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What is 'K' in K=1/4pi Epsilon 0?

by kenshi64
Tags: coulomb's law, electric constant
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Aug27-11, 03:59 AM
P: 34
Hey So for those that don't know, I'm reading this from Atomic Physics, basically where they teach you how the size of a nucleus was determined by shooting alpha particles at it. due to repulsion an alpha particle can get only 'so-close' to nucleus(they're both positively charged), and the the so-close is labelled as point P, the closest to the nucleus and alpha gets.

So heres a formula they teach us to use:

1/2mv2 = kQq/r

What is k called? what is the name of this constant, and what is it equal to since I was told it was the electric constant and went about solving it with that value, but at the back in the answer section they used the value 9x10^9!!
Thanks guy!!! :D
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Aug27-11, 04:37 AM
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P: 26,157
hi kenshi64!

that's the Coulomb's law equation

k (or ke) is the Coulomb constant, 8.988 109 Nm2/C2

k = 1/4πε0

ε0 (not k) is the electric constant, also called the permittivity of the vacuum

see and for more details

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