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voidnoise

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Apologies if this has been posted/answered else where but I could not find it.

I am trying to develop a model in MATLAB for a simple (short cylindrical coil) air cored transformer. So far I am capable of defining the coil such as core diameter, turns, length etc.., calculate the coil resistance, input current, magnetic field produced, flux density at a given distance along the central axis, and potential emf for the secondary coil.

The next thing I need to work out is the impedance Z.

Z = sqrt(R^2 + X^2)

where X = XL - XC

I can calculate XL because I have found an equation to work out the inductance of the coil, L.

L = (r^2 * N^2)/(9r + 10l)

*from the wiki inductor page

so XL = 2πfL.

I run into problems with capacitive reactance XC. I cannot find anywhere online explaining how to work out the capacitance of a coil so I can calculate the capacitive reactance XC.

XC = 1/(2πFC)

Does anyone here know how to calculate the capacitance of a coil, or even if my understanding is completely off?