Question

If in the circuit, power dissipation is $150W$ , then $R$ is

• A. $2\Omega$
• B. $6\Omega$
• C. $5\Omega$
• D. $4\Omega$

Answer 1

Answer: (B)

Power $=\frac{V^2}{R}$
$150=\frac{V^2}{R_{\text{net}}}$
$=\frac{{\text{15}}^2}{R_{\text{net}}}$
$\frac{1}{R_{\text{net}}}=\frac{1}{R}+\frac{1}{2}$
$\therefore R_{\text{net}}=\frac{2R}{R+2}$
$\therefore \text{150 =}\frac{{\left(\text{15}\right)}^2\left(R+2\right)}{2R}$
$\therefore R=6\Omega$