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If voltage across a bulb rated 220 volt-...

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

A

`10%`

B

`20%`

C

`2.5%`

D

`5%`

Text Solution

Verified by Experts

The correct Answer is:
D
`"Power", R=(V^(2))/(R)`
As the resistance of the bulb is constant
`therefore (DeltaP)/(P)=(2DeltaV)/(V)`
`"% decrease in power"=(DeltaP)/(P)xx100=(2DeltaV)/(V)xx100`
`2xx2.5%=5%`
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