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

Is there any difference between using a positive versus a negative charge to test an electric field?

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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

You can use a negative charge to test an electric field. You just have to remember that the electric field points opposite to the force on the charge, rather than parallel to it. That's just a convention, though; we could have defined the electric field to point parallel to the force on a negative charge, and physics would work the same, except for a couple of negative signs in some formulas.

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This is actually the answer I was looking for... –  wizlog Sep 13 '11 at 6:30
@wizlog: the system allows you to change which answer you've accepted if you think that's appropriate. –  David Z Sep 13 '11 at 7:11