Calculating Charge on Each Plate of a Capacitor

02 Dec 2021

Question:

It takes 18 J of energy to move a 0.30 mC charge from one plate of a 15 mF capacitor to the other. How much charge is on each plate?

The amount of charge on each plate is equal to 0.9 Coulombs.

To calculate the amount of charge on each plate:

The formula for work done is: Work = qV

Given data:
Work done (W) = 18 J
Charge (q) = 0.30 mC
Capacitance (C) = 15 mF

We know that work done is equal to the product of charge and potential difference:

W = qV

But, we also know that potential difference (V) across a capacitor is given by V = Q/C, where Q is the total charge on the capacitor plates.

Substitute V = Q/C in the formula for work:

W = q(Q/C)

Making q the subject of the formula:

q = W(C)/Q

Substitute the given values in the formula:

q = (18 * 15 * 10^-6) / (0.3 * 10^-3)

Charge(q) = 0.9 Coulombs.