Unit of Charge - Coulomb
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The unit of charge is Coulomb and is denoted by C. One coulomb of charge, is that charge which when placed one metre from another charge in vacuum experiences an electrical force of repulsion of magnitude 9 x 109 N .
(b) If the charges are immersed in matter, then
e0 is replaced by
e, a
e is called absolute electric permitivity of the dielectric medium.
or relative permittivity . So Coulomb's law is written as
Vector form of Coulomb's Law
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(a) If q
1q
2 > 0, that is either both q
1 and q
2 are positive or both are negative, then the charges repel each other.
(b) If q1q2 < 0, that is if the charges are dissimilar, then the charges attract each other.
Thus, Coulomb's law agrees with Newton's third law.
