The question is: if I were to insert a brass plate between two charges, what will happen to the force between the charges? Would it increase, decrease or stay the same?
Does the brass plate increase the value of permittivity of the medium and therefore the force decreases?
The correct answer is that it will increase. But I do not understand how.
Best Answer
The brass plate is a conductor, so the potential will be the same on both sides. The thickness of the brass plate therefore subtracts from the effective distance between the two charges, making the electric field strength higher in the remaining open space between the charges. This stronger field will cause more force to be experienced by each charge.
Another effect is that the shape of the field will change. Since the conductive plate has the same potential everywhere on its surface, each charge now sees a plane at half the voltage and half the distance, as apposed to the point charge before.