NDA PHYSICS

1. The SI unit of heat is

(a) calorie                  (b) joule  (c) watt                       (d) erg

2. Therm is associated with

(a) heat                  (b) light  (c) magnetism         (d) none of these

3. The absorptive power of a perfectly black body is

(a) zero      (b) 0.5  (c) 1     (d) infinite

4. A heat engine takes heat from a source at a certain temperature and

(a) converts it all into work

(b) converts some of it into work and gives out the rest to the                                   surroundings at lower temperature

(c) converts some of it into mechanical energy and gives out the rest to                 the source from which the heat was taken

(d) converts some of it into work and gives out the remaining to the                      surroundings at higher temperatures.

5. Which one of the following converts heat energy into mechanical energy?

(a) Dynamo               (b) Motor  (c) Heat generator  (d) Heat engine

6. Water is boiling in a flask on a burner. To reduce its boiling point, one              must

(a) reduce the surrounding temperature

(b) connect the mouth of the flask to an evacuating system

(c) supply heat from a very intense heat source

(c) close the container with an air tight cork

7. Water boils when its saturated vapour pressure

(a) is very high

(b) is equal to that of the surroundings

(c)  is equal to a pressure of 76 cm of Hg

(d)  is equal to a few points of the surrounding

8. Melting point of ice

(a) Increases with an increase in pressure

(b) Decreases with an increase in pressure

(c) Is independent of pressure

(d) Is proportional to pressure

9. Which one of the following devices is used for measuring very high                  temperature ?

(a) Gas thermometer

(b) Mercury thermometer

(c) Pyrometer

(d) Platinum resistance thermometer

10. Paraffin wax contracts on solidification. The melting point of wax will

(a) increase with an increase in pressure

(b) decrease with an increase in pressure

(c) not change by variation of pressure

(d) decrease linearly with pressure

11. A fan produces a feeling of comfort during hot weather because

(a) fan supplies cold air

(b) our perspiration evaporates rapidly

(c) our body radiates more heat in air

(d) conductivity of air increases

12. Two blocks of ice when pressed together join to form one block because

(a) heat is produced on pressing

(b) heat is absorbed during pressing

(c) melting point of ice decreases with an increase in pressure

(d) melting point of ice increases with an increase in pressure

13.The absolute zero is the temperature at which

(a) water freezes

(b) molecular motion stops

(c) substances exist in solid state

(d) none of these

14. An iron ball is heated. The percentage increase will be largest in

(a) diameter              (b) density  (c) mass                      (d) volume

15. The first law of thermodynamics is a special case of

(a) Newton’s law

(b) Charles’s law

(c) The law of heat exchange

(d) The law of conservation of energy

16. Iron, lead, brass and glass spheres of equal masses heated to the same             temperature are placed on a paraffin plate. Which will come out

through the plate first?

(a) Iron                        (b) Lead  (c) Brass                     (d) Glass

17. The second law of thermodynamics states that

(a) heat is neither created nor destroyed

(b) heat can be converted into other forms of energy

(c) heat flows from a hot object to a cool one

(d) heat and work are the same

18. Which of the following has two specific heats?

(a) Solid        (b) Gas  (c) Liquid      (d) all of the above

19. A thermos bottle containing coffee is vigorously shaken. Consider coffee as the system, then its temperature

(a) rises     (b) falls  (c) remains the same           (d) falls below C

20. The transmission by conduction is most prominent in

(a) solids   (b) fluids  (c) solids, liquids and gases    (d) none of these

21. Heat radiations cannot be

(a) reflected      (b) refracted  (c) polarised

(d) ordinarily used for producing fluorescence

22. For which of the following processes, transmission of heat does not need

any medium?

(a) Conduction         (b) Convection  (c) Radiation      (d) all of the above

23. Which of the following has the maximum thermal conductivity?

(a) Iron                        (b) Silver  (c) Gold                       (d) Copper

24. In which case does the thermal conductivity increase from left to right?

(a) Al, Cu, Ag              (b) Ag, Cu, AI  (c) Cu, Ag, AI             (d) AI, Ag, Cu

25. The absorptive power of a perfectly black body is

(a) 0%                          (b) 25%  (c) 58%                       (d) 100%