Question 677: Current Electricity

Question

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

Accepted Answer

Resistance of bulb is constant
$$P = {{{V^2}} \over R} \Rightarrow {{\Delta p} \over p} = {{2\Delta V} \over V} + {{\Delta R} \over R}$$
$$ 	herefore {{\Delta p} \over p} = 2 	imes 2.5 + 0 = 5\% $$

Answer

20%

Answer

2.5%

Answer

5%

Answer

10%

Current Electricity

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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