Question

Two charges q1 and q2 exert a force of 20 N on each other. If the charge of q1 is doubled, what will the new force be? 1) 40N 2) 80N 3) 20 N 4) 10 N​

Answer 1

Given :

Two charges q1 and q2 exert a force of 20 N on each other.

To Find :

If the charge of q1 is doubled, what will the new force be?

1) 40 N 2) 80 N 3) 20 N 4) 10 N​

Solution :

We know, electrostatic force between two charges is given by :

$F = \dfrac{kq_1q_2}{r^2}$

Here, F = 20 N.

$20 = \dfrac{kq_1q_2}{r^2}$

Now, if $q_1$ is doubled :

$F'= \dfrac{k(2q_1)q_2}{r^2}\\\\F'= 2\dfrac{kq_1q_2}{r^2}\\\\F'= 2\times F\\\\ F'= 2\times 20 \ N\\\\F'= 40 \ N$

Therefore, if the charge of q1 is doubled, new force will be 40 N.