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Three rods of material x and three of material y are joined as shown, all rods being identical in length and cross-section. End A is kept at 60 C and the junction E at 10 C. The thermal conductivity of x is 800 W/m/C and of y is 400 W/m/C. Find the temperature of junction B.

1. 30 C
2. 35 C
3. 40 C
4. 45 C

Correct answer: 30 C

Solution

Treating the rods as a resistor network between A (60 C) and E (10 C) and balancing heat currents at the junctions gives the temperature of B as 30 C.

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