Magnetism And Matter

Previous Years' CBSE Board Questions

5.2 The Bar Magnet

MCQ

1 A bar magnet has magnetic dipole moment <math>\hat{M}</math>. Its initial position is parallel to the direction of uniform magnetic B. In this position, the magnitudes of torque and force acting on it respectively are

1. 0 and MB (b) MB and MB
2. 0 and 0 (d) <math>|M \times B|</math> and 0 (Term I 2021-22)

2 Which of the following statements is correct?

1. Magnetic field lines do not form closed loops.
2. Magnetic field lines start from north pole and end at south pole of a magnet.
3. Two magnetic field lines may intersect each other. (Term I 2021-22) [1]
4. The tangent at a point on a magnetic field line represents the direction of the magnetic field at that point.

Question No. 3 is Assertion (A) and Reason (R) type questions. Given below are the two statements labelled as Assertion (A) and Reason (R). Select the most appropriate answer from the options given below.

Assertion (A): The poles of a bar magnet cannot be separated.

Reason (R): Magnetic monopoles do not exist.

1. Both (A) and (R) are true and (R) is correct

hold the magnet in equilibrium at an angle of 30°

with the field.

Calculate the value of F.

How will the equilibrium be effected if F is

withdrawn? (Al 2020)

(a) Show that a current carrying solenoid behaves

like a small bar magnet. Obtain the expression

for the magnetic field at an external point lying

on its axis.

(b) A steady current of 2 A flows through a circular

coil having 5 turns of radius 7 cm. The coil lies in

X-Y plane with its centre at the origin. Find the

magnitude and direction of the magnetic dipole

moment of the coil. (AI 2020) EV

5.3 Magnetism and Gauss's Law

SA II (3 marks)

State Gauss's law for magnetism. Explain its

significance. (1/3, Delhi 2019) R

5.5 Magnetic Properties of Materials

MCQ

Which of the following has its permeability less than

that of free space? (c)

1. Copper (b) Aluminium

explanation of (A).

1. Both (A) and (R) are true, and (R) is not correct explanation of (A).

1. (A) is true, but (R) is false.
2. (A) is false and (R) is also false. (Term I 2021-22)

Silicon

Copper (2023)

SA II (3 marks)

1. Write the four important properties of the magnetic field lines due to a bar magnet. (2/3, Delhi 2019)

1. A bar magnet of magnetic moment 6 J T -1 is aligned at 60° with a uniform external magnetic field of 0.44 T. Calculate (a) the work done in turning the magnet to align its magnetic moment (i) normal to the magnetic field, (ii) opposite to the magnetic field, and (b) the torque on the magnet in the final orientation in case (ii). (2018) Ap

Above Curies temperature, a

1. (b) ferromagnetic material become paramagnetic
2. (d) paramagnetic material become diamagnetic (Al 2020)

(5 marks)

1. (a) Derive the expression for the force acting between two long parallel current carrying conductors. Hence, define 1 A current.

1. A bar magnet of dipole moment 3 Am2 rests with its centre on a frictionless pivot. A force F is applied at right angles to the axis of the magnet, 10 cm from the pivot. It is observed that an external magnetic field of 0.25 T is required to

The magnetic susceptibility χ of a given material is -0.5. Identify the magnetic material. (Al 2019)

Write one important property of a paramagnetic material. (Al 2019)

1. Do the diamagnetic substances have resultant magnetic moment in an atom in the absence of external magnetic field? (Al 2019)
2. In what way is the behaviour of a diamagnetic material different from that of a paramagnetic, when kept in an external magnetic field? (Al 2016)
3. Depict the behaviour of magnetic field lines in the presence of a diamagnetic material. (Foreign 2016)

Relative permeability of a material μ_r = 0.5. Identify the nature of the magnetic material and write its relation to magnetic susceptibility. (Delhi 2014C) [U

(Al 2018) Ap

SAI (2 marks)

1. Two identical bars, one of paramagnetic material and other of diamagnetic material are kept in a

10. Which of the following

cannot modify an external

magnetic field as shown in

the figure? (c)

1. Nickel (b)

Which one of the following has relative magnetic

permeability between 0 and 1?

1. Aluminium (b) Alnico
2. Water (d) Sodium (2023)[ ]

VSA (1 mark)

1. The magnetic field lines are by a diamagnetic substance. (Al 2020)
2. The magnetic susceptibility of magnesium at 300 K is 1.2 × 10⁵. At what temperature will its magnetic susceptibility become 1.44 × 10⁵?

(Al 2019)

uniform external magnetic field parallel to it. Draw

diagrammatically the modifications in the magnetic

field pattern in each case. (Al 2020)

22. Give two points to distinguish between a

paramagnetic and a diamagnetic substance.

(Foreign 2014)

SA II (3 marks)

23. Write three points of differences between para-,

dia- and ferro- magnetic materials giving one

example for each. (Delhi 2019)

The susceptibility of a magnetic material is 0.9853.

Identify the type of magnetic material. Draw the

modification of the field pattern on keeping a piece

of this material in a uniform magnetic field.

Show diagrammatically the behaviour of magnetic

field lines in the presence of (i) paramagnetic and (ii)

diamagnetic substances. How does one explain this

distinguishing feature. (Al 2014)