Question

A bulb rated (220V, 100W) is connected across a power supply of 110V. The power consumed by bulb is : (A) 100W (B) 50W (C) 25W (D) 200W

Answer 1

First, let R be the resistance of the bulb.

We know that P=V^2/R

Therefore, R=V^2/P

So, R=220×220/100

R=484 ohm

We know that Resistance of a bulb never changes.

So, P=110×110/484

P=25 W

Hence, option (C) is correct.

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