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Re: Tesla Coil RF Transmitter

Original poster: Jim Lux <jimlux@xxxxxxxxxxxxx>

At 10:18 AM 9/15/2005, you wrote: 
Original poster: "Malcolm Watts" <m.j.watts@xxxxxxxxxxxx>


> So, if one takes a charged macroscopic body and waves it
> longitudnally back and forth a longitudinal time variable electric
> field is produced.  This field is a variable E field (sans magnetic
> field) and may be received at a distance by various methods empolying
> dielectrics in the receiver.  Real energy is conveyed.  If in doubt,
> this is an experimentally proven fact that you may wish to reproduce
> for youself.
>
> In this electrostatic event energy is surely transferred without the
> benefit of a magnetic field or current.  If you see it otherwise,
> please produce the experiment.
>
> Regards,
>
> Stork

Doesn't a moving charge or charged body generate a magnetic field
component?

Malcolm

Taking a lump of charge and moving it back and forth is a fine description of an antenna. Not surprisingly, it radiates an EM wave. If the magnitude of motion is small compared to the speed of moving/speed of light, then it is, in antenna terms, a "physically small radiator", and, in the limit, a Hertzian dipole. If the magnitude is large compared to the speed of moving it (say, I move a lump of charge 5 meters back and forth every 33 nsec) then what I've basically done is build a half wave dipole (at 30MHz in this example)

You can analyze this pretty simply. Consider what the E field (in the static case) is, at your "distant observation point" for each possible position of the lump of charge. Then, figure out what the field would be, delayed by a time corresponding to the distance from the lump.