COMEDK · Physics · 19. Current Electricity
If voltage across a bulb rated \(220 \mathrm{~V}, 50 \mathrm{~W}\) drops by \(5 \%\) of its rated value, the percentage of the rated value by which the power would decrease is
- A \(2.5 \%\)
- B \(10 \%\)
- C \(5 \%\)
- D \(15 \%\)
Answer & Solution
Correct Answer
(B) \(10 \%\)
Step-by-step Solution
Detailed explanation
The power \(P\) consumed by a bulb is related to the voltage \(V\) by the formula \(P = \dfrac{V^2}{R}\), where \(R\) is the constant resistance of the bulb. Taking the logarithmic derivative of both sides, we get \(\dfrac{dP}{P} = 2 \dfrac{dV}{V}\). Given that the voltage drops…
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