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A rod CD of thermal resistance 10.0 K/W is attached at its end C to the midpoint of an identical rod AB. The ends A, B and D are held at 200 deg C, 100 deg C and 125 deg C respectively. If the heat current flowing in rod CD is P watt, find P.

1. 2 W
2. 1 W
3. 3 W
4. 4 W

Correct answer: 2 W

Solution

Balancing heat currents at C with T_C = 145 deg C gives the current in CD = (145 - 125)/10 = 2 W.

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