Two very large parallel sheets a distance d apart have their centers directly opposite each other. the sheets carry equal but opposite uniform surface charge densities. a point charge that is placed near the middle of the sheets a distance d/2 from each of them feels an electrical force f due to the sheets. if this charge is now moved closer to one of the sheets so that it is a distance d/4 from that sheet, what force will feel?

(a) f
(b) 4f
(c) 2f
(d) f/2
(e) f/4

Option (A) is the correct answer.

Explanation:

According to the Gauss law, electric field due to very large sheet of charge is as follows.

                    E =

where,     = charge per unit area

Since, it is given that there are two sheets of equal and opposite charge. Therefore, electric field between the plates will be as follows.

                  E =

Also, we know that relation between force and electric field is as follows.

                       F = qE

Hence, force felt by the charge present inside the plates will be as follows.

                    F =

This shows that force is not dependent on the distance and the charge is kept from one of the plate. Therefore, we can say that the force F felt by the charge is same when it is placed at a distance and at a distance from one of the plate.

Thus, we can conclude that the force we will feel is F.