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Home Q & A Board Science-Related Homework Help Physics
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micro01 micro01
wrote...
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11 years ago
And please help with this one as well. Trying to teach self from book and internet for extra. Thank you.

What is the force on two point charges of 10-6 C that are 20 cm apart?
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wrote...
#1
11 years ago
1/e   electrons in a coulomb

e is 1.6 x10^-19
(e is the charge of one electron, if you didnt know)
you can work that out
wrote...
#2
11 years ago
If the charge on the electron is e = 1.6021176462 x 10^-19 C. Then in 1 coulomb of charge there will be: -


number of electrons = 1/1.6021176462 x 10^-19

Which is 6.241509745 x 10^18 electrons.

The force between two point charges q1 and q2, separated by a distance 'r' is given by Coulomb's law: -

F = ...1 . q1.q2
......__  . ____
..... 4??0 . r²

Substituting values this equation becomes: -


F = 10^-6 x 10^-6/(4 x 3.14 x 8.854 x 10^-12 x 0.2²)

Hence, F = 0.2247 N (rounded to 4 DP)  (Using calculator constants for ??0)
wrote...
#3
11 years ago
None. Electrons have a negative charge, therefore one coulomb of charge can only result from a net of positive charge, thus no electrons.
wrote...
#4
11 years ago
A Coulomb is the amount of charge carried by one ampere in one second, which comes out to 6.24 * 10^18  electrons of charge.  

Just to clarify, a Coulomb is neither positive nor negative, it's just a scalar magnitude of charge.  This means a Coulomb of charge could consist of protons OR electrons (or positrons or antiprotons).  If something has 5C of charge, you have to say whether it's +5C or -5C,

As for the force, David probably got it right.
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