⚡ Master "Electromagnetic Induction" with 100 MCQs (Set - 2) ⚡
⚡ From Basic to Expert Level! ⚡
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Are you preparing for exams or aiming to strengthen your understanding of Physics – Electromagnetic Induction? Looking for a complete set of 100 high-quality MCQs from basic to expert level to sharpen your concepts and boost your exam confidence?
This carefully curated collection of Multiple Choice Questions (MCQs) covers all major topics of the unit, including:
• Magnetic Flux & Faraday’s Laws
• Lenz’s Law & Induced EMF
• Motional EMF
• Self Induction & Mutual Induction
• Inductance & Energy Stored in an Inductor
• AC Generators & Transformers
• RL Circuits & Time Constant
• Eddy Currents & Magnetic Braking
• Fleming’s Left & Right Hand Rules
• Applications of Electromagnetic Induction
Each MCQ is provided with a clear solution or explanation, helping you:
- Understand concepts step-by-step
- Improve numerical problem-solving skills
- Revise quickly before exams
- Build strong conceptual clarity
Whether you’re revising for school exams, board exams, or competitive entry tests, this comprehensive MCQ set is designed to take your preparation to the next level.
💡 Study Tip: Start with basic questions, move to moderate, and finally challenge yourself with expert-level MCQs for maximum learning and exam readiness.
Are you preparing for exams or aiming to strengthen your understanding of Physics – Electromagnetic Induction? Looking for a complete set of 100 high-quality MCQs from basic to expert level to sharpen your concepts and boost your exam confidence?
This carefully curated collection of Multiple Choice Questions (MCQs) covers all major topics of the unit, including:
• Magnetic Flux & Faraday’s Laws
• Lenz’s Law & Induced EMF
• Motional EMF
• Self Induction & Mutual Induction
• Inductance & Energy Stored in an Inductor
• AC Generators & Transformers
• RL Circuits & Time Constant
• Eddy Currents & Magnetic Braking
• Fleming’s Left & Right Hand Rules
• Applications of Electromagnetic Induction
Each MCQ is provided with a clear solution or explanation, helping you:
- Understand concepts step-by-step
- Improve numerical problem-solving skills
- Revise quickly before exams
- Build strong conceptual clarity
Whether you’re revising for school exams, board exams, or competitive entry tests, this comprehensive MCQ set is designed to take your preparation to the next level.
💡 Study Tip: Start with basic questions, move to moderate, and finally challenge yourself with expert-level MCQs for maximum learning and exam readiness.
What You’ll Get in this post:
Set-1: Basic Level – Perfect for beginners, focusing on fundamentals like Magnetic Flux, Faraday’s Law, Lenz’s Law, and Force on a Current Carrying Conductor.
Set-2: Intermediate Level – Strengthens application skills with Motional EMF, Ampere’s Law, Solenoids, Motion of Charged Particles, and Velocity Selector.
Set-3: Advanced Level – Develops deeper understanding through Torque on a Current-Carrying Coil, Determination of e/m for an Electron, Galvanometer Conversions, and Measurement Instruments (Ammeter, Voltmeter, Avometer).
Set-4: Expert Level – High-level conceptual and numerical MCQs covering the entire Electromagnetic Induction unit, designed to test speed, accuracy, and critical thinking.
Electromagnetic Induction MCQs (Set-1: Basic Level
MCQs No. 1–25 (Basic Concepts)
MCQ No. 1
Magnetic flux through a surface is given by:
a) B × A
b) B/A
c) B · A
d) B + A
Correct answer: c) B · A
Explanation:
Magnetic flux (Φ) is defined as the dot product of magnetic field B and area vector A, i.e., Φ = B A cosθ.
MCQ No. 2
SI unit of magnetic flux is:
a) Tesla
b) Weber
c) Henry
d) Volt
Correct answer: b) Weber
Explanation:
The SI unit of magnetic flux is Weber (Wb). One weber equals one tesla·meter².
