Jump to a New ChapterIntroduction to the SAT IIIntroduction to SAT II PhysicsStrategies for Taking SAT II PhysicsVectorsKinematicsDynamicsWork, Energy, and PowerSpecial Problems in MechanicsLinear MomentumRotational MotionCircular Motion and GravitationThermal PhysicsElectric Forces, Fields, and PotentialDC CircuitsMagnetismElectromagnetic InductionWavesOpticsModern PhysicsPhysics GlossaryPractice Tests Are Your Best Friends
 14.1 Voltage 14.2 Current 14.3 Resistance 14.4 Energy, Power, and Heat 14.5 Circuits

 14.6 Capacitors 14.7 Key Formulas 14.8 Practice Questions 14.9 Explanations
Voltage
The batteries we use in flashlights and clock radios operate on chemical energy. This chemical energy—which you may learn more about in chemistry class—separates charges, creating a potential difference. To separate charges and create a positive and negative terminal, the battery must do a certain amount of work on the charges. This work per unit charge is called the voltage, V, or electromotive force, emf, and is measured in volts (V). Remember, one volt is equal to one joule per coulomb.
You’ll notice that voltage is measured in the same units as potential difference. That’s because they are essentially the same thing. The voltage of a battery is a measure of the work that has been done to set up a potential difference between the two terminals. We could draw an analogy to the amount of work required to lift an object in the air, giving it a certain amount of gravitational potential energy: both work and gravitational potential energy are measured in joules, and the amount of work done on the object is exactly equal to the amount of gravitational potential energy it acquires.
When a current flows about a circuit, we say there is a certain “voltage drop” or “drop in potential” across the circuit. An electric current converts potential energy into work: the electric field in the circuit does work on the charges to bring them to a point of lower potential. In a circuit connected to a 30 V battery, the current must drop 30 volts to send the electrons from the negative terminal to the positive terminal.
 Jump to a New ChapterIntroduction to the SAT IIIntroduction to SAT II PhysicsStrategies for Taking SAT II PhysicsVectorsKinematicsDynamicsWork, Energy, and PowerSpecial Problems in MechanicsLinear MomentumRotational MotionCircular Motion and GravitationThermal PhysicsElectric Forces, Fields, and PotentialDC CircuitsMagnetismElectromagnetic InductionWavesOpticsModern PhysicsPhysics GlossaryPractice Tests Are Your Best Friends
Test Prep Centers
SparkCollege
 College Admissions Financial Aid College Life