Question

The electrostatic force on a small sphere of charge $0.4\mu C$ due to another small sphere of charge $-0.8\mu C$ in the air is $0.2N$.
What is the force on the second sphere due to the first?

Answer 1

Given that force on a sphere of charge $0.4\mu C$ due to another sphere of charge $-0.8\mu C$ is $0.2N$. We have to find the force on the second sphere due to first.

Since two charges are: $q_1=0.4\mu C$

$q_2=-0.8\mu C$

So, force is attractive and is equal to $0.2N$

And force on $-0.8\mu C$ charge due to $0.4\mu C$ charge is also same since the medium of two charges and distance between the charges is kept same.

So, force is also same, equal to $0.2N$ but its direction is opposite.