Chapt. 22
Electric Charge
177
a) Given that copper’s atomic mass is 63
.
5 in atomic mass units (i.e., in units of 1
.
66
×
10
−
27
kg), how many copper atoms are there in the penny?
HINT:
If you have 10 kg of
eggs and each egg weighs 50 g, then you how many eggs?
b) Given that a copper atom has 29 protons (i.e., atomic number Z=29), how much gross
positive charge in Coulombs does the penny have?
c) Imagine (contrafactually as they say in Washington) that the absolute value of the
elementary proton charge was 1
.
000001 times larger than the absolute value of the
elementary electron charge (i.e., there was a fractional charge difference of (
δe/e
) = 10
−
6
),
what would be the force between two pennies a distance 1 meter apart assuming that the
pennies would be neutral if there were no fractional charge difference.
d) Is a charge difference between proton and electron of the order suggested in the part (c)
question likely? Explain.
022 qfull 00200 3 3 0 tough math: a vector calculation with charges
3. Four point charges are set at the corners of a square 2 meters on a side. Going clockwise from

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