Question

The electrostatic force between the metal plates of an isolated parallel plate capacitor C having a charge Q and area A, is?

• A. Proportional to the square root of the distance between the plates
• B. Independent of the distance between the plates
• C. Inversely proportional to the distance between the plates
• D. Linearly proportional to the distance between the plates

Answer 1

The correct option is B Independent of the distance between the plates

Since Electric field due to one plate of capacitor is given as

$E=\frac{\sigma }{2{ϵ}_o}$

$E=\frac{Q}{2A{ϵ}_o}$

Now force on another plate due to first plate will be given by

$F=QE$

$F=\frac{Q^2}{2{ϵ}_o}$

Hence, it is independent of distance between plates.