Calculate the inductance of a unit length of a double tape line if the tapes are separated by a distance h which is considerably less than their width b, namely, $\text{b/h}=50$ .

Field between plates $=\frac{{\mu }_{0}i}{2}+\frac{{\mu }_{0}i}{2}={\mu }_{0}i$

$\text{B}={\mu }_{0}i=\frac{{\mu }_{0}I}{\text{b}}\left(\because i=I\text{/b}\right)$

Energy stored perunit volume$=\frac{{\text{B}}^{\text{2}}}{2{\mu }_0}=\frac{{\mu }_0^2{I}^2}{2{\mu }_0{\text{b}}^{\text{2}}}$

Energy $=\frac{{\mu }_0{I}^2}{{\text{2b}}^2}$  (volume) $=\frac{{\mu }_0{I}^2}{{\text{2b}}^2}\left(l\text{bh}\right)$

$\Rightarrow \frac{1}{2}L{i}^2=\frac{{\mu }_0{I}^2}{2\text{b}}l\text{h}$

$\text{L}=\frac{{\mu }_0\text{h}l}{\text{b}}$

$\frac{\text{L}}{l}=\frac{{\mu }_0\text{h}}{\text{b}}$