Question

The incorrect formula for the specific heat of an ideal gas in terms of specific heat ratio of a gas and universal gas constant is_____

(a) cp-cv=2R

(b) \(\frac {c_p}{c_v}\)=γ

(c) cv=\(\frac {R}{\gamma -1}\)

(d) cp=\(\frac {\gamma R}{\gamma -1}\)

The question was posed to me in a job interview.

My doubt is from A Brief Review of Thermodynamics in portion Compressible Flow – Preliminary Aspects of Aerodynamics

Answer 1

The correct choice is (a) cp-cv=2R

Easiest explanation: The specific heat ratio of a gas is defined as the ratio \(\frac {c_p}{c_v}\) and the difference in cp and cv is defined as the universal gas constant. From these, the following relations for the specific heat of an ideal gas are obtained cp=\(\frac {\gamma R}{\gamma -1}\) and cv=\(\frac {R}{\gamma -1}\).