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Direct Current Short Questions

           1.   Why do we use connecting wires made of copper?
2.      A wire carrying current remains electrically neutral. Why?
3.      A large number of free electrons are present in metals. Why is there no current in the absence of electric field across it?
4.      Why do electrons acquire a steady drift velocity after applying a voltage?
5.      A wire of resistivity ρ is stretched to three times its length. What will be its new resistivity?
6.      Name any two physical parameters on which the resistivity of the material depends?
7.      Manganin and constantans are used for making standard resistors. Why?
8.      Two wires of equal length, one of copper and other manganin, have equal resistance. Which wire is thicker?
9.      Why is it dangerous to operate electrical appliances with wet hands?
10.   What is the effect of heating a conductor on the drift velocity of free electrons?
11.   Is it possible to make the resistance of metals equal to zero by any way?
12.   If the radius of wire is doubled, what will be the effect on its specific resistance?
13.   What is the effect of rise in temperature on the resistivity of semiconductor?
14.   State the condition on which the ohm's law is not obeyed in a conductor?
15.   Why are electrons not accelerated indefinitely in a conductor when electric potential difference is set up across its ends?
16.   On what factor does the resistance of a conductor depends on?
17.   A wire is stretched to double its length, what happens to its resistance and resistivity?
18.   Distinguish between ohmic and non-ohmic conductors?
19.   How do the resistance and resistivity of a conductor vary with temperature?
20.   Current density is a vector quantity, but current is a scalar quantity. Explain?
21.   The element of a heater is very hot while the wires carrying current are cold. Why?
22.   Explain why a bending of wire does not affect the value of drift speed of free electrons and hence the current?
23.   Although the drift velocity of free electrons is of the order of few mm/s, a bulb lights almost instantly. Why?
24.   A cylindrical rod has resistance R. If we double its length and diameter, what is the resistance in terms of R?
25.   Two copper wires of different diameter are joined end to end. If a current flows in the wire combination, what happens to the drift velocity of the electrons when they are moved from the larger diameter of the wire to smaller diameter wire?
26.  Why does an electric bulb nearly always burn out just as we turn on the light, but almost never while light is shining?
27.   Is there any difference between "resistance of wire" and "resistivity of wire"? Explain.
28.   What is the ratio of maximum to minimum resistance obtainable from n wires of resistance R each?
29.   Why is voltmeter connected in parallel with the load resistance?
30.   Why ammeter is connected in series?
31.   Explain the significant of shunt with a diagram?
32.   The electron drift speed in metals is small and the charge of electron is also very small, but we can still obtain a large amount of current in a metal. Why?
33.   When electrons drift in a metal from a lower potential to higher potential, all the free electrons of  the metals move in the same direction. Is this statement true? Explain.
34.    Is the ohm's law applicable to all conductors of electricity?
35.   A proton beam is going from east to west. Is there an electric current? If yes, in what direction?
36.   Explain how do you know whether two resistances in a circuit are connected in parallel or in series?
37.   What is the main difference between voltmeter and ammeter?
38.   How are lamps connected in a house? How is the fuse connected?
39.   Which of the quantities current, current density, electric field and drift speed remains constant along a non uniform conductor when a current is passed?
40.   What happens when ammeter connected in parallel and voltmeter connected in series in the circuit?
41.   Does the value of temperature coefficient of resistance always positive?
42.   By connecting suitable resistance in series, two identical galvanometers are converted into voltmeter and milli-voltmeter, which has higher resistance?
43.  Why don't we consider a drift velocity of positive ions?
44.   What are the factors on which the resistance of conductor depend?
45.   Alloys of metals have greater resistivity than that of their constituent metals? Why?
46.  What is the difference between static electricity and current electricity.
47.  Currents of the order of 0.1A through human body are fatal what causes death: heating due to current o something else?
48.  If electron drift speed is small, and the charge on electron is also very small, how can we obtain large amount of current in the conductor?
49.  There is an impression among people that person touching a high power line gets stuck with it. Is that true? Explain.
50.  A wire is carrying current. Is it charged?


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