JEE Main - Magnetic dipole, bar magnet and magnetic materials Question Bank with Options

1. The magnetic field at the center of a bar magnet is approximately:

A) Zero

B) Equal to the field at the poles

C) Maximum

D) Half the field at the poles

2. When a ferromagnetic material is heated above its Curie temperature, it becomes:

A) Diamagnetic

B) Paramagnetic

C) Ferromagnetic

D) Antiferromagnetic

3. The force between two magnetic poles is proportional to:

A) The square of the distance between them.

B) The inverse square of the distance between them.

C) The distance between them.

D) The inverse of the distance between them.

4. Which of the following is a characteristic of magnetic field lines?

A) They intersect each other.

B) They start from negative poles and end at positive poles.

C) They are closed loops.

D) They are always straight lines.

5. The magnetic dipole moment of a bar magnet is zero if:

A) Its length is zero.

B) Its pole strength is zero.

C) It is placed in a zero magnetic field.

D) It is perfectly symmetrical.

6. Which of the following is a measure of how easily a magnetic material can be demagnetized?

A) Permeability

B) Retentivity

C) Coercivity

D) Saturation magnetization

7. What is the direction of the magnetic field at the equatorial point of a bar magnet?

A) Along the axis, towards the north pole

B) Along the axis, towards the south pole

C) Perpendicular to the axis, pointing outwards

D) Along the axis, in the direction opposite to the magnet's dipole moment

8. The magnetic susceptibility of iron at room temperature is approximately:

A) 10⁻⁵

B) 10⁻³

C) 10³

D) 10⁶

9. A bar magnet is cut into two equal halves by a plane perpendicular to its length. What happens to the pole strength of each half?

A) It remains the same.

B) It becomes half.

C) It doubles.

D) It becomes zero.

10. Which of the following is a property of magnetic materials that describes their ability to support the formation of a magnetic field?

A) Susceptibility

B) Coercivity

C) Permeability

D) Remanence

11. The magnetic field lines are discontinuous at:

A) The poles of a magnet

B) The center of a magnet

C) Magnetic monopoles (if they existed)

D) The neutral points

12. Which of the following represents the magnetic flux density of a bar magnet at a distance 'r' along its axis?

A) μ₀M / (2πr²)

B) μ₀M / (4πr³)

C) μ₀M / (2r³)

D) μ₀M / (4πr²)

13. The Curie temperature is associated with which type of magnetic material?

A) Diamagnetic

B) Paramagnetic

C) Ferromagnetic

D) All of the above

14. A magnetic dipole of moment 'M' experiences a torque 'τ' in a magnetic field 'B'. The torque is given by:

A) M . B

B) M / B

C) M × B

D) B / M

15. Which of the following materials has the highest magnetic permeability?

A) Paramagnetic

B) Diamagnetic

C) Ferromagnetic

D) Vacuum

16. The magnetic field at the axial point of a short bar magnet is proportional to:

A) r

B) r²

C) 1/r

D) 1/r³

17. What is the property of a material that indicates how easily it can be magnetized?

A) Permeability

B) Permittivity

C) Susceptibility

D) Reluctivity

18. The magnetic moment of an atom is primarily due to:

A) The motion of electrons around the nucleus.

B) The spin of electrons.

C) The motion of protons in the nucleus.

D) The nuclear spin.

19. When a paramagnetic material is placed in a non-uniform magnetic field, it tends to move towards:

A) The region of stronger field

B) The region of weaker field

C) It experiences no net force

D) It moves randomly

20. The magnetic field lines of a solenoid carrying current are similar to those of a:

A) Point charge

B) Electric dipole

C) Bar magnet

D) Ring current

21. Which of the following is NOT a unit of magnetic flux?

A) Weber

B) Tesla meter squared

C) Gauss

D) Maxwell

22. At the neutral point of a bar magnet, the magnetic field is:

A) Maximum

B) Minimum

C) Zero

D) Equal to the Earth's magnetic field

23. The ratio of magnetic field intensity to magnetic field strength in a material is called:

A) Magnetic susceptibility

B) Magnetic permeability

C) Relative permeability

D) Magnetization

24. Which type of magnetism is characterized by strong attraction to magnets and the ability to form permanent magnets?

A) Diamagnetism

B) Paramagnetism

C) Ferromagnetism

D) Antiferromagnetism

25. The force acting on a magnetic pole of strength 'm' in a magnetic field 'B' is given by:

A) m/B

B) mB

C) B/m

D) 1/(mB)

26. Which of the following correctly describes the magnetic field lines of a bar magnet?

A) They start at the north pole and end at the south pole outside the magnet.

B) They start at the south pole and end at the north pole outside the magnet.

