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Electric potential energy is a measurement of the amount of electrical energy that is stored in a certain location or device, such as a battery. The most common measurement of electrical potential energy is volts. This technically simplifies the potential energy into electric potential, the difference being that it is measured per unit of charge instead of taking all of the specific charges into account. It is the amount of work that can possibly be done as a result of the position or particular configuration of the electric charges.
Understanding gravitational potential energy is a good way for one to begin to understand the idea of electric potential energy. Gravity is a force that pulls all bodies of matter towards one another, and the gravitational pull of the Earth keeps things on the ground. If someone was to hold a 2.2-pound (1-kg) rock 3.28 feet (1 m) above the Earth, he or she would basically be fighting gravity. The gravitational force of the Earth would be trying to pull that rock down, and that force on the unmoving rock is gravitational potential energy, dependent upon the distance from the Earth and the weight of the object. The potential energy is released when the rock is dropped.
An electrical charge can have stored energy in the same way that a rock held above the Earth does. One might imagine a Van de Graff sphere — an electrical device that has a positive charge around the outside of it and that is often used in science experiments to show things such as static electricity — and another positive electrical charge held away from the sphere. To push the positive charge to the outer edge of the sphere would require a certain amount of energy to overcome the electrical repulsion created by the opposing field. This amount of energy is the electric potential energy, and it is affected by the distance from the source of the electric field, like a rock held further above the Earth has more gravitational potential energy. If the charge held away from the sphere was twice as powerful, it would have twice the potential energy, like a heavier rock would in the gravitational example.
To simplify the process of determining the specific electric potential energy for a certain object or circuit, the term usually is simplified to account for differing charges. This measurement is given in joules per coulomb, with joules being a unit of energy and coulomb being a unit of electrical force. This means that a certain location within an electrical field would have an electric potential of 12 joules per coulomb, and the specific electric potential energy can be determined from this. A one coulomb charge would have 12 joules of energy, and a two-coulomb charge would have 24.