i. When two bodies are rubbed against each other, this process results in the production of charges on the bodies involved.

ii. The charges on each body will be of equal magnitude but of opposite nature. This happens because charges are always created in pairs.

This phenomenon of charging bodies by rubbing them against each other is termed as charging by friction. However, the net charge of the system – of both the bodies – is zero.

iii. This is because equal amounts of charge of opposite nature cancel each other out.

iv. When a glass rod is rubbed with a silk cloth, then opposite charges appear on both the bodies. This is in accordance with the law of conservation of energy. (Net charge of isolated system remains constant) This phenomenon is also observed when other pairs of bodies are also rubbed with each other.