A section of railway track is made of steel rails which are laid end-to-end at 5∘C. Each rail has a length of 12m at this temperature.
a. (i) Define the term coefficient of linear expansion for a solid.
b. (ii) Giving physical reasons, describe why a small clearance must be left between successive rails when they are laid during winter.
c. (iii) Show that the minimum gap g to be left between two such rails so that they just avoid buckling when the ambient temperature may rise to 45∘C is given by g=αlΔT, where the symbols have their usual meaning.