absorption of neutron | ||||
| supercriticality | an exponential increase in fissions | ||||
| Feynman diagram | a graph of time versus position that describes the exchange of virtual particles between subatomic particles | ||||
| gluons | exchange particles, analogous to the exchange of photons that gives rise to the electromagnetic force between two charged particles | ||||
| quantum electrodynamics | the theory of electromagnetism on the particle scale | ||||
| boson | particle with zero or an integer value of intrinsic spin | ||||
| baryons | hadrons that always decay to another baryon | ||||
| baryon number | a conserved physical quantity that is zero for mesons and leptons and \(\pm 1\) for baryons and antibaryons, respectively | ||||
| 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 muon family number | a general rule stating that the total muon family number stays the same through an interaction | ||||
| electron family number | the number \(\pm 1\) 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 | ||||
| fermion | particle with a half-integer value of intrinsic spin | ||||
| gauge boson | particle that carries one of the four forces | ||||
| hadrons | particles that feel the strong nuclear force | ||||
| leptons | particles that do not feel the strong nuclear force | ||||
| meson | hadrons that can decay to leptons and leave no hadrons | ||||
| muon family number | the number \(\pm 1\) 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 | ||||
| strangeness | a physical quantity assigned to various particles based on decay systematics | ||||
| tau family number | the number \(\pm 1\) 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 | ||||
| electroweak theory | theory showing connections between EM and weak forces | ||||
| grand unified theory | theory that shows unification of the strong and electroweak forces | ||||
| gluons | eight proposed particles which carry the strong force | ||||
| Higgs boson | a massive particle that, if observed, would give validity to the theory that carrier particles are identical under certain circumstances | ||||
| quantum chromodynamics | the governing theory of connecting quantum number color to gluons | ||||
| standard model | combination of quantum chromodynamics and electroweak theory | ||||
| superstring theory | a theory of everything based on vibrating strings some \(10^{-35} \mathrm{~m}\) in length |