Re: Displacement Current Revisited

On 03/23/99 23:30:19 John H. Couture wrote:

>  Richard W. -
>  I understand the near field to be due to the RF currents that are flowing
>in the secondary coil. According to Faraday an osillating current creates a
>magnetic field around the conductor. I believe this field could be dectected
>by a compass if the it is strong enough and if the sine wave is
>unsymmetrical as Tesla indicated. This current is the same RF current that
>produces the electromagnetic field radiating from the coil. It is also the
>same current that charges the toroid.
>  Do I understand correctly that you performed the compass test?
>  If this test works I agree with you that it would give the polarity
>regarding the offset of the wave.
>  John Couture


John and List,

The TC and compass test requires the TC to be aligned horizontally because
the compass needle must always lie in a horizontal plane. The reason for 
this is that the magnetic field around the TC is longitudnal to the long 
axis of the coil.  The compass will align itself with the longitudnal axis 
of the TC and its magnetic field.  My current TC cannot be placed in the 
horizontal position due to size and construction.

I placed a small gauge CU wire above, perpendicular to the needle and 
across the center of a small compass.  Passing a DC current through 
the wire causes the needle to deflect and align itself with the wire.
Placing the wire under the compass causes reverse alignment with the wire.
The circular magnetic fields around a wire with DC current cause alignment 
or the magnetic field of the compass needle.  The circular magnetic
fields are 180 degrees out of phase above and below the compass.

I made a small air core solenoid out of a plastic drinking straw.  The 
straw is 1/4" OD.  I placed a wooden chop stick inside the straw and 
wound 27 ga enameled CU wire on the straw.  It's very easy to hold 
and rotate the wooden dowel with one hand while guiding the wire with 
the opposite hand.  It took about 20 minutes to make a close wound coil
about 6" long.  It's like a minature TC.  Probably an extremely high 
resonate frequency.  Still a fun thing to do and experiment with.

I placed the air core solenoid coil above, perpendicular to the needle and 
across the center of a small compass.  Passing a DC current through the 
solenoid causes deflection and alignment of the needle with the long 
axis of the coil and its magnetic field.  The N seeking end of the needle 
aligns with the Negative end of the coil.  This happens with the coil 
below or above the compass.  A piece of 1/8" Fe rod in the air coil 
accentuates the effect.

I charged a 1 uF cap to 24 vDC and discharged it through the coil and
there was no compass deflection.  I put a forward biased diode in the 
circuit and discharged the cap into the coil.  There was a strong 
deflection.  The explanation is that the cap and coil in series form 
an ordinary tank circuit.  The tank oscillations, although damped, were 
essentially symetrical and affected the compass equally in both 
directions.  There is a significant amount of mechanical inertia in 
a compass and it has a very low frequency response.  Of course, the 
diode only permits the DC current in one direction and the compass 
responds accordingly.

Without doubt there will have to be DC bias in a TC to affect a
compass.  TC DC current has been independantly shown to exist 
my multiple experimenters.  Perhaps some one on this list will approach 
a horizontal TC with a compass on a long insulated pole.  Let us 
know what happens.