Heat and Thermodynamics Model Question Paper

11th Standard

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Physics

Time : 02:00:00 Hrs
Total Marks : 50
6 x 1 = 6
1. In hot summer aft er a bath, the body’s

(a)

internal energy decreases

(b)

internal energy increases

(c)

heat decreases

(d)

no change in internal energy and heat

2. When you exercise in the morning, by considering your body as thermodynamic system, which of the following is true?

(a)

ΔU > 0, W > 0,

(b)

ΔU < 0, W > 0,

(c)

ΔU < 0, W < 0,

(d)

ΔU = 0, W > 0,

3. Identify the state variables given here?

(a)

Q, T, W

(b)

P, T, U

(c)

Q, W

(d)

P, T, Q

4. The efficiency of a heat engine working between the freezing point and boiling point of water is

(a)

6.25%

(b)

20%

(c)

26.8%

(d)

12.5%

5. An ideal refrigerator has a freezer at temperature −12°C. The coefficient of performance of the engine is 5. The temperature of the air (to which the heat ejected) is

(a)

50°C

(b)

45.2°C

(c)

40.2°C

(d)

37.5°C

6. 1 mole of a gas with $\gamma =\frac { 7 }{ 5 }$  is mixed with 1 mole of gas with $\gamma =\frac { 5 }{ 3 }$ then value of g of the resulting mixture is

(a)

$\frac { 7 }{ 5 }$

(b)

$\frac { 2 }{ 5 }$

(c)

$\frac { 3 }{ 2 }$

(d)

$\frac { 12 }{ 7 }$

7. 10 x 2 = 20
8. A refrigerator has COP of 3. How much work must be supplied to the refrigerator in order to remove 200 J of heat from its interion?

9. Define one mole.

10. What is a thermal expansion?

11. What is Wien’s law?

12. What is a black body?

13. Define one calorie.

14. State the first law of thermodynamics.

15. What is PV diagram?

16. Define heat engine.

17. Consider the following cyclic process consist of isotherm, isochoric and isobar which is given in the figure.

Draw the same cyclic process qualitatively in the V-T diagram where T is taken along x direction and V is taken along y-direction. Analyze the nature of heat exchange in each process.

Process 1 to 2 = increase in volume. So heat must be added.
Process 2 to 3 = Volume remains constant. Increase in temperature. The given heat is used to increase the internal energy.
Process 3 to 1 : Pressure remains constant. Volume and Temperature are reduced. Heat flows out of the system. It is an isobaric compression where the work is done on the system.

18. 3 x 3 = 9
19. Give an example of a quasi-static process.

20. 500 g of water is heated from 30°C to 60°C. Ignoring the slight expansion of water, calculate the change in internal energy of the water? (specific heat of water 4184 J/kg.K)

21. A steam engine boiler is maintained at 250°C and water is converted into steam. This steam is used to do work and heat is ejected to the surrounding air at temperature 300K. Calculate the maximum efficiency it can have?

22. 3 x 5 = 15
23. A student comes to school by a bicycle whose tire is filled with air at a pressure 240 kPa at 27°C. She travels 8 km to reach the school and the temperature of the bicycle tire increases to 39°C. What is the change in pressure in the tire when the student reaches school?

24. Discuss the ideal gas laws.

25. Explain in detail Newton’s law of cooling.