# Re: [TCML] Tesla help

```The inductive reactance X(L) can be found by measuring the impedance Z and applying the equation Z= Sq Rt [ X(L)^2 + R^2].  The impedance Z is simply the AC resistance which for a typical tesla secondary would require a low input AC voltage (such as a variac)  to measure that AC current and then applying  V=IZ, where Z is simply the AC analogy of V=IR in DC circuits. The actual inductance L of the secondary could then be deduced from  the equation X(L)= 2 pi* f *L where solving for L yields L =X(L)/2pi*f.

On Thursday, February 7, 2019, 10:05:46 AM EST, jimlux <jimlux@xxxxxxxxxxxxx> wrote:

On 2/6/19 8:05 PM, Anthony Dresden wrote:
> First off, this is amazing thank you so much for providing this site.
> I am having some difficulty with resonance formula. I can solve for
> Xc(because frequency,and capacity are given numbers) but how do I get
> inductive reactance figures,

Xl = 2*pi*f*L

There are many formulas for calculating L using number of turns and the
dimensions of the coil.
Wheeler's equation is widely used as a pretty good approximation.

the two forms that turn up in tesla coils are the single layer solenoid
(for the secondary) and the flat single layer pancake (for the primary)

I don't know that the secondary links on my Wheeler page still work.

What most folks do is use a program like JavaTC (google for it, there's

I have tried formulas that involve the number
> of coils, gauge of wire, resistance, frequency,ect. Could you please she'd
> some light on the subject. As I don't have the instraments to collect this
> data.
> Thank you much.
> Marcus Anthony.
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> Tesla mailing list
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> https://www.pupman.com/mailman/listinfo/tesla
>

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```