Example:Inside the magnetic material with permeability u is a straight long wire and rectangular loop as the figure shows.find the multi inductance solution B= 2πr dΦ=BdS =41 ldr dr 2元r a+b Φ L= n 2元r 2元 a Φ M= =w1 a+b 2π aExample: Inside the magnetic material with permeability  is a straight long wire and rectangular loop as the figure shows.find the multi inductance solution r dr a b l I r I B o   2  ldr r I d BdS o   2    a Il a b dr r a b Il a o o       ln 2 2    a l a b I M o     ln 2 