Question:
A current of $2 \mathrm{~mA}$ was passed through an unknown resistor which dissipated a power of $4.4 \mathrm{~W}$. Dissipated power when an ideal power supply of $11 \mathrm{~V}$ is connected across it is:
Correct Option: 1
Solution:
(1) Power, $\mathrm{P}=\mathrm{I}^{2} \mathrm{R}$
$4.4=4 \times 10^{-6} \times \mathrm{R}$
$\Rightarrow \mathrm{R}=1.1 \times 10^{6} \Omega$
When supply of $11 \mathrm{v}$ is connected
Power, $\mathrm{P}^{\prime}=\frac{\mathrm{v}^{2}}{\mathrm{R}}=\frac{11^{2}}{1.1} \times \frac{11^{2}}{1.1} \times 10^{-6}$
$=11 \times 10^{-5} \mathrm{~W}$
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