Question

Capacity of a parallel plate condenser is $10\mu F$ when the distance between the plates is 8 cm. If the distance between the plates is reduced to 4 cm, its capacity will be :

• A. $15\mu F$
• B. $40\mu F$
• C. $20\mu F$
• D. $10\mu F$

Answer 1

Answer: (C)

We know $C=\frac{{ϵ}_{0}A}{d}$
When $d$ is halved $C$ becomes
$C_1=\frac{2{ϵ}_{0}A}{d}$
$\therefore C_1=2C$
$\therefore C_1=20\mu F$