MCQ No. 3
According to Michael Faraday, induced emf is proportional to:
a) Magnetic field
b) Current
c) Rate of change of flux
d) Resistance
Correct answer: c) Rate of change of flux
Explanation:
Faraday’s law states that induced emf is directly proportional to the rate of change of magnetic flux.
MCQ No. 4
The negative sign in Faraday’s law represents:
a) Magnitude
b) Direction
c) Resistance
d) Voltage drop
Correct answer: b) Direction
Explanation:
The negative sign represents Lenz’s law, indicating the induced emf opposes the change in flux.
MCQ No. 5
According to Heinrich Lenz, induced current:
a) Supports the change
b) Opposes the change
c) Increases resistance
d) Stops completely
Correct answer: b) Opposes the change
Explanation:
Lenz’s law states that induced current flows in such a direction that it opposes the cause producing it.
MCQ No. 6
When magnetic flux linked with a circuit remains constant, induced emf is:
a) Maximum
b) Minimum
c) Zero
d) Infinite
Correct answer: c) Zero
Explanation:
If there is no change in magnetic flux, no emf is induced.
MCQ No. 7
Motional emf is produced when:
a) Magnet is stationary
b) Conductor moves in magnetic field
c) No magnetic field
d) Resistance changes
Correct answer: b) Conductor moves in magnetic field
Explanation:
When a conductor moves across magnetic field lines, emf is induced due to cutting of flux lines.
MCQ No. 8
Expression for motional emf is:
a) ε = B l v
b) ε = B/lv
c) ε = Bl/v
d) ε = B + l + v
Correct answer: a) ε = B l v
Explanation:
Motional emf equals magnetic field × length of conductor × velocity (when perpendicular).
MCQ No. 9
Unit of inductance is:
a) Weber
b) Tesla
c) Henry
d) Volt
Correct answer: c) Henry
Explanation:
Inductance is measured in Henry (H).
MCQ No. 10
Self induction occurs in:
a) Two coils
b) One coil
c) Capacitor
d) Battery
Correct answer: b) One coil
Explanation:
Self induction is the phenomenon in which changing current in a coil induces emf in the same coil.
MCQ No. 11
Mutual induction occurs between:
a) Two coils
b) One coil
c) Two resistors
d) Two capacitors
Correct answer: a) Two coils
Explanation:
Changing current in one coil induces emf in a nearby coil.
MCQ No. 12
Energy stored in an inductor is:
a) LI²
b) ½ LI²
c) I²/L
d) ½ I/L
Correct answer: b) ½ LI²
Explanation:
Energy stored in magnetic field of an inductor is given by U = ½ LI².
MCQ No. 13
Induced emf in a coil of N turns is:
a) −dΦ/dt
b) −N dΦ/dt
c) NΦ
d) Φ/N
Correct answer: b) −N dΦ/dt
Explanation:
Faraday’s law for N turns: ε = −N dΦ/dt.
MCQ No. 14
If flux increases rapidly, induced emf will be:
a) Small
b) Zero
c) Large
d) Constant
Correct answer: c) Large
Explanation:
Induced emf depends on rate of change of flux; greater rate gives greater emf.
MCQ No. 15
AC generator works on the principle of:
a) Electrostatics
b) Electromagnetic induction
c) Resistance
d) Capacitance
Correct answer: b) Electromagnetic induction
Explanation:
AC generators operate based on Faraday’s law of electromagnetic induction.
MCQ No. 16
In electromagnetic induction, mechanical energy converts into:
a) Heat energy
b) Electrical energy
c) Chemical energy
d) Light energy
Correct answer: b) Electrical energy
Explanation:
In generators, mechanical work is converted into electrical energy.
MCQ No. 17
Magnetic flux becomes maximum when θ equals:
a) 0°
b) 45°
c) 90°
d) 180°
Correct answer: a) 0°
Explanation:
Flux Φ = BA cosθ is maximum when cosθ = 1 (θ = 0°).
