Bulk Modulus for GasesGases have an equation of state that connects pressure, density and temperature i.e., equation of state. This enables us to deduce an explicit relationship between pressure and density. Such a relationship depends upon the process being considered - isothermal (at constant temperature) or isentropic (at constant entropy). The deduced equations are
and
where By substituting equations 1.20 and 1.21 in the definition for bulk modulus, Eqn. 1.19 we have,
Thus we see that the bulk modulus for a gas depends upon its
pressure. Given that for air the atmospheric pressure at STP
conditions is
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