A bar of iron is 10 cm at 20°C. At 19°C it will be ( α α of…

Physics Thermometry, Thermal Expansion and Calorimetry Thermal Expansion Single Correct MCQ

Published by: CGP EDU Academic Team

Published on: September 12, 2026

A bar of iron is 10 cm at 20°C. At 19°C it will be ( α α of iron = 11 × × 10 –6 /°C)

11 × × 10 –6 cm longer

11 × × 10 –6 cm shorter

11 × × 10 –5 cm shorter

11 × × 10 –5 cm longer

Text Solution

Verified by Experts

The correct answer is:

$L = L_0 \left(1 + \alpha \Delta \theta \right)$ ⇒ ⇒ $\frac{L_1}{L_2} = \frac{1 + \alpha(\Delta \theta)_1}{1 + \alpha(\Delta \theta)_2}$

⇒ ⇒ $\frac{10}{L_{2}} = \frac{1 + 11 \times 10^{-6} \times 20}{1 + 11 \times 10^{-6} \times 19}$ ⇒ ⇒ $L_2 = 9.99989$

⇒ ⇒ Length is shorten by

$10 - 9.99989 = 0.00011 = 11 \times 10^{-5} \, cm$

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