Conceptual Questions Based on Class 12 Physics Magnetism and Matter

Conceptual Questions Based on Class 12 Physics Magnetism and Matter

Q.1. Does a magnetic monopole exist? Justify your answer. How magnetic field is produced?

Solution. No, a magnetic monopole does not exist. The reason is that a magnetic field is produced by a current loop and not by monopole of a magnet.

Q.2. How does the (i) pole strength and (ii) magnetic moment of each part of a bar magnet change if it is cut into two equal pieces transverse to its length?

Solution. (i) Pole strength of each part remains same as that of the original magnet.

(ii) Magnetic moment of each part is half of that of the original magnet because length of each part is halved.

Q.3. What is the origin of the word magnetism?

Solution. The word magnetism (or magnet) is derived from the name of an island in Greece called ‘Magnesia’ where deposits of natural magnet were found as early as the sixth century B.C.

Q.4. Repulsion is the surer test of magnetism. Comment.

Solution. A magnet can attract another magnet or a magnetic substance like iron. However, a magnet can repel another magnet only. So, repulsion is the surer test of magnetism.

Q.5. What is the source of magnetic field (or magnetism)?

Solution. The electrons revolving in atoms behave as current loops. These current loops give rise to magnetism.

Q.6. How are the magnetic field lines diff­erent from the electrostatic field lines?

Solution. An electric field line starts from a positive charge and ends on a negative charge and does not form a closed loop. A magnetic field line always forms a closed loop which runs from N-pole to S-pole outside a magnet and from S-pole to N-pole inside a magnet.

Q.7. How does the (i) pole strength and (ii) magnetic moment of each part of a bar magnet change if it is cut into two equal pieces along its length?

Solution. (i) Pole strength of each part becomes half of the original pole strength.

(ii) Magnetic moment of each part becomes half of the original magnetic moment.

Q.8. Why is a current loop considered a magnetic dipole?

Solution. Like a bar magnet, a current loop possesses a magnetic dipole moment (m = IA). Like a bar magnet, a current loop experiences a torque in a magnetic field due to which it aligns its axis parallel to the external magnetic field.

Q.9. What happens when a diamagnetic substance is placed in a varying magnetic field?

Solution. A diamagnetic substance tends to move from stronger to the weaker parts of the varying magnetic field.

Q.10. How does the magnetic induction of a para­magnetic material vary with temperature?

Solution. The magnetic induction of a paramagnetic material decreases with the increase in temperature.

Q.11. Why is diamagnetism independent of temperature?

Solution. The induced dipole moment in a diamag­netic sample is always opposite to the magnetising field, no matter what the internal motion of the atom is.

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