Physics - Practical

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      1.Worthy Links for Physics Practicals

      2.Tips And tricks to crack VIVA     

     3.XII Physics Together With - Viva Voce - ULTIMATE Guide :


                                                                                                                                                                                    

4.An Exemplary Viva Voce (CBSE Class XII Physics Practical) (plustwophysics.com)

(Assuming that the student was assigned the experiment "To determine the internal resistance of a cell using potentiometer")

Examiner (E): What was the experiment allotted to you?

Students(S): Sir, I was assigned the experiment to determine the internal resistance of a primary cell using potentiometer.

E: OK, Tell me the principle of a potentiometer

S: Sir. The principle of a potentiometer is that the potential drop across any length of a wire of uniform cross section and composition and carrying a constant current is directly proportional to the length.

E: Good. What is internal resistance?

S: The resistance offered by the electrodes and electrolyte of a cell is called internal resistance.

E: What are the factors affecting internal resistance?

S: Sir. the internal resistance of a cell depends on the nature of electrodes and electrolyte, the temperature of electrolyte, the area of electrodes, the concentration of electrolyte and the distance between electrodes.

E: Good; How does the internal resistance change if we increase the area of electrodes?

S: Sir, the internal resistance will decrease if we increase the area of electrodes.

E: What will happen to internal resistance if we increase the temperature?

S: The internal resistance of the cell will decrease with increase in temperature.

E: How does the Resistance of a conductor vary with temperature?

S: For a conductor the resistance increases with increase in temperature due the decrease in relaxation time.

E: Oh! What is relaxation time?

S: The average time interval between two successive collisions of electrons is called relaxation time.

E: Why does the relaxation time decrease with an increase in temperature?

S: Sir, as temperature increases, the collisions become more frequent and therefore the average time interval between collisions decreases.

E: Define potential gradient of a potentiometer.

S: The potential drop per unit length of the potentiometer wire is called potential gradient.

E: How does the sensitivity of a potentiometer vary with potential gradient?

S: The sensitivity of the potentiometer decreases with an increase in potential gradient.

E: Can you explain why?

S: As the potential gradient increases, greater potential difference is obtained for a small change in length of the wire. Or the length of the potentiometer for a given change in potential will be less. The potentiometer is more sensitive if we get a considerably larger change in length for a given change in potential. Therefore, with an increase in potential gradient, the sensitivity decreases.

E: OK

(Thereafter the examiner may go on to questions based on the activities and demonstration experiments performed by the student.)

Hope that the above post gave you an idea of what happens in a viva voce. These were just some of the typical questions which could be asked. Depending upon the creative mind of the examiner and the response of the students, the style of asking and the nature of questions may vary.

5) VIVA Ques : 

  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.
  40. State the Principle of a potentiometer. (The students say that potential drop is proportional to length but the constant quantities are not mentioned)
  41. How can we increase the sensitivity of a potentiometer?
  42. Define figure of merit of a galvanometer.
  43. Which has more resistance – a galvanometer or a milliammeter?
  44. How does an LED emit light?
  45. What is the difference between an ordinary diode and an LED?
  46. Define principal axis of a convex lens?
  47. What happens to the focal length of a concave mirror if it is immersed in water?
  48. What are the factors affecting the internal resistance of a cell?
  49. What are the difference between primary and secondary cell?
  50. Why can’t we use a dry cell for starting a car?
  51. What happens to the resistivity of a wire when it is doublefolded?
  52. How does the resistance of a wire depend on its dimensions?
  53. What are the precautions to be observed while doing electricity experiments in general?
  54. What is a galvanometer?
  55. What is the resistance of an ideal ammeter?
  56. Why is ammeter always connected in series and voltmeter always connected in parallel?