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Interrelation Between P, V, I and R

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**ELECTRIC POWER:** Rate of consumption of energy.

SI unit of electric power is watt (W).

P = VI

or P = I^{2}R = `("V"^2)/"R"`

It is the power consumed by a device that carries 1 A of current when operated at a potential difference of 1 V.

Therefore: 1 W = 1 volt × 1 ampere = 1 V A

-The unit ‘watt’ is very small. Therefore, in actual practice we use a much larger unit called ‘kilowatt’.

-It is equal to 1000 watts. Since electrical energy is the product of power and time, the unit of electric energy is, therefore, watt hour (W h).

-One watt hour is the energy consumed when 1 watt of power is used for 1 hour. The commercial unit of electric energy is kilowatt hour (kW h), commonly known as ‘unit’.

1 kW h = 1000 watt × 3600 second

= 3.6 × 106 watt second

= 3.6 × 106 joule (J)