Re: Inertial-dampening systems

msadkins04_at_yahoo.com
Date: 02/11/05 

Date: 11 Feb 2005 14:33:52 -0800

Timo Nieminen wrote:
> On Fri, 10 Feb 2005 msadkins04@yahoo.com wrote:
>
> > Timo Nieminen wrote:
> >
> > > According to Hansen, it would be wise to check if the
> > > current induced by the changing magnetic field is
> > > dangerously high. Conductivity of tissue at
> > > low frequencies is about 1 S/m, which tells you the
> > > resistance. Then one just needs to know the capacitance,
> > > and dB/dt. Is the peak current biologically dangerous?
> >
> > More interestingly, what do you mean by "low frequency" in
> > the current application? A static magnetic field of some
> > particular strength is increased in strength. What is
> > the "frequency" of a change in field strength that occurs
> > only once? Does its "frequency" depend upon the magnitude
> > of the change? The time in which the change occurs?
> > Remember, this change occurs in connection with some
> > acceleration. The parameters are wide open.
>
> As you presumably know, writing the constitutive equations
> with permittivity (which I'll write as e), permeability (m),
> and conductivity (s) as constants is at best a crude
> approximation, and the usual "solution" to this problem
> is to consider them as functions of frequency (w):
> D(w) = e(w) E(w), B(w) = m(w) H(w), J(w) = s(w) E(w)

<snip>

You may be optimistic. :) Now, I do not mean to dismiss what appears
to be a carefully wrought piece of technical exposition, and perhaps it
is simple-minded of me, but I asked a very simple question as to how
"frequency" can be defined in such a case, and I do not see a clear
response to this question in your reply. Does the concept of frequency
apply in such a case, meaningfully?

Now, as long as we are on the subject of possibly stupid questions, let
me pose the following to you.

A transformer primary coil is fed half-wave rectified current in the
form of a train of DC pulses (each from zero to peak and back to zero).
 This produces a series of varying magnetic pulses.

Near the primary is another wire:

       ------>------

which is part of an isolated circuit such that current induced in it
flows in the direction indicated by the arrow.

Below this is a second wire which is part of a separate isolated
circuit parallel to that of the first wire:

       ------>------

       ------>------

so that it too has induced current flowing in the same direction (as
indicated by its arrow).

Next, each of these secondary circuits is interrupted by removing all
but the already depicted sections of straight wire near the transformer
primary. (Removal is suggested by "xxx".)

    xxx------>------xxx

    xxx------>------xxx

(Here, the arrows are left merely to recall the direction of induced
current flow before each secondary circuit was interrupted.)

Next, the two remaining wires are joined into a single circuit by
soldering a vertical straight wire across each end as shown:

      |------>------|
      | |
      |------>------|

The resulting circuit is now identical to Hansen's "one-loop
secondary". Of course, the arrows depicting the previous current flows
would, if applicable to the new circuit, indicate contrary and mutually
cancelling induced electromotive forces.

The current induced in the new circuit can flow in only one direction.
Which of the two horizontal wires "flips its polarity", and why? Does
the magnetic field act non-locally? Does it know that the circuit
configuration (but not the orientation of the original wire sections
near the primary) has changed? Doesn't the magnetic pulse induce EMF
in those original sections nearest the primary *before* propagating to
parts of the circuit which are farther away? How do the field lines
moving through near portions know what the configuration of the rest of
the circuit is?
 
    .
Mark Adkins
msadkins04@yahoo.com

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