Three vertical wires, one of steel and two of copper, are suspended in the same vertical plane from a horizontal support. They are all of same length and same area of cross-section and carry a load by means of a rigid cross bar at their cnds. The load is increased and the temperature is changed in such a way that the stress in each wire is increased by \( 10 N / mm ^{2} \). Find the change in temperature. \( E_{s}=2 E_{s u}=200 GPa , \alpha_{ r }=11 \times 10^{-6} /{ }^{\circ} C , \alpha_{s w }=18 \times \) \( 10^{-6 /{ }^{\circ} C } \)
