Deck 13: Thermodynamics and Entropy Principles

Question 1

Efficiency of a reversible heat engine is given by

A)1-(t1/t2)
B)1-(t2/t1)
C)(t1/t2)-1
D)(t2/t1)-1

Answer 1

1-(t2/t1)

Question 2

For a reversible refrigerator, Coefficient of Performance is given by

A)t2/(t1-t2)
B)t1/(t1-t2)
C)t2/(t2-t1)
D)t1/(t2-t1)

Answer 2

t2/(t1-t2)

Question 3

Entropy principle is the quantitative statement of the second law of thermodynamics.

Answer 3

True

Question 4

Which of the following can be considered as an application of entropy principle?

A)transfer of heat through a finite temperature difference
B)mixing of two fluids
C)maximum temperature obtainable from two finite bodies
D)all of the mentioned

Question 5

The final temperatures of two bodies, initially at T1 and T2 can range from

A)(t1-t2)/2 to sqrt(t1*t2)
B)(t1+t2)/2 to sqrt(t1*t2)
C)(t1+t2)/2 to (t1*t2)
D)(t1-t2)/2 to (t1*t2)

Question 6

Which of the following processes exhibit external mechanical irreversibility?

A)isothermal dissipation of work
B)adiabatic dissipation of work
C)both of the mentioned
D)none of the mentioned

Question 7

Which of the following is an example of low grade energy?

A)heat or thermal energy
B)heat from nuclear fission or fusion
C)heat from combustion of fossil fuel
D)all of the mentioned

Question 8

Which of the following is an example of high grade energy?

A)mechanical work
B)electrical energy
C)water power and wind power
D)all of the mentioned

Question 9

The unavailable energy is the product of the lowest temperature of heat rejection and the change of entropy of system during the process of supplying heat.

Question 10

The lowest practicable temperature of heat rejected is the

A)given temperature
B)0k
C)temperature of surroundings
D)273k

Question 11

Exergy is lost due to

A)irreversible heat transfer
B)through finite temperature difference
C)during the process of heat addition
D)all of the mentioned

Question 12

Which of the following is a type of energy?

A)high grade energy
B)low grade energy
C)both of the mentioned
D)none of the mentioned

Question 13

The complete conversion of heat into shaft- work is impossible.

Question 14

Energy is said to be degraded each time it flows through a finite temperature difference.

Question 15

When considering a finite energy source, its working fluid expands,

A)reversibly
B)adiabatically
C)reversibly and adiabatically
D)none of the mentioned

Question 16

The entropy of any closed system can increase in which if the following way?

A)by heat interaction in which there is entropy transfer
B)dissipative effects or internal irreversibilities
C)both of the mentioned
D)none of the mentioned

Question 17

The entropy increase due to internal irreversibility is also called entropy production or entropy generation.

Question 18

Which of the following statement is true?

A)if the isentropic process is reversible, it must be adiabatic
B)if the isentropic process is adiabatic, it cannot but be reversible
C)if the process is adiabatic and reversible, it must be isentropic
D)all of the mentioned

Question 19

Lost work is given by

A)pdv-dw
B)pdv+dw
C)-pdv-dw
D)pdv*dw

Question 20

Which of the following statement is false?

A)for a reversible process, entropy generation is zero
B)the entropy generation does not depend on the path the system follows
C)for an irreversible process, entropy generation is greater than zero
D)none of the mentioned

Question 21

Mass and energy are conserved quantities, but entropy is generally not conserved.

Question 22

A chip dissipates 2 kJ of electric work and rejects it as heat transfer from its surface which is at 50°C to 25°C air. How much entropy is generated outside the chip?

A)0.419 j/k
B)0.519 j/k
C)0.619 j/k
D)0.719 j/k

Question 23

Entropy increase dS of the system can be expressed as

A)ds=ds(due to external heat interaction)- ds(due to internal irreversibility)
B)ds=ds(due to external heat interaction)+ds(due to internal irreversibility)
C)ds=-ds(due to external heat interaction)- ds(due to internal irreversibility)
D)ds=-ds(due to external heat interaction)+ds(due to internal irreversibility)

Question 24

If the path A causes more entropy generation than path B, then

A)path a is more irreversible than path b
B)path a involves more lost work
C)both of the mentioned
D)none of the mentioned

Question 25

In an open system, there is a transfer of which of the following quantity?

A)mass
B)energy
C)entropy
D)all of the mentioned