An electric bulb marked as 50 W-200 V is connected across a 100 V supply. The power consumed by the bulb at present is

Question

An electric bulb marked as 50 W-200 V is connected across a 100 V supply. The power consumed by the bulb at present is (A) 37.5 W (B) 25 W (C) 12.5 W (D) 10 W

Tardigrade Admin · Accepted Answer

We know that R=(V2/P) Given V=200 V , P=40 W and V'=100 V Hence, R=(V2/P)=(200 × 200/50) P'=(V2/R)=(100 × 100 × 50/200 × 200) P'=12.5 W

Q. An electric bulb marked as $50 W - 200 V$ is connected across a $100 V$ supply. The power consumed by the bulb at present is

37.5 W

25 W

12.5 W

10 W

We know that $R = \frac{V ^{2}}{P}$
Given $V = 200 V, P = 40 W$
and $V^{'} = 100 V$
Hence, $R = \frac{V ^{2}}{P} = \frac{200 \times 200}{50}$
$P^{'} = \frac{V ^{2}}{R} = \frac{100 \times 100 \times 50}{200 \times 200}$
$P^{'} = 12.5 W$

Q. An electric bulb marked as 50W−200V is connected across a 100V supply. The power consumed by the bulb at present is