Re: Magnetic Force with Tesla Coil?

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Bob \(R.A.\) Jones" <a1accounting-at-bellsouth-dot-net> 

Hi,

Actually the magnetic field will only penetrate to a skin depth(1/e) of  the
material at the relevant frequency.   Which in the case of typical Tesla
coil frequencies is going to be 1mm or less for usually metals including
ferrous. In addition at typical Tesla coil frequencies phase of the induced
magnetic filed will be such that on average its  repulsive. i.e. the induced
surface currents shield the bulk of the material. (Lenze's Law).

  However I am not certain why the average force is less compared to the same
low frequency or dc field. Presumably at low frequencies or DC the filed can
be increased say a hundred times by ferromagnetic materials were as at Tesla
frequencies the most that can happen if its conductive is to cancel the
field.  So the force will be 100 times less and opposite.

Bob Jones

----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Tuesday, July 06, 2004 6:05 PM
Subject: Re: Magnetic Force with Tesla Coil?


 > Original poster: Zagarus Rashkae <arbitrarily_random-at-yahoo-dot-com>
 >
 > Hi Chris,
 >
 > I think that it is because the Tesla coil operates at
 > hundreds of kHz and one isn't likely to notice, say, a
 > variac casing vibrating at that frequency. Plus the
 > magnetic field diminishes rapidly with distance, and
 > you (hopefully ;) ) aren't right under the primary and
 > so you won't really notice the magnetic field.
 >
 > Regards,
 >
 > Chris Lu
 >
 > --- Tesla list <tesla-at-pupman-dot-com> wrote:
 >  > Original poster: Chris Roberts
 >  > <quezacotl_14000000000000-at-yahoo-dot-com>
 >  >
 >  > Hello list,
 >  > I have recently been thinking about the large
 >  > magnetic field generated by a
 >  > tesla coil, and was puzzled by why a coil doesn't
 >  > behave like a giant
 >  > electromagnet as well? I mean, a large coil's
 >  > primary can run at a
 >  > considerable amount of power, (I'm not just talking
 >  > about pulsed power, I
 >  > mean RMS as well) and it's field is great enough to
 >  > light a flouresent tube
 >  > at a considerable distance, then why is there almost
 >  > no attraction (at
 >  > least, that I have heard of) on ferrous materials?
 >  > Thanks for your insight.
 >  >
 >  > -Chris
 >  >
 >  >
 >  >
 >