Michel Jullian wrote:
----- Original Message ----- From: "Paul" <[EMAIL PROTECTED]>
To: <[email protected]> Sent: Wednesday, January 24, 2007 3:46 PM
Subject: Re: [Vo]: Energy *Violations* using *standard* physics
Michel Jullian wrote:
Indeed both kinetic and magnetic field energies are
increasing in the process. Is this a violation of energy
conservation? No. Electric potential energy is decreasing
somewhere, I'll let you find where :)
Michel
The old "I know, but I don't want to tell you" trick? :)
Not at all, I will give the answer eventually, say on Sunday if
nobody finds it before, which I doubt very much. The fun is in the
searching, I have given away far too much already :)
Frankly I don't see what you think has been neglected. We've already
touched on the fact that as electromagnets draw together, you get
mechanical energy out _and_ the field inside each coil gets stronger, as
a result of which the net field energy actually increases. But at the
same time you're "paying the bill" in the form of back EMF in _both_
coils, and everything balances.
Is that what you're referring to, or is it something else?
As I already observed, the field shape of a macroscopic wire loop is
more complex than an infinitesimal dipole which makes the analysis more
confusing; when the coils are side by side the fields "outside" the
loops tend to cancel while the fields "inside" reinforce. When you open
the circuit, the energy you get back is from the field "inside".
(Imagine a simple loop: as long as the surface over which you integrate
-dB/dt to find the EMF is reasonably close to coplanar with the loop,
all portions of the surface "outside" the loop must double back on
themselves and their contributions will cancel. For a more complex
surface the mental picture isn't as obvious and we need to fall back on
Stokes' theorem to claim that it makes no difference.)
