Spiral Strip Inductor

Hi :

I take a strip of copper, width w and thickness t, wind a spiral coil of N
turns with an inner diameter d1 and an outer diameter d2 (no iron, just
plastic spacers and air).

Does anyone know a method (numerical or closed-form) for determining the
inductance ?

There are a few Java calculators for spiral coils online, but it's not clear
if they refer to wire or strip in a spiral.

Thanks
Gary


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