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Question: Answered & Verified by Expert
A metal rod is fixed rigidly at two ends so as to prevent its thermal expansion. If $L, \alpha$ and $Y$ preventively denote the length of the rod, respective of linear thermal expansion and coefficient of Young's modulus of its material, then for an Young's modulus of its material, then for an increase in temperature of the rod by $\Delta T$, the longitudinal stress developed in the rod is
PhysicsMechanical Properties of SolidsWBJEEWBJEE 2014
Options:
  • A inversely proportional to $\alpha$
  • B inversely proportional to Y
  • C directly proportional to $\Delta T / Y$
  • D independent of $L$
Solution:
2404 Upvotes Verified Answer
The correct answer is: directly proportional to $\Delta T / Y$
Strain $=\alpha \cdot \Delta T$
Stress $Y \propto \Delta T$
where $L=$ length of the rod $\boldsymbol{\alpha}=$ coefficient of linear thermal expansion
$Y=$ Young's modulus of its material So, the longitudinal stress developed in the rod is directly proportional to $\frac{\Delta T}{Y}$

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