Date of this Version
You have no doubt noticed that TV sets, light bulbs, and other electric appliances operate on 115 V, but electric ovens and clothes dryers usually need 220 V. Batteries may be rated at a harmless 1.5, 6, 9, or 12 V, but a high-tension electric transmission line may provide electric power at 400,000 V. Now just what physical quantity is measured by all these volts? How do volts relate to force, energy, and power, about which you have learned in earlier modules? The answer is that volts measure electric potential difference (sometimes called "voltage"), which is derived from the potential energy acquired by electrically charged objects as a result of the electric forces they experience. Even though your familiarity with volts probably stems from electric power supplied to your household, your introduction to the concept of electric potential in this module will be in the context of the interaction of stationary (static) electric charges.