The rate at which electrical work is done by an electrical appliance is called electric power, i.e.
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.
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:
- What is electric power?
- What is definition of 1 watt?
- What is definition of kilowatt?
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