Q119 / 200 · NEET 2011 (Screening) · Physics
If power dissipated in the $9 \Omega$ resistor in the circuit shown is $36 \mathrm{~W}$, the potential difference across the $2 \Omega$ resistor is
- A$8 \mathrm{~V}$
- Correct answerB$10 \mathrm{~V}$
- C$2 \mathrm{~V}$
- D$4 \mathrm{~V}$
Solution
Electric power, $P=i^2 R$
$\therefore$ Current, $\quad i=\sqrt{\frac{P}{R}}$
For resistance of $9 \Omega$
$$
i_1=\sqrt{\frac{36}{9}}=\sqrt{4}=2 \mathrm{~A}
$$
$$
\begin{aligned}
i_2 & =\frac{i_1 \times R}{6}=\frac{2 \times 9}{6}=3 \mathrm{~A} \\
i & =i_1+i_2=2+3=5 \mathrm{~A} \\
V_2 & =I R_2=5 \times 2=10 \mathrm{~V}
\end{aligned}
$$
Hence, the correct answer is option: 'B'.