During charging by friction,
A. charge is created
B. charge is destroyed
C. charge is conserved
D. None of these

Hint: Friction is a type of force that develops between the two surfaces that are sliding, or trying to slide, across each other. For example, when we try to push a book along the floor, friction makes this difficult for us to do. We will consider the movement of electrons from one surface to another while rubbing each other, then determine which type of charge is created or destroyed in the process.

Complete step-by-step answer:
Friction is described as the resistance to motion of one object moving relative to another object. Unlike gravity or electromagnetism, friction is not a fundamental force. It is assumed to be the result of the electromagnetic attraction between charged particles of two surfaces in contact.
When insulating materials are rubbed against each other, they may become electrically charged. Electrons, which are negatively charged, can be rubbed off one material onto the other material. The material which gains electrons becomes negatively charged and the one that loses electrons is left with a positive charge.

Example of charging by friction:
When a polythene rod is rubbed with a plastic duster, the friction causes the electrons to gain some energy. The electrons gain enough energy to leave the atom and rub off the surface of the duster onto the polythene rod. The polythene rod gains electrons, resulting in gaining negative charge, while the duster loses electrons resulting in gaining positive charge. Both the rod and the duster are made of insulating materials. Insulators prevent the electrons from their movement and the charge remains static.

When these surfaces rub each other, then due to friction, electrons from one surface get transferred to the other surface. The one which loses electrons becomes positively charged and the other, negative. Thus, the charging by friction is only due to the transfer of electrons. No charge gets created or destroyed in this process.

So, the correct answer is “Option D”.

Note: Frictional force always acts in the direction opposite to the direction in which the object is moving, or trying to move. Friction always tends to slow a moving object down. The amount of frictional force depends on the materials from which the two surfaces are made. The rougher the surface, the more friction is produced. Friction also results in the production of heat. If we rub our hands together quickly, we will feel them getting warmer.