# NCERT solutions for Class 12 Physics Textbook chapter 5 - Magnetism and Matter [Latest edition]

#### Chapters ## Chapter 5: Magnetism and Matter

Exercise
Exercise [Pages 200 - 202]

### NCERT solutions for Class 12 Physics Textbook Chapter 5 Magnetism and MatterExercise [Pages 200 - 202]

Exercise | Q (a) | Page 200

Answer the following question regarding earth’s magnetism:

A vector needs three quantities for its specification. Name the three independent quantities conventionally used to specify the earth’s magnetic field.

Exercise | Q (b) | Page 200

Answer the following question regarding earth’s magnetism:

The angle of dip at a location in southern India is about 18°. Would you expect a greater or smaller dip angle in Britain?

Exercise | Q (c) | Page 200

Answer the following question regarding earth’s magnetism:

If you made a map of magnetic field lines at Melbourne in Australia, would the lines seem to go into the ground or come out of the ground?

Exercise | Q (d) | Page 200

Answer the following question regarding earth’s magnetism:

In which direction would a compass free to move in the vertical plane point to, if located right on the geomagnetic north or south pole?

Exercise | Q (e) | Page 200

Answer the following question regarding earth’s magnetism:

The earth’s field, it is claimed, roughly approximates the field due to a dipole of magnetic moment 8 × 1022 J T−1 located at its centre. Check the order of magnitude of this number in some way.

Exercise | Q (f) | Page 200

Answer the following question regarding earth’s magnetism:

Geologists claim that besides the main magnetic N-S poles, there are several local poles on the earth’s surface oriented in different directions. How is such a thing possible at all?

Exercise | Q (a) | Page 200

The earth’s magnetic field varies from point to point in space. Does it also change with time? If so, on what time scale does it change appreciably?

Exercise | Q (b) | Page 200

The earth’s core is known to contain iron. Yet geologists do not regard this as a source of the earth’s magnetism. Why?

Exercise | Q (c) | Page 200

The charged currents in the outer conducting regions of the earth’s core are thought to be responsible for earth’s magnetism. What might be the ‘battery’ (i.e., the source of energy) to sustain these currents?

Exercise | Q (d) | Page 200

The earth may have even reversed the direction of its field several times during its history of 4 to 5 billion years. How can geologists know about the earth’s field in such distant past?

Exercise | Q (e) | Page 200

The earth’s field departs from its dipole shape substantially at large distances (greater than about 30,000 km). What agencies may be responsible for this distortion?

Exercise | Q (f) | Page 200

Interstellar space has an extremely weak magnetic field of the order of 10–12 T. Can such a weak field be of any significant consequence? Explain.

Exercise | Q 5.03 | Page 200

A short bar magnet placed with its axis at 30° with a uniform external magnetic field of 0.25 T experiences a torque of magnitude equal to 4.5 × 10–2 J. What is the magnitude of magnetic moment of the magnet?

Exercise | Q 5.04 | Page 200

A short bar magnet of magnetic moment m = 0.32 J T–1 is placed in a uniform magnetic field of 0.15 T. If the bar is free to rotate in the plane of the field, which orientation would correspond to its (a) stable, and (b) unstable equilibrium? What is the potential energy of the magnet in each case?

Exercise | Q 5.05 | Page 201

A closely wound solenoid of 800 turns and area of cross-section 2.5 × 10–4 m2 carries a current of 3.0 A. Explain the sense in which the solenoid acts like a bar magnet. What is its associated magnetic moment?

Exercise | Q 5.06 | Page 201

If the solenoid is free to turn about the vertical direction and a uniform horizontal magnetic field of 0.25 T is applied, what is the magnitude of torque on the solenoid when its axis makes an angle of 30° with the direction of applied field?

Exercise | Q 5.07 | Page 201

A bar magnet of magnetic moment 1.5 J T –1 lies aligned with the direction of a uniform magnetic field of 0.22 T.

(a) What is the amount of work required by an external torque to turn the magnet so as to align its magnetic moment: (i) normal to the field direction, (ii) opposite to the field direction?

(b) What is the torque on the magnet in cases (i) and (ii)?

Exercise | Q 5.08 | Page 201

A closely wound solenoid of 2000 turns and area of cross-section 1.6 × 10–4 m2, carrying a current of 4.0 A, is suspended through its centre allowing it to turn in a horizontal plane.

(a) What is the magnetic moment associated with the solenoid?

(b) What is the force and torque on the solenoid if a uniform horizontal magnetic field of 7.5 × 10–2 T is set up at an angle of 30° with the axis of the solenoid?

