A Long Iron Rod Initially at a Temperature of 20°C

question 28

Multiple Choice

A long iron rod initially at a temperature of 20°C has one end dipped in boiling water (100°C) at time, t = 0. The curved surface of the rod is insulated so that heat conduction is one dimensional in the axial direction. The temperature at a distance 100 mm from the dipped end becomes 40°C at time, t = 200 s. The same temperature is achieved at a distance of 200 mm from the dipped end at time

• A)t = 283 s
• B)t = 356 s
• C)t = 400 s
• D)t = 800 s