Temperature and Length Expansion – Rankers Physics

Thermal Expansion: Practice Problem & Solution

Assertion (A): Temperature of a rod is increased and again cooled to same initial temperature then its final length is equal to original length. Reason (R): For a small temperature change, length of a rod varies as \( l = l_0 (1+\alpha \Delta T) \) provided \( \alpha \Delta T is small  \). Here symbol have their usual meaning.  
Both (A) & (R) are true and the (R) is the correct explanation of the (A)
Both (A) & (R) are true but the (R) is not the correct explanation of the (A)
(A) is true but (R) is false
Both (A) and (R) are false

Solution Explained:

To solve this problem, we apply the core principles of Thermal Expansion. Understanding the underlying formula is key to arriving at the correct answer below:

Assertion is true as thermal expansion is reversible for elastic materials. Reason is the formula for linear expansion, \( l = l_0 (1+\alpha \Delta T) \), which confirms the assertion if \( \Delta T \) is reversed. Thus, both are true and (R) explains (A).

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Similar Practice Questions

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1. Assertion (A): The amount of radiation from sun's surface varies as the fourth power of its absolute temperature. Reason (R): The sun is a black body.
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