Question

A parallel plate capacitor of area, A, and plate separation, d, has a voltage, V₀, applied by a battery. The battery is then disconnected and a dielectric slab of permittivity ε₁ and thickness, d₁, (d₁ < d) is inserted. (a) Find the new voltage V₁ across the capacitor, (b) Find the capacitance C₀ before and its value C₁ after the slab is introduced. (c) Find the ratio V₁/V₀ and the ratio C₁/C₀ when d₁ = d/2 and ε₁ = 4ε₀.

Answer 1

(b) Since the capacitor charge remains the same

(c) As seen from above, V₁ = V₀ 5/8 ; C₁ C₀ = (8ε₀A(/5d x d/(ε₀A)))= 5/8