Questions and Answers on Thermodynamics

Questions and Answers on Thermodynamics

1-If ‘n’ is the index of compression, then the work done in compressing air is proportional to

(A) n

(B) n2

(C) (n / n-1)

(D) (n-1 / n)


2-For the same compression ratio

(A) Otto cycle is more efficient than Diesel cycle

(B) Diesel cycle is more efficient than Otto cycle

(C) The efficiency of Otto and Diesel cycle are same

(D) None of the above


3-Reheating in gas turbine is done

(A) between compressor stages

(B) between turbine stages

(C) between compressor and turbine

(D) with combustion chamber


4-Intercooling in compressors is meant for

(A) reducing the work of compression

(B) increasing the compressor efficiency

(C) reducing the power input

(D) all of the above


5-Compression ratio is the ratio between

(A) total volume and clearance volume

(B) total volume and swept volume

(C) maximum pressure and minimum pressure

(D) delivery pressure and suction pressure


6-The following cycle provides the maximum work output between two temperature inputs

(A) Otto cycle

(B) Diesel cycle

(C) Brayton cycle

(D) Carnot cycle


7-The first law of thermodynamics deals with

(A) Conservation of mass

(B) Conservation of enthalpy

(C) Conservation of energy

(D) Conservation of momentum


8-The quantity H-TS is termed as

(A) Flow work

(B) Gibbs function

(C) Helmholtz function

(D) excergy


9-The work done in a constant volume process is

(A) Very high

(B) Very low

(C) Moderate

(D) Zero


10-In a process PVn=C, If n=1, then the process is

(A) Constant pressure

(B) Constant temperature

(C) Constant volume

(D) Constant entropy


11-A thermodynamic system which permits only energy transfer through its boundaries is a (an)

(A) open system

(B) closed system

(C) isolated system

(D) rigid system


12-The Carnot cycle consists of

(A) Two constant volume process

(B) Two constant pressure process

(C) Two isenthalpic process

(D) Two isothermal process


13-The property of a system whose value does not depend upon the mass of the system is known as

(A) Intensive property

(B) Extensive property

(C) Constant property

(D) Variable property


14-Ideal ‘operating characteristics curve’ looks like

(A) Triangle

(B) Circle

(C) Rectangle

(D) Square


15-Which of the following defines the ideal gas equation?

Where p=absolute pressure, v=specific volume, T=absolute temperature and R=Gas constant

(A) pv=RT

(B) pR=vT

(C) pT=vR

(D) p=v/RT


16-Internal energy of an isolated system

(A) increases with addition of heat

(B) increases with increase in mass of the system

(C) remain same

(D) increases with addition of work


17-Which is a single phase system?

(A) Mixture of water and alcohol

(B) Mixture of oil and water

(C) Liquid water, ice and water vapour

(D) Water and ice


18-ITS-90 defines which of the following as a reference for calibration of temperature scale

(A) Ice point

(B) Lamda point

(C) Normal boiling point of water

(D) Triple point of water


19-Pressure of the atmosphere is equivalent to

(A) 0.101325 MPa

(B) 750 mm of mercury

(C) 1 bar

(D) 0.101325 KPa


20-Attemperation is done

(A) Just after the secondary superheater

(B) Just before the primary superheater

(C) Between the primary and secondary superheater

(D) At the entry of steam from boiler


21-The air standard cycle with the following processes in sequence: 1. Reversible adiabatic compression, 2. Reversible constant pressure heat addition, 3. Reversible adiabatic expansion and, 4. Reversible constant volume heat rejection, is

(A) Otto cycle

(B) Diesel cycle

(C) Dual cycle

(D) Brayton cycle


22-In convergent divergent nozzle, normal shock can generally occur:

(A) Along the divergent portion and throat

(B) Along the convergent portion

(C) Anywhere along the length

(D) Near the inlet


23-Isenropic flow is

(A) Irreversible adiabatic flow

(B) Reversible adiabatic flow

(C) Ideal fluid flow

(D) Frictionless reversible flow


24-An aeroplane is cruising at a speed of 800kmph at an altitude, where the air temperature is zero degree Celsius. The flight Mach number at this speed is nearly

(A) 1.5

(B) 0.254

(C) 0.67

(D) 2.04


25-An IC engine has a bore and stroke of 2 units each. The area to calculate heat loss can be taken as

(A) 4π

(B) 5π

(C) 6π

(D) 8π


26-With increasing temperature of intake air, IC engine efficiency

(A) Decreases

(B) Increases

(C) Remains the same

(D) Depends on other factor



1-(C), 2-(A), 3-(B), 4-(D), 5-(A), 6-(D), 7-(C), 8-(B), 9-(D), 10-(B), 11-(B), 12-(D), 13-(B), 14-(C), 15-(A), 16-(C), 17-(A), 18-(D), 19-(A), 20-(C), 21-(B), 22-(A), 23-(B), 24-(C), 25-(D), 26-(A)