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Re: Jacobsladder-Oscillator
Original poster: "Kurt Schraner" <k.schraner@xxxxxxxxxxx>
Tesla list wrote:
Original poster: Jim Lux <jimlux@xxxxxxxxxxxxx>
At 05:24 PM 3/28/2007, you wrote:
Original poster: "Kurt Schraner" <k.schraner@xxxxxxxxxxx>
<snip>
Hi Jim,
I generally concur with your review of the situation, as long as the
Jacobsladder is used in its usual way, with the climbing arcs.
BTW: In our case, we have tried to determine the induction-coil
short circuit current, by measuring it with a moving iron armature
ammeter, and have found a value of 0.4A(rms). Well, may be not very
precise, but should give an order of magnitude (measured at the same
conditions, as our experiment). I've not yet calculated the
repelling magnetic force (with spark), which should be compared to
the attracting electric force (without spark, at ~50-60kV). (JL
heigth is 2m; average distance of rods ~5cm; rod diameter 0.8cm).
1 amp, 1 meter spacing, 1 meter long, = 1 Newton
Your wires are 5 cm apart. Average length is 1 meter (when spark is
half way up), and you have 0.4A, so
0.4/0.05 or about 8 N.. that's a fair amount of force...
Sorry Jim, I've to disagree respectfully. I
think, in the speed of answering, happened a
little error: In my physics textbooks I read:
1 amp, 1 meter spacing, 1 meter long, = 2*1e-7 Newton
(which is connected with the definition of the Ampère)
And the formula for magnetic force between 2 (long-)parallel wires:
F = (mue0/2pi)*(length/distance)*current^2
with mue0 = 4pi*1e-7 [H/m]; length=2m; distance=0.05m; current=0.4A
leads to a repelling force of 1.28e-6 Newton for the case of my JL.
This result also seems more plausible for my
gut-feelings, considering the small currents involved.
I can't imagine the electrostatic force being that high. I seem to
recall that the electrostatic force between the top of my 400kV Van
de Graaff with a 40cm spheroid to a similar sphereoid 20cm away was
about 1 Newton... That's a lot more area and a lot more voltage.
By calculation I get around 0.4 Newton. And the
wires were attracting, not repelling each other,
in the experiment below. There was also no
measurable current, except at the very end of the
movie, when we intentionally provoked a spark.
An experiment, proposed by Gerry Reynolds, which also is
demonstrating the electric/elecrostatic-force influence, was posted
yesterday.
Better, I had given the archive link before:
http://www.pupman.com/listarchives/2007/Mar/msg00635.html
...or, at least the link to the (3.6M)movie:
http://twfpowerelectronics.com/~kurt/InductionCoils/P1000678.MOV
Thanks, and best regards,
Kurt