# Re: Classic coil

```>
>>From Hans.Grimstad-at-maxware.no Sun Dec  1 22:28:46 1996
>Date: Sun, 1 Dec 1996 23:34:05 +0100
>To: tesla-at-pupman-dot-com
>Subject: Classic coil
>
>Hello everyone !
>
>I have been rereading my reprint of Teslas lecture to the Institution of
Electrical
>Engineers in London. On page 15, he describes a small bipolar coil. Each of
the
>terminals of the coil is connected to a circle, one is 80 cm in diameter,
the other is
>30 cm in diameter. During operation of the coil, the discharges between the
>terminals produce a "luminous sheet" with an area of about 0.43 square
metre. He
>states that he in earlier experiments, using bigger circles had covered an
area of
>more than one square metre.
>This coil has 2 primaries with 96 turns in each, and two secondaries with
260 turns in
>each. When both the primaries and the secondaries are connected in series,
this
>gives a ratio of conversion of about 1:2.7.
>
>It seems that a lot of people are designing coils with much bigger
conversion ratios
>(1:67 for a coil with 1000 windings on the secondary and 15 on the
primary). I would
>say that Teslas results with this coil are quite impressive. Why the big
secondaries
>in "modern" coils ?
>
>
>

Hans,
I do not believe that Tesla coils 'use' the ratio concept.
I believe it is the product of resonance. In the resonance formula:
1
RFrequency = ------------------
2 * pi * SQRT(L*C)

it is possible to adjust L(inducatnce) and C(capacitance) of the
circuit while still attaining a certain frequency. In the Tesla
coil it is Large C, Small L in the primary while in the secondary
it is Big L, Small C. When both work out to the same resonant
frequency, you have a resonant transformer, as with a Tesla coil
and I dont think turns ratio plays much of a part, if any.

Bob
```