There are two types of charges, namely positive and negative and their effects tend to cancel each other. Smallest electric charge is charge of electron e = 1.6 x 10-19 coulombs. If the sizes of charged bodies are very small as compared to the distances between them, we treat them as point charges. All the charge content of the body is assumed to be concentrated at one point in space.
Properties of Electric charges :
(1) Type of charges : Only two types of charges exist namely positive and negative.
(2) Nature of charges :
(i) like charges repel and
(ii) unlike charges attract each other.
(3) Additivity of charges : If a system contains two point charges q1 and q2, the total charge of the system is obtained simply by adding algebraically q1 and q2 , i.e., charges add up like real numbers or they are scalars like the mass of a body. If a system contains n charges q1, q2, q3, …, qn, then the total charge of the system is q1 + q2 + q3 + … + qn. Charge has magnitude but no direction, similar to the mass. However, there is one difference between mass and charge. Mass of a body is always positive whereas a charge can be either positive or negative. Ex : +2C + 5C - 3C = +4C
(4) Conservation of charges : Within an isolated system consisting of many charged bodies, due to interactions among the bodies, charges may get redistributed but it is found that the total charge of the isolated system is always conserved.
It is not possible to create or *** net charge carried by any isolated system although the charge carrying particles may be created or destroyed in a process. Sometimes nature creates charged particles: a neutron turns into a proton and an electron. The proton and electron thus created have equal and opposite charges and the total charge is zero before and after the creation.
(5) Quantisation of charge : The electric charge exists in discrete packets and is always an integral multiple of e. i.e., q = ± ne; where n = 1, 2, 3, 4, ---- and e =1.6 x 10-19 coulombs is termed as quantisation of charge.
(6) Scalar quantity : Electric charge is scalar quantity.
