Question

A parallel plate capacitor with air between the plates has a capacitance of 8 pF. The separation between the plates is now reduced by half and the space between them is filled with a medium of dielectric constants. Calculate the value of the capacitance of the capacitor in the second case.

Answer 1

In first case,

The capacitance of the capacitor with air as medium is given by

C₁ = \(\frac{ɛ_oA}{d}\) = 8 pF ........................(i)

In 2nd case

The distance is reduced to half i.e. d/2 and K = 5.

So C₂ = \(\frac{Kɛ_oA}{d/2} = 2K(\frac{ɛ_oA}{d})\)

Using Eq. (i) we get

C₂ = 2K x 8 = 2 x 5 x 8 = 80 pF.