Tuesday, January 31, 2012

Random collection of Physics Viva Questions

1. State the Principle of a potentiometer. (The students say that potential drop is proportional to length but the constant quantities are not mentioned)

2. How can we increase the sensitivity of a potentiometer?

3. Define figure of merit of a galvanometer.

4. Which has more resistance – a galvanometer or a milliammeter?

5. How does an LED emit light?

6. What is the difference between an ordinary diode and an LED?

7. Define principal axis of a convex lens?

8. What happens to the focal length of a concave mirror if it is immersed in water?

9. What are the factors affecting the internal resistance of a cell?

10. What are the difference between primary and secondary cell?

11. Why can’t we use a dry cell for starting a car?

12. What happens to the resistivity of a wire when it is doublefolded?

13. How does the resistance of a wire depend on its dimensions?

14. Why are the resistances used in a resistance box is like 1,2,2,5,10,20,20,50,100,200,200,500,1000,2000,2000,5000 etc?

15. Why constantan or manganin wires are used for making the resistance coils in resistance box?

16. What is a standard resistance?

17. What are the characteristics of a standard resistance?

18. What are the precautions to be observed while doing electricity experiments in general?

19. What is a galvanometer?

20. What is the resistance of an ideal ammeter?

21. Why is ammeter always connected in series and voltmeter always connected in parallel?

22. How can we convert a galvanometer into an ammeter or a voltmeter?

23. What is shunt?

24. What is AVO meter?

25. What is the effect of temperature on the resistance of a conductor?

26. Why does the resistance of a conductor increases with temperature, whereas that of a semiconductor decreases with temperature.

27. What is conductance?

28. What are non ohmic devices? give an example.

29. What are superconductors?

30. Define emf

31. Why emf is said to be a misnomer?

32. What happens if the battery used in the primary circuit of a potentiometer has less emf compared to the emf of the cell used in the secondary circuit?

33. If you find that the galvanometer reading is shaky, what error can you expect?

34. What do you mean by figure of merit of a galvanometer?

35. Why a moving coil galvanometer is called so?

36. What is the principle of a galvanometer?

Monday, January 30, 2012

Questions from Physics Viva

1. What happens to the resistivity of a wire when it is doublefolded?

2. How does the resistance of a wire depend on its dimensions?

3. Why are the resistances used in a resistance box is like 1,2,2,5,10,20,20,50,100,200,200,500,1000,2000,2000,5000 etc?

4. Why constantan or manganin wires are used for making the resistance coils in resistance box?

5. What is a standard resistance?

6. What are the characteristics of a standard resistance?

7. What are the precautions to be observed while doing electricity experiments in general?

8. What is a galvanometer?

9. What is the resistance of an ideal ammeter?

10. Why is ammeter always connected in series and voltmeter always connected in parallel?

11. How can we convert a galvanometer into an ammeter or a voltmeter?

12. What is shunt?

13. What is AVO meter?

14. What is the effect of temperature on the resistance of a conductor?

15. Why does the resistance of a conductor increases with temperature, whereas that of a semiconductor decreases with temperature.

16. What is conductance?

17. What are non ohmic devices? give an example.

18. What are superconductors?

19. Define emf

20. Why emf is said to be a misnomer?

21. What happens if the battery used in the primary circuit of a potentiometer has less emf compared to the emf of the cell used in the secondary circuit?

22. If you find that the galvanometer reading is shaky, what error can you expect?

23. What do you mean by figure of merit of a galvanometer?

24. Why a moving coil galvanometer is called so?

25. What is the principle of a galvanometer?

26. What is parallax? How is it removed?

27.  Define dispersion of light. Give its cause.

28.  Show dispersion of white light into seven colours.

29. Define lateral displacements and give the factor on which it depends.

30. Define critical angle and deduce the relation between refractive index and critical angle.

31. Explain U-V graph in case of image formation in a convex lens.

32. Distinguish between primary and secondary cell. (give two differences)

33.  How does rheostat act as a variable resistor, potential divider? (draw a diagram)

34. What a non inductive coil? Give one special feature of non inductive coil?

35. Draw neat and label diagram of leclanche cell.

36. Write chemical equation in Daniel cell.

37. Why is the emf of auxiliary battery greater than the emf to be measured?

38. Why are standard resistances made up of constantan and Manganin?

39. Define figure of merit and give it is S.I unit.

Sunday, January 15, 2012

Why moon has no atmosphere?

The escape velocity (the minimum velocity with which a body is to be projected so as to escape from the gravitational pull) on the surface of moon is very much less, less than the RMS velocity (Root Mean Square velocity) of the molecules of gas at the surface temperature of moon. Therefore the molecules will escape and therefore moon cannot hold an atmosphere.

