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