Question

In the circuit, $5\Omega$ resistor develops 45J/s due to current flowing through it. The power developed per second across $12\Omega$ resistor is:

• A. 16W
• B. 192W
• C. 36W
• D. 64W

Answer 1

The correct option is B 192W

Voltage across $5\Omega$ $V=\sqrt{PR}=\sqrt{45\times 5}=15$ volts

$\therefore$ Current $I_1=\frac{15}{5}=3$ A

Equivalent resistance of series combination of $3\Omega$ and $6\Omega$ $R^{\prime }=9+6=15\Omega$

$\therefore$ Current $I_2=\frac{15}{15}=1$ A

Thus total current flowing through $12\Omega$ $I=I_1+I_2=3+1=4$ A

$\therefore$ Power developed across $12\Omega$ $P=I^2\left(12\right)=4^2\times 12=192$ W