The expression for escape velocity is √2gR

The value of escape velocity on earth is 11200 m/s

The value of escape velocity on moon is 2400 m/s (approximately)

The moon's surface temperature cycles between −155°C and 100° C (−247° and 212° Fahrenheit). As temperature increases the speed of molecules become more than the escape velocity.

However, moon has an extremely thin atmosphere.

Saturday, January 14, 2012

CBSE EXPLAINS THE WAY TO ATTEMPT EXAM

Excerpt from http://cbse.nic.in/helpline/final_2012.pdf

IN THE EXAMINATION HALL
• Try to think positive and maintain positive attitude giving the test.
• Once in the hall, take time to settle down and set your table.
• Do not hurry into reading the question paper.
• Read the directions slowly and carefully. If there are any doubts clarify with the instructor, teacher or invigilator.
Budget the time and plan the answers. Allocate time for each question.
• Do the simple questions first to help you build up your confidence for the harder questions.
• Choose the best known questions if choices are available.
• If you do not know a question, move on to the next after leaving some space; try it later. If not sure of an answer, do not spend long time thinking and recalling answers. Go to the next question. Handle the less known questions later.
• Leave space after each answer so that you can add later if you need to.

Friday, January 13, 2012

DEBATE ON EFFICACY OF CCE HEATING UP

CBSE IS TAKING STOCK ON THE EFFICACY OF THE NEWLY INTRODUCED CCE.

There has been wide complaint among teachers of higher secondary section that the standard of students reaching class XI has declined after the introduction of CCE. Students who do not have real aptitude and interest get admission to science stream because of their high grades which they do not really deserve. The system of education upto class X and that of class XI are widely different. The students find it extremely difficult to cope up with the level and standard of class XI science.

Many feel frustrated when they find out that they have reached the wrong place. They wonder what to do next. Many of them even get ready to lose one year for the right stream for which they are really fit.

Now CBSE has also started receiving the feedback from various sources and they are now taking data and analyzing what has gone wrong.

Do you find CCE wrong?

Is it necessary to replace it with the old system?

OR can it be modified and implemented effectively without harming the future of students?

What is your response on CCE? Post them as comments to this post and let the higher authorities read it.

Saturday, January 7, 2012

Problem from Surface Tension

A liquid drop of diameter 4mm breaks into 1000 droplets of equal size . Calculate resultant change in surface energy. the surface tension of liquid is 0.07N/m.

Hints.

• The volume of droplets remains the same. from this you can calculate the new radius.

• Change in surface energy = surface tension x increase in surface area

Thursday, January 5, 2012

AISSE 2012 DATE SHEET (CLASS X CBSE)

Thursday,01st March, 2012 10:30 AM
PAINTING 049
Friday,02nd March, 2012 10:30 AM
MATHEMATICS 041
Monday,05th March, 2012 10:30 AM
URDU COURSE-A 003
BENGALI 005
TAMIL 006
TELUGU 007
SINDHI 008
GUJARATI 010
MANIPURI 011
ORIYA 013
ASSAMESE 014
ARABIC 016
TIBETAN 017
PORTUGUESE 019
GERMAN 020
RUSSIAN 021
PERSIAN 023
NEPALI 024
LIMBOO 025
LEPCHA 026
BODO 092
TANGKHUL 093
JAPANESE 094
BHUTIA 095
SPANISH 096
KASHMIRI 097
MIZO 098
BAHASA MELAYU 099
URDU COURSE-B 303

CBSE Exam Time Table - Class 12 (AISSCE 2012)

Thursday,01st March, 2012 10:30 AM

ENGLISH ELECTIVE 001

FUNCTIONAL ENGLISH 101

ENGLISH CORE 301

Saturday,03rd March, 2012 10:30 AM

POLITICAL SCIENCE 028

LENDING OPERATIONS 620

Monday,05th March, 2012 10:30 AM

PHYSICS 042

ELECTRIC MACHINES 623

AUTOSHOP REP& PRAC 628

FABRICATN.TECH-II 630

AC & REFRGTN-III 632

M PROD TPT &M COOP 640

FLORICULTURE 643

B THERAPY &H DR-II 654

OPTICS 658

CLINICAL BIO-CHEM. 661

COMM. HEALTH NURII 664

ESTB & MGMT OF FSU 677

DESG & PAT MAKING 685

DYEING & PRINTING 688

ACCOMODAT.SERVICES 691

CONFECTIONERY 698

CLSFN.&CATALOGUING 703

POULTRY PDTS& TECH 717

C HEALTH NURSING 731

Wednesday, January 4, 2012

CBSE Published Date Sheet for Class X (AISSE) and Class XII (AISSCE) 2012

CBSE Published Date Sheet for Class X (AISSE) and Class XII (AISSCE) 2012