Physics Demo Number: 149

Approximate

Run Time: 5 min

Linear Expansion and Heat Conduction

Demo Description

Use a torch with

1)  two tubes of same geometry but made of different metals 

 2) a bimetallic strip

 to show some of the properties of heat conduction and change of size with temperature changes.

Scientific Principles

• Coefficient of Linear Expansion

• Thermal Conductivity of Materials

Equipment

• Torch

• Two Metal Tubes

• Bimetallic Strip

Equipment Location

• Kit (149) on [D-3-5] (shares box with (098) and (125)

Instructions

Pictured are a propane torch, two metal tubes ( one of stainless steel, the other of copper ) and a bi-metallic strip with a wooden handle.

One may enlist a student volunteer to hold one tube in each hand and place the free ends simultaneously in the flame of the torch.

The student is told to let go of the first tube to get too hot for comfortable holding.

This shows the better thermal conductivity of copper as contrasted with stainless steel.

The bi-metallic strip is of course straight at room temperature and curved (as seen in the photo) after being heated briefly in the torch flame.

Writeup created by David A. Burba

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