When the key is at position (B) for a long time; the energy stored in the inductor is :

${\text{U}}_{\text{B}}=\frac{1}{2}{\text{Li}}_0^2=\frac{1}{2}·\text{L}·{\left(\frac{\text{E}}{{\text{R}}_2}\right)}^2=\frac{{\text{LE}}^2}{2{\text{R}}_2^2}$

          

This whole energy will be dissipated in the form of heat when the inductor is connected to ${\mathrm{R}}_1$ and no source is connected.