## Lecture 32: Heat - Thermal Expansion

author: Walter H. G. Lewin, Center for Future Civic Media, Massachusetts Institute of Technology, MIT
recorded by: Massachusetts Institute of Technology, MIT
published: Oct. 10, 2008,   recorded: December 1999,   views: 27495
released under terms of: Creative Commons Attribution Non-Commercial Share Alike (CC-BY-NC-SA)

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# Description

1. Heat and Temperature:

Various temperature scales are discussed: Celsius, Fahrenheit, Kelvin.

2. Linear Thermal Expansion:

The linear thermal expansion coefficient is introduced. Expansion leads to a need for expansion joints in railroad rails to avoid bulging on hot days. Thermal expansion is demonstrated by heating and cooling a brass rod. An important application of thermal expansion is bi-metals which are used in thermostats, safety devices and thermometers, as demonstrated.

3. Cubical Thermal Expansion:

The fractional change in volume with temperature is given by the coefficient of cubical expansion. A mercury thermometer is discussed.

4. Shrink Fitting:

Shrink fitting is a technique that makes use of the thermal expansion by heating one object (of two). After the two objects are assembled, they cool, and the fit is perfect and "for ever".

5. Cubical Thermal Expansion of Water:

Water has a maximum density at 4 degrees Celsius; between 0 and 4 degrees Celsius the cubic thermal expansion coefficient is negative so the water expands as it cools below 4 degrees Celsius. The density of ice is about 8% lower than water, so ice cubes and icebergs float in water.

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1 hehehehe, October 27, 2008 at 4:33 p.m.:

2 Javier Galvan, September 3, 2009 at 11:32 p.m.:

Great, loud, clear and useful.
Good tool and useful in the learning process.

Thanks.

3 João Carlos P Carvalho, September 12, 2009 at 3:28 p.m.:

Hello,
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