[Prev][Next][Index][Thread]
Re: Displacement current
Tesla List wrote:
>
> Original Poster: "B**2" <bensonbd-at-erols-dot-com>
>
> Hi All,
> I found an article wherein the radiated energy from a loop of 1.5
> meter radius, that has an 8 microFarad capacitor charged to 60 kV
> discharged into it, is calculated. The frequency is about 67
> kiloHertz. The author claims that, with an initial stored energy of
> 14.4 kiloJoules and with a discharge current of 45,000 Amperes, the
> total radiated energy is 1.12 microJoules. The calculations were done
> on a computer with subroutines from the CERN program library. This
> loss mechanism would seem to be very small for a Tesla coil primary
> and secondary if this calculation is correct (at this frequency). The
> article also gives references to several papers by Peter Graneau, P.
> T. Pappas, Hatzikonstantinou, and P. G. Moyssides the author.
>
> PENDULUM EXPERIMENTS AND THE FUNDAMENTAL LAWS OF ELECTRODYNAMICS
> By P. G. Moyssides
> IEEE TRANSACTIONS ON MAGNETICS
> March 1999, Volume 35, Number 2, Pages1060 to 1069
>
> Barry
>
Did they give a loss for the loop/capacitor?
This sounds about right.... If you calculate the radiation resistance of
the loop using Rr = 31200 * Area^2/lambda^4 = 31200 * (1.76^2)/ (4500^4)
you get about 2.4E-10 ohms. They showed a radiation efficiency of
7E-11, implying that the loop resistance/loss must have been around 3
ohms, which is actually quite high for a loop that size (unless they
made it out of something quite lossy, or maybe the cap is lossy).
Small loops (compared to a wavelength) make terrible antennas.