Exercise | Q 5.09 | Page 201

A circular coil of 16 turns and radius 10 cm carrying a current of 0.75 A rests with its plane normal to an external field of magnitude 5.0 × 10−2 T. The coil is free to turn about an axis in its plane perpendicular to the field direction. When the coil is turned slightly and released, it oscillates about its stable equilibrium with a frequency of 2.0 s−1. What is the moment of inertia of the coil about its axis of rotation?

Exercise | Q 5.1 | Page 201

A magnetic needle free to rotate in a vertical plane parallel to the magnetic meridian has its north tip pointing down at 22° with the horizontal. The horizontal component of the earth’s magnetic field at the place is known to be 0.35 G. Determine the magnitude of the earth’s magnetic field at the place.

Exercise | Q 5.11 | Page 201

At a certain location in Africa, a compass points 12° west of the geographic north. The north tip of the magnetic needle of a dip circle placed in the plane of magnetic meridian points 60° above the horizontal. The horizontal component of the earth’s field is measured to be 0.16 G. Specify the direction and magnitude of the earth’s field at the location.

Exercise | Q 5.12 | Page 201

A short bar magnet has a magnetic moment of 0.48 J T−1. Give the direction and magnitude of the magnetic field produced by the magnet at a distance of 10 cm from the centre of the magnet on (a) the axis, (b) the equatorial lines (normal bisector) of the magnet.

Exercise | Q 5.13 | Page 201

A short bar magnet placed in a horizontal plane has its axis aligned along the magnetic north-south direction. Null points are found on the axis of the magnet at 14 cm from the centre of the magnet. The earth’s magnetic field at the place is 0.36 G and the angle of dip is zero. What is the total magnetic field on the normal bisector of the magnet at the same distance as the null point (i.e., 14 cm) from the centre of the magnet? (At null points, field due to a magnet is equal and opposite to the horizontal component of earth’s magnetic field.)

Exercise | Q 5.14 | Page 201

If the bar magnet is turned around by 180°, where will the new null points be located?

Exercise | Q 5.15 | Page 202

A short bar magnet of magnetic moment 5.25 × 10−2 J T1 is placed with its axis perpendicular to the earth’s field direction. At what distance from the centre of the magnet, the resultant field is inclined at 45° with earth’s field on (a) its normal bisector and (b) its axis. Magnitude of the earth’s field at the place is given to be 0.42 G. Ignore the length of the magnet in comparison to the distances involved.

## Chapter 5: Magnetism and Matter

Exercise ## NCERT solutions for Class 12 Physics Textbook chapter 5 - Magnetism and Matter

NCERT solutions for Class 12 Physics Textbook chapter 5 (Magnetism and Matter) include all questions with solution and detail explanation. This will clear students doubts about any question and improve application skills while preparing for board exams. The detailed, step-by-step solutions will help you understand the concepts better and clear your confusions, if any. Shaalaa.com has the CBSE Class 12 Physics Textbook solutions in a manner that help students grasp basic concepts better and faster.

Further, we at Shaalaa.com provide such solutions so that students can prepare for written exams. NCERT textbook solutions can be a core help for self-study and acts as a perfect self-help guidance for students.

Concepts covered in Class 12 Physics Textbook chapter 5 Magnetism and Matter are Magnetic Substances, Magnetic Dipole Moment of a Revolving Electron, Current Loop as a Magnetic Dipole and Its Magnetic Dipole Moment, Introduction of Magnetism, Magnetisation and Magnetic Intensity, Curie Law of Magnetism, Magnetism and Gauss’s Law, Hysteresis Loop, Magnetic Properties of Materials, The Earth’s Magnetism, The Bar Magnet, Torque on a Magnetic Dipole (Bar Magnet) in a Uniform Magnetic Field, Dipole in a Uniform External Field, Magnetic Field Intensity Due to a Magnetic Dipole (Bar Magnet) Perpendicular to Its Axis, Magnetic Field Intensity Due to a Magnetic Dipole (Bar Magnet) Along Its Axis, Permanent Magnet and Electromagnet.

Using NCERT Class 12 solutions Magnetism and Matter exercise by students are an easy way to prepare for the exams, as they involve solutions arranged chapter-wise also page wise. The questions involved in NCERT Solutions are important questions that can be asked in the final exam. Maximum students of CBSE Class 12 prefer NCERT Textbook Solutions to score more in exam.

Get the free view of chapter 5 Magnetism and Matter Class 12 extra questions for Class 12 Physics Textbook and can use Shaalaa.com to keep it handy for your exam preparation