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 : (\(\alpha_{Cu} \)= 1.7 × 10^–5 K^–1 and (\(\alpha_{Al}\) = 2.2 × 10^–5 K^–1)

68 cm

\(\alpha_{Cu} L_{Cu}\) = \(\alpha_{Al} L_{Al}\)

\(\alpha_Cu \)= 1.7 × 10^–5 K^–1 ; (\(\alpha _{Al} \) = 2.2 × 10^–5 K^–1

\(L_{Cu}\) = 88 cm

\(L_{Al}\) = 68 cm