Question

A parallel plate capacitor has a capacity $C$. The separation between the plates is doubled and a dielectric medium is inserted between the plates. If the capacity is $3C$, then · the dielectric constant of the medium will be

• A. 1.5
• B. 3
• C. 6
• D. 12

Answer 1

Answer: (C)

Capacity ofa parallel plate capacitor, $C=\frac{{\epsilon }_{0}A}{d}$ ...(i)
Whert plate separation is increased and a dielectric is' inserted, its capacity becomes $3C$.
$3C=\frac{{\epsilon }_{0}KA}{d^{\prime }}=\frac{{\epsilon }_{0}KA}{2d}(\because d^{\prime }=2d)$
$3C=\frac{K}{2}C$ [Using eqn. (i)]
Hence, $K=6$