Electric Power

 The rate at which electrical work is done by an electrical appliance is called electric power, i.e.

                 Power    =    

                        P    =    

              but,    W    =    VIt

              So       P    =    

              So       P    =    VI watt    (1)

    Where,    V   =    potential difference (in volt)

                   I    =    current (in ampere)

Therefore,    P =   potential difference (in volt)   X   current (in ampere)

Also we know that according to Ohm’s law V   =   I R

Putting the value of I in equation (1), we get

                        P    =    IR   X   I
              or       P    =    I²R

The S.I.unit of power is watt. It is denoted by the letter W.

1Watt
The power is said to be of 1 watt if 1 joule of work is done in 1 second. Thus,

                        1 watt    =    

The S.I. unit of power represents a small amount of power and therefore it is inconvenient to use it where a large amount of power is involved. So, for commercial purposes a bigger unit of electric power called kilowatt is used.

                        1 kilowatt    =    1000 watt
              or       1 KW          =    1000 W

Test Your Understanding and Answer These Questions:

1. What is electric power?
2. What is definition of 1 watt?
3. What is definition of kilowatt?