YOU ARE LEARNING:
Applied Thermal Expansion
Applied Thermal Expansion
In construction, thermal expansion and contraction in solids must be taken into account. For example, bridges are built with expansion joints. Thermal expansion and contraction in liquids is also useful, for example how mercury in a thermometer will rise or fall depending on the temperature.
Joe is trying to open a jar, but he can't get it open. His mother suggests he **** run the lid under the hot tap. Why does she suggest this?
Joe's mother tells him there are other examples of thermal expansion in solids. Which of these options is another example of thermal expansion in solids?
Now Joe is intrigued by the concept of thermal expansion. One day he is traveling over a bridge made of metal, and he starts to worry that it will **** expand when it gets hot. Will it?
We are aware of the fact that solids expand when heated and as a result of this we have taken this into account when building things. For example, bridges are built with expansion joints which allow parts of the bridge to expand without the bridge collapsing.
If an object expands when heated what do you think might occur when an object is cooled?
Having been over the bridge, Joe notices the electricity cables going to a pylon hanging quite low, his mother tells him this is to combat thermal expansion, but he does not think this is the case. Who is correct?
Whilst we build structures with thermal expansion in mind, we also have to think about if an object cools and shrinks. This is why the wires going into a pylon are longer than they need to be to allow for contraction when the object cools.
Why does the mercury in a thermometer go up as the temperature increases?
As well as solids, we need to be aware of the expansion of liquids due to heat. Mercury is used in thermometers as it expands when heated, and we can measure the increase in temperature using this principle.
Joe's mother likes to fill the car with petrol on a cold day. Joe asks her why and she says that due to thermal expansion you get more petrol on a colder day. Is she correct?