JEE Main 2012 Physics question

A large cylindrical rod of length L is made by joining two identical rods of copper and steel of length each. The rods are completely insulated from the surroundings. If the free end of copper rod is maintained at 100°C and that of steel at 0°C then the temperature of junction is (Thermal conductivity of copper is 9 times that of steel)

• (1)90°CCorrect
• (2)50°C
• (3)10°C
• (4)67°C