## IIT JEE Previous Question Papers & Answers

Categories: CBSE Physics   Tags:

## 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.

Categories: CBSE Physics, Physics Practical Help, Question Bank   Tags:

## 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.

Categories: CBSE Physics   Tags:

## 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.

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## CTET Sample Papers

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