# Thermodynamics-SSC JE Mechanical Engineering Practice Questions

Thermodynamics questions for practice for SSC JE Mechanical Engineering exam. The answers for the questions have been shared below, in case of any doubt or query, feel free to leave a comment in the comment box below.

Q1) According to Gay Lussac law for a perfect gas, the absolute pressure of a given mass varies directly as

1. Temperature
2. Absolute temperature
3. Absolute temperature, if volume is kept constant
4. volume, if temperature is kept constant

Ans: c

Q2) Temperature of a gas is produced due to

1. its heating value
2. kinetic energy of molecules
3. repulsion of molecules
4. attraction of molecules

Ans: b

Q3) The pressure of a gas in terms of its mean kinetic energy per unit volume E is equal to

1. E/3
2. E/2
3. 3E/4
4. 2E/3

Ans: d

Q4) In order that a cycle be reversible, following must be satisfied

1. free expansion or friction resisted expansion/compression process should not be encountered
2. when heat is being absorbed, temperature of hot source and working substance should be same
3. when heat is being rejected, temperature of cold source and working substance should be same
4. all options are correct

Ans: d

Q5) The property of a working substance, which increases or decreases according to the heat supplied or removed in a reversible manner, is called _____.

1. enthalpy
2. entropy
3. reversibility
4. none of these

Ans: b

Q6) Non quasistatic process is ____.

1. free expansion of gas
2. expansion of a gas in a cylinder under constant pressure
3. rapid compression of a gas in a cylinder
4. gradual compression of a gas in a cylinder

Ans: a

Q7) If a gas vapor is allowed to expand through a very minute aperture, then such a process is known as ____.

1. free expansion
2. throttling
3. hyperbolic expansion
4. parabolic expansion

Ans: b

Q8) Entropy change depends on ____.

1. heat transfer
2. mass transfer
3. change of temperature
4. thermodynamic state

Ans: a

Q9) An engine working between positive temperatures _____.

1. can be a heat pump
2. cannot be a heat pump
3. must be a heat pump
4. can be a heat pump if frictionless machine is used

Ans: c

Q10) Superheated vapor behaves ______.

1. exactly as gas
2. as steam
3. as ordinary vapor
4. approximately as gas

Ans: d

Q11) When a gas flows through a very long pipe of uniform cross section, the flow is approximately

1. isentropic
2. isobaric
3. isothermal

Ans: c

Q12) A football was inflated to a gauge pressure of 1 bar when the ambient temperature was . When the game started next day, the air temperature at the stadium was . Assume that the volume of the football remains constant at 2500 cc. Gauge pressure of air to which the ball must have been originally inflated so that it would equal 1 bar gauge at the stadium is ____.

1. 2.23 bar
2. 1.94 bar
3. 1.07 bar
4. 1 bar

Ans: c

Q13) The valves mounted on the boilers which change the direction of flow of steam by  and valves fitted in the pipelines which allow the steam in the same direction are respectively called as ______.

1. stop valves and junction valves
2. junction valves and stop valves
3. junction valves and safety valves
4. feed safety valves and stop valves

Ans: b

Q14) In a cross compound steam engine ______.

1. one high and one low pressure cylinders are set side by side, driving the same shaft, cranks being set  apart
2. two cylinders are centred on the same piston rod, the 1.p cylinder being placed nearest the crankshaft
3. two cylinders are set at , usually to save floor space
4. none of these

Ans: a

Q15) Maximum work by an expansion of a gas in a closed system is possible when process takes place at constant

1. pressure
2. temperature
3. volume
4. enthalpy

Ans: a

Q16) Which of the following represents the perpetual motion machine of the first kind

1. engine with 100% thermal efficiency
2. a full reversible engine
3. transfer of heat energy from low temperature source to high temperature source
4. a machine that continuously creates its own energy

Ans: d

Q17) When a process undergoes a complete cycle then the change of entropy will be

1. +ve
2. -ve
3. zero
4. +ve or -ve depending on initial condition

Ans: c

Q18) When a liquid boils at constant pressure, the following parameter increases

1. temperature
2. heat of vaporization
3. kinetic energy
4. entropy

Ans: d

Q19) it is proposed to make a direct heat-to-work transfer converter out of an elementary system which absorbs heat while doing isothermal work exactly equal to

1. not possible
2. possible
3. not desirable
4. commendable

Ans: a

Q20) When two gases suddenly mix up with each other then resultant entropy of the system will

1. decrease
2. increase
3. remain same
4. may increase or decrease depending upon the initial conditions of the gases

Ans: b