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NEET 2012 (AIPMT, Prelims) · Electrical Power & Heating Effect

Electrical Power & Heating Effect question from NEET 2012 (AIPMT, Prelims)

Q55NEET 2012 · AIPMT · PRELIMSEasy

Electrical Power & Heating Effect

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

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Answer: (c)

  1. P=V2R⇒ΔPP=2ΔVVP = \frac{V^2}{R} \Rightarrow \frac{\Delta P}{P} = 2\frac{\Delta V}{V} (small change).
  2. ΔPP=2×2.5%=5%\frac{\Delta P}{P} = 2 \times 2.5\% = 5\%.
  3. So the answer is (c) 5%.
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