Explanation

Magnetic energy $= \frac{1}{2}Li^{2} = \frac{LQ^{2}}{2t^{2}}$ $\lbrack L = inductance,\ i = current.\rbrack$ Energy has the dimensions $= \left\lbrack ML^{2}T^{- 2} \right\rbrack.$ Equate the dimensions, we have $\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \left\lbrack ML^{2}T^{- 2} \right\rbrack = (henry) \times \frac{\left\lbrack Q^{2} \right\rbrack\ }{\left\lbrack T^{2} \right\rbrack}$ $\Rightarrow \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \lbrack henry\rbrack = \frac{\left\lbrack ML^{2} \right\rbrack}{\left\lbrack Q^{2} \right\rbrack}$