Re: Magnetic Force with Tesla Coil?

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

Original poster: davep-at-quik-dot-com 


 >  > I have recently been thinking about the large magnetic field
 >> generated by a tesla coil,
    How large is it?
    Have you measured it?

 >> and was puzzled by why a coil doesn't behave like a giant
 >> electromagnet as well?
    How do electromagnets at 100KHz (or whatever) behave?
     Hint 1) Compasses, etc ignore them.  Too Fast.
     Hint 2) maths (somewhat simplified) for mag field
     strenghts are current times turns.
       Primaries have few turns.
       Primary currents are low (in 'giant elemtromagnet'
       terms.) Such like deal in hundreds of amps of DC.

 >> I mean, a large coil's primary can run at a
 >> considerable amount of power,
    cf as above.  mag fiekd depends on current, rather than power.

 >> (I'm not just talking about pulsed power, I mean RMS as well) and
 >> it's field is great enough to light a flourescent tube
     Hint 3) Is this lit by _mag_ field or electrical?
     Hint 4) How large a field is required to do this?

 >  > at a considerable distance, then why is there almost no attraction
 >> (at least, that I have heard of) on ferrous materials?
     As noted by others  frequencies are high, leading to inefficient
     attraction, mag fields such as they are fall of rapidly with
     distance, Also, mag fields are (in 'giant electromagnet' terms)
     relatively low.

     (Story:
      I worked, briefly around a spot welder, doing EMI
      measurements.  Long time ago.   DC, 100s amps.
      THAT field would reach out and shake the electrons in the
      scope driving the display crazy...  8)>>)

best
  dwp