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If voltage across a bulb rated 220Volt-1...

If voltage across a bulb rated 220Volt-100 Watt drops by 2.5% of its rated value, the percentage of the rated value by which the power would decrease is :

A

0.1

B

0.05

C

0.2

D

0.025

Text Solution

Verified by Experts

The correct Answer is:
B
`P = V^2/R`
`(Delta V)/V xx 100 = 2.5 %`
Since R is constant
`(Delta P)/P = (2Delta V)/V`
`:." % drop in power "`
` = (Delta P)/p xx 100 `
` = (2 Delta V)V xx 100 `
` = 2 xx 2.5 % = 5 % `
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