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Electric charge is a fundamental property of matter that causes it to experience a force in an electromagnetic field. Charge is measured in coulombs (C) with dimensional formula [A T]. There are two types: positive (proton, +e) and negative (electron, -e), where e = 1.6 x 10^(-19) C is the elementary charge.
Three fundamental properties govern charge behavior. First, quantization: charge always appears in integer multiples of e (q = ne). This was confirmed by Millikan's oil drop experiment and means no object can carry a fractional electron charge. Second, conservation: the total charge in an isolated system remains constant through all physical and chemical processes. Charge can be transferred between bodies but never created or destroyed. Third, additivity: charges are scalars and add algebraically with their signs.
Charging methods include friction (electron transfer between dissimilar materials), conduction (charge flow on contact), and induction (charge separation using a nearby charged body and grounding). In friction charging, the material with higher electron affinity gains electrons and becomes negative. In induction, no physical contact with the charged body is needed — the induced charge is always opposite to the inducing charge.
For JEE, key applications include calculating the number of electrons transferred (n = ), understanding that neutral bodies have equal positive and negative charges, and recognizing that charge is relativistically invariant — it does not change with the velocity of the charged particle.