Question

A composite metal bar of uniform section is made

up of length 25 cm of copper, 10 cm of nickel and

15 cm of aluminium. Each part being in perfect

thermal contact with the adjoining part. The

copper end of the composite rod is maintained at

${100}^{\circ }C$ and the aluminium end at $0^{\circ }C$ . The whole

rod is covered with belt so that there is no heat

loss occurs at the sides. If $K_{Ca}=2K_{Al}$ , and

$K_{Al}=3K_{Ni}$ , then what will be the temperatures of

Cu - Ni and Ni- Al junctions respectively

• A. 78.2°C and 26.08°C
• B. 83.33°C and 20°C
• C. 50°C and 30°C
• D. 30°C and 50°C

Answer 1

The correct option is A

78.2°C and 26.08°C

$Inseriesrateofflowofheatisconstatnt\frac{100-{\theta }_1}{\frac{25}{6KA}}=\frac{{\theta }_1-{\theta }_2}{\frac{10}{KA}}=\frac{{\theta }_2-0}{\frac{15}{3KA}}Solving{\theta }_1={78.2}^{0}c,{\theta }_2={26.08}^{0}c$