Posts Tagged ‘answer’

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?

Which way is better for giving AIEEE exam? ONLINE or OFFLINE.

Which way is better for giving AIEEE exam? ONLINE or OFFLINE.

-Yash asked -

Answer:

I would personally recommend online. But the choice is up to you.

Please follow the following check to decide. Try to identify for yourself the plus points and negative points of writing AIEEE online and OFFLINE.

The most important disadvantage of choosing the OFFLINE version is the rarity of choices. You may have to travel long if you are not nearby the centre.

The decision is yours. But, think well before you decide.

Does gravity travel instantaneously?

Does gravity travels instantaneously? Or it travels equal to the speed of light.

Answer:

No clear answer now. If we believe in the Theory of relativity, Gravity (Gravitational Waves travel with the same speed as that of light in vacuum. If gravitons are like photons, then it makes sense too.

However I invite you to think more and post your thoughts as comments here. Let the discussion begin.

I found the following links to know more

• http://metaresearch.org/cosmology/speed_of_gravity.asp
• http://en.wikipedia.org/wiki/Speed_of_gravity
• http://www.desy.de/user/projects/Physics/Relativity/GR/grav_speed.html

Speed of sound

Why sound travels faster in humid air than normal air as humid air is denser than normal air? (Akash asked)

Answer:

The speed of sound in a medium is inversely proportional to the square root of its density. Humid air is less dense than dry air. Therefore the speed of sounf in humid air is greater than that in dry air.

Confused?

Are you thinking why dry air is more than that of humid air? This is a common misconception. Students used to think that humid air is denser than dry air. But it is not so. Just like skimmed milk (milk removed off its cream) is more dense than normal milk (with cream). Density of cream is much less than that of the rest of milk. So when it is removed, the residual milk becomes denser.

Humid air contains water vapor content. Water vapor is lighter than air. So when air contains water vapor, its density is less. When the water content is removed, it becomes denser.

What is present in between the atoms of gases?

What is present in between the atoms of gases?

(Aniket Mukherjee asks)

Answer: Nothing. Vacuum

Parallel Universe

Is there really a parallel universe?

Answer:

As of now, the answer is not final. There are different ideas and explanation given on parallel universes. Some say if parallel universe are far away from us, whereas others say that they are very close to us.

String theorists say that there are actually 11 dimensions. They’d come to the conclusion that our Universe is just one bubble among an infinite number of membranous bubbles which ripple as they wobble through the eleventh dimension.

If we think on probability also, we cannot just be selfish to say that we are alone. There is an equal probability of many such universes with life too.

I feel the space is not sufficient to explain all these thing here. The following links will help you know further.

http://space.mit.edu/home/tegmark/multiverse.pdf

http://www.scientificamerican.com/article.cfm?id=parallel-universes

http://www.bbc.co.uk/science/horizon/2001/paralleluni.shtml

http://en.wikipedia.org/wiki/Parallel_universe_(fiction)

Electric Current and flow of electrons

I have read that the FLOW OF ELECTRONS is called electricity. I wanna know that what is meant by flow of electrons? Pleaz answer me….

(Asked Kiruthika)

Answer:

Electric current is the flow of charges. (Measured as the rate of flow of charges).

In conductors electric current is caused by the flow of free electrons. When a potential difference is applied across a conductor, the electrons are accelerated towards the positive potential. (But, due to the presence of plenty of electrons, they cannot move with acceleration as they collide with each other during their motion.) There is a net drift of electrons across any cross section and a current is developed.