Then the ratio of normal stress to the volumetric strain within the elastic limits is called as Bulk modulus. This is denoted by K.
Where P = increase in pressure; V = original volume; ∆V = change in volume
Gases have two bulk moduli, namely isothermal elasticity E0 and adiabatic elasticity E0.
(1) Isothermal elasticity (E0) : Elasticity possessed by a gas in isothermal condition is defined as isothermal elasticity.
For isothermal process, PV = constant (Boyle’s law)
Differentiating both sides
(2) Adiabatic elasticity (E0) : Elasticity possessed by a gas in adiabatic condition is defived as adiabatic elasticity.
For adiabatic process, PVr = constant (Poisson’s law)