NCERT Class 12 Physics Chapter 6 Notes, Electromagnetic Induction Class 12 Chapter 6 Notes

Ever wondered how a bicycle dynamo lights the headlight while you pedal? This is an example of electromagnetic induction in action, when motion in a magnetic field produces electricity.

The NCERT Class 12 Physics Chapter 6 notes explores this interesting phenomenon of electric currents being produced by changing magnetic fields in the chapter electromagnetic induction. The fundamental concepts and ideas behind this phenomenon are explained briefly in the Class 12 Physics Chapter 6 notes.

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This Story also Contains

1. NCERT Class 12 Physics Chapter 6 Notes-
2. Faraday’s Law of Electromagnetic Induction
3. Lenz’s Law:
4. Motional emf:-
5. Inductor
6. AC Generator
7. Importance of NCERT Class 12 Physics Chapter 6 Notes
8. NCERT Class 12 Notes Chapterwise
9. NCERT Books and Syllabus

These notes briefly cover key topics including motional electromotive force, eddy currents, self and mutual inductance, magnetic flux, Faraday's laws, Lenz's law, and how AC generators operate. Even though these CBSE-aligned notes lack thorough derivations, they still provide a great deal of conceptual depth and formulae to help you develop a firm grasp of the subject.

Also, students can refer,

• NCERT Notes Class 12 Physics
• NCERT Solutions for Class 12 Physics Chapter 6 Electromagnetic Induction
• NCERT Exemplar Class 12 Physics Chapter 6 Solutions Electromagnetic Induction

NCERT Class 12 Physics Chapter 6 Notes-

• Electromagnetic Induction (EMI) is the phenomenon of generating current or emf by changing the magnetic flux.
• Magnetic Flux:- The total number of magnetic lines of force travelling naturally through any surface equals the magnetic flux associated with it. It's a Scalar Quantity

Faraday’s Law of Electromagnetic Induction

The First Law:

When the magnetic flux in a closed-loop or circuit varies, an emf is generated in the loop or circuit that lasts as long as the flux is changing.
Second Law:

The rate of change of magnetic flux in a closed loop or circuit is directly proportional to the induced emf in the closed-loop or circuit.

$E=-\mathbf{d}\mathrm{\Phi }/dt$ where the negative sign indicates that e is induced in the opposite direction of changing flux.

Lenz’s Law:

The direction of induced emf is determined by Lenz's law.

According to this law, the direction of induced emf in a circuit opposes the change in magnetic flux responsible for its formation. The law of Lenz is based on the idea of energy conservation.

Fleming's right-hand rule:

Fleming's right-hand rule also determines the direction of induced emf or current in a conductor travelling in a magnetic field. According to this rule, if we stretch our right hand's forefinger, central finger, and thumb in mutually perpendicular directions, the forefinger will point in the direction of the field and the thumb will point in the direction of conductor motion, the central finger will point in the direction of induced current or emf.

Lenz's law is used in a variety of situations.

- When a bar magnet's north pole is shifted towards a coil, the current produced in the coil will be anticlockwise.

- When a bar magnet's north pole is moved away from the coil, the current produced in the coil rotates clockwise.

-The direction of current induced in a stationary coil changes as a current-carrying coil is pushed near it.
-The direction of current induced in a stationary coil changes when a current-carrying coil is moved away from it.

Motional emf:-

The generated emf across the ends of a conducting rod of length l moving with a velocity v perpendicular to a uniform magnetic field B is.

$\mathrm{E}=\mathrm{vBl}$

Motional emf is the name for this type of emf.

The induced emf if the rod makes an angle with the field direction is.

$|E|=\mathrm{Blv}\sin \theta$

When a length l conducting rod is rotated perpendicular to a uniform magnetic field B, the induced emf between the rod's ends is

$\begin{array}{rl}& |E|=\frac{B\omega I^2}{2}=\frac{B(2\pi v)I^2}{2}\\ & |E|=B\cup \left(\pi 1^2\right)=BvA\end{array}$

The emf produced between the centre and rim of a conducting solid disc of radius r rotates with a uniform angular velocity w with its plane perpendicular to a uniform magnetic field B.

$|E|=\frac{B\omega r^2}{2}=B\cup A$

Eddy currents:

Eddy currents are currents induced in the body of a conductor as a result of a change in magnetic flux associated with the conductor.

• Lenz's law, often known as Fleming's right-hand rule, determines the direction of eddy currents.

• Eddy currents form in a metallic conductor in such a way that they oppose the change in magnetic flux associated with it, according to Lenz's law.

• Eddy currents cannot be completely removed, but they can be reduced by - laminating the core – taking the metallic core in the form of thin laminated sheets that are joined together.

Electromagnetic dampers, induction furnaces, electric brakes, and speedometers all benefit from eddy currents.

Inductor

A device for storing energy in a magnetic field is an inductor. Inductance is the common term for an inductor. In most cases, a coil or solenoid is used as an inductor.

Self-induction: As the current going through a coil or circuit varies, so does the magnetic flux associated with it.

As a result, an emf is generated in the coil or circuit, which opposes the change that is causing it.

Self-induction is the term for this occurrence, and the resulting emf is known as self-induced emf or reverse emf.

-When a current I flows through a coil and phi is the magnetic flux associated with the coil, then, the self-induced emf is given by-

$E=-\mathbf{d}\mathrm{\Phi }/dt=-L\mathbf{d}\mathbf{I}/d\mathbf{d}\mathbf{t}$

where L is the coil's coefficient of self-induction.

