In electromagnetism, charges of equal sign are attracted to each other, whereas charges of opposite sign repel each other.
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If the two charges are of opposite signs, Coulomb's law gives a negative result. This means that the force between the particles is attractive. If the two charges have the same signs, Coulomb's law gives a positive result. This means that the force between the particles is repulsive.
(+) attracts (-)
(=) Repels..................