Question

Which of the following cannot be charged easily by friction?
(A) A plastic rod
(B) A copper rod
(C) An inflated balloon
(D) A woolen cloth
(E) Piece of wood

Answer 1

Charging by friction also called triboelectric charging process. In this process when one body is rubbed with another body in close contact then free electrons jump from one body to the another and in such process, one body becomes deficient in charge while another gets excess of charge and thus one becomes negatively charged and another positively charged respectively.

Complete step by step answer:
Now we are being provided with five options. We see except copper which is a very good conductor of electricity, other four options are poor conductors of electricity.
Let us look at all the materials provided. First, it is the plastic scale. If we take the scale and rub it across our dry hairs and then if we bring it near to the piece of paper, we know they get attracted to the scale. This clearly shows that the scale gets charged and that too easily by simply rubbing with our hairs.
Next is a balloon and most of us have done the similar act in our childhood by rubbing an inflated balloon against our hairs and then we bring it close to our hand. The hairs on the hand gets straight up. This attraction is due to electrostatic force and so the balloon also gets charged up easily.
Next is woolen cloth and the same phenomenon we have observed during winters while in a dark room if we rub our hands with cloth or while changing clothes, we get some light which is evident of charges being produced. So, it can also be charged easily by rubbing.Now comes copper rod and wooden and we don’t know about them. One is a good conductor while the other is a bad conductor. Also, we should keep in mind that only non-conducting materials can be changed easily by friction. So copper is the correct answer.

Note: The process of charging or discharging depends upon the ability of substance to give & take electrons respectively which in turn depends upon the distribution of electrons and nature of substance. It wholly depends upon the nature of the material to give or take the extra electrons.