Bihar Board - Class 12 Physics - Chapter 6: Electromagnetic Induction Handwritten Notes

Electromagnetic induction is the process by which a changing magnetic field induces an electromotive force (EMF) or current in a conductor. This phenomenon forms the basis of many electrical devices, such as generators and transformers. The chapter explores Faraday's laws of electromagnetic induction, Lenz's law, and their applications in modern technology.

Key Points

1. Faraday’s Laws of Electromagnetic Induction

   • First Law: An EMF is induced in a conductor whenever the magnetic flux linked with it changes.
   • Second Law: The magnitude of the induced EMF is proportional to the rate of change of magnetic flux:
     $\text{EMF} = -\frac{d\Phi}{dt}$
     where $\Phi = B \cdot A \cdot \cos \theta$ (magnetic flux).

2. Lenz’s Law

   • The direction of the induced current is such that it opposes the change in magnetic flux causing it.
   • Ensures conservation of energy in electromagnetic induction.

3. Induced EMF and Current

   • Motional EMF: Induced when a conductor moves in a magnetic field:
     $\text{EMF} = B \cdot l \cdot v$
     where $B$ is the magnetic field strength, $l$ is the length of the conductor, and $v$ is its velocity.

4. Self-Induction

   • The phenomenon where a changing current in a coil induces an EMF in the same coil.
   • Inductance ($L$): A measure of a coil’s ability to induce EMF:
     $\text{EMF} = -L \frac{dI}{dt}$

5. Mutual Induction

   • The phenomenon where a changing current in one coil induces an EMF in a nearby coil.
   • Depends on mutual inductance ($M$) between the coils:
     $\text{EMF} = -M \frac{dI}{dt}$

6. Applications of Electromagnetic Induction

   • Generators: Convert mechanical energy into electrical energy using electromagnetic induction.
   • Transformers: Transfer electrical energy between circuits, changing voltage levels.
   • Induction Motors: Operate on the principle of electromagnetic induction to produce rotational motion.
   • Eddy Currents: Circulating currents induced in a conductor, used in braking systems and metal detectors.

7. Alternating Current (AC) Generation

   • An alternating current is produced when a conductor rotates in a uniform magnetic field.
   • The induced EMF varies sinusoidally with time.

Conclusion

Electromagnetic induction is a fundamental principle that drives the operation of many electrical systems and devices. Understanding its laws and applications is essential for advancements in energy generation, electrical engineering, and modern technologies.

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