Question

The value of resistor $R$, when total power dissipated in the circuit is $150\text{W}$, is

• A. $2\Omega$
• B. $6\Omega$
• C. $7\Omega$
• D. $5\Omega$

Answer 1

The correct option is B $6\Omega$

The equivalent resistance can be calculated as:
$R_{eq}=\frac{R\times 2}{R+2}=\frac{2R}{2+R}$
Power, $P=\frac{V^2}{R_{eq}}=\frac{{15}^2}{\left(\frac{2R}{2+R}\right)}$
$\Rightarrow 150=\frac{225\times (2+R)}{2R}$
[As power dissipated in the circuit, $P=150\text{W}$]
$\Rightarrow R=6\Omega$
Hence, the correct answer is option (b).