Engineering

Thermal Expansion

Definition

Thermal expansion is the tendency of matter to change its volume in response to temperature changes, characterized by the coefficient of thermal expansion (CTE), measured in units of 1/°C or 1/K.

Explanation

Steel expands about 12x10⁻⁶ per °C; a 100-meter steel bridge lengthens roughly 12 mm over a 100°C temperature swing. Engineers account for this with expansion joints in bridges, rail gaps, and building facades. Invar (an iron-nickel alloy) has a CTE near zero (1.2x10⁻⁶/°C), making it invaluable for precision instruments and telescope mirrors.

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RELATED TERMS

Torque

Torque is the rotational equivalent of force, equal to the applied force multiplied by the perpendicular distance from the pivot point, measured in newton-meters (N·m) or pound-feet (lb·ft).

Stress

Stress is the internal force per unit area within a material resulting from externally applied forces, measured in pascals (Pa) or pounds per square inch (psi).

Strain

Strain is the dimensionless ratio of a material's deformation (change in length) to its original length under applied stress: ε = ΔL/L₀.

Viscosity

Viscosity is a fluid's resistance to deformation or flow, quantifying internal friction between fluid layers; dynamic viscosity is measured in pascal-seconds (Pa·s) or centipoise (cP).

RPM

RPM (revolutions per minute) is a unit of rotational speed measuring how many complete turns an object makes in one minute.