Engineering Thermodynamics (3131905) MCQs

MCQs of Exergy

Showing 21 to 20 out of 30 Questions
1 2 3
21.

When the closed system is allowed to undergo a spontaneous change from a given state to a dead state, its exergy is ____ destroyed ____ producing useful work.

(a)

not completely, though
(b)

not completely, without
(c)

completely, though
(d)

completely, without
Answer:

Option (d)

22.

The exergy of an isolated system can ________.

(a)

increase
(b)

decrease
(c)

never increase
(d)

never decrease
Answer:

Option (c)

23.

For a closed system, availability or exergy transfer occurs through

(a)

heat interactions
(b)

work interactions
(c)

both of the mentioned
(d)

none of the mentioned
Answer:

Option (c)

24.

The first law of efficiency 

(a)

on energy basis 
(b)

on exergy basis 
(c)

both on energy and exergy basis 
(d)

none of these
Answer:

Option (a)

25.

The first law efficiency is defined as 

(a)

actual exergy intake / minimum exergy intake
(b)

minimum exergy intake / actual exergy intake
(c)

actual exergy intake / maximum exergy intake
(d)

output energy/input energy
Answer:

Option (d)

26.

Second law efficiency is defined as

(a)

actual exergy intake / minimum exergy intake
(b)

minimum exergy intake / actual exergy intake
(c)

actual exergy intake / maximum exergy intake
(d)

maximum exergy intake / minimum exergy intake
Answer:

Option (b)

27.

Two engines having same thermal efficiency but supplied with heat from a source at different temperatures

(a)

will convert same fraction of heat they receive into work
(b)

from second law, one will perform better than other
(c)

this can be considered as a deficiency of the first law
(d)

all of the mentioned
Answer:

Option (d)

28.

Second law efficiency can also be given as

(a)

1first law efficiency × Carnot efficiency

(b)

Carnot efficiency × First law efficiency

(c)

 Carnot efficiencyFirst law efficiency

(d)

 First law efficiencyCarnot efficiency

Answer:

Option (d)

29.

Which of the following statement is true?

(a)

Kinetic energy is entirely available energy
(b)

Potential energy is entirely exergy
(c)

The exergy of thermal energy of reservoirs is equivalent to the work output of a Carnot engine operating between the reservoir at temperature T and environment To.
(d)

all of the mentioned
Answer:

Option (d)

30.

Which of the following is true?

(a)

For work producing devices, second law efficiency = useful work / reversible work
(b)

For work absorbing devices, second law efficiency = reversible work/useful work
(c)

Both of the mentioned
(d)

None of the mentioned
Answer:

Option (c)

Showing 21 to 20 out of 30 Questions
1 2 3