\( = \frac{1}{2} \times Y{(\alpha \,\Delta \theta )^2} \times A \times L\)\(\left( {{\rm{Thermal \,\,\,strain}}\frac{l}{L} = \alpha \,\Delta \theta } \right)\)
\( = \frac{1}{2} \times (2 \times {10^{11}}) \times {(18 \times {10^{ - 6}} \times 100)^2} \times 1 \times {10^{ - 4}} \times 1\)\( = 324 \times {10^{ - 1}}\)\(= 32.4 \,J.\)