Engineering Thermodynamics Set 13 MCQs

Q1 | Example of reversed heat engine is

heat pump

refrigerator

both of the mentioned

none of the mentioned

Q2 | Efficiency of a reversible heat engine is given by

1-(t1/t2)

1-(t2/t1)

(t1/t2)-1

(t2/t1)-1

Q3 | For a reversible refrigerator, Coefficient of Performance is given by

t2/(t1-t2)

t1/(t1-t2)

t2/(t2-t1)

t1/(t2-t1)

Q4 | Entropy principle is the quantitative statement of the second law of thermodynamics.

true

false

Q5 | Which of the following can be considered as an application of entropy principle?

transfer of heat through a finite temperature difference

mixing of two fluids

maximum temperature obtainable from two finite bodies

all of the mentioned

Q6 | The final temperatures of two bodies, initially at T1 and T2 can range from

(t1-t2)/2 to sqrt(t1*t2)

(t1+t2)/2 to sqrt(t1*t2)

(t1+t2)/2 to (t1*t2) d) (t1-t2)/2 to (t1*t2)

Q7 | Which of the following processes exhibit external mechanical irreversibility?

isothermal dissipation of work

adiabatic dissipation of work

both of the mentioned

none of the mentioned

Q8 | Which of the following is an example of low grade energy?

heat or thermal energy

heat from nuclear fission or fusion

heat from combustion of fossil fuel

all of the mentioned

Q9 | Which of the following is an example of high grade energy?

mechanical work

electrical energy

water power and wind power

all of the mentioned

Q10 | 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.

true

false

Q11 | The lowest practicable temperature of heat rejected is the

given temperature

0k

temperature of surroundings

273k

Q12 | Exergy is lost due to

irreversible heat transfer

through finite temperature difference

during the process of heat addition

all of the mentioned

Q13 | Which of the following is a type of energy?

high grade energy

low grade energy

both of the mentioned

none of the mentioned

Q14 | The complete conversion of heat into shaft- work is impossible.

true

false

Q15 | Energy is said to be degraded each time it flows through a finite temperature difference.

true

false

Q16 | When considering a finite energy source, its working fluid expands,

reversibly

adiabatically

reversibly and adiabatically

none of the mentioned

Q17 | The entropy of any closed system can increase in which if the following way?

by heat interaction in which there is entropy transfer

dissipative effects or internal irreversibilities

both of the mentioned

none of the mentioned

Q18 | The entropy increase due to internal irreversibility is also called entropy production or entropy generation.

true

false

Q19 | Which of the following statement is true?

if the isentropic process is reversible, it must be adiabatic

if the isentropic process is adiabatic, it cannot but be reversible

if the process is adiabatic and reversible, it must be isentropic

all of the mentioned

Q20 | Lost work is given by

pdv-dw

pdv+dw

-pdv-dw

pdv*dw

Q21 | Which of the following statement is false?

for a reversible process, entropy generation is zero

the entropy generation does not depend on the path the system follows

for an irreversible process, entropy generation is greater than zero

none of the mentioned

Q22 | Mass and energy are conserved quantities, but entropy is generally not conserved.

true

false

Q23 | 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?

0.419 j/k

0.519 j/k

0.619 j/k

0.719 j/k

Q24 | Entropy increase dS of the system can be expressed as

ds=ds(due to external heat interaction)- ds(due to internal irreversibility)

ds=ds(due to external heat interaction)+ds(due to internal irreversibility)

ds=-ds(due to external heat interaction)- ds(due to internal irreversibility)

ds=-ds(due to external heat interaction)+ds(due to internal irreversibility)

Q25 | If the path A causes more entropy generation than path B, then

path a is more irreversible than path b

path a involves more lost work

both of the mentioned

none of the mentioned