Re: On permittivity and permeability

"Timo Nieminen" <timo@xxxxxxxxxxxxxxxxx> wrote in message
news:Pine.LNX.4.50.0510131623280.28876-100000@xxxxxxxxxxxx
| In some recents posts, the claim was made that the permittivity and
| permeability of free space are zero, and that the concepts of
| permittivity and permeability are somehow intrinsically related to
matter
| or ether.
|
| So, what ARE permittivity and permeability all about?
|
| Consider that the Maxwell equations:
|
| curl H - dD/dt = J
| curl E + dB/dt = 0
| div D = rho
| div B = 0
|
| contain 4 fields: E, D, B, and H, which, being 3D vector fields means
that
| there are 12 unknown quantities. Since the 2 vector equations + 2
scalar
| equations only provides a total of 8 equations in vector components,
| something more is needed. Enter the consitutive relations:
|
| D = eE
| B = mH
|
| where e and m are the permittivity and permeability respectively. (We
| could also add J = sE, where s is the conductivity.) Finally, we have
the
| Lorentz force law:
|
| F = rho E + JxB
|
| This can be read as a definition of E and B in terms of forces on
charges
| and currents.
|
| From the Lorentz force law, we see that E must have dimensions of
| force/charge, while from div D = rho, D must have dimensions of
| charge/area. The permittivity of free space is essentially a
conversion
| between these two quantities, so e has dimensions of
| charge^2/(force*area). One can of course choose units such that e0 has
a
| numerical value of one, allowing it, perhaps unwisely, to be omitted
from
| equations.

Hi Timo,

There is no system of units that I know of that sets e0 = 1. In
gaussian cgs units and natural units of hbar = c = 1, e0 = 1/4pi. There
is a big mistake in Jackson's appendix on units Table 2 where he shows
e0 = 1. At least it is this way in the third ed. I think that should
read k1 and k2 at the top of the table and not eps0 and mu0.

Of course it is my belief that quantum "vacuum" charge = +,-
sqrt(hbar*c) easily explains all of this. ;-)

FrediFizzx

http://www.vacuum-physics.com/QVC/quantum_vacuum_charge.pdf
or postscript
http://www.vacuum-physics.com/QVC/quantum_vacuum_charge.ps

http://www.vacuum-physics.com

.

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