Everyone surely familiar clatter of carriage wheels.Or the sound of wheels tram.Everyone knows that the reason is a gap at the junction between the rails.And what he's done?The answer is simple - to compensate for the expansion of the rail when heated.This is also a known fact that when heated body expands and contracts when cooled.A measure of the expansion or contraction of a coefficient of linear expansion.
Molecular theory of the expansion of body heat due to an increase in the speed of movement of atoms and molecules.As a result, the lattice atoms of the oscillation amplitude increases, and as a consequence - increase the linear dimensions of the body.And how much will increase, it can be determined using a formula that uses a coefficient of linear expansion.
is now necessary to clarify the physical meaning of the coefficient.It shows how much increased when heated at 1 ° C the length of the body.The value of this small and each has its own material.Thus, the linear expansion coefficient of steel is 0.000011 to 1 ° C.What is the real value of such, it can be understood by a simple example.If the Earth at the equator wrap iron wire, the length of which will amount to 40,000 km, the temperature increases by 1 ° C increase in the length of wire is 400 meters.
coefficient of linear expansion is extremely important for any engineer.It allows to take into account the change in the size of the body temperature drops.Thus, if within a year the temperature in the city will change from plus fifty degrees Celsius to minus fifty degrees Celsius, it will cause significant changes in the length of the same rail.If they are solid, the result will bend them.This is to avoid such a phenomenon, and make the gap between the rails during their laying.
For a variety of materials coefficient will be different.For steel, its value has been cited, and coefficient of linear expansion of aluminum 0.0000024 be 1 ° C.
However, the above arguments and examples suffer a lopsided.When we talk about increasing the size of the body when heated, increasing not only the length, but also other dimensions - height and width.The increase in size will lead to an increase in, and then we can talk about the volumetric expansion of bodies.The truth is a concept rather not applicable to solids and to liquids.
simple experiment that will confirm this, everyone can do their own.Put the kettle on the fire, filled with water up to the top.When the water warms up, it will increase in the volume and "run away" from the kettle.But there is a positive use of this effect.Anyone familiar liquid thermometers - that street that medical.They, too, are built on the effect of increasing the volume when heated.
The technique sometimes ignore such an increase leads to sad consequences.To compensate for the increase necessary to use special measures.Many have seen a long series of pipes (pipe), laid on the surface.And suddenly out of the blue tube to form a huge zigzag.This is not a simple Zigzag, its value is strictly defined, was used in the calculation of the coefficient of linear expansion.It is like a zigzag line to compensate for the increase in the size of the pipes.
You can still give many examples of the technique of linear and volumetric expansion, but the above examples is enough to understand the essence of the phenomenon.Of course, very curious anomalous behavior of certain substances, the same water.It freezes when the volume is not reduced, but increased.This will be yet another factor confirming the unique properties of water.
So, in this article on the basis of simple and illustrative examples from the life of such a concept as defined by the linear expansion of the body and the coefficient of linear expansion.Examples of the use of expansion in the art and in life, given the concept of the order of magnitude of said coefficient.
