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Question: Answered & Verified by Expert
Consider a brass rod and a steel rod (80 cm longer than the brass rod) at 0 °C. It is observed that on increasing temperatures of the two rods by same amount difference in lengths of the two rods does not change. Given that the thermal coefficient of linear expansion for steel and brass are 11×10-6 -1 and 19×10-6 -1 respectively. The sum of lengths of the two rods at 0o C is
PhysicsThermal Properties of MatterJEE Main
Options:
  • A m
  • B m
  • C m
  • D 1.5 m
Solution:
1427 Upvotes Verified Answer
The correct answer is: m
The length and coefficient of thermal expansion for the rods are respectively;
λ1,α1 steel rod
λ2,α2 Brass rod
As difference in lengths is constant
Δλ1=Δλ2
λ1α1ΔT=λ2α2ΔT
λ1α1=λ2α2..i
Also λ1-λ2=λii
λ1=1α2α2-α1 and λ2=1α1α2-α1
sum =1α2+α1α2-α1=80×308
=300 cm=m

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