On Tue, 01 Jul 2008 17:28:17 GMT, "Bill Miller"
<billmillerkt4ye@[EMAIL PROTECTED]
> wrote:
>
>"John C. Polasek" <jpolasek@[EMAIL PROTECTED]
> wrote in message
>news:olsi64dpq3djae7k2p3qk1nb92ja7da625@[EMAIL PROTECTED]
snip
>>>
>>>Even in introductory texts, it wouldn't be terribly difficult to say
>>>something like, "Maxwell's equations demonstrate a clear relation****p
>>>between Electric(E) and Magnetic (H) fields. This is sometimes
erroneously
>>>interpreted as meaning that E causes H and H causes E. However, a
careful
>>>analysis shows that E fields and H fields are sololy caused by charges
and
>>>the movement of charges.""
>>>
>>>Not too hard.
>> You are full of beans.
>
>Yep... Had some last night.
>
>As soon as the currents pulse up and down in
>> the antenna, a good ****tion of the energy exits as EM waves that take
>> off across the country. They're on their own and don't need overt
>> charges or currents. E, D, B and H are taken care of by polarization
>> of eps0 and mu0, properties of the vacuum. They exchange energies as
>> they go along.
>
>Your case would be stronger if E and H (in an EM wave) were out of phase.
>Then we would have a situation analagous to -- say -- a spring or water
>waves, wherein kinetic energy gets swapped for potential energy, etc.
>
>BUT E and H are in phase! How in the world can anyone imagine that two in
>phase and contiguaous signals are *swapping* energy? If you can do so, I
>believe we would all love to hear how it works.
OK, here's how they swap energy, (and remember, you promised to love
to hear this).
Using spring mass for simplicity and recognizing that the wave will be
sinusoidal, the force on the spring is pro****tional to displacement
Fk = F0 sin wt (say)
The force on the mass is pro****tional to acceleration, two derivatives
removed, so it's 180 degrees out of phase.
Fm = - w^2F0 sin wt
The energies likewise peak 180 degrees apart.
So you were approximately correct, that they are in phase, yes, in a
larger sense. After all, what's a minus sign? Well, shucks, let's just
admit that they are out of phase, as you were opining, making my case
stronger as you point out. I'm gratified.
>THEN stand by your phone for the Stockholm call!
>
>> Your assumption of currents and charges being present and essential is
>> just as valid as the teams now looking for Wimps and Machos to explain
>> the dark matter problem.
>
>Currents and charges are essential to LAUNCH the wave(s). Afterwards, the
>separate E and H signals are in lock step and isolated.
>
>> By the way which do you prefer:
>> D = E and B = H
>> or D = eps0E and B = mu0H ?
>
>I pick....
>
>Let's see...
>
>Door number... Ummm...Well...
>
>Oh gosh, I just can't decide!
You dodged the D=E bullet. That's a sure sign of a benighted cgs'er
who at least has the decency to feel a little guilty.
>>>Bill
>>>> Timo Nieminen - Home page:
http://www.physics.uq.edu.au/people/nieminen/
>>>> E-prints: http://eprint.uq.edu.au/view/person/Nieminen,_Timo_A..html
>>>> Shrine to Spirits:
>>>> http://www.users.bigpond.com/timo_nieminen/spirits.html
John Polasek
|
