percentage will the illumination of...| Current Electricity

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JEE MAIN 2024

310124 S2

Question

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

Select the correct option:

A

46%

B

26%

C

36%

D

56%

✓ Correct! Well done.

✗ Incorrect. Try again or view the solution.

Solution

Sol. $$ \begin{aligned} & P=i^2 R \\ & P_{\text {int }}=I^2{ }_{\text {int }} R \\ & P_{\text {final }}=\left(0.8 I_{\text {int }}\right)^2 R \\ & \% \text { change in power }=\frac{P_{\text {final }}-P_{\text {int }}}{P_{\text {int }}} \times 100=(0.64-1) \times 100=-36 \% \end{aligned} $$

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