Magnetism and Matter Mock Test – Class 12 Physics

1. The magnetic field magnitude on the equatorial line of a short magnetic dipole is

2. A closed box is placed in a magnetic field. The magnetic flux through five faces of the box adds up to . The flux through the sixth face is

3. A magnetic dipole is placed in a uniform magnetic field. In one case, is parallel to ; in another case, is antiparallel to . The torque magnitudes in the two cases are

4. A table of material data is given below.

The row that is internally inconsistent is

5. A dip needle shows , while the horizontal component of Earth's magnetic field is . The total field is

6. A graph of against for three linear materials is described below.

The most suitable identification of P, Q, and R is

7. At an axial point of a short bar magnet, the distance from the centre is changed from to , while is unchanged. The axial magnetic field becomes

8. A graph is plotted with on the vertical axis and on the horizontal axis for a fixed short magnetic dipole. The slope of this graph is

9. A dipole is rotated slowly in a uniform magnetic field from to . The change in potential energy is

10. The SI unit of magnetic field is

11. A closed surface is drawn around a bar magnet placed inside a high-permeability shield. The magnetic field distribution changes, but the net magnetic flux through the closed surface remains

12. A plane current loop lies in the -plane. When viewed from , the current is anticlockwise. The direction of its magnetic dipole moment is

13. Two observations are made for the same short magnetic dipole.

The ratio is

14. A circular coil is viewed from one side. In Case 1, the current appears clockwise; in Case 2, the current appears anticlockwise. The magnetic moments as seen from that side are

15. A sample has net magnetic moment and volume . Its magnetisation is

16. A ferromagnetic specimen is heated above its Curie temperature and then placed in a weak magnetic field. The most suitable description of its behaviour is that it

17. A compass needle placed at a point near a magnet turns so that it has one definite direction. This behaviour shows that magnetic field at a point is treated as

18. A magnetic dipole with is placed in a uniform field . It is slowly rotated from to . The work done by an external agent is

19. Magnetic field lines outside a bar magnet are directed

20. A magnetic dipole of moment is first placed at in a uniform magnetic field and then rotated slowly to . The work done by the external agent is

21. A naturally occurring magnetic mineral that can attract small pieces of iron is best described as

22. A magnetic dipole is kept exactly opposite to a uniform magnetic field, so that . The torque is zero at that instant, but the orientation is called unstable because

23. The potential energy of a magnetic dipole is . If , , and , then is

24. A closed surface is placed around only one side of a current loop, so that several magnetic field lines pass through it. According to Gauss's law for magnetism, the net magnetic flux through the closed surface is

25. A ferromagnetic material is heated gradually while its ability to retain strong domain alignment is observed.

The temperature described is

26. A table of component behaviour at a point on the equatorial line of a bar magnet is given below.

The unsupported row is

27. A paramagnetic material is placed in a magnetising field . Its magnetisation is generally

28. A material has a high value of coercivity but only moderate retentivity. Its high coercivity mainly means that

29. A magnetic dipole in a uniform field is slightly disturbed from the orientation . Its tendency is to return toward the parallel orientation. This orientation is

30. A magnetic dipole of moment is placed in a uniform magnetic field . The torque on it is represented by

31. Assertion: A bar magnet is called a magnetic dipole.
Reason: Its -pole and -pole behave as a pair, and an isolated magnetic pole is not obtained by cutting the magnet.

32. A bar magnet is placed in a non-uniform magnetic field so that one pole lies in a stronger field region than the other. The magnet can experience

33. A short magnetic dipole has magnetic moment . Find the magnetic field magnitude at an equatorial point from its centre. Take .

34. A closed surface is drawn around an entire bar magnet. The magnetic flux through the surface is zero because

35. Assertion: At the same distance from a short magnetic dipole, the axial field magnitude is twice the equatorial field magnitude.
Reason: The axial field is directed along , while the equatorial field is directed opposite to .

36. In a closed cubical surface, flux values through five faces are , , , , and . The flux through the sixth face is

37. A magnetic field passes through a closed surface. The outward flux through one part is , and the inward flux through the remaining part is . The net magnetic flux is

38. A dipole has . In a uniform field, its torque is when . The magnetic field magnitude is

39. The net magnetic flux through any closed surface is

40. Consider the following statements about a magnetic dipole in a uniform magnetic field.
Statement I: At , torque is maximum.
Statement II: At , potential energy is zero.
Statement III: At , torque is maximum and potential energy is minimum.

41. A material is made of many tiny magnetic dipoles. In an unmagnetised ferromagnetic sample, the domains are usually arranged so that

42. Consider the following statements about Earth's magnetic components.
Statement I: .
Statement II: If increases while is fixed, decreases.
Statement III: If , then .

43. A material has in a weak magnetic field. If , the magnetisation is

44. A specimen is first magnetised strongly and then the magnetising field is reduced to zero. The remaining magnetisation is large, but a small reverse field is enough to reduce it to zero. The specimen has

45. The magnetic analogue of Gauss's law is based on the idea that ordinary magnets do not provide

46. A graph of magnetisation against magnetic intensity for a ferromagnetic specimen is not a single straight line through the origin when is cycled. This behaviour is called

47. A magnetised steel needle is heated strongly, then hammered, and finally placed in an alternating magnetic field of gradually decreasing strength. The combined effect is most likely to

48. A -turn rectangular coil has sides and , and carries current . It is in a field . The maximum torque and the work required to rotate it slowly from stable equilibrium to unstable equilibrium are respectively

49. A graph of magnetic susceptibility against absolute temperature is drawn for an ideal paramagnetic material obeying Curie's law.

The graph is best described by

50. A hysteresis graph for a material has a large vertical intercept when , a large reverse -intercept where , and a large enclosed area. The most consistent interpretation is that the material is suitable for