1 Physics -- Second Law of Thermodynamics

7 .Which of the following is the largest unit of energy?electron voltjoulecalorieerg8. A perfect black body has a unique characteristic feature asa good absorber onlya good radiatora good absorber and a good radiatorneither a radiator nor an absorber9. A thermodynamic process where no h...

7 .Which of the following is the largest unit of energy?

electron volt

joule

calorie

8. A perfect black body has a unique characteristic feature as

a good absorber only

a good radiator

a good absorber and a good radiator

neither a radiator nor an absorber

9. A thermodynamic process where no heat is exchanged with the surroundings is

isothermal

adiabatic

isobaric

isotropic

10. Which of the following laws was formulated by Nernst?

First law of thermodynamics

Second law of thermodynamics

Third law of thermodynamics

None of the above

11) The irreversibility of a process occurs due to

a. lack of equilibrium during the process
b. involvement of dissipative effects
c. either a. or b. or both
d. none of the above

12 Efficiency of heat engine cycle is the ratio of

a. total heat input to the cycle (Q_in) to net work output of the cycle (W_net)
b. net work output of the cycle (W_net) to total heat input to the cycle (Q_in)
c. net work output of the cycle (W_net) to heat rejected from the system (Q_out)
d. none of the above

13. A cyclic heat engine operates between a source temperature of 927 ^oC and a sink temperature of 27 ^oC. What will be the maximum efficiency of the heat engine?

a. 100 %
b. 80 %
c. 75 %
d. 70 %

14. When a process becomes irreversible due to heat interaction between system and surrounding at the boundary due to finite temperature gradient, then the irreversibility is

a. internal irreversibility
b. external irreversibility
c. mechanical irreversibility
d. chemical irreversibility

15. PMM2 is the machine which violates ___________

a. Kelvin-Planck statement
b. Clausius statement
c. both a. and b.
d. none of the above

1 Answers

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7: Calorie is the largest unit of energy, among the given.

8: A perfect black body has a unique characteristic feature as a good absorber and a good radiator.

9: A thermodynamic process where no heat is exchanged with the surroundings is adiabatic.

10: Nernst formulated the Third law of thermodynamics.

11: The irreversibility of a process occurs due to either a) lack of equilibrium during the process or b) involvement of dissipative effects or both.

12: Efficiency of heat engine cycle is the ratio of net work output of the cycle (Wnet) to total heat input to the cycle (Qin).

13: A cyclic heat engine operates between a source temperature of 927 ^oC and a sink temperature of 27 ^oC. The maximum efficiency of the heat engine is 75%.

14: When a process becomes irreversible due to heat interaction between system and surrounding at the boundary due to finite temperature gradient, then the irreversibility is external irreversibility.

15: PMM2 is the machine which violates both a) Kelvin-Planck statement and b) Calusius statement.

Why does a refrigerator consume more power in summer than in winter to cool the same quantity of food by the same degree?

Answer: Heat pumps are designed to move thermal energy opposite to the direction of spontaneous heat flow by absorbing heat from a cold space and releasing it to a warmer one.Due to surrounding temperaturea refrigerator consume more power in summer than in winter to cool the same quantity of food by same degree.

A Carnot engine whose high-temperature reservoir is at 620 K takes in 550 J of heat at this temperature in each cycle and gives up 335 J to the low-temperature reservoir. (a) How much mechanical wo...

A Carnot engine whose high-temperature reservoir is at 620 K takes in 550 J of heat at this temperature in each cycle and gives up 335 J to the low-temperature reservoir. (a) How much mechanical work does the engine perform during each cycle? (b) What is

Solution:

Given,

Temperature of high-temperature reservoir (T1) = 620 K

Energy taken in each cycle (Q1) = 550 J

Energy given to low-temperature reservoir (Q2) = 335J

Now,

Mechanical work done in each cycle = Q1 - Q2

= 550 J - 335 J

= 215 J

Let the...

What happens to mileage per litre of diseal vehicle when it moves from hot terai to colder mustang?

The mileage per litre of diesel vehicles increases in moving from Terai to Mustang due to the decrease in surrounding temperature. With this, the density of air increases as we move from Terai to Mustang.

Does a refrigerator full of food consume more power if the room temperature is 20°C than if it is 15°C?

The efficiency of a refrigerator is expressed as:

Beta = T2 / (T1 - T2)

where T1 is the temperature of the source and T2 is the temperature of the sink. The smaller the value of (T1 - T2), the larger will be the efficiency of refrigerator. Hence, the refrigerator consumes more power when the room temperature is 20^oC than when it is 15^oC.

Q1. A measure of the degree of disorder of a system is known as Enthalpy Isobaric Isotropy EntropyQ2. If ΔThe efficiency of Carnot engine operating with reservior temperature at 100 K and –23 K wil...

1: A measure of the degree of disorder of a system is known asenthalpy.

2:If ΔThe efficiency of Carnot engine operating with reservior temperature at 100 K and –23 K will be(100+23)/100.

3:Coefficient of performance of an ideal refrigerator working between temperature T1 and T2 (T1 > T2) isBeta = T2 / (T1 - T2).

4:Entropy of a thermodynamic system does not change when this system is used for conduction of heat from a hot reservoir to a cold reservoir.

5:The second law of thermodynamics states...

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