Current Electricity - Result Question 68

73. If power dissipated in the $9-\Omega$ resistor in the circuit shown is 36 watt, the potential difference across the $2-\Omega$ resistor is

[2011]

(a) 4 volt

(b) 8 volt

(c) 10 volt

(d) 2 volt

Show Answer

Answer:

Correct Answer: 73. (c)

Solution:

  1. (c) We have, $P=\frac{V^{2}}{R}$

$\Rightarrow 36=\frac{V^{2}}{9}$

$\Rightarrow V=18 V$

Current passing through the $9 \Omega$ resistor is

$i_1=\frac{V}{R}=\frac{18}{9}=2 A$

The $9 \Omega$ and $6 \Omega$ resistors are in parallel, therefore

$i_1=\frac{6}{9+6} \times i$

where $i$ is the current delivered by the battery.

$\therefore i=\frac{2 \times 15}{6}=5 A$

Thus, potential difference across $2 \Omega$ resistor is $V=iR$

$=5 \times 2$

$=10 V$