Passage - II:
A copper rod of length `I_1` and a steel rod of length `I_(2)`, both having the same area of cross-section, are placed end to end between two rigid supports X and Y such that their system just fits between the supports with no initial stress in the rods. Temperature of the rods is now increased by `Delta T`. If `Y_( Cu)` is the Young's modulus of copper and `alpha_(Cu)` its coefficient of linear expansion, while `Y_(St)` is the Young's modulus of steel and `alpha_(St)` its coefficient of linear expansion, answer the following questions. (Assume that area of cross-section does not change and the rods do not bend. Also assume that there is no deformation of the supports.)
As the temperature is increased

Options

A. the length of the composite rod (copper + steel) does not change but that of each individual rod changes
B. the length of the composite rod does not change and that of each individual rod also does not change
C. the length of the composite rod increases and that of each individual rod also increases
D. the length of the composite rod decreases, length of one of the two rods increases while that of the other decreases

Answer

A