Elementary charge

Also called e, Fundamental charge

The elementary charge e is the magnitude of the charge carried by one proton or one electron, 1.60 times 10 to the power minus 19 coulombs. AP treats it as the smallest indivisible amount of charge, so every net charge is a whole-number multiple of it.

e=1.60×10−19 Ce = 1.60 \times 10^{-19} \ \mathrm{C}

Printed in the Constants and Conversion Factors box on the AP Physics 2 Table of Information and again on the AP Physics C: Electricity and Magnetism one. It appears on neither the AP Physics 1 nor the AP Physics C: Mechanics sheet, since neither course covers electrostatics.

What the CED claims for it. EK 10.1.A.1.ii in AP Physics 2, and the identical EK 8.1.A.1.ii in C: E&M, say the magnitude of the charge of a single electron or proton can be considered to be the smallest indivisible amount of charge. The next statement assigns the signs: an electron carries −e-e, a proton carries +e+e, and a neutron carries none. Note the hedge in "can be considered". It is a modelling statement for this course, not a claim about every particle in physics.

The consequence is quantization. Any net charge is nene for some integer nn, so the coulomb is a badly sized unit for counting: one coulomb is 6.25×10186.25 \times 10^{18} elementary charges, and a 1.0 μC1.0 \ \mu\mathrm{C} charge is 6.25×10126.25 \times 10^{12} of them. No AP question hands you a fraction of an elementary charge.

Same number, different quantity. The sheets also print 1 eV=1.60×10−191 \ \mathrm{eV} = 1.60 \times 10^{-19} J. That is not a coincidence and not the same thing: the electron volt is an energy, obtained by multiplying ee by one volt.

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