Current Electricity Mock Test – Class 12 Physics

1. For a metallic wire of number density , cross-sectional area , electron charge magnitude , and drift speed , the current is

2. A balanced Wheatstone bridge has , , , and . If the galvanometer branch is removed after balance is achieved, the equivalent resistance between the battery terminals is

3. A metal has , , and . If the electron drift is opposite to , the magnitude of drift velocity is

4. Study the table and identify the device most likely to be non-ohmic.

5. A metal wire obeys Ohm's law only while its physical conditions remain unchanged. A strong heating of the wire during measurement can make the - graph deviate from a straight line because

6. In a uniform metallic wire carrying steady current, , , and electron drift velocity have which relative directions?

7. A semiconductor has a negative temperature coefficient of resistance. When its temperature is increased moderately, its resistance generally

8. A wire carries the same current before and after its cross-sectional area is reduced to one-third of its original value. Assuming the same material and carrier density, the new drift speed is

9. During a potentiometer comparison, for two cells on the same wire. If the second cell has emf , the emf of the first cell is

10. A fixed number of identical cells is arranged as rows in parallel, each row containing cells in series. For maximum current through an external resistance , the battery is best arranged so that its equivalent internal resistance is approximately

11. A wire has , , and . Its resistance is

12. A cell has emf , internal resistance , and is connected to an external resistance of . The current in the circuit is

13. A small lamp is marked and . In this marking, refers to

14. The following drift-speed graph is described for a metal at constant temperature.

The slope of this graph represents

15. A resistor obeys Ohm's law and has . When the current through it is increased from to at constant temperature, the increase in potential difference is

16. For a metallic conductor, resistance generally increases when temperature rises because

17. A wire has resistance , length , and cross-sectional area . Its resistivity is

18. Two cells of emfs and are connected in series aiding, with internal resistances and . The equivalent emf and internal resistance are respectively

19. The potentiometer measurement gives open-circuit balance length and loaded balance length for the same cell. The internal voltage drop in the cell is represented by

20. A Wheatstone bridge has , , , and . The galvanometer current is

21. During a potentiometer experiment, a cell balances at when no current is drawn from it. When it is connected to an external resistance , the balance length becomes . The internal resistance of the cell is

22. Study the table and identify the row with the unsuitable unit.

23. A wire has resistance , length , and cross-sectional area . The resistivity of the material is

24. A m long potentiometer wire is used, and a cell balances at . If the potential difference across the full wire is uniform, the total potential drop across the wire is

25. Assertion: In a balanced Wheatstone bridge, the resistance of the galvanometer does not affect the balance condition.
Reason: At balance, the potential difference across the galvanometer is zero.

26. In a parallel combination of resistors, the same potential difference appears across every branch because

27. Compare the two resistor graphs described below.

The comparison of their resistances is

28. A total of identical cells is arranged as parallel rows, each row containing cells in series. Each cell has internal resistance , and the external resistance is . The grouping that gives the best internal-resistance match is

29. When the series resistance in the primary circuit is increased, the potentiometer wire has a smaller potential gradient. For the same test cell, the new balance length becomes

30. A switch in a torch is opened after the torch was glowing. The lamp goes off mainly because

31. The potentiometer method can measure the emf of a cell more accurately than a voltmeter because the balance condition avoids

32. In comparing emf and terminal voltage of the same cell with a potentiometer, the open-circuit balance length is , and the loaded balance length is . The terminal voltage is represented by

33. Study the table and identify the row that gives an unsuitable potentiometer conclusion.

34. The meter-bridge balance point is at from the left end with unknown in the left gap and in the right gap. The value of is

35. In a mixed circuit, two resistors are not necessarily in parallel just because they are drawn side by side. They are in parallel only if

36. A resistor is connected in series with an unknown resistor across a source. If the current is , the unknown resistance is

37. When an electric field is applied inside a metallic conductor, the free electrons

38. The graph described below shows terminal voltage variation for a cell.

The internal resistance of the cell and the power delivered to the external circuit at are

39. Two resistors and are connected in parallel across a fixed voltage . The current division relation gives the current through as

40. A metal has electron relaxation time . If the applied electric field is and , the drift speed magnitude is

41. For a conductor, the relation is more general than because it gives

42. A metal wire is connected to a cell so that electrons drift from right to left through the wire. The conventional current in the same wire is directed

43. Use the loop equation below for a single closed circuit:

The physical circuit represented by this equation is most directly

44. Two resistors and are connected separately across the same ideal voltage source . The power dissipated in compared with that in is

45. Consider the following statements about limitations of Ohm's law.
I. Ohm's law applies only under constant physical conditions.
II. A diode is an example of a device with non-linear - behavior.
III. Any curved - graph through the origin still represents constant resistance.

46. Two primary-circuit settings are possible for a potentiometer. Setting P gives , and setting Q gives . For measuring a cell of emf , the more sensitive setting and its balance length are

47. A current of flows in a wire of cross-sectional area . If and , the drift speed is closest to

48. A closed loop is traversed clockwise. The chosen current in a resistor is anticlockwise and has magnitude . The potential change across the resistor during the clockwise traversal is

49. The resistance of a uniform conductor of length , cross-sectional area , and resistivity is

50. The SI unit of resistivity is