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# Xam Idea Class 12 Physics Chapter 5 Solutions: Magnetism And Matter

Xam Idea Class 12 Physics Solutions for Chapter 5 ‘Magnetism of Matter’ are based on current loops that form a magnetic dipole. With lucid explanations of each concept involved and problems based on the latest CBSE curriculum, this book is surely something you must go through to score high in board exams. The book also serves as a great resource for preparing for higher education in Physics and many competitive exams like IIT-JEE. By going through our solutions to these questions, you will have an edge over others on any topic in Physics and can confidently sit for your exams.

Xam Idea Class 12 Physics Solutions Chapter 5 Magnetism of matter has a total of 88 questions that are spread across 8 segments. The questions range from short to long answer types, along with MCQs and some HOTS (high order thinking skills). In this chapter you learn about magnetic dipole moment’s intensity and field, how a revolving electron can have a magnetic dipole moment, torque on a magnetic dipole, magnetic field lines, how the earth has a magnetic field, what is electromagnetic force and what affects its strength, para, dia, and ferromagnetic substances, and lot more.

Xam Idea has collated it’s questions from many reputed books like NCERT Exemplar and previous year CBSE questions to give you a thorough practice on the topic. Our experts at Instasolv have provided Xam Idea solutions to each of the questions, which are reliable and accurate. Our team has a lot of experience on the subject matter hence they give you an in-depth analysis of any problems so that you can take up many kinds of questions presented to you, without any hassle.

## Important Topics for Xam Idea Class 12 Physics Solutions Chapter 5: Magnetism of Matter

Magnetic dipole moment – A magnetic dipole is the north and South Pole of a magnet separated by a short distance. A magnetic dipole moment defines the strength and orientation of a magnet. Its formula is: Here q is the strength of the pole and 2L is the separation between poles. It is measured in Ampere(meter)2 or Am2

The magnetic dipole moment of a current loop- For a loop which has area A with N number of turns and carries a current I, its magnetic dipole moment is given by:

M = NIA, the direction of M is perpendicular to the loop and given by right-hand rule.

The magnetic dipole moment of a revolving electron – When an electron with charge e and mass me is revolving around in a circle of radius r, with a velocity v, it generates a current I due to its motion. The current is given by:

I = – e/2πr, the current is in the opposite direction of electrons movement since the electron is a negatively charged particle.

The magnetic moment of the electron is given by:

= iA = -ev/2 πr * A = -ev/2 πr * πr2 = -evr/2

If we divide and multiply the above result with the mass of the electron we get  = – evr me/2me

Now angular momentum L = mevr

Hence we can write  = – e/2me X L

Magnetic field intensity due to a magnetic dipole – If a point with polar coordinates (r, θ) is near a small magnet, then the magnetic intensity at that point due to the magnet is given by:

M = (0/4π * /r3 ) * √(1 + 3 Cos2 θ)

Here 0 – permeability constant = = 4π x 10-7 T * m/A

– The magnetic moment of the magnet

Gauss’ Law for Electromagnetism: When we break a bar magnet with a north and a south pole, we form 2 magnetic dipoles as each fragment would have a north and South Pole. Hence it is concluded that a magnetic dipole is the simplest magnetic structure, and monopoles do not exist in magnets. Gauss law states this with its theory that the net magnetic flux Φx, through any Gaussian surface is 0. Earth as a magnetic dipole – Earth itself is a huge magnet and to find its magnetic field, we can consider a huge magnetic dipole lying at its centre. Its magnetic south pole is in the geographical South Pole and magnetic north pole in the geographical North Pole. The direction of the magnetic dipole moment is at an angle of 11.5º to earth’s rotation axis.

Elements of Earth’s magnetic field:

• The angle of declination (α)– Angle between geographical and magnetic meridians
• The angle of dip (q) – The angle made by the magnetic field Be with the horizontal is the angle of dip and measured by dip circle. Also called magnetic inclination, the angle of dip is 0° at the magnetic equator and 90° at magnetic poles.
• The horizontal component of Earth’s magnetic field

H = Be Cos

V = Be Sin  (Vertical component)

So Be = √(H2 + V2)

• Diamagnetism – Diamagnetic materials exhibit magnetism only when placed in an external magnetic field are. Their magnetic dipoles are formed opposite to the external magnetic field. In a non-uniform magnetic field, a diamagnetic material is repelled by the region of the higher magnetic field.
• Paramagnetism – Paramagnetic materials have atoms with a permanent magnetic dipole moment. The moments are oriented randomly unless placed in an external field where they tend to align with the field. Magnetization M is the extent to which the alignment happens within a given volume V:

M = measured magnetic moment/V

When there is a complete alignment of all N atomic dipole moments it is called saturation and gives the maximum value of magnetization:

Mmax = N * /V

Curie’s law states that the level of magnetization in a paramagnetic material is proportional to the magnitude of the external magnetic field ext and inversely proportional to temperature T (in Kelvins):

M = C * ( ext/T), Here C is Curie’s constant

• Ferromagnetism –Ferromagnetic materials are those which retain alignment partially in regions (domain), even after the external magnetic field is removed. Curie temperature of the material removes this alignment. If the field is non-uniform then a Ferromagnetic sample gets attracted to the region of the higher magnetic field.

### Discussion of Exercises of Xam Idea Class 12 Physics Solutions Chapter 5: Magnetism of Matter

• The first exercise has 11 selected NCERT questions where you need to find the magnetic moment of a magnet, its potential energy, the direction of the magnetic field, amount of work required by an external torque to move a magnet, and some questions on earth’s magnetic properties.
• The 2nd set has 20 questions which are MCQs. There are some basic questions on magnetism and also sums on finding magnetic force and torque, earth’s angle of dip.
• The 3rd set has 1 question which is assertion-reason type. 4 statements are given with an assertion and a reason and you need to select the correct combination.
• The 4th set requires very short answers for its 20 questions. Questions cover topics like the magnetic moment, dia-para and ferromagnetic substances, magnetic susceptibility and permeability, angle of dip.
• The 5th set has 9 questions that need short answers. You brush your knowledge on types of magnetic substances, magnetic torque, magnetic susceptibility.
• The 6th set is a long answer type with a total of 11 questions. There are questions in which time period of oscillation of a magnetic dipole is to be calculated, sums on Gauss’s law, properties of magnetic field lines, etc.
• The 7th set has 3 questions and needs long answers. There are 2 questions that need derivation for magnetic field intensity due to a magnetic dipole.
• In the 8th set, there are 13 questions to assess you with questions ranging from all the topics discussed in the chapter.

## Why Use Xam Idea Class 12 Physics Solutions Chapter 5: Magnetism of Matter by Instasolv?

• What makes our Xam Idea solutions different is the research that our experts have done on each topic of Magnetism of Matter for Class 12 Physics.
• Our subject experts understand the need to do a question quickly and so have some tips and tricks to memorize formulas and get your root level concepts cleared.
• Our Xam Idea Class 12 Physics solutions are designed in a way to cater to CBSE board exam preparation thoroughly.
• Our solutions are free of cost hence it will be a wise decision for you to take the help of our services for acing CBSE or competitive exams.
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