1. Module 3

1.40. Page 11

Module 3 Lesson 5

Module 3—Electrical Phenomena

 

Lesson Summary

 

At the beginning of this lesson you were asked the following essential questions:

  • What is electric potential energy? How is it similar to gravitational potential energy?
  • What is voltage? How is voltage calculated?

Both electric potential energy and gravitational potential energy result when work is done to move an object in a field. In both cases, work is done by applying an external force on the object that is opposite to the force that the field would exert on the object. Gravitational potential energy can be increased when a mass is moved up, away from Earth’s surface, parallel to the gravitational field. Electric potential energy can be gained by moving a positive charge toward a positive source, or by moving a negative charge away from a positive source. In both cases, the distance moved is parallel to the electric field.

 

While potential energy is measured in joules, electric potential is measured in volts. A volt is a joule per coulomb because electric potential is the change in electric potential energy stored per unit of charge. Many people prefer to use the term voltage for electric potential because it reminds them how this quantity is measured. In most applications, potential difference is used instead of electric potential because the change in energy stored per charge is measured relative to some other point in the electric field rather than using infinity as the reference point.

 

Dangers associated with high voltage increase with increasing amounts of charge. At very high voltages, the amount of energy per unit of charge is high, but the total amount of electrical energy can be limited by having few charges held at this voltage. In the case of high-voltage power lines, the product of high energy per unit of charge and the high number of charges can lead to electrocution and death.

 

Lesson Glossary

 

electric potential difference: the change in electric potential experienced by a charge moving from one point to another in an electric field

 

It is sometimes called potential difference.

 

voltage: the value, in volts, of the change in electric potential energy stored per unit of charge

 

It is also called electric potential.