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## Main Question or Discussion Point

Why the 4π in Coulomb's Law, SI version? The CGS version does well without it...

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\mbox{thanks in advance!}

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\mbox{thanks in advance!}

[/tex]

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- Thread starter Rats_N_Cats
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Why the 4π in Coulomb's Law, SI version? The CGS version does well without it...

[tex]

\mbox{thanks in advance!}

[/tex]

[tex]

\mbox{thanks in advance!}

[/tex]

Last edited:

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Pythagorean

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They're not dimensionally equivalent. The 4pi is a result of the spherical geometry of the field created by a point charge.

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I've read that link you provided...I understand the difference between statcoulomb and coulomb, that they're not dimensionally equivalent. however this comes from the ε

They're not dimensionally equivalent. The 4pi is a result of the spherical geometry of the field created by a point charge.

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Born2bwire

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http://en.wikipedia.org/wiki/Gaussian_units#.22Rationalized.22_unit_systems

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Born2bwire

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This is where we get the 4\pi from. In terms of statics, we can look at Gauss' Law. If I place a single point charge at the center of a spherical Gaussian surface, then the total flux through the Gaussian surface of the electric field is proportional to the charge. Through the use of spherical symmetry we can actually derive the actual electric field from this relationship. The result is of course Coulomb's law and once again due to the spherical geometry we acquire the 4\pi factor. But since Coulomb's law is incorporated into Maxwell's Equations, we can move the 4\pi off of Coulomb's law to Gauss' law and not change the resulting physics.

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Jackson, J.D. Appendix on Units and Dimensions on

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[tex]

\mbox{hmmm....got that}

[/tex]

Thanks, born2bwire! Your explanation was good.

\mbox{hmmm....got that}

[/tex]

Thanks, born2bwire! Your explanation was good.

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