Question

Coefficient of linear expansion is always ___________________ with the increase in temperature.
A. Increases
B. Decreases
C. Remains the same
D. Doubles itself

Answer 1

Hint: The typical property of any solid is to expand when heated. The amount of expansion depends on various factors like initial length and temperature difference we applied to it and some inbuilt properties of that sold too. Based on this information we can solve the given question.

Formula used:
$\mathrm{\Delta }l=l\alpha \mathrm{\Delta }T$

Complete step-by-step answer:
When heat is given matter expands and when heat is taken out it contracts. It might be any solid or liquid or gas. Now heat can be given by increasing the temperature and it can be taken by decreasing the temperature. For the same amount of temperature difference created the amount of heat consumed depends on the material. Obviously when heat consumed is different then the expansion also will be different. This clearly means there is some materialistic property which decides the amount of expansion of the material irrespective of the temperature difference because the same temperature difference is creating different amounts of expansion in different materials.
Now let us assume the temperature difference created is $\mathrm{\Delta }T$ and the initial length of the solid is $l$ and the coefficient of thermal expansion is $\alpha$so when the temperature difference is created the amount of expansion a solid undergoes is $\mathrm{\Delta }l=l\alpha \mathrm{\Delta }T$
Where $\mathrm{\Delta }l$ is the change in length.
From the formula it is clearly evident that the expansion is directly proportional to the initial length and temperature change and the coefficient of thermal expansion $\alpha$.
It is to be noted that the $\alpha$ is the materialistic property and constant for a material and doesn’t vary with the temperature.
So even though temperature is changed $\alpha$ remains the same.

So, the correct answer is “Option C”.

Note: There are some materials which contract on heating like grey cast iron, water at 4 degree Celsius, our hair and Indian rubber. Not only linear expansion there will be change in volume and area of the material too when heated. For those expansions there are different thermal coefficients.