Electromagnetic Induction Class 12 Physics Important Questions 2026–27
Official CBSE Physics Curriculum 2026–27 · Official Class XII SQP & Marking Scheme
1. Most Important Topics to Prepare
Φ = BA cos θ, area-vector angle, maximum/zero flux and flux change.
Induced EMF, rate of flux change, average and instantaneous forms.
Direction of induced current and conservation-of-energy reasoning.
Moving conductor, ε = Bℓv and direction.
L, ε = −L dI/dt, long-solenoid inductance and stored energy.
M, induced EMF in a second coil and coupled-solenoid relation.
2. High-Priority Concepts Before Practice
For a simple closed circuit of resistance R, the total induced charge for a flux change is obtained from q = N|ΔΦ|/R. This is useful when a question gives total flux change rather than the time taken.
Eddy currents are circulating currents induced in bulk conductors when magnetic flux through different parts changes. Learn the concept and common applications, but keep this separate from the explicitly named CBSE 2026–27 Chapter 6 core.
3. Very Short Answer Questions — 1 Mark
What is electromagnetic induction?
Write the expression for magnetic flux through a plane surface in a uniform magnetic field.
What is the SI unit of magnetic flux?
State Faraday's law for an N-turn coil.
What does the negative sign in Faraday's law signify?
Can an induced EMF exist in an open circuit?
What is the SI unit of self-inductance?
Write the expression for the motional EMF of a rod of length ℓ moving with speed v perpendicular to a magnetic field B in the standard geometry.
What is mutual induction?
Write the energy stored in an inductor carrying current I.
4. Conceptual and Reasoning Questions — 2 Marks
A magnet is held stationary near a conducting coil. The galvanometer shows no sustained deflection. Explain why.
A magnet is moved towards a coil and then away from it. Why does the galvanometer deflection reverse?
Why is the angle in Φ = BA cos θ measured between the magnetic field and the area vector rather than the plane of the coil?
Distinguish between induced EMF and induced current.
Why does Lenz's law agree with the law of conservation of energy?
What happens to the induced EMF if the same change in magnetic flux occurs in half the time?
Why can a changing current in one coil induce EMF in a nearby second coil even when there is no electrical connection between them?
State two factors on which the self-inductance of a long solenoid depends.
5. Numerical and Application Questions — 3 Marks
A 200-turn coil of area 0.020 m² is placed with its area vector parallel to a 0.50 T magnetic field. The field falls uniformly to 0.10 T in 0.40 s. Calculate the magnitude of the average induced EMF.
Initial flux per turn = 0.50 × 0.020 = 0.010 Wb.
Final flux per turn = 0.10 × 0.020 = 0.002 Wb.
|ΔΦ| = 0.008 Wb.
|εavg| = N|ΔΦ|/Δt = 200 × 0.008/0.40 = 4.0 V.
A conducting rod of length 0.80 m moves at 5 m/s perpendicular to a uniform magnetic field of 0.30 T. Find the motional EMF. If the circuit resistance is 2 Ω, find the current assuming the simple closed-circuit model.
ε = Bℓv = 0.30 × 0.80 × 5 = 1.20 V.
I = ε/R = 1.20/2 = 0.60 A.
An inductor of 2 H carries a current of 3 A. Calculate the energy stored in its magnetic field. What happens to the stored energy if the current is doubled?
U = ½LI² = ½ × 2 × 3² = 9 J.
If current doubles, U ∝ I², so the energy becomes four times: 36 J.
The current in a 4 H inductor changes from 2 A to 5 A in 0.30 s. Find the magnitude of the average self-induced EMF.
|εavg| = L|ΔI|/Δt = 4 × 3/0.30 = 40 V.
Two long coaxial solenoids have 500 and 1000 turns respectively, a common area of 4 × 10−3 m² and common length 0.50 m. Assuming an air core, calculate their mutual inductance.
M = μ0N1N2A/ℓ
= (4π × 10−7)(500)(1000)(4 × 10−3)/0.50
≈ 5.03 × 10−3 H = 5.03 mH.
A 100-turn coil of area 0.010 m² is rotated in a 0.40 T field so that the angle between its area vector and the field changes from 0° to 90° in 0.20 s. Find the magnitude of the average induced EMF.
Initial flux per turn = BA cos0° = 0.40 × 0.010 = 0.004 Wb.
Final flux per turn = BA cos90° = 0.
|εavg| = N|ΔΦ|/Δt = 100 × 0.004/0.20 = 2.0 V.
6. Higher-Order Questions — 3 to 5 Marks
A closed conducting loop has resistance 5 Ω. The magnetic flux linked with the loop changes from 0.08 Wb to 0.03 Wb. Find the total charge that passes through the loop.
A conducting loop is moved into a region of uniform magnetic field and then completely inside the field, where it remains stationary. During which stage is an induced EMF produced? Explain.
Explain briefly why eddy currents are produced in a bulk conductor placed in a changing magnetic field. State one useful application and one disadvantage.
Two coils are close to each other. The current in the primary coil changes rapidly but the secondary coil is open. What is induced in the secondary coil, and what happens if the secondary circuit is then closed?
Why is the induced EMF larger when the same change in flux occurs in a coil with more turns?
