Electricity is distributed from the power station where the energy is generated to the different points where it is to be utilized for power or lighting. The amount of work done or "power" consumed in transmitting electricity from the power station to the point of consumption is found in the following manner: Multiply the electromotive force, determined by the voltmeter, and the strength of the current, determined by the ammeter, and the time in seconds; the result is the power consumed and is expressed in joules, the electrical unit of energy. This formula may be written:

Energy = Pressure X quantity X time Joules = Volts X amperes X seconds

Power is the rate of doing work and the electrical unit is the number of joules per second. It is expressed as watts.