# Fluid Mechanics Questions and Answers – Thermodynamic Relations

This set of Fluid Mechanics Multiple Choice Questions & Answers (MCQs) focuses on “Thermodynamic Relations”.

1. The symbol of Helmholtz free energy is_________
a) A
b) H
c) B
d) E

Explanation: Helmholtz free energy is defined as the thermodynamic potential that measures the useful work obtained from a closed thermodynamic system. It is done at a constant volume and temperature. IUPAC name is ‘A’.

2. Which among the following is the formula for Helmholtz free energy?
a) U+TS
b) U+TV
c) U-TS
d) UTV

Explanation: Helmholtz free energy is defined as the thermodynamic potential that measures the useful work obtained from a closed thermodynamic system. It is done at a constant volume and temperature. IUPAC name is ‘A’. (A= U-TS).

3. What is the unit of Helmholtz free energy?
a) Kelvin
b) Joule
c) Kilowatt
d) Newton

Explanation: Helmholtz free energy is defined as the thermodynamic potential that measures the useful work obtained from a closed thermodynamic system. The SI unit of Helmholtz free energy is Joule.

4. What is the symbol for Gibbs free energy?
a) A
b) H
c) G
d) E

Explanation: Gibbs free energy is defined as the thermodynamic potential that is used to calculate the maximum amount of reversible work. It takes place at a constant pressure and temperature. The IUPAC name for Gibbs free energy is ‘G’.

5. Gibbs free energy is also known as______
a) Free energy
b) Free entropy
c) Free enthalpy
d) Free motion

Explanation: Gibbs free energy is defined as the thermodynamic potential that is used to calculate the maximum amount of reversible work. Gibbs free energy is also known as free enthalpy. It takes place at a constant pressure and temperature.

6. What is the unit of Gibbs free energy?
a) Kelvin
b) Joule
c) Kilowatt
d) Newton

Explanation: Gibbs free energy is defined as the thermodynamic potential that is used to calculate the maximum amount of reversible work. It takes place at a constant pressure and temperature. The SI unit is Joule.

7. Which among the following is the formula for Gibbs free energy?
a) H-T∆S
b) H-T
c) T∆S
d) H-S

Explanation: Gibbs free energy is defined as the thermodynamic potential that is used to calculate the maximum amount of reversible work. It takes place at constant temperature and pressure. It is given by H-T∆S.

8. All the energy relations satisfy the mathematical condition in thermodynamics.
a) True
b) False

Explanation: All the thermodynamic energy relations satisfy the mathematical condition of being a set of continuous variables. They are a function of state variables themselves.

9. The performance of a flow device is expressed in terms of _________
b) Isentropic efficiency
c) Thermal efficiency
d) Mechanical efficiency

Explanation: The performance of a flow device is expressed in terms of its isentropic efficiency. The actual performance of the device is compared with that of its isentropic device. It happens at the same inlet and exit conditions.

10. Isentropic efficiency is defined as ________
a) The power output of actual turbine/ power output if the turbine were isentropic
b) The power input of actual turbine/ power output if the turbine were isentropic
c) The power output of actual turbine/ power output if the turbine were adiabatic
d) The power output of actual turbine/ power output if the turbine were polytropic

Explanation: The performance of a flow device is expressed in terms of its isentropic efficiency. The actual performance of the device is compared with that of its isentropic device. It happens at the same inlet and exit conditions.

Sanfoundry Global Education & Learning Series – Fluid Mechanics.

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