Question

An electric bulb is rated 220volt and 100watt. When it is operated on 110volt the power consumed will be?

Answer 1

P1 = 100 W

P2 = ?

V1 = 220 V

V2 = 110 V

In both the case, resistance will be same

R1 = R2

Using P = V2/R

V²1/P1 = V²2/P2

P2 = (V2/V1)²*P1 = (110/220)²*100 = 1/4*100 = 25 W

Answer 2

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ANSWER :-

Energy consumed by an appliance can be given by the expression -

P=VI =V^2/R
R=V^2/P

Given, P=100 W, V= 220V
So, R = 220^2/100 = 48400/100=484 ohm

Now, The resistance of the bulb remains constant if the supplied voltage is reduced to 110V. If the bulb is operated at 110V, then the energy consumed by it is -

P'=V'^2/R=110^2/484=12100/484=25W

Hence,the power consumed is 25 W.

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