Electric power & Energy

Electric Power

Electric power is the electric work done per unit time.

1 Watt = 1 Joule / 1 Second

Though Watt is unit of power, it is too small for measuring domestic consumption of electricity. Thus we use a larger unit of power called Kilowatt.

Electrical Energy

It is usually measured in a unit called Kilowatt hour(KWh) which is amount of electrical energy consumed when an electrical appliance with a power rating of 1 KiloWatt is used for 1 hour.

1 KWh= 3.6 x 10 ^ 6 Joules

Power Rating of Domestic Appliances

The power rating of an electrical appliance tells us the rate at which the appliance uses electrical energy.
An electric iron box marked 220V, 1000W has a power consumption of 1000W at 220V AC, i.e it consumes electrical energy at the rate of 1000Joules per second when a potential difference of 220V is applied across it (which is potential difference at which electricity is supplied to our homes).  

The electrical energy consumed (in KWh) by an electrical appliance is given by the product of its power rating (in KW) and the time for which it is used(in hrs).