Calculate the inuctance of a unit length of a double tape line (Fig) if the tapes are separated by a distance `h` which is considerabley less than their width `b`, namely, `b//h = 50`.

Explanation

Neglecting end effects the magnetic fileld `B`, between the planes, which is mainly parallel to the plates, is `B = mu_(0) (I)/(b)`
(For a derivation see 3.299 b)
Thsu the associated flux per unit length of the plates is
`Phi = mu_(0) (I)/(b) xx h xx 1 = (mu_(0) (h)/(b)) xx L`
So, `L_(1)` = inductance per unit length `= mu_(0) (h)/(b) = 25 nH//m`.