Chapter 6 of NCERT Class 12 Physics, Electromagnetic Induction, is one of the most significant chapters in understanding the relationship between electricity and magnetism. This chapter explores how changing magnetic fields can induce electric currents in a conductor. This phenomenon is central to the working of electrical devices like transformers, electric generators, and motors.
Electromagnetic induction is a crucial concept for both theoretical understanding and practical applications in engineering and technology.
Table of Contents
Key Topics Covered in Chapter 6
- Introduction to Electromagnetic Induction
- Concept of electromagnetic induction
- Faraday’s Law of Induction
- Lenz’s Law and its significance
- Faraday’s Law of Induction
- Statement and mathematical form of Faraday’s Law
- Different forms of Faraday’s law of induction
- Lenz’s Law
- Explanation and importance of Lenz’s Law
- Conservation of energy and Lenz’s Law
- Induced EMF and Current
- Factors affecting induced EMF
- Induced current and its direction
- Self-Induction and Mutual Induction
- Definition and working of self-induction
- Mutual induction and its applications
- The coefficient of mutual induction (M)
- Applications of Electromagnetic Induction
- Transformers
- Electric generators and motors
- Induction coils and other devices
- Eddy Currents
- Concept and effects of eddy currents
- Applications of eddy currents
Important Formulas from Electromagnetic Induction
- Faraday’s Law of Induction:ε=−NdΦdt\varepsilon = -N \frac{d\Phi}{dt}ε=−NdtdΦWhere:
ε\varepsilonε = Induced EMF
NNN = Number of turns in the coil
Φ\PhiΦ = Magnetic flux - Lenz’s Law:
The negative sign in Faraday’s law represents the opposition of the induced EMF to the change in flux, ensuring energy conservation. - Self-Induction:
The self-induced EMF in a coil is given by:ε=−Ldidt\varepsilon = -L \frac{di}{dt}ε=−LdtdiWhere:
LLL = Self-inductance of the coil
di/dtdi/dtdi/dt = Rate of change of current - Mutual Induction:
The mutual induction between two coils is given by:ε=−Mdidt\varepsilon = -M \frac{di}{dt}ε=−MdtdiWhere:
MMM = Coefficient of mutual induction
Multiple-Choice Questions (MCQs) from Chapter 6: Electromagnetic Induction
20 MCQs on Electromagnetic Induction (in English and Hindi)
English MCQs
- Electromagnetic induction occurs when:
A. A conductor moves in a magnetic field
B. A magnetic field changes around a conductor
C. Both A and B
D. None of the aboveAnswer: C. Both A and B - Faraday’s law states that the induced EMF is:
A. Directly proportional to the magnetic flux
B. Inversely proportional to the magnetic flux
C. Proportional to the rate of change of magnetic flux
D. Independent of the magnetic fluxAnswer: C. Proportional to the rate of change of magnetic flux - Lenz’s law is related to:
A. Conservation of energy
B. Conservation of momentum
C. Conservation of charge
D. None of the aboveAnswer: A. Conservation of energy - The SI unit of magnetic flux is:
A. Tesla
B. Weber
C. Henry
D. JouleAnswer: B. Weber - Self-induction is the phenomenon where:
A. A changing magnetic field induces a current in the same coil
B. A magnetic field is created in a nearby coil
C. Eddy currents are formed
D. None of the aboveAnswer: A. A changing magnetic field induces a current in the same coil - The direction of the induced current can be determined by:
A. Faraday’s Law
B. Ampere’s Law
C. Lenz’s Law
D. Coulomb’s LawAnswer: C. Lenz’s Law - The unit of self-inductance is:
