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Re: Displacement Current Revisited

At 03:43 PM 3/31/99 -0600, you wrote:
snip...............
>I point out that the above rectification would also produce a net DC current 
>in the secondary.  Unsymmetrical wave form?  These secondary waves are damped 
>sinusoidal waveforms.  Terry has some beautiful examples of these waveforms 
>from his coils.  I guess someone could intregrate the areas of the wave form 
>above and below RF ground looking for asymmetry.  I'm not a math wizard 
>though, so I'll pass.
> 
>>
>>  It is my belief that the instanstaneous currents in the secondary winding
>>are sufficient to affect a compass. The next question is whether the
>>polarity at the secondary terminal is positive or negative. Tests made to
>>date have been contraditory.
>>
>>  John Couture
>
>What is the source of the instantaneous currents in the secondary winding 
>and how would they affect the compass?  The compass has a lot of mechanical 
>inertia and low frequency response.  It will not respond to an instantaneous
>current.  Only a net DC current and magnetic field.
>
snip............
>
>
>RWW

        Although the currents of hundreds of amps in the primary are high, the
time is very short.  The DC "bias" of the wave form is really very low,
especially considering that the firing of the gap is often AC unto itself.  In
my coil's case, the integrated DC bias is in the milliampere/second region in
very short time windows (5 mS) and practically zero for time frames that would
be expected to affect the mass of a mechanical compass (100mS).
        The modeling I have done seems to suggest that the DC "time averaged"
currents are not likely to affect a compass.  However, the sudden currents
would mechanically shock metal objects and I wonder if the shock effects and
not the DC bias is the reason the dial moves.  I wonder, if a number of
compasses were placed in the region, if they all are affected and move in the
same direction as a DC bias would cause or if they would move in random
directions as would be caused by a magnetic shock wave mechanically "hitting"
them?  As anyone who has ever used a compass knows, there are all kinds of
forces that affect the movement of a compass needle...  thus the modern GPS
equivalent :-))

        Terry