耦合係數K = Φ12Φ1 = 4m5m = 0.8
L1 = N1 Φ1I1 = 100 5m5 =0.1H
M = N2 Φ12I1 = 200 4m5 = 0.16H
M = K √L1L2
0.16 = 0.8√0.1L2
L2=0.4H