Free electrons are attracted to atoms that have an electron missing. When these leaps occur repeatedly, the electrons move in a stream, a river of electrical energy that we call "current," as if it were made of water.

An electrical current is the flow of electricity through a conductor--a substance like copper wire that transfers electrons easily from atom to atom. The force needed to make the electrons flow is measured in units called volts. The amount of current actually flowing is measured in units called amperes (amps). Considered together, volts and amps determine how much work an electric current can do. The product of volts and amps is called power. Power is measured in watts.