( ii ) Pressure Coefficient ( γp ) At constant volume , the change in pressure per unit pressure per degree celsius is called pressure coefficient .
where p0 , p1 and p2 are pressure of the gas at 0 ° C , t1 ° C and t2 ° C . Practical Applications of Expansion
1 . When rails are laid down on the ground , space is left between the end of two rails .
2 . The transmission cables are not tightly fixed to the poles .
3 . The iron rim to be put on a cart wheel is always of slightly smaller diameter than that of wheel .
4 . A glass stopper jammed in the neck of a glass bottle can be taken out by warming the neck of the bottles .
Important Points
Due to increment in its time period a pendulum clock becomes slow in summer and will lose time .
Loss of time in a time period ΔT =( 1 / 2 ) α ΔθT ∴ Loss of time in any given time interval t can be given by ΔT =( 1 / 2 ) α Δθt
At some higher temperature a scale will expand and scale reading will be lesser than true values , so that
true value = scale reading ( 1 + α Δt ) Here , Δt is the temperature difference .
However , at lower temperature scale reading will be more or true value will be less .