Question

Out of the following material whose elasticity is independent of temperature

• A. steel
• B. copper
• C. invar steel
• D. glass

Answer 1

The correct option is C

invar steel

Step 1: Elasticity

1. The ability of a material to resist a distorting influence on it by an external force and to return to its original shape when the external influence is withdrawn is known as elasticity.
2. The atomic vibrations in the crystal structure increase as the temperature of the substance rises. The atomic distances in the crystal increase as the atomic vibration rise, and the atomic force decreases. The young's modulus of the material decreases as the atomic forces diminish.
3. The effect of temperature on the value of Young’s modulus of elasticity for various substances, in general, is that it decreases with rising in temperature.

Step 2: The explanation of the correct option

In case of option C

1. Invar is a $Fe-Ni$ alloy steel does not experience any thermal expansion in the extremely low-temperature environment or the above room temperature environment.
2. Since the temperature effect on it is very low, it is tough and ductile.
3. Hence, its elasticity remains constant when the temperature is changed.

The explanation of the incorrect option

In case of option A

With an increase in temperature, the elasticity of steel generally decreases.

In case of option B

With an increase in temperature, the elasticity of copper generally decreases.

In case of option D

With an increase in temperature, the elasticity of glass generally decreases.

Hence, option C is the correct answer.