Question

Explain repulsion is the sure test of electrification?

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Answer 1

Electrostatic force of attraction can be observed between two bodies when they are oppositely charged and also when one is charged and the other is not charged. In the second case the the attraction occurs because of induced charges on the uncharged body.
While electrostatic force of repulsion between two bodies are observed only when they have like charges. That is both the bodies must be charged. Thus, repulsion is the sure test of electrification than attraction.