Moving Charges and Magnetism Mock Test – Class 12 Physics

1. A finite straight conductor carrying current produces magnetic field at a point a perpendicular distance away. In the usual angle form, the magnitude is

2. Two long vertical wires are placed side by side. The left wire carries current upward, and the right wire carries current downward. The force between the wires is

3. Use the graph description below.

The graph is expected to be

4. Assertion: A stationary charged particle placed in a magnetic field experiences no magnetic force.
Reason: Magnetic force on a charge contains the velocity of the charge.

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

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

7. The torque on an -turn rectangular current loop in a uniform magnetic field is given by

8. Two points P and Q are at distances and from a long straight wire carrying current . The ratio is

9. 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

10. A current-carrying wire is placed parallel to a uniform magnetic field. If the current and magnetic field are both non-zero, the force on the wire is

11. A moving-coil galvanometer has current sensitivity . If its coil resistance is , its voltage sensitivity is

12. A galvanometer has coil resistance . Its voltage sensitivity is . Since , the voltage sensitivity is

13. A closed path is chosen near a long straight wire, but the wire lies outside the closed path. For that path, Ampere’s law gives

14. Study the table about maximum energy in a cyclotron.

The row with the incorrect dependence is

15. A galvanometer has and . It is converted into an ammeter using a shunt . The full-scale range of the ammeter is

16. A finite straight wire carries current . At a point a perpendicular distance from the wire, the two end angles in are both . Taking , the magnetic field is closest to

17. 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

18. Read the following passage.

Particles emerging undeflected from the region have

19. 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

20. A wire is bent into a curved shape and placed in a uniform magnetic field. For finding the net force on the wire, the curved wire can be replaced by

21. A circular coil and a long straight wire carry the same current . The field at the centre of a single circular loop of radius is compared with the field at distance from the long straight wire. The ratio is

22. A conductor carries through a length of in a uniform field of . The force is . The angle between the conductor and the magnetic field is

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 magnetic-relations sheet lists the following pairs.

The row that should be removed from the relation sheet is

25. A particle of mass and charge magnitude moves with speed perpendicular to a field of . Its centripetal acceleration is

26. For a charged particle in magnetic circular motion, the statement is constant but is not constant means that

27. A long solenoid and a toroid both carry steady currents. A key difference between their ideal magnetic fields is that

28. A statement about magnetic force says, “Since , a magnetic field cannot change momentum.” The correct correction is

29. In a cyclotron, the oscillator frequency is kept fixed for a given particle and magnetic field. This works in the non-relativistic case because

30. A galvanometer of resistance is converted into an ammeter with shunt . If , the effective resistance of the ammeter is approximately

31. Two ions with the same charge magnitude and mass enter the same uniform magnetic field perpendicular to it. Ion P has speed , and ion Q has speed . Their radii and time periods are related as

32. The area vector of a flat current loop is directed

33. A positive ion and a negative ion have the same mass, the same charge magnitude, and the same oblique velocity components in a uniform magnetic field. Their helical paths have

34. When the axial-field expression is used at the centre of the loop, the value of is

35. In a cyclotron, if the final orbit radius is , the maximum speed of a non-relativistic particle is

36. Use the arrangement described below: a particle moves to the right on the page, and the magnetic field is into the page. If the particle is an electron, the magnetic force is

37. The SI unit of magnetic field is

38. A straight wire carries current toward the north in a horizontal plane. A uniform magnetic field is directed vertically upward. Taking east as , north as , and upward as , the magnetic force on the wire is directed

39. For a charged particle moving perpendicular to a uniform magnetic field, the radius written in terms of kinetic energy is

40. An electron moves toward the east in a magnetic field directed toward the north. With east as , north as , and upward as , the magnetic force on the electron is directed

41. A cyclotron accelerates charged particles using

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

43. Use the graph description below.

The slope of the graph represents

44. Since , the dimensional formula of from the unit is

45. A magnetic field acts on two particles moving with the same speed at the same angle to . Particle P has charge , and particle Q has charge , with equal masses. Comparing the magnetic forces at entry,

46. The shunt resistance needed to convert a galvanometer of resistance and full-scale current into an ammeter of range is

47. A long straight wire carries current into the page. The magnetic field pattern on the page is

48. 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

49. A cyclotron is designed for protons. If an alpha particle is used in the same magnetic field, its cyclotron frequency compared with that of the proton is approximately

50. 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