CBSE Class 12 Physics Revision Notes Chapter-1 Electric Charges and Fields Like Charges and Unlike Charges:  Like charges repel and unlike charges attract each other. Conductors and Insulators:  Conductors allow movement of electric charge through them, insulators do not. Quantization of Electric Charge:  It means that total charge (q) of a body is always an integral multiple of a basic quantum of charge (e) q = ne where  n  =   0 ,   ± 1 ,   ± 2 ,   ± 3 n  =   0 ,   ± 1 ,   ± 2 ,   ± 3 , …. Additivity of Electric Charges:  Total charge of a system is the algebraic sum of all individual charges in the system. Conservation of Electric Charges:  The total charge of an isolated system remains uncharged with time. Superposition Principle:  It is the properties of forces with which two charges attract or repel each other are not affected by the presence of a third (or more) additional charge(s). The Electric Field E at a point due to a charge configuration:  It is the force on a small pos