How many electrons are there in 1 coulomb of charge?

Question

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?

Answer 1

None. Electrons have a negative charge, therefore one coulomb of charge can only result from a net of positive charge, thus no electrons.

Answer 2

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.

Answer 3

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

......__  . ____

..... 4πε0 . 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 πε0)  

Answer 4

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