Re: Inertial-dampening systems

msadkins04_at_yahoo.com
Date: 02/08/05 

Date: 8 Feb 2005 15:05:16 -0800

  Adkins:
> >> >
> >> >(2) Take your silly "one-turn secondary" comment literally,
> >> >for a moment; take that wire, disconnect it from the
> >> >transformer circuit, and suspend it in mid-air by some
> >> >well-insulated means, but well within the same distance
> >> >of the magnetic field generated by the primary. Now send
> >> >high-voltage *DC* through the primary; then quickly
> >> >increase that voltage to a much higher DC level. Does
> >> >the "varying magnetic field" generated by it cause gross
> >> >current to flow through the body of that disconnected
> >> >secondary wire?

  Hansen:
> >>
> >> I've just done that. A spool of wire (I don't know how many
> >> turns) connected to a function generator (Stanford Research
> >> Systems DS345) with a 10 ohm resistor in series, and a
> >> scope (Tektronics 2445B) across the resistor to monitor the
> >> current. And a one turn secondary with a 10 ohm series
> >> resistor, and a second channel on the scope across that
> >> resistor. I put a square wave on the primary, and damned
> >> if the secondary didn't spike every time the primary changed
> >> state. I put a sawtooth wave on the primary, and found a
> >> square wave on the secondary with an amplitude that
> >> increases with the frequency of the sawtooth on the primary.
> >

  Adkins:
> >Of course you did. Do you know why? Because you created a completed
> >circuit consisting of: the first part of the wire, the resistor in
> >series with it, the lead of your scope coming off the far side of
the
> >resistor, the scope innards, and the other scope lead connected to
the
> >near side of the resistor. You created a grounded, completed
circuit,
> >and lo and behold, the magnetic pulse induced an electric current.
But
> >only through that circuit. There was no current flow through the
rest
> >of that wire, of course.
>

  Hansen:
>
> You're halfway through freshman physics, right?
>
> The scope, and voltmeters in general, have an input impedence at
least in
> the megaohms. FET inputs are easily in the gigaohms. It's true that
some
> current was flowing into the scope, but a realistic figure is that
about
> a millionth of the current flowed through the scope while the rest
flowed
> through the resistor. The scope has approximately no effect on the
> circuit, which is exactly the intent of its design.

The *intent* of the design is no proof against the ingenuity of fools.
If you design a circuit where the full current flows through the scope
because, in effect, the scope is in series rather than parallel, the
intent cannot prevent the user from drawing false inferences. All of
the current flowed through both the resistor and the scope, because
both were in series. You still don't realize what you did. Snip off
the secondary wire outside the scope leads and repeat the experiment.

  Adkins:
>
> >And if there had been no resistor and no
> >scope, but just a piece of wire, why on earth would you claim to
think
> >that current would flow down its length? Electric current requires
two
> >things: (1) a path; (2) an electromotive potential difference. A
> >straight length of isolated wire provides neither. A closed loop of
> >isolated wire provides neither. There is no current flow there.
> >(Another possibility is direct induction on your scope, but I tend
to
> >discount that.)

  Hansen:
>
> You haven't gotten to Maxwell's equations yet, have you? It's true
that a
> potential that drives a current around in a loop of wire cannot be
created
> by a collection of static charges. I never said otherwise. Now I'm
going
> to quote that equation again, are you ready for it?

You still haven't gotten the gist of what I said above. I don't think
I'll bother repeating myself again.

>
> curl E = -dB/dt
>
> What is the definition of the curl, and how does that relate to
currents
> going around in a circle? You know what dB/dt means, right?

First of all, this is not the integral form of Faraday's law. Curl x E
= -dB/dt is a partial differential equation applying at each point in
space. Do you know the difference between a point and a closed loop?
Curl is an operator of the vector calculus. Faraday's law refers to
the circulation of electric charge, but don't be so bloody
literal-minded ("circles of current")or you'll get into trouble. The
visual models of Victorial gentleman scientists have long since been
dismissed.

  Adkins:
> >> >(3) You can't have it both ways. If a magnetic field of
> >> >16 T, propagating, washing over a frog in an ambient
> >> >magnetic field of 0, is "quasi-stationary", then so is a
> >> >propagated change in that field from 16 T to 32 T. The
> >> > difference in both cases is 16T.

  Hansen:
> >>
> >> Quasi-stationary (I suppose quasistatic is a more common
> >> term) means the field changes slowly enough in the region
> >> of interest that propagation effects can be ignored.
> >> That doesn't mean the magnetic field won't change in the
> >> region of interest. The field versus time will be
> >> determined by the current versus time in the magnet.
> >> But in the quasistatic approximation, if you change the
> >> current at point A, you don't worry about how long it
> >> takes that to affect the field at point B.
> >

  Adkins:
> >First, a field propagating at c does not cause changes slowly. A
> >faster influence cannot be postulated in contemporary physical
models.
>
> What we have here is a failure to communicate.
>
> Suppose you have a magnet that happens to put one tesla per amp into
a
> test region, it starts with zero current, and you have your finger on
the
> current adjust.

<snip>

Suppose we have a fully magnetized chamber with a 16 T ambient magnetic
field. Suppose a frog is shielded from that field, and sits in an
environment with an ambient magnetic field of essentially zero.
Suppose that shielding is eliminated. The change in B over the length
of the frog takes place in the time it takes a field propagating at c
to move that distance. Say the frog is about 2 cm. c is 300,000
meters per second. Do the math and calculate dB/dt. Then explain why,
if things work the way you say, the frog is not electrocuted.

<snip>

  Adkins:
> >And you can't ignore it, because that change in magnetic field
strength
> >is what causes magnetization. The subsequent, continuing, field of
the
> >same strength merely maintains it, and does work if it moves the
frog.
> >Consider how a cyclotron works. The magnets cannot impart
additional
> >rotational energy to an electron whirling around in it: they can
only
> >maintain its orbit.
>
> STATIC magnetic fields cannot do work on a particle. A dB/dt is not
> static, it produces a -curl E, and an electric field can do work.

No kidding.

>
> >
> >In order to magnetize that frog, you have to increase atomic
> >spin-energy in each of its atoms. That's what that 2 amps of
> >non-dissipative atomic microcurrent represents (and by the way,
these
> >are ubiquitous, not surface, currents, because every molecule in its
> >body is magnetized. This magnetization is negative relative to the
>
> Maybe you're thinking of a flux. A current is a net flow. I had
assumed
> at some point you'd seen in your text a diagram with a bunch of
little
> boxes with arrows drawn inside an object that shows how a segment of
> current about one point is cancelled out by the segment of current
about
> an adjacent point.

I'm overwhelmed by your command of nomenclature. Now go to the
Netherlands site I gave a URL for and read page 312 of the Eur. J.
Phys. article there:

http://www.hfml.science.ru.nl/frog.ejp.pdf
 
          .
Mark Adkins
msadkins04@yahoo.com

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