Two different wires having lengths L1 and L2,
and respective temperature coefficient of linear
expansion $\alpha $1 and $\alpha $2, are joined end-to-end.
Then the effective temperature coefficient of
linear expansion is :
$2\sqrt {{\alpha _1}{\alpha _2}} $
$4{{{\alpha _1}{\alpha _2}} \over {{\alpha _1} + {\alpha _2}}}{{{L_2}{L_1}} \over {{{\left( {{L_2} + {L_1}} \right)}^2}}}$
${{{\alpha _1} + {\alpha _2}} \over 2}$
${{{\alpha _1}{L_1} + {\alpha _2}{L_2}} \over {{L_1} + {L_2}}}$
