Deck 3: Thermodynamics and Entropy

Question 1

The main cause of the irreversibility is

A)mechanical & fluid friction
B)unrestricted expansion
C)heat transfer with a finite temperature difference
D)all of the above

Answer 1

all of the above

Question 2

An isentropic process is always

A)irreversible & adiabatic
B)reversible & isothermal
C)frictionless & irreversible
D)reversible & adiabatic

Answer 2

reversible & adiabatic

Question 3

In the polytropic process equation pv? = constant, if n is infinitely large, the process is termed as

A)constant volume
B)constant pressure
C)constant temperature
D)diabatic

Answer 3

constant volume

Question 4

For a reversible adiabatic process, the change in entropy is

A)zero
B)minimum
C)maximum
D)infinite

Question 5

For any reversible process, the change in entropy of the system & surroundings is

A)zero
B)unity
C)negative
D)positive

Question 6

For any irreversible process the net entropy change is

A)zero
B)positive
C)negative
D)infinite

Question 7

The processes of a Carnot cycle are

A)two adiabatic & two constant volume
B)one constant volume &one constant pressure & two isentropies
C)two adiabatics & two isothermals
D)two isothermals & two isentropies

Question 8

Isentropic flow is

A)irreversible adiabatic flow
B)ideal fluid flow
C)reversible adiabatic flow
D)frictionless reversible flo

Question 9

In a carnot engine, when the working substance gives heat to the sink

A)the temperature of the sink increases
B)the temperature of the sink remains the same
C)the temperature of the source decreses
D)the temperature of the source decrease

Question 10

If the temperature of the source is increased, the efficiency of the Carnot engine

A)decrease
B)increase
C)does not change
D)will be equal to the efficiency of a practicalengine

Question 11

The efficiency of an ideal Carnot engine depends on

A)working substance
B)on the temperature of the source only
C)on the temperature of the sink only
D)on the temperatures of both the source & the sink

Question 12

In a reversible cycle, the entropy of the system

A)increases
B)decreases
C)does not change
D)first increases & thendecreases

Question 13

Kelvin-Plank's law deals with

A)conservation of energy
B)conservation of heat
C)conservation of mass
D)conversion of heat intowork

Question 14

Which of the following statements is correct according to Clausius statement of second law of thermodynamics?

A)it is impossible to transfer heat from a body at a lower temperature to a body at a higher temperature
B)it is impossible to transfer heat from a body at a lower temperature to a body at a higher temperature, without the aid of an external source
C)it is possible to transfer heat from a body at a lower temperature to a body at a higher temperature by using refrigeration cycle
D)none of the above

Question 15

The property of a working substance which increases or decreases as the heat is supplied or removed in a reversible manner is known as

A)enthalpy
B)internal energy
C)entropy
D)external energy

Question 16

The entropy may be expressed as a function of

A)pressure & temperature
B)temperature & volume
C)heat & work
D)all of the above

Question 17

The change of entropy when heat is absorbed by the gas is

A)positive
B)negative
C)positive or negative
D)all of the above

Question 18

Which of the following statements is correct?

A)the increase in entropy is obtained from a given quantity of heat at a low temperature
B)the change in entropy may be regarded as a measure of the rate of the availability of heat fortransformation into work
C)the entropy represents the maximum amount of work obtainable per degree drop in temperature
D)all of the above

Question 19

In an irreversible process, there is a

A)loss of heat
B)no loss of work
C)gain of heat
D)no gain of heat

Question 20

The efficiency of the Carnot cycle may be increased by

A)increasing the highesttemperature
B)decreasing the highesttemperature
C)increasing the lowesttemperature
D)decreasing the lowesttemperature

Question 21

Which of the following is the correct statement?

A)all the reversible engines have the same efficiency
B)all the reversible & irreversible engines have the same efficiency
C)irreversible engines have maximum efficiency
D)all engines are designed as reversible in order to obtain maximum efficiency

Question 22

The reversible engines are

A)least efficient
B)most efficient
C)having same efficiency asirreversible engines
D)none of the above

Question 23

Gases could have an infinite number of specific heats but only ……. Specific heats are defined

A)one
B)two
C)three
D)four

Question 24

The area under the T-s (temperature - entropy) curve of any thermodynamic process represents

A)heat rejected only
B)heat absorbed only
C)work done during the process
D)heat absorbed or rejected