Which of the following describes the coefficient of thermal expansion?

• A. It is the fractional change in size of a material per degree of temperature change.
• B. It is the thermal conductivity of a material.
• C. It is the color change of a material with temperature.
• D. It is the magnetic response of a material to temperature change.

Answer: (C)

The coefficient of thermal expansion measures how much a material’s size changes when its temperature changes. It is defined as the fractional change in size per unit temperature change, often expressed as α = (ΔL/L0) / ΔT for a change in length. This means a material with a larger α will expand more for the same temperature rise, which is crucial for designing components that must fit together across temperature ranges.

Other descriptions don’t match this concept: thermal conductivity describes how easily heat flows through a material; color change with temperature relates to optical properties or phase effects rather than dimensional change; and magnetic response to temperature concerns how magnetism varies with temperature.