NEET Solved Paper 2017 Question 37
Question: Two rods A and B of different materials are welded together as shown in figure. Their thermal conductivities are $ K _1 $ and $ K _2. $ The thermal conductivity of the composite rod will be
Options:
A) $ 2(K _1+K _2) $
B) $ \frac{K _1+K _2}{2} $
C) $ \frac{3(K _1+K _2)}{2} $
D) $ K _1+K _2 $
Show Answer
Answer:
Correct Answer: B
Solution:
Thermal current $ H=H _1+H _2 $
$ =\frac{K _1A(T _1-T _2)}{d}+\frac{K _2A(T _1-T _2)}{d} $ $ \frac{K _{EQ}2A(T _1-T _2)}{d}=\frac{A(T _1-T _2)}{d}[K _1+K _2] $ $ K _{EQ}=[ \frac{K _1+K _2}{2} ] $
