Question

The capacity of a parallel plate condenser is 5 μF. When a glass plate is inserted between its two plates, its potential difference reduces to `1/8`th of the original. The value of the relative dielectric constant is ______.

Options

• 5

• 1.6

• 40

• 8

Answer 1

The capacity of a parallel plate condenser is 5 μF. When a glass plate is inserted between its two plates, its potential difference reduces to `1/8`th of the original. The value of the relative dielectric constant is 8.

Explanation:

Given, C = 5μF

The potential of a capacitor without dielectric,

`V = Q/C = (Qd)/(Aε_0)`

The potential of the capacitor with dielectric,

V' = `Q/C^' = (Qd)/(KAε_0) = V/K`

Given, V' = `V/8`, so on comparing, we get

⇒ K = 8