Two steel rods and an aluminium rod of equal length `l_(0)` and equal corss-sectional area are joined rigidly at their ends. All the rods are in state of zero tension at `0^(0)C`. Find the length of the system when the temperature is raised to `theta`. Coefficient of liner expansion of aluminium and steel are `alpha_(a) and alpha_(s)` respectively Young.s modulus of aluminium and steel are `Y_(a) and Y_(s)`.

Answer

`l_(0)[1+(alpha_(a)+2alpha_(s)Y_(s))/(Y_(a)+2Y_(s)).Delta theta]`