JEE Main 2014PhysicsThermal Properties of MatterHardMCQ

JEE Main 2014 — Thermal Properties of Matter Question with Solution

JEE Main 2014 (06 Apr)

Question

Three rods of Copper, Brass and Steel are welded together to form a Y-shaped structure. Area of cross-section of each rod is 4 cm2. End of copper rod is maintained at 100°C. Where as ends of brass and steel are kept at 0°C. Lengths of the copper, brass and steel rods are 46, 13 and 12 cms respectively. The rods are thermally insulated from surroundings except at ends. Thermal conductivities of copper, brass and steel are 0.92, 0.26 and 0.12 CGS units respectively. Rate of heat flow through copper rod is :

Choose an option

Show full solutionCorrect option: C
Correct answer
C4.8 Cal/s

Step-by-step explanation

LCu = 46 cm; LB = 13 cm & LS=12 cm.



KCu=0.92KB=0.26KS=0.12}CGSunit

We know that R=LKA

RCu=460.92×4=12.5

RB=130.26×4=12.5

RS=120.12×4=25

Now, if T is temperature of junction then

  100-TRCu=T-0RB+T-0RS

  100-T12.5=T12.5+T25

  ∴100-T12.5=3T25

  200=5T

  ∴T=40∘

⇒QCu=100-TRCu

              =100-4012.5

              =6012.5

  ⇒QCu=4.8 Cal/s

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About this question

This is a previous-year question from JEE Main 2014, covering the Thermal Properties of Matter chapter of Physics. PrepSharp catalogues every PYQ from JEE Main with a verified answer key and step-by-step solution prepared by IIT alumni — so you can search by chapter, topic or year and revise efficiently.