MCQ No. 18
Magnetic flux becomes zero when θ equals:
a) 0°
b) 30°
c) 60°
d) 90°
Correct answer: d) 90°
Explanation:
At 90°, cosθ = 0, so flux is zero.
MCQ No. 19
The induced emf is zero when conductor moves:
a) Perpendicular to B
b) Parallel to B
c) At angle 45°
d) Circularly
Correct answer: b) Parallel to B
Explanation:
When conductor moves parallel to field lines, no flux is cut.
MCQ No. 20
The direction of induced current can be found using:
a) Fleming’s Right Hand Rule
b) Fleming’s Left Hand Rule
c) Ohm’s Law
d) Kirchhoff’s Law
Correct answer: a) Fleming’s Right Hand Rule
Explanation:
Fleming’s right-hand rule determines direction of induced current.
MCQ No. 21
If number of turns increases, induced emf:
a) Decreases
b) Increases
c) Remains same
d) Becomes zero
Correct answer: b) Increases
Explanation:
Induced emf is directly proportional to number of turns N.
MCQ No. 22
Self inductance depends on:
a) Shape and size of coil
b) Current only
c) Voltage only
d) Resistance only
Correct answer: a) Shape and size of coil
Explanation:
Inductance depends on number of turns, area, length, and core material.
MCQ No. 23
Unit of mutual inductance is:
a) Weber
b) Tesla
c) Henry
d) Joule
Correct answer: c) Henry
Explanation:
Mutual inductance is also measured in Henry.
MCQ No. 24
Lenz’s law is based on conservation of:
a) Charge
b) Mass
c) Energy
d) Momentum
Correct answer: c) Energy
Explanation:
It ensures energy conservation by opposing the cause producing emf.
MCQ No. 25
If current in a coil is constant, induced emf is:
a) Maximum
b) Zero
c) Infinite
d) Variable
Correct answer: b) Zero
Explanation:
Induced emf appears only when current (and hence flux) changes.
Electromagnetic Induction MCQs (Set-2: Intermediate Level, Q26–50)
MCQ No. 26
A magnetic flux of 0.02 Wb changes to 0.01 Wb in 0.1 s in a single loop. The induced emf is:
a) 0.1 V
b) 0.2 V
c) 1 V
d) 2 V
Correct answer: a) 0.1 V
Explanation:
ε = ΔΦ/Δt = (0.02 − 0.01)/0.1 = 0.01/0.1 = 0.1 V.
MCQ No. 27
A coil of 200 turns experiences a change in flux of 5 × 10⁻³ Wb in 0.02 s. Induced emf is:
a) 5 V
b) 10 V
c) 20 V
d) 50 V
Correct answer: d) 50 V
Explanation:
ε = N(ΔΦ/Δt) = 200 × (5×10⁻³ / 0.02)
= 200 × 0.25 = 50 V.
MCQ No. 28
If magnetic field doubles while area remains constant, flux becomes:
a) Half
b) Double
c) Same
d) Zero
Correct answer: b) Double
Explanation:
Φ = BA cosθ. If B doubles, flux doubles.
MCQ No. 29
A conductor of length 0.5 m moves with 4 m/s perpendicular to 0.2 T field. Motional emf is:
a) 0.2 V
b) 0.4 V
c) 0.8 V
d) 1.6 V
Correct answer: b) 0.4 V
Explanation:
ε = Blv = 0.2 × 0.5 × 4 = 0.4 V.
MCQ No. 30
If a conductor moves at an angle θ to magnetic field, motional emf becomes:
a) Blv cosθ
b) Blv sinθ
c) Bv/l
d) B/lv
Correct answer: b) Blv sinθ
Explanation:
Only perpendicular component contributes; hence ε = Blv sinθ.
