Teaching Physics with the Physics Suite

Edward F. Redish

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But it's just a leetle bit different

We know that within the limits of measurement, the magnitudes of the negative charge on the electron and the positive charge on the proton are equal. Suppose, however, that the magnitude of the charge on the proton was bigger than that on the electron by 1 part in a million. Estimate with what force two copper pennies, placed one meter apart, would then repel each other. You may find some of the following parameters useful (or not).
kC (Coulomb’s constant) ~ 9 x 109 N-m2/C2 e (charge on proton) ~ 1.6 x 10-19 C
me (mass of electron) ~ 9 x 10-31 kg mp (mass of proton) ~ 1.7 x 10-27 kg
mCu (mass of a copper atom) ~ 10–25 kg Number of electrons in a copper atom = 29

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