I was searching for few hours on this topic but I was unable to find any formula/research so I'm asking here. Please if this question is a duplicate let me know.
Right now I do not have the equipment to prove or deny the following formula I came up with.
I have two (same) tht axial inductors. Those in a 1/4w resistor-like shape (with PVC coating). I do not know the core material or the number of windings. But I'm trying to estimate the Mutual inductance M.
Knowing that inductance L of each inductor is given by:
L = u0 * ur * N^2 * A / l
(Better here: http://www.electronics-tutorials.ws/inductor/inductance.html)
And having the M impedance formula (found here: http://www.electronics-tutorials.ws/inductor/mutual-inductance.html)
M = u0 * ur * N1 * N2 * A / d
(Distance referred as 'l' in the article replaced with 'd' for clearance)
Assuming the following:
ur - all cores are of same material N1 = N2 A - all cores areas are same
I came up that M of two same axial inductors with inductance L, length 'l' at distance 'd' is:
M = L * l / d
...sounds too simple, to be real... But is this correct? It mean that my 47uH inductors with l=2.9mm at a distance d=6mm has a mutual inductance M=22uH sounds huge?