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Thermal Properties of Matter

JEE Main level, single correct, medium

29 of 126

Question 29 of 126

Given below are two statements: one is labelled as Assertion $A$ and the other is labelled as Reason $R$ .
Assertion $A$ : When a rod lying freely is heated, no thermal stress is developed in it.
Reason $R$ : On heating, the length of the rod increases.
In the light of the above statements, choose the correct answer from the options given below:

Show answer and solution

Answer: (C) Both $A$ and $R$ are true but $R$ is NOT the correct explanation of $A$

Thermal stress is mechanical stress created by any change in temperature of a material. When the body is under some constraints, thermal stress is generated. But if it is lying freely, no thermal stress is developed.
The increase in length of a body with temperature is given by

∆L=L\alpha ∆T

So, with the increase in temperature, the length of the rod increases.

A

and

R

are true but

R

is not the correct explanation of

A

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JEE Main 2025 Apr 2 Shift 1 question paper

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