Question

The power dissipated in the circuit shown in the figure is $30$ watts. The value of $R$ is

• A. $20\Omega$
• B. $15\Omega$
• C. $10\Omega$
• D. $30\Omega$

Answer 1

Answer: (C)

The equivalent resistance of the given circuit is
$R_{eq}=\frac{5R}{5+R}$
Power dissipated in the given circuit is
$P=\frac{V^2}{R_{eq}}$
$30=\frac{(10{)}^2}{\left(\frac{5R}{5+R}\right)}$
$150R=100(5+R)$
$150R=500+100R$
$50R=500$
$R=\frac{500}{50}=10\Omega$