Heat and Thermodynamics 3 Question 4

4. Temperature difference of 120C is maintained between two ends of a uniform rodAB of length 2L. Another bent rodPQ, of same cross-section as AB and length 3L2 is connected across AB (see figure). In steady state, temperature difference between P and Q will be close to

(2019 Main, 9 Jan I)

(a) 45

(b) 35C

(c) 75C

(d) 60C

Show Answer

Solution:

  1. According to the given question, the given figure with its length for each section is given as below

The above figure considering that every section has the same thermal conductivity, then in terms of thermal resistance is shown in the figure below,

Net resistance of the section PQRS is =R×3R25R2=3R5

Total resistance of the net network, Rnet 

=R2+R2+3R5=8R5

Thermal current, I=ΔTABRnet 

I=1200(8R5)=120×58R

Thus, the net temperature difference between point P and Q is

TPTQ=I×3R5=120×58R×3R5=45C



जेईई के लिए मॉक टेस्ट

एनसीईआरटी अध्याय वीडियो समाधान

दोहरा फलक