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**Electrical energy**

- The SI unit of electrical work done for electrical energy expanded in a circuit is also joule exactly the same as for mechanical energy. It is defined as under :

- Suppose a charge of Q coulombs moves through a potential difference of V volts . Then electrical energy expended is given by ;

Electrical energy expended = VQ joules

Here (Q = It)

(V = IR)

- It may be mentioned here that joule is also known as watt - second . i.e. 1 joule = 1 Watt - sec.
- When we are dealing with large amount of electrical energy, it is often convenient to express it in kilowatt hours (Kwh).

1kwh = 1000 watt - hours = 1000 × 3600 watt - sec or joules

1kwh = 36 ×1000000 joules or watt-sec.

1kwh = 36 ×1000000 joules or watt-sec.

- Although practical unit of electrical energy is kwh, yet it is easy to see that this unit is readily converitable to joules with the help of above relation.

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