1.

Obtain relation between coefficient of volume expansion (alpha_(V)) and coefficient of linear expansion (alpha_(l)).

Answer»

Solution :Suppose there is a cube of side of length .l.. When its TEMPERATURE is increased by `DeltaT`, it expands EQUALLY in all DIMENSIONS.
Hence from `V=l^(3)`
`DeltaV=(l+Deltal)^(3)-l^(3)`
`=l^(3)+3l^(2)Deltal+3l(Deltal)^(2)+(Deltal)^(3)-l^(3)`
But `(Deltal)^(2)` and `(Deltal)^(3)` are much more less than l, hence by neglecting them
`DeltaV=3l^(2)Deltal`. . .(1)
But, from LINEAR expansion.
`Deltal=alpha_(l)lDeltaT`. . .(2)
`:.` By using value of equation (1) in equation (2),
`DeltaV=3l^(2)(alpha_(l)lDeltaT)`
`=3l^(3)alpha_(l)DeltaT`
`DeltaV=3Valpha_(l)DeltaT""`. . .(3)
`""(becausel^(3)=" VOLUME of cube")`
By comparing equation (3) with general equation of volume expansion `DeltaV=alpha_(V)VDeltaT`.
`alpha_(V)=3alpha_(l)` which is relation between coefficient of volume and linear expansion.


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