1.

Deduce the dimensional formulae for the following physical quantities : (i) Specific heat (ii) Entrophy (iii) Thermal conductivity (iv) Stepan's constant (v) Boltzmann's constant (vi) Universal gas constant.

Answer»

Solution :(i) Specific HEAT `=("Heat")/("Mass" xx "Temperature")`
`=("Work")/("Mass" xx "Temperature")`
`=("Force" xx "distance")/("Mass" xx "Temperature")=([MLT^(-2)][L])/([M][K])`
`=[M^(0)L^(2)T^(-2)K^(-1)]`
(II) ENTROPY `=("Heat")/("Temperature")=([ML^(2)T^(-2)])/([K])`
`=[ML^(2)T^(-2)K^(-1)]`
(iii) Thermal conductivity `=("Heat"xx "Distance")/("Area"xx"Temperature"xx"Time")`
`=([ML^(2)T^(-2)]*[L])/([L^(2)]*[K]*[T])`
`=MKT^(-3)K^(-1)`
(IV) Stefan.s constant `=("Energy")/("Area"xx"Time"xx("temperature")^(4))`
`=([ML^(2)T^(-2)])/([L^(2)]*[T]*[K]^(4))`
`=[ML^(0)T^(-3)K^(-4)]`
(v) Boltzmann.s constant `=("Energy")/("Temperature")`
`=([ML^(2)T^(-2)])/([K])`
`=[ML^(2)T^(-2)K^(-1)]`
(vi) Universal gas constant `=("Pressure"xx"Volume")/("No. of moles" xx "Temperature")`
`=(PV)/(nT)`
`=([ML^(-1)T^(-2)][L^(3)])/(["mol.]*[K])`
`=[ML^(2)T^(-2)K^(-1) "mol"^(-1)]`


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