If voltage across a bulb rated 220 V , 100 W drops by 2.5 % of its rated value, the percentage of the rated value by which the power would decrease is

Question

If voltage across a bulb rated 220 V , 100 W drops by 2.5 % of its rated value, the percentage of the rated value by which the power would decrease is (A) 5 % (B) 10 % (C) 20 % (D) 2.5 %

Tardigrade Admin · Accepted Answer

P =( V 2/ R ) P propto V 2 (Δ P / P ) × 100=2 (Δ V / V ) × 100 =2 × 2.5=5 %

Q. If voltage across a bulb rated $220 V, 100 W$ drops by $2.5%$ of its rated value, the percentage of the rated value by which the power would decrease is

$5%$

$10%$

$20%$

$2.5%$

$P = \frac{V ^{2}}{R}$
$P \propto V^{2}$
$\frac{Δ P}{P} \times 100 = 2 \frac{Δ V}{V} \times 100$
$= 2 \times 2.5 = 5%$

Q. If voltage across a bulb rated 220V,100W drops by 2.5% of its rated value, the percentage of the rated value by which the power would decrease is

5%

10%

20%

2.5%