- Henry (H) is the SI unit of L, and its dimensional formula is ML²T^-2A^-2

– A circular coil's self-inductance is

$\mathbf{L}={\mu }_0{\mathbf{N}}^2\pi \mathbf{R}/2$

where R is the coil's radius and N is the number of turns.

Mutual induction:

As the current going through a coil or circuit varies, so does the magnetic flux coupled to a neighbouring coil or circuit.

As a result, an emf will be induced in the next coil or circuit.

Mutual induction is the term for this occurrence.

The primary coil or circuit is where current changes, while the secondary coil or circuit is where emf is created.

– Assume that at any given time, I_P is the current flowing through the primary coil.

If ϕ_s is the flux connected to the secondary coil, then

${\mathrm{\Phi }}_{\mathrm{s}}\propto {\mathbf{I}}_{\mathrm{P}}$ or ${\mathrm{\Phi }}_{\mathrm{S}}={\mathrm{MI}}_{\mathrm{P}}$

where M is the mutual inductance coefficient of the two coils.

$E_s=-\mathbf{M}\mathbf{d}\mathbf{I}{I}_p/\mathbf{d}\mathbf{t}$

is the induced emf in the secondary coil.

- Henry (H) is the SI unit of M and its dimensional formula is ML²T^-2A^-2.

Coefficient of coupling (K):

The coefficient of coupling of two coils is defined as $\mathbf{K}=\mathbf{M}/\sqrt{}{\mathbf{L}}_1{\mathbf{L}}_2$

where L₁ and L₂ are the self-inductance coefficients of the two coils, and M is the mutual inductance coefficient of the two coils, respectively.

$\mathbf{M}={\mu }_0{\mathbf{N}}_1{\mathbf{N}}_2\mathbf{A}/\mathbf{l}$

M is the mutual inductance coefficient of two long co-axial solenoids, each of length l, area of cross-section A, wound on air core, where N1, N2 are the total number of turns of the two solenoids.

Inductance combination – Two self-inductance inductors L₁ and L₂ are kept so far apart that their mutual inductance is zero.

These are linked together in a series.

L=L₁+L₂is the equivalent inductance.

– Self-inductance L₁ and L₂ inductors are coupled in series and have mutual inductance M.

The combination's equivalent inductance is hence

$\mathbf{L}={\mathbf{L}}_1+{\mathbf{L}}_2\pm 2\mathbf{M}$

– The plus sign appears when the windings in the two coils are in the same direction, whereas the minus sign appears when the windings are in the opposite direction.

– Inductors L₁ and L₂ of self-inductors are connected in parallel.

The mutual inductance of the inductors is insignificant because they are so far away.

The equivalent inductance is then

$\frac{1}{L}=\frac{1}{L_1}+\frac{1}{L_2}$

Energy stored in an inductor: The energy stored in an inductor is given by when a current I flows through it.

$\mathbf{U}=\frac{1}{2}\mathbf{L}{\mathbf{I}}^{\mathbf{2}}$

Magnetic energy is the form of energy stored in an inductor.

AC Generator

• An electrical generator turns mechanical energy into electrical energy.

• The phenomenon of electromagnetic induction is used to generate alternating currents (ac).

• An emf is induced in the coil whenever the magnetic flux changes.

• A device that converts mechanical energy into electrical energy is known as an AC generator (alternating currents).

• By altering the magnetic field and area vector, an AC generator can induce an emf or current in a loop.

Principle:-

• A change in the loop's orientation or effective area causes current to flow through it.

• Modifying the area vector or changing the induced emf produces induced emf.

• Fleming's right-hand rule determines the direction of the current.

• The up and down movement of the loops changes the direction of the current in the circuit.

It based on The phenomenon of electromagnetic induction asserts that whenever the magnetic flux associated with a conductor (or coil) changes, an emf is induced in the coil.

If E is the induced emf in the coil, then

$\begin{array}{rl}& E=NBA\omega \sin \omega t\\ & E=E_0\sin \omega t\end{array}$

E₀=NBAω is the induced EMF's maximum or peak value.

Importance of NCERT Class 12 Physics Chapter 6 Notes

• The notes explain how changing magnetic fields produce electric currents, which is the principle behind devices like generators and transformers.

• They are perfectly aligned with the CBSE syllabus, making them ideal for board exam preparation.

• Complex topics such as Faraday’s Laws, Lenz’s Law, and Motional EMF are explained in a simple, easy-to-understand manner.

• These notes are also helpful for competitive exams like JEE and NEET, where conceptual clarity is important.

• They are great for quick revision, especially before exams, as they highlight key formulas and core concepts.

• Available in PDF format, they can be accessed anytime for convenient study on the go.

NCERT Class 12 Notes Chapterwise

Subject Wise NCERT Exemplar Solutions

• NCERT Exemplar Class 12 Solutions

• NCERT Exemplar Class 12 Maths

• NCERT Exemplar Class 12 Physics

• NCERT Exemplar Class 12 Chemistry

• NCERT Exemplar Class 12 Biology

Subject Wise NCERT Solutions

• NCERT Solutions for Class 12 Mathematics

• NCERT Solutions for Class 12 Chemistry

• NCERT Solutions for Class 12 Physics

• NCERT Solutions for Class 12 Biology

NCERT Books and Syllabus