Area Expansion

Area expansion: ΔA = β·A₀·ΔT, where β = 2α is the area expansion coefficient.

Holds for isotropic materials (same α in all directions).

Twice the linear coefficient because A ∝ L².

Useful for thin plates, sheet metals, surface areas of objects.

Hole in a plate: increases in area same as solid plate (β·A·ΔT).

Differential expansion can warp thin plates if heated asymmetrically.

Most metals: β ~ 20-50 × 10⁻⁶/K. Glass: ~18 × 10⁻⁶/K.

Bimetallic plates curl into spherical caps when heated uniformly.