Obtain an expression for the mutual inductance of two long co-axial solenoids.

Define mutual inductance. Write its SI unit. Derive an expression for the mutual inductance of two long co-axial solenoids of same length wound one over the other.

Write an expression for mutual inductance of two co-axial solenoids.

Define mutual inductance between a pair of coils. Derive expression for the mutual inductance of two long coaxial solenoids of same length wound one over the other.