Most
substances expand when heated and contract when cooled.
The change in length / area or volume (due to contracting/expanding)
is directly related to temperature change. Every linear
dimension increases by the same percentage with a change
in temperature
Not all materials contract/expand at the same rate; the
amount of contraction/expansion varies depending on the
material. The coefficient of linear expansion, is a proportionality
constant that determines the rate of change in length in
different materials when they are heated and cooled.
Applications
:
In thermometers, thermal expansion is used for measurement.
Liquid expand more than solids. Stained red ethanol has
a relatively large coefficient of cubic expansion than glass
. Temperature can be measured as it rises through the capillary
faster.
-If a lid of a glass jar is tight, holding it under hot
water for a short time will make it easier to open. This
is because the lid will be struck by the hot water more
directly than the glass, and so it will expand sooner. Furthermore,
metals generally expand more than glass for the same temperature
change.
Problems:
- If steel bridge expand or contract, it can cause structural
damage.
However, steel bridges are often mounted on rollers to prevent
this problem.
-Expansion gaps also exist in train tracks.
-Water and steam pipes often have a U-bend in them to allow
for thermal expansion. |
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