Consider two point charges `q_1 and q_2` at rest as shown in the figure.

They are separated by a distance of 1m. Calculate the force experienced by the two charges for the following cases:
`q_1 = 2 mu C and q_2 = -3 mu C`

Explanation

`q_1 = + 2 mu C, q_2 = - 3 mu C, and r = 1m`. They are unlike charges. So the force will be attractive.
Force experienced by the charge `q_2` due to `q_1` is given by
`vec(F)_(21) = (9 xx 10^(9) xx (2 xx 10^(-6) ) xx (-3 xx 10^(-6) ) )`
` - 54 xx 10^(-3) N hat(i) (" Using" hat(r)_(12) = hat(i) )`
The charge `q_2` will experience an attractive force towards `q_1` which is in the negative x direction.
According to Newton’s third law, the force experienced by the charge `q_1` due to `q_2` is
`vec(F)_(12) = - vec(F)_(21)`
so that `vec(F)_(12) = 54 xx 10^(-3)"N" hat(i)`
The directions of `vec(F)_(21) and vec(F)_(12)` are shown in the figure (case (b)).