• # question_answer If two rods of length L and 2L having coefficients of linear expansion $\alpha$ and $2\alpha$ respectively are connected so that total length becomes 3L, the average coefficient of linear expansion of the composite rod equals : A) $\frac{3}{2}\alpha$                              B) $\frac{5}{2}\alpha$ C) $\frac{5}{3}\alpha$                  D) none of these

 $(3L){{\alpha }_{_{eff}}}\Delta \theta =L\alpha \Delta \theta +2L(2\alpha )(\Delta \theta )$ $\therefore$      ${{\alpha }_{eff}}=\frac{5}{3}\alpha$