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

Question

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

Answer 1

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.

Answer 2

There is no fundamental difference between positive and negative charges. Anything that couples to positive electric charge couples to negative charge and vice versa. Practically, the main difference is that negative charge is on electrons and positive charge is in protons in atomic nuclei, so on a day-to-day basis they play different roles. However, these signs are reversed for antimatter, so we see there really is nothing special about the sign of a charge.

Answer 3

You can also use the positive charges. what happens is that usually the negative charges are used because, by convention, these were the charges that they decided to use to determine the direction of the electric current. besides, you can see it from this perspective: negative charges can move on the "lattice" and they are more "fun", while the protons are "boring", there are always "stuck" in the atomic nucleus.