Electrostatic Potential and Capacitance - Result Question 40
42. The capacity of a parallel plate condenser is $10 \mu F$ when the distance between its plates is $8 cm$. If the distance between the plates is reduced to $4 cm$ then the capacity of this parallel plate condenser will be
(a) $5 \mu F$
(b) $10 \mu F$
(c) $20 \mu F$
(d) $40 \mu F$
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Answer:
Correct Answer: 42. (c)
Solution:
- (c) $C=10 \mu F \quad d=8 cm$
$C^{\prime}=? \quad d^{\prime}=4 cm$
$C=\frac{A \epsilon_0}{d} \Rightarrow C \propto \frac{1}{d}$
If $d$ is halved then $C$ will be doubled.
Hence, $C^{\prime}=2 C=2 \times 10 \mu F=20 \mu F$
