Re: Displacement Current Revisited

  Richard W. -

  Thank you for doing the compass test. To my knowledge no one has ever made
this test before now. As Ed  points out it is a known fact that there is a
DC bias in the operating Tesla coil. The question is whether this bias is
due to currents in the secondary or due to rectification in the discharge of
a spark. Is this bias due to an unsymmetrical waveform?

  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


At 07:17 PM 3/28/99 -0700, you wrote:
>Original Poster: rwall-at-ix-dot-netcom-dot-com 
>Yesterday I lashed up a horizontal TC.  I bolted my 4" coil to a piece of
>1/2 plywood with three 1/4" nylon bolts and fastened an old 6" helical primary

>to the same bolts.  There was only 1" between the primary and secondary.  
>Without major retuning, I placed it in the horizontal position.  The TC was 
>placed horizontally with the base East and ball termination West.  I attached 
>a cheap plastic compass to a 5' wooden stick with masking tape.
>With the coil firing at low power I approached the side of the coil with the 
>compass.  The compass reacted to the TC magnetic field(s).  The fields were
>nonuniform, probably due to poor tuning.  At this point I noticed occasional
>racing sparks at the lower 1/3 of the coil arcing to the top of the primary. 
-------------------   snip