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Topic Notes · Easy summaries with diagrams
Chapter 10 — Chapter 10 — Thermal Physics
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📘Easy summary
Most substances expand on heating because molecules vibrate/move faster and their average separation increases. Linear expansion of solids: ΔL = αL₀ΔT, where α = coefficient of linear expansion (fractional increase in length per kelvin, unit K⁻¹). Volume expansion: ΔV = βV₀ΔT, β ≈ 3α. Factors: original length, temperature change, nature of material (α differs: aluminium > copper > steel > glass). Liquids expand more than solids, gases most. Consequences: expansion gaps in bridges and rails, sagging power lines in summer, bimetallic strips in thermostats, loosening tight lids with hot water.
⭐Key points
- ΔL = αL₀ΔT
- β ≈ 3α
🔬Diagram
🌿Real-life example
2 m steel rod, α=1.2×10⁻⁵, ΔT=80 → ΔL ≈ 1.9 mm.
💡Exam tip
- Convert cm to m; ΔT in °C = in K.
✅Quick check
1. Heated copper rod length:
2. Unit of α:
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