Transmission Of Heat Question 25
Question: In which case the thermal conductivity increases from left to right
[NCERT 1974, 76; AFMC 2000]
Options:
A) Al, Cu, Ag
B) Ag, Cu, Al
C) Cu, Ag, Al
D) Al, Ag, Cu
Show Answer
Answer:
Correct Answer: A
Solution:
$ \frac{K _{1}A({\theta _{1}}-\theta )}{l _{1}}=\frac{K _{2}A(\theta -{\theta _{2}})}{l _{2}} $ is better conductor than $ l _{1}=l _{2} $ and
$ \Rightarrow K _{1}A({\theta _{1}}-\theta )=K _{2}A(\theta -{\theta _{2}}) $ is better conductor than
$ \Rightarrow \theta =\frac{K _{1}{\theta _{1}}+K _{2}{\theta _{2}}}{K _{1}+K _{2}} $ . Hence conductivity in increasing order is $ K=\frac{2K _{1}K _{2}}{K _{1}+K _{2}}=\frac{2.K.2K}{K+2K}=\frac{4}{3}K $ .
BETA
