Question
Define the term ‘mutual inductance’ between the two coils. Obtain the expression for mutual inductance of a pair of long coaxial solenoids each of length l and radii r1 and r2 (r2 >> r1). Total number of turns in the two solenoids is N1 and N2 respectively.
Solution
The ratio of magnetic flux passing through one coil to the current passing through the other is known as mutual inductance between the two coils.
Consider current I2 flowing through the outer coil.
Magnetic field due to current I2 is given by,
Therefore, resultant magnetic flux linked with the inner coil is,