ZingPath: Electrical Energy and Power

A fundamental concept in electrostatics is that particles have either positive or negative electrical charges, and that similarly charged particles repel each other while oppositely charged particles attract. This force between two charged particles is the coulomb force, a vector given by F = (keqQ)/r2 (Coulomb's Law); it is measured in coulombs (C). To move a positively charged particle, for example, closer to another positive charge requires work to be done. This work increases the potential energy of the particle, and the amount of work done equals the change in potential energy. Electrical potential energy is the energy required to overcome the repulsive force between two similarly charged particles. Just as gravitational potential energy is the work required to move a body away from a gravitational field, electrical potential energy is the work required to move a charged particle to a point near a second charged particle, from an infinite distance.

Electric potential energy can be defined as E = (keqQ)/r, where q and Q are the particle charges, r is the distance between them, and ke is Coulomb's electrostatic constant, approximately (C is the speed of light). By convention, Q is the stationary charge and q is the moving or test charge. Electrical potential energy is directly proportional to the product of the charges and inversely proportional to the distance. Twice as much energy is required to move a charge with twice the magnitude to within the same distance.

Electrical (or electrostatic) potential is a the electrical potential energy per unit of charge. It is measured in volts (V), or joules per coulomb (J/C). The potential difference is the difference in electrical potential energy between two locations. It is also known as a voltage difference and is also measured in volts.