Moving Charges and Magnetism Mock Test – Class 12 Physics

1. A converted ammeter has appreciable resistance. When it is connected in series in a circuit, the measured current may be smaller than the original current because

2. A moving charged particle is observed to pass through a magnetic field without any magnetic deflection. One possible reason is that

3. A metal wire carries conventional current upward. Electrons in the wire drift downward. For finding the magnetic force on the wire using , the direction of is taken

4. A charged particle moves in a region where both electric field and magnetic field are present. The total force on the particle is represented by

5. For a charged particle moving perpendicular to a uniform magnetic field, the angular frequency of circular motion is

6. A graph of magnetic field against distance for a long straight wire is not a straight line. A straight-line graph can be obtained by plotting against

7. The magnetic force on a moving charge is zero in both parallel and anti-parallel motion because

8. A voltmeter made from a galvanometer has range and total resistance . The full-scale galvanometer current is

9. A very long straight wire can be treated as the limiting case of a finite wire. If and in , the result becomes

10. For a charge moving in a magnetic field, the expression uses instead of when force magnitude is required. The reason is that

11. A data record for a particle moving perpendicular to a magnetic field shows that doubling halves the radius and doubles the magnetic force. This is consistent because

12. A metal wire carries conventional current to the right in a uniform magnetic field directed into the page. Electrons drift to the left. For the force on the wire, the direction should be found by using

13. A circular loop of radius carries current . The magnetic field is required at a point on the axis from the centre. Taking , the field is

14. Use the graph description below.

The graph is symmetric about because

15. A cyclotron accelerates charged particles using

16. Study the table for converting a galvanometer into an ammeter.

The row that contains the wrong evaluation is

17. The starting idea behind magnetic effects of currents is that they are closely connected with ______.

18. A circular loop of radius carries current . At a point on the axis, the magnetic field is half of the field at the centre. The axial distance satisfies

19. A particle in a cyclotron has maximum speed . If is doubled and is halved while the same particle is used, the new is

20. A galvanometer of resistance and full-scale current is converted into an ammeter of range , where . The required shunt resistance is

21. A circular loop is viewed from the front, and the current appears anticlockwise. The magnetic field at the centre points

22. A moving charge enters a magnetic field. The magnetic force depends on the angle between and because

23. A current element is directed along , and the observation point is located along from the element. The magnetic field contribution points along

24. A cyclotron operating at high particle speeds becomes less effective when relativistic effects become significant because

25. Match the quantities with their common symbols.

26. A high-resistance voltmeter is accidentally connected in series with a circuit branch. The branch current becomes very small mainly because

27. To convert a galvanometer into a voltmeter of range , a resistance is connected in series. The purpose of this series resistance is to

28. A rectangular current loop is arranged so that the plane of the loop is parallel to a uniform magnetic field. The area vector of the loop is then perpendicular to , so the torque is

29. A square loop of side carries current and is placed in a uniform magnetic field. If the field lies in the plane of the loop and is parallel to one pair of opposite sides, then the force on those parallel sides is

30. Use the graph description below.

The graph is a straight line whose slope is

31. Use the graph description below.

If the slope of the graph is , and , the magnetic field magnitude is

32. A toroid has inner radius , outer radius , turns, and current . Taking , the magnetic field at inside the core is

33. Study the table about improving a moving-coil galvanometer.

The row with the incorrect effect is

34. A galvanometer is converted into an ammeter of range . If is made larger while and remain the same, the required shunt resistance should

35. Reversing the current in a current loop changes the magnetic dipole moment because

36. A galvanometer gives full-scale deflection for current and has resistance . To convert it into an ammeter of range , where , a shunt resistance is connected

37. A circular Amperian loop encloses two long wires carrying currents out of the page and into the page. The value of in Ampere’s law, taking out of the page as positive, is

38. A magnetic dipole of moment is rotated slowly in a field from to . The work done by the external agent is

39. A current in wire P creates a magnetic field at the position of wire Q. Wire Q then experiences force because

40. Consider two statements about a magnetic dipole in a uniform magnetic field.
I. At , the dipole has minimum potential energy.
II. At , the torque magnitude is maximum.
The best evaluation is

41. A charged particle completes one semicircle inside a dee of a cyclotron. The time taken for this semicircle is

42. The permeability of free space appears in magnetic field expressions due to currents. Its SI value is

43. A force sensor compares two long parallel-wire setups. Setup P has currents and separated by . Setup Q has currents and separated by . The ratio is

44. Assertion: An ideal voltmeter has infinite resistance.
Reason: A voltmeter is connected in parallel and should draw no current from the circuit element being measured.

45. A small current element and an observation point are arranged so that points toward the observation point. The Biot-Savart contribution at that point is

46. A charged particle enters a magnetic field at to the field direction. If the speed is , the part of velocity responsible for magnetic force is

47. The direction of in Biot-Savart law is perpendicular to the plane containing and because

48. The force per unit length between two long parallel wires separated by distance , carrying currents and , is

49. Study the table for a straight current-carrying conductor in a uniform magnetic field.

The row that contains an incorrect force magnitude is

50. A rectangular coil in a radial magnetic field has , , , and . The deflection produced by current is