The Attempt at a Solution
For part a, I used the coefficient of linear expansion for copper and the change in temperature to find the change in length (0.068%). I thought part b had the same answer. The two are attached, and I would imagine that the elongation would be controlled by the thick rod rather than the thin wire. For part c , I found the length the natural strain of the wire due to thermal expansion (0.048%). I then took the difference between the actual strain and the natural strain and multiplied by young's modulus to find the additional stress (2.4*10^7 N/m^2). I then added that to the original stress (1.00*10^6 N/m^2) to get 2.5*10^7 N/m^2. Is this the correct approach? Thanks.