The self inductance of a solenoid of length L, area of cross-section A and having N turns is-

Explanation

The magnetic field inside a long solenoid.
`B = mu_0 nI = mu_0 (N/l) l`
The flux associated with each turn `phi_(turn) = B.A`
`phi_(turn) = mu_0 (N/l) lA`
`phi_("total") = N.phi_(turn) = ((mu_0 N^2 A)/(l))l`
`L = (phi_("total"))/(l) rArr L = ((mu_0 N^2 A)/(l))`
The self-inductance depends purely on geometric parameters.