7: Electricity
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- 7.1: Prelude to Electric Charge and Electric Field
- Franklin demonstrated a connection between lightning and static electricity. Sparks were drawn from a key hung on a kite string during an electrical storm. These sparks were like those produced by static electricity, such as the spark that jumps from your finger to a metal doorknob after you walk across a wool carpet.
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- 7.2: Static Electricity and Charge - Conservation of Charge
- When various materials are rubbed together in controlled ways, certain combinations of materials always produce one type of charge on one material and the opposite type on the other. By convention, we call one type of charge “positive”, and the other type “negative.” E.g., when glass is rubbed with silk, the glass becomes positively charged and the silk negatively charged. Since the glass and silk have opposite charges, they attract one another like clothes that have rubbed together in a dryer.
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- 7.3: Conductors and Insulators
- Some substances, such as metals and salty water, allow charges to move through them with relative ease. Some of the electrons in metals and similar conductors are not bound to individual atoms or sites in the material. These free electrons can move through the material much as air moves through loose sand.
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- 7.4: Coulomb's Law
- Through the work of scientists in the late 18th century, the main features of the electrostatic force—the existence of two types of charge, the observation that like charges repel, unlike charges attract, and the decrease of force with distance—were eventually refined, and expressed as a mathematical formula. The mathematical formula for the electrostatic force is called Coulomb’s law after the French physicist Charles Coulomb.
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- 7.5: Introduction to Electric Potential and Electric Energy
- Two of the most familiar aspects of electricity are its energy and voltage. But energy and voltage are not the same thing. In this chapter, we shall examine the relationship between voltage and electrical energy and begin to explore some of the many applications of electricity.
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- 7.6: Electric Potential Energy- Potential Difference
- Electric potential is potential energy per unit charge. The potential difference between points A and B, VB−VA , defined to be the change in potential energy of a charge qmoved from A to B, is equal to the change in potential energy divided by the charge, Potential difference is commonly called voltage, represented by the symbol ΔV .
Contributors and Attributions
Benjamin Crowell (Fullerton College). Conceptual Physics is copyrighted with a CC-BY-SA license.