Magnetism and Matter Mock Test – Class 12 Physics

1. Consider the following statements about a full magnetisation cycle and device choice.
Statement I: The area of a hysteresis loop represents energy loss per unit volume per cycle.
Statement II: A transformer core should have a narrow loop and low coercivity.
Statement III: A permanent magnet should have low retentivity so that it can lose magnetisation easily.

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

3. 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

4. The angle of dip at a place is the angle made by Earth's magnetic field with

5. Earth's magnetic field at a place has horizontal component . A short magnet is arranged so that its equatorial neutral points are from its centre. Taking , the magnetic moment of the magnet and the axial neutral distance for the same magnet when reversed are approximately

6. A student says, "Every material with must be ferromagnetic." The best correction is that

7. A small current loop has area vector directed along . The current is increased from to , while the area and direction remain unchanged. The magnetic moment vector becomes

8. The equatorial field setup differs from the axial field setup mainly because

9. A coil of turns, current , and area is slowly rotated in a uniform magnetic field from to , where is the angle between and . The work done by the external agent is

10. A navigator wants the geographic north-south direction at a place where the magnetic declination is west. If the compass points along magnetic north, then geographic north is

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

12. The dimensional expression of magnetic intensity , given that its SI unit is , is

13. A closed surface is drawn around a current loop that behaves like a magnetic dipole. The magnetic field lines pass through the surface in several places. The net magnetic flux through the closed surface is

14. Assertion: A bar magnet in a uniform magnetic field can rotate but does not experience a net force.
Reason: In a uniform field, the magnetic effects on the two poles can be equal and opposite but separated in space.

15. Consider the following statements about magnetic field lines of a bar magnet.
Statement I: Outside the magnet, they are directed from to .
Statement II: Inside the magnet, they are directed from to .
Statement III: They form closed continuous curves.

16. Read the situation below and answer the question.

The better shielding action is expected from Shell P because

17. For a linear isotropic magnetic material, the relation between relative permeability and magnetic susceptibility is

18. A ferromagnetic material is taken through a hysteresis cycle. The area of the loop on a graph has unit

19. A current loop has magnetic moment along . It is placed in a uniform magnetic field along . The torque direction on the loop is

20. The vector direction of magnetisation in a uniformly magnetised specimen is along

21. A circular loop of radius carries a current . Its magnetic dipole moment is

22. The direction of is

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

24. A circular current loop is very small compared with the distance of observation. Its magnetic field pattern at large distances resembles that of

25. At a point on the equatorial line of a bar magnet, the components of the two pole fields perpendicular to the magnetic axis cancel. The remaining components make the resultant field

26. Study the comparison below and identify the supported row.

27. A magnetic material has volume , susceptibility , and is placed in a magnetising field . Taking , the net magnetic moment and magnetic field inside the material are

28. A diamagnetic material and a paramagnetic material are placed one by one in the same non-uniform magnetic field. Which row gives the correct comparison?

29. Match the current-loop feature with its correct meaning.

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

31. A student says, "Magnetic shielding works because field lines are blocked at the surface like light rays at an opaque wall." The better explanation is that magnetic shielding

32. Match the field-line feature with the physical meaning.

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

34. A dip triangle is drawn with along the horizontal direction and vertically downward. The resultant makes angle with the horizontal. The correct set of relations is

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

36. Consider the following statements about care of magnets.
Statement I: Heating can weaken a magnet.
Statement II: Hammering or dropping can reduce magnetisation.
Statement III: A soft iron keeper helps preserve magnetisation during storage.

37. 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

38. The magnetic dipole moment of a bar magnet has SI unit . Its dimensional expression is

39. A ferromagnetic core of volume has hysteresis loop area per cycle at . If the operating frequency is changed to and a new material has loop area per cycle with the same volume, the new hysteresis power loss is what fraction of the old one?

40. A -turn current loop has area and carries current . It is placed in a uniform magnetic field , with its magnetic moment making with the field. The torque on the loop is

41. A freely suspended compass needle settles approximately along the geographic north-south direction because Earth has

42. A ferromagnetic sample is taken through a complete hysteresis cycle. If the area of the loop is reduced by choosing a softer material, the main practical effect is

43. A field-line sketch around a bar magnet is useful for finding the direction of , but not for reading an exact numerical value of , because

44. A magnetic dipole has and is placed in a uniform field . If , the torque magnitude is

45. The net magnetic flux through any closed surface is

46. Study the following rows and select the one that contains a mistaken comparison.

47. Match the magnetic material with a suitable example.

48. At a place, and . A short magnet of moment is placed with opposite to . Taking , the total Earth field and axial neutral distance are respectively

49. In a rough field-line diagram, a region between two nearby magnets has very few lines passing through it because the fields due to the magnets nearly cancel there. Such a region is best described as

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