Electromagnetic Induction – Class 12 Physics Notes | CBSE NCERT Based
๐ Chapter: Electromagnetic Induction – Full Detailed Notes
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๐ธ 1. Introduction
Electromagnetic Induction is the phenomenon of inducing current or EMF in a conductor when the magnetic flux linked with it changes.
Discovered by Michael Faraday in 1831.
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๐น 2. Faraday’s Laws of Electromagnetic Induction
✅ First Law
Whenever magnetic flux linked with a coil changes, an EMF is induced.
✅ Second Law
The magnitude of induced EMF is directly proportional to the rate of change of magnetic flux:
\text{EMF} = -\frac{d\Phi}{dt}
Negative sign from Lenz’s Law
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๐น 3. Lenz’s Law
The direction of induced EMF is such that it opposes the cause that produced it.
It ensures conservation of energy.
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๐น 4. Magnetic Flux (ฮฆ)
\Phi = B \cdot A \cdot \cos\theta
= Magnetic field
= Area
= Angle between B and normal to area
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๐น 5. Induced EMF Types
Static (by changing area/orientation)
Dynamic (by relative motion of coil and magnet)
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๐น 6. Motional EMF
When a conductor of length moves in magnetic field:
\varepsilon = B \cdot l \cdot v \cdot \sin\theta
Special case when conductor moves perpendicular to field:
\varepsilon = B \cdot l \cdot v
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๐น 7. Eddy Currents
Circulating currents induced in bulk conductors
Produce heating (used in induction furnace, speedometers)
Reduced using lamination
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๐น 8. Self Induction
A changing current in a coil induces EMF in the same coil
\varepsilon = -L \frac{di}{dt}
Where = Self-inductance (Henry, H)
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๐น 9. Mutual Induction
Changing current in one coil induces EMF in another nearby coil
\varepsilon = -M \frac{di}{dt}
Where = Mutual inductance
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๐น 10. Energy Stored in Inductor
U = \frac{1}{2} L i^2
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๐น 11. Applications of Electromagnetic Induction
Electric generators
Transformers
Induction cookers
Magnetic brakes
AC dynamo
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๐ Conclusion:
Electromagnetic Induction
is the foundation of electricity generation and modern-day electromechanical technology. Faraday’s discovery revolutionized the world.
๐ผ Important Diagrams – Electromagnetic Induction
1. ✅ Faraday’s Experiment (Magnet & coil – galvanometer deflection)
2. ✅ Magnetic flux through loop (changing area/angle)
3. ✅ Motional EMF (Rod moving in magnetic field)
4. ✅ Eddy current formation in metallic plate
5. ✅ Self-induction (Coil + galvanometer)
6. ✅ Mutual induction (Two coils – primary & secondary)
7. ✅ Induced current direction using Lenz’s law
8. ✅ AC Generator working principle
9. ✅ Energy stored in inductor
10. ✅ Magnetic braking & transformer basic concept
✍️ Written by: Shahid – Study with Shahid
๐ Visit: https://shahidnotes12.blogspot.co
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