# Re: Notes on Terry's observations

```Tesla List wrote:

> The wire on the
> coil is 2690 feet long.  That gives a 1/4 wave frequency of 91410 Hz. I
> could not find any correlation between the frequency and anything I
> measured but I don't think that is a surprise.  However, I did try...

There is absolutely no relation between the wire length and the
resonances
of a spiral (other than geometrical consequences, of course). What
counts
are the inductance and the capacitance (to infinity) per unit of length
of
the coil. This is clearly stated on Fleming's book (1910). The line so
formed is somewhat irregular, because the inductance decreases at the
ends (Fleming says this), and also probably because the capacitance is
higher at the bottom end, for a vertical coil (Fleming used horizontal
coils to avoid this).

What I said about the extra resonances of a coil is that they are
related to the resonances of a -coil- without top load. A top load
shifts the extra modes to low frequency, but not more than to the
next lower multiple of the main resonance frequency without top load.
Of course, these frequencies are all somewhat "out of place" due to
the irregularities in the "line".

> IMHO, I think racing arcs are caused by pure transformer action as the
> secondary coil is suddenly hit by the first impulse from the primary.  A 15
> turn primary mixed with the lower say 300 turns of the secondary gives a
> voltage transformation ratio of 20.  So the 20kV on the primary gets
> transformed to 400kV before the resonant action can start.  Raising the
> secondary lowers the coupling and reduces the initial induced voltages so
> the arcs can be stopped by moving the coils away from each other.  I have
> not spent a great deal of time thinking about that, so perhaps I am wrong
> there??

Can't be. The capacitances of the secondary coil don't allow this sudden
increase in voltage. What happens is just the usual transient, that
starts from zero voltage and zero current in the secondary coil.

Antonio Carlos M. de Queiroz

```