# Re: Question about capacitors for coil

```Original poster: John <guipenguin@xxxxxxxxx>

```
Well I am limited to #28g wire..... so with a 4 inch diameter...what would be a better ratio? If I go 4" Diameter and 20" winding heigth... I am at about 1460 turns.... if I do 1:6 for a heigth of 24 I am at about 1751 turns.... and I read some where I shouldn't go much over 1k turns....
```
On 10/2/06, Tesla list <<mailto:tesla@xxxxxxxxxx>tesla@xxxxxxxxxx> wrote:
```
Original poster: "resonance" <<mailto:resonance@xxxxxxxxxxxx>resonance@xxxxxxxxxxxx>
```

Sounds like an interesting project.  I've often wondered how the 5:1
coils work so well.  I now am convinced the energy is pumped into the
base of the coil and it is propogated up like coil in a standing wave
effect.  Seems to be the only explanation when a coil has a base very
low to the concrete floor or has a large nst case under
it.  Otherwise the mag field would be distorted or shorted by all the
nearby metal.  In the case of the nst this is connected directly to
ground which would make matters worse.

Dr. Resonance
```
----- Original Message ----- From: "Tesla list" <<mailto:tesla@xxxxxxxxxx> tesla@xxxxxxxxxx>
```To: <<mailto:tesla@xxxxxxxxxx>tesla@xxxxxxxxxx>
Sent: Monday, October 02, 2006 2:41 AM
Subject: Re: Question about capacitors for coil

```
>Original poster: "Gerry Reynolds" < <mailto:gerryreynolds@xxxxxxxxxxxxx>gerryreynolds@xxxxxxxxxxxxx>
```>
>Hi DC,
>
>I've been thinking that the relationship of inductance to number of
>turns squared has a lot of error in it for tall skinny coils.  I
>believe the equation of:
>
>L = uo*N^2*Area / length
>
>assumes that the coupling from each turn on the solenoid is 100%
>into all the other turns so that the total flux thru any one turn is
>proportional to the number of turns.  For a very short and very fat
>coil, I believe this relationship would be close.  For TC
>secondaries with H/D ratio of say 5:1, there is a lot of error in
>the number_of_turns squared relationship.  I bet the real exponent
>is between 1 and 2 for typical TC geometries.  I might try to plot
>this using JavaTC and see if there is an effective exponent given H/D.
>
>Gerry R.
>
```
>>Original poster: "resonance" < <mailto:resonance@xxxxxxxxxxxx>resonance@xxxxxxxxxxxx>
```>>
>>Also, inductance varies as the square of the number of turns, so
>>you want a lot of turns on the sec.
>
>
>
>

```