A. Weber
B. Henry
C. Tesla
D. AmpereAnswer: B. Henry - Mutual induction occurs when:
A. A magnetic field changes in a coil nearby
B. A current flows in a single coil
C. Eddy currents flow in the conductor
D. None of the aboveAnswer: A. A magnetic field changes in a coil nearby - Eddy currents are used in:
A. Electric motors
B. Transformers
C. Magnetic braking systems
D. GeneratorsAnswer: C. Magnetic braking systems - The energy loss due to eddy currents can be minimized by:
A. Using thick conductors
B. Using laminated cores
C. Using pure iron cores
D. Increasing the resistanceAnswer: B. Using laminated cores - An electric generator works on the principle of:
A. Static electricity
B. Electromagnetic induction
C. Electrostatics
D. ElectromagnetismAnswer: B. Electromagnetic induction - The magnetic flux through a surface is given by:
A. B×AB \times AB×A
B. B⋅AB \cdot AB⋅A
C. A×B⃗A \times \vec{B}A×B
D. B/AB/AB/AAnswer: B. B⋅AB \cdot AB⋅A - The induced EMF in a closed loop is:
A. Zero
B. Equal to the magnetic flux
C. Equal to the rate of change of flux
D. None of the aboveAnswer: C. Equal to the rate of change of flux - The working of a transformer is based on:
A. Static electricity
B. Electromagnetic induction
C. Coulomb’s Law
D. Ohm’s LawAnswer: B. Electromagnetic induction - The core of a transformer is laminated to:
A. Reduce weight
B. Increase strength
C. Minimize eddy currents
D. Reduce powerAnswer: C. Minimize eddy currents - The coefficient of mutual induction depends on:
A. The number of turns in the coil
B. The material of the core
C. Both A and B
D. None of the aboveAnswer: C. Both A and B - If the current in a coil changes, the self-induced EMF:
A. Opposes the change
B. Enhances the change
C. Has no effect
D. Is constantAnswer: A. Opposes the change - Which device works on the principle of electromagnetic induction?
A. Electric fan
B. Transformer
C. Capacitor
D. ResistorAnswer: B. Transformer - The direction of induced EMF can be determined by:
A. Right-hand rule
B. Left-hand rule
C. Lenz’s Law
D. Fleming’s Right-Hand RuleAnswer: D. Fleming’s Right-Hand Rule - In electromagnetic induction, the induced current opposes the:
A. Magnetic field
B. Source of flux change
C. Conductor motion
D. None of the aboveAnswer: B. Source of flux change
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Hindi MCQs
- विद्युत चुंबकीय प्रेरण तब होता है जब:
A. एक चालक चुंबकीय क्षेत्र में गति करता है
B. एक चालक के चारों ओर चुंबकीय क्षेत्र बदलता है
C. A और B दोनों
D. इनमें से कोई नहींउत्तर: C. A और B दोनों - फैराडे का नियम कहता है कि प्रेरित EMF:
A. चुंबकीय फ्लक्स के समानुपाती है
B. चुंबकीय फ्लक्स के व्युत्क्रमानुपाती है
C. चुंबकीय फ्लक्स में परिवर्तन की दर के समानुपाती है
D. चुंबकीय फ्लक्स से स्वतंत्र हैउत्तर: C. चुंबकीय फ्लक्स में परिवर्तन की दर के समानुपाती है - लेंज़ का नियम किससे संबंधित है?
A. ऊर्जा का संरक्षण
B. संवेग का संरक्षण
C. आवेश का संरक्षण
D. इनमें से कोई नहींउत्तर: A. ऊर्जा का संरक्षण - चुंबकीय फ्लक्स की SI इकाई क्या है?
A. टेस्ला
B. वेबर
C. हेनरी
D. जूलउत्तर: B. वेबर - स्व-प्रेरण वह घटना है जिसमें:
A. बदलते चुंबकीय क्षेत्र में उसी कुंडली में धारा उत्पन्न होती है
B. पास की कुंडली में चुंबकीय क्षेत्र उत्पन्न होता है
C. एडी धारा उत्पन्न होती है
D. इनमें से कोई नहींउत्तर: A. बदलते चुंबकीय क्षेत्र में उसी कुंडली में धारा उत्पन्न होती है - प्रेरित धारा की दिशा का निर्धारण किससे किया जाता है?
A. फैराडे का नियम
B. एंपेयर का नियम
C. लेंज़ का नियम
D. कूलॉम्ब का नियमउत्तर: C. लेंज़ का नियम