Magnetism and Matter Mock Test – Class 12 Physics

1. A record gives and . The dip angle is

2. A short bar magnet has magnetic dipole moment . Find the axial magnetic field at a point from its centre. Take .

3. A short bar magnet has at a point from its centre. At an axial point at the same distance, the field magnitude is

4. A ferromagnetic core of volume has hysteresis loop area per cycle at . If a new material reduces the loop area by while volume and frequency remain unchanged, the reduction in power loss is

5. A specimen has volume and magnetisation . Its net magnetic moment is

6. Consider the following statements about neutral points near a bar magnet.
Statement I: They are explained by superposition of magnetic fields.
Statement II: At a neutral point, the magnet's field and Earth's field are equal in magnitude and opposite in direction.
Statement III: At a neutral point, both individual fields must be absent.

7. Study the field-line behaviour in different materials.

The unsupported row is

8. 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

9. A small magnet is placed in a non-uniform field. Its magnetic moment is already parallel to the local field direction, but the field strength increases to the right. The magnet's behaviour is best described as

10. Assertion: Soft iron is preferred for electromagnet cores.
Reason: Soft iron has low coercivity and can be magnetised and demagnetised easily.

11. A short bar magnet of moment is placed with . At a neutral point on its equatorial line, the distance from the centre is . The relation used to find is

12. A statement says, "Declination and dip are the same because both are angles related to Earth's magnetic field." The better correction is that

13. A permanent magnet should be made from a material whose hysteresis loop has

14. A material has . When , the magnetisation and relative permeability are respectively

15. A compass needle turns and settles along a particular direction even when no object is touching it. This observation mainly shows that magnetism can produce

16. A field-line sketch around a bar magnet is symmetric about its magnetic axis. Two points are chosen at equal distances above and below the axis in corresponding positions. The most reasonable conclusion is that

17. A map gives true north, but a compass at the same place points east of true north. The magnetic declination is best written as

18. In a simple bar magnet, the end that tends to point approximately toward geographic north when freely suspended is called the

19. A magnetic dipole of moment in a uniform magnetic field is released from rest at . Neglecting losses, it tends to rotate toward

20. The magnetic dipole moment of a plane current loop carrying current and enclosing area has magnitude

21. A current loop is viewed from a side where it behaves as a north face. The far-field analogy with a bar magnet means that this face corresponds to

22. Study the hysteresis-loop features in the table below.

The unsupported row is

23. A uniformly magnetised rod has net magnetic moment directed from its left end toward its right end. The direction of its magnetisation is

24. A short bar magnet is placed with its magnetic moment parallel to Earth's horizontal magnetic field . Neutral points are expected on the equatorial line because the dipole field there is

25. Study the classification table and identify the correctly matched row.

26. A permanent magnet is accidentally dropped several times and then heated. Its magnetic field becomes weaker. The explanation most consistent with the domain model is that

27. A magnet is exposed to a strong alternating magnetic field whose direction keeps reversing. The likely result is

28. At a place where Earth's magnetic field has total magnitude and dip angle , the vertical component is

29. Magnetisation of a material describes

30. A short bar magnet has pole strength and magnetic length . It is placed in Earth's horizontal field . Taking , the axial neutral-point distance when is opposite to and the equatorial neutral-point distance when are approximately

31. A paramagnetic material obeys Curie's law and has at . At what absolute temperature will its susceptibility become ?

32. Consider the following statements about points near a bar magnet.
Statement I: Field lines are usually more crowded near the poles.
Statement II: At a point on a field line, the tangent gives the direction of .
Statement III: A weaker field region must contain intersecting field lines.

33. In a short note, the magnetic field is written only as , while the compass direction at that point is also known. A more complete physical description should include

34. 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

35. A material is described as having high permeability, low coercivity, and a narrow hysteresis loop. The most suitable application is

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

37. A report lists and for a material. The two values have the same unit because

38. Magnetic susceptibility is dimensionless because

39. A compass is moved slowly near a bar magnet kept in Earth's field. At one point, the needle becomes uncertain and does not settle along a stable direction. The best explanation is that

40. A ferromagnetic material has a wide hysteresis loop and large coercivity. It is more suitable for making

41. A specimen shows a large positive magnetisation even after the external field is removed, but heating it above a certain temperature destroys this retained magnetisation. The temperature is most closely related to

42. Consider the following statements about a small current loop and a short bar magnet.
Statement I: Both can be described by magnetic dipole moment.
Statement II: Both have similar far-field magnetic patterns.
Statement III: Both must contain separated isolated magnetic poles.

43. A transformer core is repeatedly magnetised and demagnetised many times each second. The main reason for choosing a material with a narrow hysteresis loop is to

44. Near a bar magnet placed in Earth's horizontal magnetic field , a point has the magnet's field exactly opposite to . If , the point is

45. At a place, Earth's magnetic field has and angle of dip . The horizontal component is

46. A field-line sketch around a bar magnet shows arrows outside the magnet going from to , but the lines stop at the -pole surface. The main defect in the sketch is that magnetic field lines

47. Match the magnetic quantity with its most suitable description.

48. In deriving the axial field of a short magnetic dipole, the two pole contributions are subtracted rather than simply added because

49. 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

50. A material is placed in a magnetising field . Its internal magnetic dipoles partly align, producing magnetisation . The best distinction is that