Miss Inductance

If a current i is establish through each of the N winding of an inductor, a magnetuc flux links those windings.

Then, the inductance of the inductor is define as

The SI unit of inductance - henry (H)

1 henry = 1 H = 1 T.m^2/A

Inductance of solenoid

Consider along solenoid of cross sectional A. There will be inductance per unit length near its middle. 

So we must calculate the flux linkage set up by a given current.

And the given magnetic field there given ;

source : http://hyperphysics.phy-astr.gsu.edu

 Hence the inductance per unit length of a solenoid is

Noted that, this Miss Inductance is like capacitor, also depends only on geometry of the device. If we have triple of n thats mean we triple the flux each turns thus the inductance of L by a factor of 9.