## 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.