Magnetism and Matter Mock Test – Class 12 Physics

1. Two axial observations of the same short bar magnet are recorded.

The field in Case Q should be

2. 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

3. A student writes that the axial and equatorial fields of a short magnetic dipole both vary as , so their values must be identical at the same . The flaw is that

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

5. 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

6. A material shows a small positive slope in its graph at room temperature. When temperature is increased, the slope decreases. The material is best described as

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

8. 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

9. The equation form of Gauss's law for magnetism is

10. A -turn circular coil of radius carries current . It is placed in a uniform field . If the coil is rotated slowly from to , where is the angle between and , the work done by the external agent is

11. A graph is plotted with on the vertical axis and on the horizontal axis for a fixed short magnetic dipole.

The slope of the graph is

12. A paramagnetic substance obeying Curie's law is tested at , , and . The correct order of susceptibilities is

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

14. 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

15. A place has dip angle and total Earth's field . The values of and are

16. Earth's magnetic field at a place has total magnitude and dip angle . Its horizontal component is

17. The SI unit for magnetic dipole moment can be understood from the relation . If has unit , the unit of must be

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

19. 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

20. Assertion: A magnetic dipole in a uniform magnetic field may experience torque even when the net translational force on it is zero.
Reason: The forces on the two poles can form a couple in a uniform field.

21. A material has when . In the same linear range, the magnetic field inside is written as . The relative permeability is

22. A paramagnetic material obeys Curie's law. At , its susceptibility is . The magnetising field is then doubled while the temperature is raised to . Compared with the original magnetisation, the new magnetisation is

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

24. A bar magnet is placed in a uniform magnetic field. If is neither parallel nor antiparallel to , the magnet may experience

25. Near a magnetic pole of Earth, a dip needle tends to become nearly vertical. This corresponds to

26. A ferromagnetic core has hysteresis loss per cycle. A second core of the same volume is chosen with loop area per cycle. If both are operated at the same frequency, the power loss in the second core is

27. 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

28. 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

29. A -turn circular coil of radius carries current . It is placed in a uniform magnetic field . If the coil is slowly rotated from to , where is the angle between and , the work done by the external agent is

30. A dipole of moment is in a field . It is rotated slowly from to . The external work done is

31. The direction of the magnetic dipole moment of a bar magnet is taken

32. 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

33. A point on the equatorial line is chosen farther away from a short magnetic dipole, while the direction of remains unchanged. The direction of the equatorial field

34. A table of material data is given below.

The row that is internally inconsistent is

35. Two specimens have the same net magnetic moment . Specimen P has volume , while specimen Q has volume . The ratio of their magnetisations is

36. A short bar magnet is placed with opposite to Earth's horizontal magnetic field . Neutral points are expected on the axial line because the axial field of the magnet is

37. A ferromagnetic specimen becomes magnetised when placed in a suitable external magnetic field mainly because

38. A short bar magnet is placed with . If is doubled while is unchanged, the equatorial neutral-point distance becomes

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

40. A short magnet of moment is placed with opposite to Earth's horizontal field . Taking , the distance of an axial neutral point from the centre is approximately

41. Use the graph description below.

For making a permanent magnet, the better loop and the reason are

42. Two ferromagnetic materials have hysteresis loop areas and per cycle. For the same operating frequency and volume, the material with loop area is preferred in a transformer because

43. Consider the following statements for a short magnetic dipole.
Statement I: At an axial point, is along .
Statement II: At an equatorial point, is opposite to .
Statement III: At an equatorial point, the two pole contributions have unequal magnitudes.

44. Bar magnets are often stored in pairs with soft iron keepers across their ends. The keepers are used mainly to

45. 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

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

47. A bar magnet is placed along the -axis with along . Point P is on the -axis far from the centre, and point Q is on the -axis far from the centre. For the axial field of a short dipole, the directions at P and Q are

48. A ferromagnetic specimen is taken around a complete hysteresis loop. The loop area is reduced from to by choosing a softer material. If the cycling frequency is unchanged, the power loss per unit volume becomes

49. 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

50. A hysteresis loop has residual magnetisation and coercive field . The points and respectively describe