Final answer:
The coefficient of thermal expansion is the ratio of unit strain to temperature change, indicating how materials expand with temperature and it differs based on material and temperature conditions.
Step-by-step explanation:
The coefficient of thermal expansion is defined as the change in length, area, or volume per unit length, area, or volume per degree Celsius change in temperature. When referring to linear thermal expansion, for instance, the coefficient of thermal expansion, denoted as α (alpha), is calculated as:
∆L = α × L0 × ∆T
where ∆L is the change in length, L0 is the original length, and ∆T is the change in temperature. This coefficient varies slightly with temperature and the material in question. For volume expansion, the concept is similar, but it refers to the change in volume per unit volume per 1°C change in temperature. The correct answer to the student's multiple-choice question is d) The ratio of unit strain to temperature change, as the coefficient of thermal expansion relates to how much strain (change in length, area, or volume) occurs with a change in temperature.