Solid Expansion Concept

Demonstrations in Solid Expansion

Straight bimetallic strip with black wooden handle on a gray surface
Safety

Bimetallic Strip

Demonstrates differential thermal expansion: two metals bonded together expand at different rates when heated, causing the strip to bend dramatically (~90°). Connects directly to thermostats, circuit breakers, and bimetallic thermometers.
Thermostat demonstration on wooden base with two incandescent bulbs in black sockets, a bimetallic strip on a copper mounting bar above, and colored banana jack binding posts in center
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Thermostat

Demonstrates how differential thermal expansion of a bimetallic strip creates mechanical switching in a thermostat circuit. Heating the strip causes it to bend, switching which of two indicator bulbs is …
Handheld ring-and-ball apparatus: two brass balls on rods with black handles and a brass ring on a wooden handle (Gravesande's ring and ball)
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Ring and Ball

A brass ball that just fits through a brass ring no longer passes through when the ball is heated, but does pass when the ring is also heated. Directly addresses …
Tyndall's bar breaker apparatus clamped horizontally to a ring stand, with a BernzOmatic propane torch positioned beneath it
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Tyndall's Bar Breaker

Demonstrates the large forces generated by thermal contraction of a constrained metal bar. A heated steel bar is clamped tight, then as it cools and tries to contract, the thermal …
Six bimetallic discs on a crystallized reusable heat pad in a clear plastic case, with a second heat pad below and two small Educational Innovations logo discs to the right

Hopping Discs

Bimetallic discs heated and inverted store elastic energy that is dramatically released as they cool, popping into the air. Demonstrates differential thermal expansion and energy conversion in a bistable mechanical …
Brass Trevelyan rocker with a T-shaped body and long handle resting across a lead cylinder
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Trevelyan Rocker

A heated brass rocker placed on a lead pipe oscillates as alternating contact points cause rapid local thermal expansion of the lead. Demonstrates thermomechanical feedback and the high thermal expansion …
Hot wire apparatus with fan-shaped scale (0-10), nichrome wire stretched across a black metal base, and variac power supply. Two views show the pointer mechanism and wire mounting.
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Hot Wire Apparatus

A nichrome wire heated by electrical current visibly expands, moving a pointer across a calibrated scale. Students observe thermal expansion directly and see that even small length changes become measurable …
Nichrome wire stretched between two ring stands with alligator clips and power cords connected to a variac (left); four progressive shots showing the wire glowing increasingly bright and sagging into a catenary as current increases (right)
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Nichrome Wire

Nichrome wire heated by resistive current elongates and sags into a visible catenary, demonstrating linear thermal expansion of solids. The progressive glow also illustrates blackbody radiation and connects to incandescent …
Clear glass Bologna bottle with thick rounded bulb and narrow neck, resting on dark surface
Safety

Bologna Bottles

Bologna bottles withstand hammer blows but shatter instantly when a small carborundum particle is dropped inside. Students see how rapid cooling creates compressive surface stress that resists impact, yet a …