Q. A copper rod of $88 \,cm$ and an aluminium rod of unknown length have their increase in length independent of increase in temperature. The length of aluminium rod is $(a_{C_{u}}=1.7 \times 10^{-5}\,K^{-1}$ and $\left.a_{A_{l}}=2.2 \times 10^{-5} K^{-1}\right)$
Solution: