CBSE Class 12 Physics Magnetism And Matter Notes Set B

Class XII: Physics

Ch5: Magnetism and Matter

Chapter Notes

Key Learnings

1. Magnetic materials tend to point in the north – south direction.

    Like magnetic poles repel and unlike ones attract.

    Cutting a bar magnet in two leads to two smaller magnets.

    Magnetic poles cannot be isolated.

5. The pole near the geographic north pole of the earth is called the north magnetic pole.

   The pole near the geographic south – pole is called the south magnetic pole.

   The magnitude of the magnetic field on the earth’s surface = 4 x 10-5 T.

6. Three quantities are needed to specify the magnetic field of the earth on its surface – the horizontal component, the magnetic declination, and the magnetic dip.

These are known as the elements of the earth’s magnetic field.

μr = 1 + X
9. Magnetic materials are broadly classified as; diamagnetic, paramagnetic and ferromagnetic.

For diamagnetic materials X is negative and small.

For paramagnetic materials X is positive and small.

For ferromagnetic materials  X lies between B and H
.
10. Substances, which at room temperature, retain their ferromagnetic property for a long period of time are called permanent magnets.

Magnetic Flux
Magnetic flux through a plane of area dA placed in a uniform magnetic field B

Electromagnetic Induction: Faraday’s Law
a). First Law: whenever there is a change in the magnetic flux linked with a circuit with time, an induced emf is produced in the circuit which lasts as long as the change in magnetic flux continues.

b). Second Law:

Induced emf, E/dt

Lenz’s Law

The direction of the induced emf or current in the circuit is such that it opposes the cause due to which it is produced, so that, E=-N(9ø/dt)

N → No. of turns in coil
Lenz’s law based on energy conservation.
EMF Current and Charge Induced in the Circuit

Charge depends only on net change in flux does not depends on time.

Emf Induced Due to Linear Motion of a Conducting Rod in a Uniform Magnetic Field

Induced EMF Due to Rotation of a Conducting Rod in a Uniform Magnetic Field

Where n is the frequency of rotation of the conducting rod

Induced EMF, Current and Energy Conservation in a Rectangular Loop Moving in a Non – Uniform Magnetic Field with a Constant Velocity
i) Net increase in flux crossing through the coil in time Δt

Please refer to the link below for CBSE Class 12 Physics Notes - Magnetism and Matter.