Page "Inductance" Paragraph 14

Here N < sub > m </ sub > denotes the number of turns in loop m, Φ < sub > m </ sub > the magnetic flux through this loop, and L < sub > m, n </ sub > are some constants.

This equation follows from Ampere's law-magnetic fields and fluxes are linear functions of the currents.

By Faraday's law of induction we have