MCQ No. 31
Self-induced emf is directly proportional to:
a) Current
b) Voltage
c) Rate of change of current
d) Resistance
Correct answer: c) Rate of change of current
Explanation:
ε = −L (dI/dt). It depends on rate of change of current.
MCQ No. 32
If current increases uniformly in a coil, induced emf will be:
a) Zero
b) Constant
c) Increasing
d) Decreasing
Correct answer: b) Constant
Explanation:
Uniform increase means constant dI/dt; hence induced emf is constant.
MCQ No. 33
A 2 H inductor carries 3 A current. Energy stored is:
a) 3 J
b) 6 J
c) 9 J
d) 18 J
Correct answer: c) 9 J
Explanation:
U = ½ LI² = ½ × 2 × 3² = 9 J.
MCQ No. 34
If number of turns in a coil is doubled, its inductance becomes:
a) Same
b) Double
c) Four times
d) Half
Correct answer: c) Four times
Explanation:
Inductance L ∝ N². Doubling turns makes inductance four times.
MCQ No. 35
In an AC generator, slip rings are used to:
a) Reverse current
b) Increase emf
c) Maintain continuous rotation
d) Reduce resistance
Correct answer: c) Maintain continuous rotation
Explanation:
Slip rings allow continuous connection of rotating coil with external circuit.
MCQ No. 36
The frequency of AC generator depends upon:
a) Magnetic field strength
b) Number of turns
c) Speed of rotation
d) Area of coil
Correct answer: c) Speed of rotation
Explanation:
Frequency f = (rotations per second). It depends on angular speed.
MCQ No. 37
If rate of change of flux is zero, induced current is:
a) Maximum
b) Minimum
c) Zero
d) Alternating
Correct answer: c) Zero
Explanation:
No change in flux means no induced emf or current.
MCQ No. 38
Back emf in a coil opposes:
a) Voltage
b) Resistance
c) Applied current
d) Magnetic field
Correct answer: c) Applied current
Explanation:
Self-induced emf opposes change in current.
MCQ No. 39
The dimension of inductance is:
a) ML²T⁻²A⁻²
b) ML²T⁻¹A⁻¹
c) MLT⁻²A⁻¹
d) ML²T⁻²
Correct answer: a) ML²T⁻²A⁻²
Explanation:
From L = Wb/A and dimensional analysis.
MCQ No. 40
When magnet approaches a coil, induced current direction is determined by:
a) Ohm’s law
b) Fleming’s left hand rule
c) Lenz’s law
d) Kirchhoff’s law
Correct answer: c) Lenz’s law
Explanation:
Lenz’s law gives direction based on opposition to flux change.
MCQ No. 41
If flux changes sinusoidally, induced emf will be:
a) Constant
b) Zero
c) Sinusoidal
d) Linear
Correct answer: c) Sinusoidal
Explanation:
Derivative of sinusoidal function is also sinusoidal.
MCQ No. 42
Induced emf in a rotating coil is maximum when:
a) Plane of coil parallel to B
b) Plane of coil perpendicular to B
c) Coil stationary
d) Current zero
Correct answer: a) Plane of coil parallel to B
Explanation:
Rate of change of flux is maximum when coil plane is parallel to field.
MCQ No. 43
If speed of rotating coil doubles, maximum emf becomes:
a) Same
b) Half
c) Double
d) Four times
Correct answer: c) Double
Explanation:
E₀ = NABω. If ω doubles, emf doubles.
MCQ No. 44
Magnetic flux density is measured in:
a) Weber
b) Tesla
c) Henry
d) Joule
Correct answer: b) Tesla
Explanation:
Tesla is unit of magnetic flux density B.
MCQ No. 45
If resistance in induced circuit increases, induced current:
a) Increases
b) Decreases
c) Remains same
d) Becomes zero
Correct answer: b) Decreases
Explanation:
From Ohm’s law, I = ε/R. Increasing R reduces current.
