# Thermodynamics Questions and Answers – Brayton Cycle-1

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This set of Thermodynamics Multiple Choice Questions & Answers (MCQs) focuses on “Brayton Cycle-1”.

1. A gas turbine power plant uses
a) Otto cycle
b) Rankine cycle
c) Brayton cycle
d) Diesel cycle

Explanation: The Brayton cycle is the air standard cycle for gas turbine power plant.

2. The Brayton cycle consists of
a) two reversible isotherms and two reversible isobars
b) two reversible isochores and two reversible adiabatics
c) two reversible isotherms and two reversible isochores
d) two reversible isobars and two reversible adiabatics

Explanation: These are the processes of Brayton cycle.

3. Which of the following is true for the Brayton cycle?
a) first sir is compressed reversibly and adiabatically
b) heat is added reversibly at constant pressure
c) air expands in turbine reversibly and adiabatically
d) all of the mentioned

Explanation: These processes take place in the Brayton cycle.
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4. The efficiency of Brayton cycle is given by (rk is the compression ratio)
a) 1/(rk)^(ɣ-1)
b) 1 – 1/(rk)^(ɣ)
c) 1 – 1/(rk)^(ɣ-1)
d) 1/(rk)^(ɣ)

Explanation: This is the expression for efficiency of Brayton cycle and rk=compression ratio.

5. The efficiency of Brayton cycle depends on
a) compression ratio
b) pressure ratio
c) either compression ratio or pressure ratio
d) both compression ratio and pressure ratio

Explanation: The reason being, compression ratio can be expressed in terms of pressure ratio.

6. For the same compression ratio, the efficiency of Brayton cycle is ____ the efficiency of Otto cycle.
a) less than
b) equal to
c) greater than
d) none of the mentioned

Explanation: The expressions for efficiency of Brayton cycle and Otto cycle are same.

7. Both Rankine cycle and Brayton cycle consists of two reversible isochores and two reversible adiabatics.
a) true
b) false

Explanation: Both Rankine cycle and Brayton cycle consists of two reversible isobars and two reversible adiabatics.

8. In Rankine cycle, working fluid ____ , in Brayton cycle working fluid ____
a) undergoes phase change, remains in gaseous phase
b) remains in gaseous phase, undergoes phase change
c) undergoes phase change, undergoes phase change
d) remains in gaseous phase, remains in gaseous phase

Explanation: This is a difference in Rankine cycle and Brayton cycle.

9. For Brayton cycle, average specific volume of air that compressor handles is ____ the same of gas in a gas turbine.
a) equal to
b) more than
c) less than
d) none of the mentioned

Explanation: This is because the gas temperature is much higher.

10. A steam power plant works on ____ and a gas turbine works on ____
a) both work on Rankine cycle
b) both work on Brayton cycle
c) Brayton cycle, Rankine cycle
d) Rankine cycle, Brayton cycle

Explanation: This is a difference in a steam power plant and a gas turbine.

11. Which of the following is more popular for electricity generation?
a) gas turbine
b) steam power plant
c) both of the mentioned
d) none of the mentioned

Explanation: Because in Rankine cycle, specific volume of water in pump is less than that of steam expanding in steam turbine.

12. For the same compression ratio and work capacity, Brayton cycle handles ____ range of volume and ____ range of pressure and temperature than does Otto cycle.
a) larger, smaller
b) smaller, larger
c) both are same
d) none of the mentioned

Explanation: This can be seen in the p-V diagram of Brayton cycle and Otto cycle.

13. Why is Otto cycle more suitable in reciprocating engine field?
a) reciprocating engine field cannot handle large volume of low pressure gas
b) the engine size increases
c) the friction losses become more
d) all of the mentioned

Explanation: This is the reason why Brayton cycle is not preferred in reciprocating engine field.

14. In turbine plants, Otto cycle is more suitable than Brayton cycle.
a) true
b) false

Explanation: In turbine plants, Brayton cycle is used instead of Otto cycle.

15. Which of the following statement is true?
a) an IC engine is exposed to highest temperature only for a short period
b) a gas turbine plant is always exposed to highest temperature used
c) in a gas turbine plant, maximum temperature used should be less than that used in IC engine
d) all of the mentioned

Explanation: This is the reason why in turbine plants, Brayton cycle is preferred.

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