# why do we test electric fields with positive charges? not negative ones?

Is there any difference between using a positive vs a negative charge to test an electric field? If so, please explain.

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 Are you asking about the definition "The electric field intensity is defined as the force per unit positive charge that would be experienced by a stationary point charge, or "test charge", at a given location in the field" en.wikipedia.org/wiki/Electric_field#Definition ? – anna v Sep 13 '11 at 7:47