Re: Displacement Current Revisited
I reply to so little nowadays as there is little new to reply to. However,
was a superb experiment and the great thing about the compass is it cannot
to sinusodial EM fields.
(such as damped waves) It is responding to a NET effect of what amounts to a
direct current flowing SOMEWHERE. Richard Wall is a first rate experimenter
this is unexpected by me, as I though the DC was all and electrostatic wave,
however there seems to be some net currents in the DC direction too! I gotta'
Richard Hull, TCBOR
Tesla List 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
> 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.
> I could actually touch the compass to the side of the coil and there was no
> arcing to the compass, although if I approached the coil termination there
> were small arcs to the compass which did not seem to affect the needle
> At about the upper 1/3 of the TC, the compass was attracted to a longitudnal
> orientation with the long axis of the coil. The attraction was not uniform
> and was intermittantly strongest with the larger and longer sparks. The
> North seeking needle was attracted to the base of the secondary. If there
> is similarity to the drinking straw air core solenoid, this would be the
> negative end of the coil.
> Strangly enough, I also noticed that the end of the compass needle tended to
> deflect and dip or rise sometimes when the side of the coil was approached.
> Could there be more than one magnetic field orientation with a TC? I turned
> the TC vertically and approached the mid section of the TC from the East.
> The North seeking end of the needle swung East away from the coil.
> Approaching from the West the North seeking end of the needle again swung
> East toward he coil.
> At this point the arcing from primary to secondary was almost constant and
> introduction of HV 60 Hz current into the secondary made it too dangerous to
> continue with this experimental platform. I stopped. Inspection reveals two
> loops of burned out Cu wire on the secondary. I attribute this to poor
> and the closeness of the primary to the secondary.
> Conclusions: There are definitely magnetic fields associated with a
> TC as measured with a compass. The compass is a crude, but easy, qualitative
> way to assess magnetic fields of a TC. There is an overall magnetic field,
> measured by the compass, that that is oriented longitudnally with the long
> of the TC secondary. There is a net sum bias of the alternating magnetic
> due to a DC current in the coil. If the DC current air coil solenoid and
> compass experiment is extended to the TC, the base of the coil has a negative
> DC bias with respect to the termination. This magnetic field is not
> but varies irregurally with the intensity of the discharges from the coil.
> (I leave it to others to determine if this DC current and magnetic field
> appears most strongly during discharges is from some type of gaseous
> rectification or is intrinsic to the TC) There is also "another" magnetic
> that appears perpendicular to the first magnetic field and the long axis of
> the coil. This magnetic field would appear consistant with the DC current
> single wire compass experiment. As improbable as it may seem, the long axis
> of the TC secondary can be viewed as a long wire. I leave it to the
> transmission ine experts to explain this one.
> The compass is quite crude, but does respond to TC magnetic fields. Further
> evaluation should be carried out with more sensitive and precise devices.
> Perhaps better detectors such as Terry's planar antenna and fiber optics or
> Hall devices will better map these fields and give a better explanation of
> TC function.