Question

Four $4\Omega$ resistors are connected together along the edges o f a square. A $12V$ battery with internal resistance of $2\Omega$ is connected across a pair of the diagonally opposite corners of the square. The power dissipated in the circuit is

• A. 36 W
• B. 192 W
• C. 24 W
• D. 48 W

Answer 1

Answer: (C)

According to the question, the circuit diagram is as shown below

Power dissipated in circuit,
$P=\frac{E^2}{R_{\text{eff }}}...(i)$
The given circuit is a balanced Wheatstone bridge.
So, its equivalent resistance is given by
$R_{\text{eff }}=(4+4)\Vert (4+4)=8\Vert 8=\frac{8\times 8}{8+8}=4\Omega$
From Eq. (i),
$P=\frac{(12{)}^2}{4}=36W$