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Electric force Coulombs Law

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Learner

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Quote~"If two one-second collections of 1 Coulomb each were concentrated at points one meter apart, the force between them could be calculated from Coulomb's Law. For this particular case, that calculation becomes

coulaw2.gif



The density of metallic copper is about 9 grams/cm3 and one mole of copper is 63.5 grams so the cubic centimeter of copper contains about 1/7th of a mole or about 8.5 x 1022 copper atoms. With one mobile electron per atom, and with the electron charge of 1.6 x 10-19 Coulombs, this means there are about 13,600 Coulombs of potentially mobile charge in one cm3 of copper."

http://hyperphysics.phy-astr.gsu.edu/hbase/electric/elefor.html#c1

I am trying to carry out a simply experiment to witness the electric force however it has been unsucessful, based on my understanding if I connect 2 pieces of metal to the positve terminal of the power supply negative charges on the metal pieces would be drawn into the positive terminal of the PSU. Therefore, becomes postively charged and would repel each other. However, this is not the case which is what I expected. Similarly, if I place the same terminal of the battery towards each other they should repel due to electric force but they don't.

Why? Can anyone help clear up my confusion on this simple problem?

Also, based on electric force concept a battery should exhibit a electric dipole field?

edip2.gif
 

Your math is right on the magnitude of the force.

I think your idea that you can easily create a charge of +/- 1e on every single atom in a specimen is wrong.
 

Well, lets look at a capacitor for example. If we charge up 2 100uF capacitors, by placing the legs of the same polarity of each capacitor 1cm apart shouldn't they repel each other?

Q=CV

if V=15V and C = 100uF Q= 1.5mC

coulaw.gif


Coulombs Law calculator
http://hyperphysics.phy-astr.gsu.edu/hbase/electric/elefor.html#c1


if r = 1cm

F= 2.022 x 10^8 Newtons

Somehow this is not the case in reality? Where have I gone wrong?
 

Learner said:
Well, lets look at a capacitor for example. If we charge up 2 100uF capacitors, by placing the legs of the same polarity of each capacitor 1cm apart shouldn't they repel each other?

Q=CV

if V=15V and C = 100uF Q= 1.5mC

coulaw.gif


Coulombs Law calculator
http://hyperphysics.phy-astr.gsu.edu/hbase/electric/elefor.html#c1


if r = 1cm

F= 2.022 x 10^8 Newtons

Somehow this is not the case in reality? Where have I gone wrong?
Click to expand...

The formula you have there is correct only for vacuum , for other medium the exact formula is:
d77296f83f2a67d2554ca0944ab649b7c857cea1.png
As given in http://electronicspani.com/coulombs-law/
 

Learner,
Assume the cap is 100uf, the plates are separated by 0.00001 meters, and sandwiched with impregated paper whose dielectric constant is 5.0 . If the cap is energized to 15 volts, then (15*100uf)/1.602E-19 = 9.36E15 charges of opposite polarity reside on each plate. Each charge attracts its opposite number with a force of (1.602E-19)^2/(4*pi*(5*8.854E-12)*(0.00001)^2)=4.614E-19 newtons, so 9.36E15 charges exert a force of 0.00431989 newtons.

Ratch
 

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