Short Question for Practice

                             Short questions:

1. A large no of electrons are present in metals. Why is there no current in the absence of electric field across it?

2. Two copper wires of different diameter are joined end to end. If a current flows in the wire combination, what happens to electrons when they move from the larger diameter wire into smaller-diameter wire? Does their drift velocity increase, decrease or stay the same?

3. Why alloys like constantan and maganin are used to make standard resistance?

4. Is there any differences between resistance of a wire and resistivity of a wire?

5. A wire is stretched to double its length. What happens to resistance and resistivity?

6. What are the factors on which the resistance and resistivity of a conductor depends?

7. You are given n wires each of resistance RΩ. What is the ratio of maximum to minimum resistance that can be obtained from these wires?

8. What happens to resistance and resistivity of two conductors of same material having same area of  cross section but one is twice the length of the other?

9.Two wires of equal lengths, one of copper and other of manganin have the same resistance. Which wire is thicker?

10. Resistance and are connected in series with an emf of source that has negligible internal resistance. What happens to the current through when a third resistance is connected in parallel with ?

11. Resistors and connected in parallel with an emf of source that hs negligible internal resistance.What happens to the current through when is removed from the circuit?

12. If different wire of same dimension carry same electric current, which one wire has more drift velocity?

13. When the resistance connected in the series with a cell is exactly halved, the current is not exactly doubled. Why?

14. Distinguish between ohmic and non-ohmic conductor.

15. Differentiate between Thermistor and LDR?

16. What is strain gauge?