Question 157: Current Electricity

Question

By what percentage will the illumination of the lamp decrease if the current drops by 20%?

Accepted Answer

$$\begin{aligned}
& \mathrm{P}=\mathrm{i}^2 \mathrm{R} \
& \mathrm{P}_{	ext {int }}=\mathrm{I}_{	ext {int }}^2 \mathrm{R} \
& \mathrm{P}_{	ext {final }}=\left(0.8 \mathrm{I}_{	ext {int }}ight)^2 \mathrm{R}
\end{aligned}$$
% change in power $$=$$
$$\frac{P_{	ext {final }}-P_{	ext {int }}}{P_{	ext {int }}} 	imes 100=(0.64-1) 	imes 100=-36 \%$$

Answer

26%

Answer

36%

Answer

46%

Answer

56%

Current Electricity

By what percentage will the illumination of the lamp decrease if the current drops by 20%?

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