Thermal Expansion

Also called

linear expansion · coefficient of linear expansion · ball and ring · Gravesande's ring · bimetallic strip · bimetal strip · thermostat · rail gaps · expansion gap · anomalous expansion of water · water at 4 degrees · density of water · pond freezes from the top · bridge rollers · expansion joint · volume expansion · ऊष्मीय प्रसार · रेखीय प्रसार · द्विधातु पट्टी

Topics

• Most solids expand on heating: ΔL = α L ΔT, where α is the coefficient of linear expansion.
• A heated brass ball grows too big for the ring it slipped through when cold; it passes again once it cools.
• A bimetal strip bends on heating towards the metal with the smaller α, because the other layer grows longer.
• A thermostat uses a bimetal strip: as it warms it bends away from a contact and switches the heater off.
• Gaps are left between rail sections so the rails can lengthen on hot days without buckling.
• Water is anomalous: cooled from 4 °C to 0 °C it expands, so water at 4 °C is densest and sinks to the bottom.
• A pond freezes from the top: ice floats, and the 4 °C water below it lets fish live through the winter.
• One end of a long bridge rests on rollers so the deck can lengthen in summer and shrink in winter without cracking.
• Area expansion has coefficient 2α and volume expansion 3α; liquids expand more than solids, gases most of all.

About this model

A GLB file of about 362 KB, shown in Lably's 3D viewer and, on a phone, placed in your room with AR. Credit: Model, science and animation: Lably (built procedurally with three.js; no downloaded meshes). | CC BY 4.0. Original geometry and animation made for Lably.

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