Q.State the law of conservation of charge.

Electric charge is a basic, intrinsic property of the elementary particles that make up all matter -- protons carry a fixed positive charge, electrons carry an exactly equal and opposite negative charge, and neutrons carry no charge at all. An object can be given a net charge by CONDUCTION (direct contact/rubbing, which transfers electrons from one body to another) or by INDUCTION (bringing a charged body close to a conductor without touching it, which merely redistributes the conductor's own free electrons, leaving its near side oppositely charged and its far side similarly charged to the inducing body, with no net charge actually transferred).

Charge obeys three fundamental properties. It is ADDITIVE, like mass, except that unlike mass it must be summed algebraically (accounting for sign), so a system's total charge may come out positive, negative, or exactly zero. It is QUANTIZED: every real charge is an integer multiple of the elementary charge $e=1.6\times10^{-19}$ C, since charging always transfers a whole number of electrons -- though this discreteness is invisible in everyday life because e is so tiny that even a modest charge involves an astronomically large number of elementary units. And it is CONSERVED: in any isolated system, charge can move from one part to another, but the total charge can never be created or destroyed, illustrated by a rubbed glass rod and silk always acquiring exactly equal and opposite charges. Finally, charges exert forces on each other purely by their sign: like charges always repel, unlike charges always attract -- the qualitative fact that Coulomb's law turns into an exact formula.