Electrical Engineering ⇒ Topic : Electrical Energy

Electrical Energy

The total work done in an electric circuit is called electrical energy i.e.

             Electrical energy = Electrical power x Time

The reader may note that formulae for electrical energy can be readily derived by multiplying the electric power by 't', the time for which the cuent flows. The unit of electrical energy will depend upon the units of electric power and time.

(1) If power is taken in watts and time in seconds, then the unit of electrical energy will be watt-sec. i.e.

Energy in watt-sec. = Power in watts x Time in sec.

(2) If power is expressed in watts and time in hours, then unit of electrical energy will be watt-hour i.e.

Energy in watt-hours = Power in watts x Time in hours

(3) If power is expressed in kilowatts and time in hours, then unit of electrical energy will be kilowatt-hour (kWh) i.e.

Energy in kWh = Power in kW x Time in hours

It may be pointed out here that in practice, electrical energy is measured in kilowatt-hours (kWh). Therefore, it is profitable to define it.

One kilowatt-hour (kWh) of electrical energy is expended in a circuit if 1 kW (1000 watts) of power is supplied for 1 hour

The electricity bills are made on the basis of total electrical energy consumed by the consumer.The unit for charge of electricity is 1 kWh. One kWh is also called Board of Trade (B.O. T.) unit or simply unit. Thus when we say that a consumer has consumed 100 units of electricity, it means that electrical energy consumption is 100 kWh