Why this topic is important for ECET
Electromagnetic Induction (EMI) is one of the most fundamental concepts in electrical engineering. It explains how voltage is induced when magnetic flux changes. This is the basis of transformers, generators, motors, and modern power systems. In ECET 2026, you can expect both conceptual and numerical problems directly from Faraday’s Law, Lenz’s Law, and practical EMI applications. Strong grip on EMI will help in scoring marks in AC Machines, Power Systems, and Power Electronics as well.
📘 Concept Notes
1. Faraday’s Laws of Electromagnetic Induction
- First Law: Whenever the magnetic flux linked with a coil changes, an emf is induced in it.
- Second Law: The magnitude of induced emf is directly proportional to the rate of change of flux linkage.
Where:
→ Induced emf (Volts)
→ Number of turns
→ Magnetic flux (Webers)
The negative sign indicates Lenz’s Law (direction opposes the cause).
2. Lenz’s Law
The direction of induced emf is such that it always opposes the change in magnetic flux that produces it.
- Example: When a magnet is pushed into a coil, the coil produces an opposing magnetic field.
3. Types of Induced EMF
- Statically Induced EMF
- Flux linkage changes when the conductor is stationary.
- Example: Transformer action.
- Dynamically Induced EMF
- Flux linkage changes because the conductor cuts across magnetic field lines.
- Example: Generator principle.
Where:
→ Flux density (Tesla)
→ Length of conductor (m)
→ Velocity of conductor (m/s)
4. Self and Mutual Inductance
- Self Inductance (L): Property of a coil to oppose change in its own current.
- Mutual Inductance (M): Induced emf in one coil due to change of current in another coil.
5. Energy Stored in Magnetic Field
⚙️ Formulas
- Induced emf (Faraday):
- Dynamically induced emf:
- Self-inductance emf:
- Mutual inductance emf:
- Energy stored:
🔟 10 MCQs
Q1. A coil of 100 turns links a flux of 0.01 Wb. Find emf induced if flux collapses uniformly in 0.1 s.
a) 10 V
b) 5 V
c) 1 V
d) 0.01 V
Q2. Which law gives the direction of induced emf?
a) Faraday’s first law
b) Lenz’s law
c) Kirchhoff’s law
d) Coulomb’s law
Q3. A conductor of length 0.5 m moves at 10 m/s in a field of 1.2 T. Find induced emf.
a) 2 V
b) 6 V
c) 12 V
d) 0.6 V
Q4. The unit of inductance is:
a) Tesla
b) Henry
c) Weber
d) Volt
Q5. If 
and 
, induced emf is:
a) 2 V
b) 4 V
c) 6 V
d) 8 V
Q6. In a transformer, emf is induced by:
a) Dynamically induced emf
b) Statically induced emf
c) Both
d) None
Q7. Energy stored in a 5 H inductor carrying 2 A current:
a) 10 J
b) 20 J
c) 5 J
d) 2 J
Q8. Mutual inductance of two coils is 0.5 H. If current in one changes at 2 A/s, induced emf in the other = ?
a) 0.25 V
b) 0.5 V
c) 1 V
d) 2 V
Q9. Which principle is used in generators?
a) Static induction
b) Dynamic induction
c) Electrostatics
d) None
Q10. If flux changes at rate 0.02 Wb/s and coil has 200 turns, induced emf = ?
a) 2 V
b) 4 V
c) 5 V
d) 10 V
✅ Answer Key
| Q.No | Answer |
|---|---|
| 1 | a |
| 2 | b |
| 3 | b |
| 4 | b |
| 5 | d |
| 6 | b |
| 7 | a |
| 8 | c |
| 9 | b |
| 10 | a |
🧠 Explanations
- Q1:
→ (a). - Q2: Lenz’s law gives direction → (b).
- Q3:
→ (b). - Q4: Inductance unit is Henry → (b).
- Q5:
→ (d). - Q6: Transformer works on statically induced emf → (b).
- Q7:
→ (a). - Q8:
→ (c). - Q9: Generators → dynamically induced emf → (b).
- Q10:
→ (a is wrong, correct is b actually)** correction ** → Answer (b).
🎯 Motivation / Why Practice Matters
Electromagnetic induction is the heart of electrical engineering. Without mastering it, solving questions in machines, transformers, and power systems is impossible. In ECET 2026, direct questions on Faraday’s law, energy stored in inductors, or induced emf calculations can appear. Practicing daily improves accuracy and speed, which are key for competitive edge.
📲 CTA
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