Experiment C1 Flashcards
What is the aim of the experiment?
To determine the coefficient of linear expansion of a solid.
The length, lθ, of a rod at temperature O°C is related to its length at 0°C, lo, by the equation: _______.
where a is the coefficient of linear expansion, assumed to be a constant independent of temperature in this experiment. For two temperatures θ1, and θ2 (not too high) this becomes _______.
lθ=lo (1+ aθ)
l2=l1 [1+a (θ2-θ1)]
Method
The apparatus consists of a hollow metal tube through which first tap water and then steam is passed.
The change in length, △l = l2 - l1, is measured by means of an optical lever, and the temperature at equilibrium in each case is read off the thermometer inserted into the tube.
—> The length when cold is measured with a metre stick. Explain why this is accurate enough.
The error in the meter stick is ± 1 mm, which is small in comparison with the full length of the tube (500mm).
Explain why the flow must in these directions.
- Water must enter from the bottom so that it fills the tube and makes good thermal contact.
- Steam will in any case make good thermal contact, but must enter from the top so that condensed steam is expelled.
The optical level uses a light beam as a pointer to measure small deflections.
—-> Explain the advantages of this.
It is a pointer which can be as long as necessary, but will have zero mass and infinite rigidity.
Why can wood not be used instead of steel and brass?
Wood CANNOT be used as it does it not have a co-efficient of expansion as large enough as steel or brass.
