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NEET 2012
Exam
NEET
Year
2012
Subject
Physics
Chapter
Current Electricity

NEET 2012 · Physics · Current Electricity

If voltage across a bulb rated 220 ~V-100 ~W drops by 2.5 \% of its...

If voltage across a bulb rated 220 V−100 W220 \mathrm{~V}-100 \mathrm{~W} drops by 2.5%2.5 \% of its rated value, the percentage of the rated value by which the power would decrease is

Options

  1. A20\%
  2. B2.5%2.5 \%
  3. C5%5 \%
  4. D10%10 \%

Correct answer

C. 5%5 \%

Step-by-step solution

Power P=V2RP=\frac{V^2}{R} For small variation ΔPP×100%=2×ΔVV×100%=2×2.5=5%\begin{aligned} \frac{\Delta P}{P} \times 100 \% & =\frac{2 \times \Delta V}{V} \times 100 \% \\ & =2 \times 2.5=5 \% \end{aligned} Therefore, power would decrease by 5%5 \%.
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