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
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Answer:
Correct Answer: 73. (c)
Solution:
- (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 $V=iR$
$=5 \times 2$
$=10 V$