Explain why the current in an ideal inductor cannot change instantaneously.
Explain, using Faraday's law, why no induced EMF is produced when a coil moves in a uniform magnetic field without changing its area, orientation or linked flux.
A coil has 400 turns and its linked magnetic flux changes by 2.0 × 10−3 Wb in 0.10 s. Find the magnitude of the average induced EMF.
State the difference between magnetic flux and flux linkage for a coil of N turns.
A 0.50 H inductor carries a current of 4 A. Find the energy stored. If the inductance becomes 2.0 H while current remains 4 A, find the new energy.
A current in one coil changes at a rate of 20 A s−1. If the mutual inductance with a second coil is 0.15 H, calculate the magnitude of the induced EMF in the second coil.
Explain, using Faraday's law and Lenz's law, what happens when the north pole of a bar magnet is pushed towards a conducting coil.
A closed loop is placed in a magnetic field that changes with time. Explain why the induced current can change direction if the rate or direction of flux change changes.
Derive the expression for the self-inductance of a long air-core solenoid having N turns, length ℓ and cross-sectional area A.
For a long solenoid, B = μ0NI/ℓ.
Flux through each turn: Φ = BA = μ0NIA/ℓ.
Flux linkage: NΦ = μ0N²IA/ℓ.
Using NΦ = LI, we obtain L = μ0N²A/ℓ.
Explain mutual induction between two coils and obtain the expression for the mutual inductance of two long coaxial air-core solenoids with common length ℓ and area A.
Current I1 in solenoid 1 produces B1 = μ0N1I1/ℓ.
Flux through each turn of solenoid 2: Φ2 = B1A.
Flux linkage with N2 turns = N2Φ2.
Thus N2Φ2 = μ0N1N2A I1/ℓ = MI1.
Therefore M = μ0N1N2A/ℓ.
Explain the principle of electromagnetic induction and discuss Faraday's laws, Lenz's law and the relation between induced EMF and magnetic flux for an N-turn coil.
1. State electromagnetic induction: changing magnetic flux produces induced EMF.
2. State Faraday's first law.
3. State Faraday's second law and write ε = −N dΦ/dt.
4. Explain the negative sign through Lenz's law.
5. State that the induced effect opposes the change in flux that causes it, consistent with energy conservation.
Compare self-induction and mutual induction. Include the cause, induced EMF expression, coefficient, SI unit and one practical conceptual distinction.
Self-induction: change of current in a coil induces EMF in the same coil; ε = −L dI/dt; coefficient is L.
Mutual induction: change of current in one coil induces EMF in another coupled coil; ε2 = −M dI1/dt; coefficient is M.
Both L and M have SI unit henry (H). Self-induction is a coil's response to change in its own current; mutual induction represents magnetic coupling between two circuits.
7. Assertion–Reason Practice
Assertion (A): A stationary magnet placed near a stationary coil does not produce a sustained induced current in the coil.
Reason (R): The magnetic flux linked with the coil remains constant if the magnetic configuration is unchanged.
Assertion (A): The induced current opposes the change in magnetic flux that produces it.
Reason (R): This is the content of Lenz's law and is consistent with conservation of energy.
8. High-Yield Practice Map
| Area | Typical skill | What you should be able to do |
|---|---|---|
| Flux | Application | Choose the correct angle and calculate/change Φ. |
| Faraday's law | Concept + numerical | Relate induced EMF to rate of flux change. |
| Lenz's law | Analysis | Determine induced-current direction from increasing/decreasing flux. |
| Motional EMF | Application | Use ε = Bℓv and determine direction. |
| Self-induction | Concept + numerical | Use ε = −L dI/dt and L of a solenoid. |
| Energy in inductor | Numerical | Use U = ½LI² and proportional reasoning. |
| Mutual induction | Concept + numerical | Use ε = −M dI/dt and ideal solenoid relations. |
| Long answers | Derivation/reasoning | Present equations in logical sequence with definitions and units. |
9. High-Yield Revision Checklist
✓ Define electromagnetic induction.
✓ Explain what magnetic flux is and identify the area-vector angle.
✓ State Faraday's laws and explain the minus sign.
✓ Apply Lenz's law to magnet-coil and changing-flux situations.
✓ Distinguish induced EMF from induced current.
✓ Solve standard motional-EMF problems.
✓ Define self-induction and self-inductance.
✓ Derive/use L = μ0N²A/ℓ for a long air-core solenoid.
✓ Use U = ½LI².
✓ Define mutual induction and mutual inductance.
✓ Derive/use M = μ0N1N2A/ℓ for ideal coaxial solenoids.
✓ Keep AC generator and transformer with Chapter 7 for current CBSE 2026–27 preparation.
10. Chapter 6 Resource Path
Start here: Electromagnetic Induction Class 12 Physics Notes
Next in the workflow: After this Important Questions page is published and verified, the next resource will be Chapter 6 MCQs, followed by Numericals, PYQs, Assertion–Reason, Case-Based Questions, Formula Sheet and Chapter Test.
The companion links will be added as each resource is actually published; no invented URLs are used.
11. Chapter 5 Connection
Chapter 5 explains magnetic fields and magnetic matter. Chapter 6 builds on that foundation by studying what happens when the magnetic flux linked with a circuit changes.
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