Question

# An electric bulb is rated 220 V and 100 W. When it is operated at 110 V, the power consumed will be

A
100 W
B
75 W
C
50 W
D
25 W

Solution

## The correct option is B 25 WPower consumed by the electric bulb, P=V2R, where V is the potential difference and R is the electrical resistance. Given for 1st case: Voltage V1=220 V  and power consumed by bulb P1=100 W, In the 2nd case: Voltage of the bulb, V2=110 V Power consumed by the bulb = P2 Since the resistance is the same as it is the same bulb P1P2=(V1)2(V2)2 100P2=(220)2(110)2 P2=100×(110)2(220)2=25W Power consumed when the bulb is operated at 110V = 25W Physics

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