Explain energy transfer in electric circuits. Prove that the energy liberated from an electric circuit is given by $\mathrm{W}=\mathrm{V} \mathrm{I} \mathrm{t}={\mathrm{I}}^{2 }\mathrm{R} \mathrm{t}={\mathrm{V}}^2\mathrm{t} /\mathrm{R},$ where symbols have usual meanings.