C) They are closed loops, passing from north to south outside and south to north inside.

D) They are open loops, extending infinitely.

27. What is the magnetic susceptibility of a vacuum?

A) Large and positive

B) Small and positive

C) Negative

D) Zero

28. The magnetic field intensity (H) is related to the magnetic flux density (B) and magnetization (M) by:

A) B = μ₀(H + M)

B) B = μ₀(H - M)

C) B = μ₀(M - H)

D) B = μ₀(M / H)

29. A material that is weakly repelled by a magnet is:

A) Ferromagnetic

B) Paramagnetic

C) Diamagnetic

D) Ferrimagnetic

30. If the pole strength of a magnet is 'm' and its length is '2l', its magnetic dipole moment is:

A) m/l

B) ml

C) m/(2l)

D) 2ml

31. The magnetic field lines are most crowded near:

A) The center of the magnet

B) The equatorial line

C) The poles of the magnet

D) The midpoint of the magnet's length

32. Which property distinguishes ferromagnetic materials from paramagnetic materials?

A) Their response to an external magnetic field.

B) Their ability to be magnetized permanently.

C) Their magnetic susceptibility.

D) Their magnetic permeability.

33. What is the relationship between magnetic permeability (μ) and magnetic susceptibility (χ) for a material?

A) μ = 1 + χ

B) μ = 1 - χ

C) μ = χ - 1

D) μ = 1 / χ

34. The magnetic dipole moment of a current loop is given by:

A) I/A

B) IA

C) I/R

D) IR

35. When a diamagnetic material is placed in a non-uniform magnetic field, it tends to move towards:

A) The region of stronger field

B) The region of weaker field

C) It experiences no net force

D) It moves randomly

36. Which of the following is an example of a ferromagnetic material?

A) Aluminum

B) Platinum

C) Steel

D) Glass

37. The magnetic field at the equatorial line of a short bar magnet is:

A) Along the axis, towards the magnet

B) Along the axis, away from the magnet

C) Perpendicular to the axis, in the plane of the poles

D) Along the axis, in the direction opposite to that at the axial line

38. What is the unit of magnetic permeability?

A) Tesla

B) Ampere-meter

C) Henry per meter

D) Weber per square meter

39. The magnetic susceptibility (χ) of a paramagnetic material is:

A) Positive and large

B) Positive and small

C) Negative and small

D) Zero

40. Which of the following factors does NOT affect the magnetic dipole moment of a bar magnet?

A) Length of the magnet

B) Pole strength

C) Temperature

D) External magnetic field strength

41. The magnetic field lines inside a bar magnet go from:

A) North pole to South pole

B) South pole to North pole

C) Are absent inside the magnet

D) From the center to the poles

42. What is the property of ferromagnetic materials that allows them to retain magnetism after the external magnetic field is removed?

A) High permeability

B) Low susceptibility

C) Hysteresis

D) Low retentivity

43. The magnetic flux density (B) at a point is defined as:

A) The magnetic dipole moment per unit volume.

B) The number of magnetic field lines passing through a unit area.

C) The force experienced by a unit magnetic pole.

D) The magnetic potential energy per unit volume.

44. Which magnetic material is used to make permanent magnets?

A) Diamagnetic materials

B) Paramagnetic materials

C) Ferromagnetic materials

D) Antiferromagnetic materials

45. A magnetic dipole is placed in a uniform external magnetic field. The potential energy is minimum when the dipole moment is:

A) Anti-parallel to the magnetic field

B) Parallel to the magnetic field

C) Perpendicular to the magnetic field

D) At an angle of 45 degrees to the magnetic field

46. What is the magnetic susceptibility of a diamagnetic material?

A) Positive and large

B) Positive and small

C) Negative and small

D) Zero

47. The magnetic field lines of a bar magnet always form:

A) Closed loops originating from the north pole and ending at the south pole.

B) Closed loops originating from the south pole and ending at the north pole.

C) Open loops starting from the north pole and ending at the south pole.

D) Open loops starting from the south pole and ending at the north pole.

48. Which of the following is a diamagnetic material?

A) Iron

B) Nickel

C) Copper

D) Cobalt

49. A bar magnet has poles of equal strength. If one pole is broken off, what is the nature of the resulting pieces?

A) Each piece will be a single pole.

B) Each piece will be a neutral object.

C) Each piece will be a bar magnet with two poles.

D) The larger piece will be a magnet, and the smaller piece will be neutral.

50. What is the SI unit of magnetic dipole moment?

A) Tesla

B) Ampere-meter

C) Joule

D) Weber

Magnetic dipole, bar magnet and magnetic materials - Question Bank