Transmission Of Heat Question 70
Question: The coefficient of thermal conductivity of copper is nine times that of steel. In the composite cylindrical bar shown in the figure. What will be the temperature at the junction of copper and steel
[MP PMT 2000; BHU 2004]
Options:
A) $ 75^{o}C $
B) $ 67^{o}C $
C) $ 33^{o}C $
D) $ 25^{o}C $
Show Answer
Answer:
Correct Answer: A
Solution:
Temperature of interface $ \theta =\frac{K _{1}{\theta _{1}}l _{2}+K _{2}{\theta _{2}}l _{1}}{K _{1}l _{2}+K _{2}l _{1}} $ It is given that $ K _{Cu}=9K _{S}. $ So if $ K _{S}=K _{1}=K $ then $ K _{Cu}=K _{2}=9K $
Therefore q $ =\frac{9K\times 100\times 6+K\times 0\times 18}{9K\times 6+K\times 18} $ =$ \frac{5400K}{72K}=75{}^\circ C $
BETA
