For these simple co-axial solenoids it is possible to
calculate M12 The magnetic field due to the current I2 in
S2 is m0n2I2 The resulting flux linkage with coil S1 is,
(
) (
) (
)
2
1
1
1
1
0
2 2
N
n l
r
n I
Φ
µ
=
π
         
2
0
1
2
1
2
n n
r l I
=µ
π
(6 8)
where n1l is the total number of turns in solenoid S1