A current of 2mA was passed through an unknown resistor which dissipated a power of 4.4 W.

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:

1. (1) $11 \times 10^{-5} \mathrm{~W}$

2. (2) $11 \times 10^{-3} \mathrm{~W}$

3. (3) $11 \times 10^{-4} \mathrm{~W}$

4. (4) $11 \times 10^{5} \mathrm{~W}$

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, $\mathrm{P}^{\prime}=\frac{\mathrm{v}^{2}}{\mathrm{R}}=\frac{11^{2}}{1.1} \times \frac{11^{2}}{1.1} \times 10^{-6}$

$=11 \times 10^{-5} \mathrm{~W}$