Magnetism and Matter Mock Test – Class 12 Physics

1. 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

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

3. A record gives and . The vertical component and total field are respectively

4. A bar magnet loses much of its magnetisation after being heated strongly. The most suitable explanation is that heating

5. 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.

6. A bar magnet is placed in a magnetic field that is stronger near its -pole end than near its -pole end. Compared with a uniform-field case, the new feature is that

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

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

9. 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

10. 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

11. 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

12. Magnetic intensity is best described as

13. Study the table and identify the row that correctly connects susceptibility with material response.

14. A small current loop and a short bar magnet can be compared because both produce, at large distances, a magnetic field pattern like that of

15. A learner says, "Since magnetic field lines are closest near the poles, two lines may cross there." The better correction is that

16. Two small magnetic needles are placed at different points near a bar magnet. Needle P turns more strongly and settles quickly, while needle Q turns weakly. The better inference is that

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

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

The unsupported row is

19. A material is placed in a uniform external magnetic field. Inside the material, magnetic field lines are found to be slightly less dense than in the surrounding space. The material is most likely

20. A specimen in a magnetising field develops . The material is most likely

21. If a material has and , then its relative permeability is

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

23. 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

24. A paramagnetic material has Curie constant . Its susceptibility at is

25. At a place, the total field is and . The horizontal component is

26. A short magnetic dipole has moment . At distance , an axial point and an equatorial point are considered. If the direction of is taken as positive, the signed fields may be represented as

27. A material with is tested at two absolute temperatures. Its susceptibility decreases when temperature increases. The material is most likely

28. A magnetic field around a magnet is best understood as the region where

29. A compass needle is placed at a neutral point formed by a bar magnet and Earth's horizontal magnetic field. If a small external field is added vertically downward at that point, the compass needle

30. A short magnetic dipole has moment . Compare the axial field at with the equatorial field at , taking both as magnitudes.

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

32. A graph is plotted for different places with on the vertical axis and on the horizontal axis.

The dip angle for these places is

33. A soft magnetic material is preferred in devices where magnetisation must follow a changing current because

34. A short magnetic dipole is observed at two points. Point P is axial at distance , and point Q is equatorial at distance . The ratio is

35. A bar magnet is cut into two equal pieces perpendicular to its length. Each piece will behave as

36. The reverse magnetic intensity required to reduce the residual magnetisation of a ferromagnetic material to zero is called

37. 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.

38. 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.

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

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

41. The axial magnetic field of a short dipole depends on magnetic dipole moment and distance from the centre. If only is doubled while remains unchanged, the axial field magnitude becomes

42. A short magnetic dipole gives an equatorial field at distance . Another dipole has magnetic moment and is observed at distance on its equatorial line. The new field is

43. A material used as the core of a transformer should have

44. A material has . Its magnetic susceptibility is

45. 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 .

46. 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

47. 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

48. 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

49. 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.

50. 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