GRE Subject 2026 Practice Test Physics Thermodynamics Free Quiz 2

11. What is the efficiency of a Carnot engine?

A. η = (TH - TC)/TH B. η = (TH - TC)/TC C. η = TH/TC D. η = 1 - (TC/TH)

12. What is COP in refrigeration?

A. COP B. Thermal efficiency C. Isentropic efficiency D. Mechanical efficiency

13. What cycle does a steam power plant operate on?

A. Otto B. Diesel C. Rankine D. Brayton

14. What cycle does an internal combustion engine operate on?

A. Rankine B. Brayton C. Carnot D. Otto or Diesel

15. Which cycle is used in compression-ignition engines?

A. Diesel B. Otto C. Rankine D. Brayton

16. Which cycle is used in gas turbines?

A. Otto B. Diesel C. Brayton D. Rankine

17. What is the compressibility factor?

A. Z = 1 for all gases B. Z = 0 C. Z = ∞ D. Z = PV/nRT

18. What is a reversible process?

A. Reversible process B. Irreversible process C. Adiabatic process D. Isothermal process

19. What is a pure substance in thermodynamics?

A. Mixture B. Solution C. Compound D. Pure substance

20. What is a saturated liquid?

A. Superheated B. Saturated liquid C. Subcooled D. Compressed