Question

A metal parallel plate capacitor has 100mm diameter and the distance between the plates is 1mm. The capacitor is placed in air. Calculate the force on each plate if the potential difference between the plates is 1kV.

(a) 350N

(b) 0.035kN

(c) 0.035N

(d) 3.35kN

This question was addressed to me during an interview.

My doubt stems from Force of Attraction Between Oppositely Charged Plates in division Capacitance and Capacitors of Basic Electrical Engineering

Answer 1

The correct option is (c) 0.035N

To explain: From the given data:

A=pi*d^2/4=0.007854m^2

Potential gradient = V/x = 10^6V/m

F=epsilon*A*(V/x)^2/2

Therefore, F=0.035N.