12 Two long co-axial
solenoids of same
length l Rationalised 2023-24
Electromagnetic
Induction
167
 EXAMPLE 6 8
We explained the above example with air as the medium within the
solenoids Instead, if a medium of relative permeability mr had been present,
the mutual inductance would be
M =mr m0 n1n2p r2
1 l
It is also important to know that the mutual inductance of a pair of
coils, solenoids, etc