Posts Tagged ‘electricity’

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?

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.

Where is electricity stored after it is generated but before it is supplied? (Chat Transcript from FaceBook)

Where is electricity stored after it is generated but before it is supplied?

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    Mahesh Sable Electrical power cannot be stored and,therefore,power plants must produce power as and when demanded.power stations r connected in parallel hence load is equally distributed,electric Power can be adjusted with help of step up or step down transformers.

     

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    Mathew Abraham Transformer does not increase power

     

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    Chitraja Rajan The demand for electricity varies randomly within a day itself…so there should be something which should be adjusted according to the demand.

     

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    Vishnu Mohan G huge capacitors? i think i read somewhere like this.

     

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    Rajat Sharma

    Hi All, the question is very smart, i think electricity stored before generation is stored in Water(DAM), Uranium Rods(Nuclear), HydroCarbons(Coal, GAS). Electricity can only store when it is in Direct Current format like in Batteries, Capacitor(its a very small time to store/release) Well there are many source where we can store electricity. When electricity is in demand then Power generation takes place within huge Alternators, this powers generation takes places in terms of Phase Shift between all the power Houses across the country, if this phase shift is disturb then power grid fails. after this the transformers come into picture so as to reduce Resistance loses.

     

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    Kannan Kannan Ps in my little knowledge electricity unable to store continuing process of generater get current
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    Chitraja Rajan at the generation side electricity is high ac current ..if it is converted into dc then there should be large containers to store them and also need suitable convertors to convert it in either form every time

     

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    Mathew Abraham In modern generators, there are equipment to control the rate of flow of water and in turn rate of rotation as well as the power generated. SO, it is quite right to say that electricity is generated as and when required. When you switch on a device power generation also increases until it reaches maximum capacity. Thereafter we will get less power. Remember the low voltage we suffer during the evening when the power consumption is maximum a few seconds ago · Like

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Where is electricity stored after it is generated but before it is supplied?

This question was posted by Chithraja. This is a common doubt arising naturally in the minds of children as well as adults who think. But they never ask, or if they ask the questions remain unanswered. I will explain the question itself first. When we switch on a bulb we get the energy. But what happens to the electricity [...]

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Why the shock of alternating current is attractive ?

Why the shock of    alternating current  is   attractive ? Answer: Shock is never attractive. I have experienced shock from AC several times, but never felt any attraction. But, during a severe shock it seems that the person  is attracted by the electricity due to the fact that the electricity temporarily disables his nervous [...]

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Class 12 Physics Study materials – Free Download

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Current Electricity : Some important Questions and Answers

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