MCQ No. 46
Self inductance of a long solenoid increases if:
a) Length increases
b) Area decreases
c) Turns increase
d) Core removed
Correct answer: c) Turns increase
Explanation:
L ∝ N². Increasing turns increases inductance.
MCQ No. 47
Induced emf is maximum when rate of change of flux is:
a) Zero
b) Minimum
c) Maximum
d) Constant
Correct answer: c) Maximum
Explanation:
Greater rate of change produces greater emf.
MCQ No. 48
Mutual inductance depends upon:
a) Distance between coils
b) Number of turns
c) Core material
d) All of these
Correct answer: d) All of these
Explanation:
Mutual inductance depends on geometry, turns, and magnetic permeability.
MCQ No. 49
In electromagnetic induction, energy conversion obeys law of:
a) Conservation of mass
b) Conservation of charge
c) Conservation of energy
d) Conservation of momentum
Correct answer: c) Conservation of energy
Explanation:
Lenz’s law ensures energy conservation.
MCQ No. 50
When a magnet is held stationary inside a coil, induced emf is:
a) Maximum
b) Minimum
c) Zero
d) Alternating
Correct answer: c) Zero
Explanation:
Stationary magnet causes no change in flux; hence no induced emf.
Electromagnetic Induction MCQs (Set-3: Advanced Level, Q51–75)
MCQ No. 51
A coil of 500 turns has area 0.01 m². It is placed perpendicular to a 0.2 T field. If the field becomes zero in 0.05 s, induced emf is:
a) 10 V
b) 20 V
c) 40 V
d) 50 V
Correct answer: b) 20 V
Explanation:
Initial flux = BA = 0.2 × 0.01 = 0.002 Wb
ε = N(ΔΦ/Δt) = 500 × (0.002/0.05) = 500 × 0.04 = 20 V.
MCQ No. 52
A 4 H inductor carries current increasing at 5 A/s. Induced emf is:
a) 5 V
b) 10 V
c) 15 V
d) 20 V
Correct answer: d) 20 V
Explanation:
ε = L (dI/dt) = 4 × 5 = 20 V.
MCQ No. 53
If magnetic flux linked with a coil changes from +0.01 Wb to −0.01 Wb in 0.02 s, induced emf is:
a) 0.5 V
b) 1 V
c) 2 V
d) 5 V
Correct answer: b) 1 V
Explanation:
Change in flux = 0.02 Wb
ε = 0.02 / 0.02 = 1 V (for single turn).
MCQ No. 54
A rod moves perpendicular to field. If velocity becomes three times, induced emf becomes:
a) Same
b) Double
c) Triple
d) Nine times
Correct answer: c) Triple
Explanation:
ε = Blv. It is directly proportional to velocity.
MCQ No. 55
Inductance of a solenoid does NOT depend upon:
a) Number of turns
b) Core material
c) Length of solenoid
d) Current flowing
Correct answer: d) Current flowing
Explanation:
Inductance depends on geometry and permeability, not on current.
MCQ No. 56
If resistance of induced circuit is zero, induced current will be:
a) Infinite (theoretically)
b) Zero
c) Constant
d) Minimum
Correct answer: a) Infinite (theoretically)
Explanation:
From I = ε/R, if R = 0, current tends to infinity theoretically.
MCQ No. 57
A coil rotates with angular velocity ω. Maximum emf is proportional to:
a) ω²
b) ω
c) 1/ω
d) Constant
Correct answer: b) ω
Explanation:
E₀ = NABω. Maximum emf is directly proportional to angular velocity.
MCQ No. 58
If number of turns is halved, maximum induced emf becomes:
a) Same
b) Double
c) Half
d) One-fourth
Correct answer: c) Half
Explanation:
E₀ ∝ N. Reducing N by half reduces emf by half.
MCQ No. 59
Time constant of RL circuit is:
a) L/R
b) R/L
c) RC
d) 1/RC
Correct answer: a) L/R
Explanation:
Time constant τ for RL circuit equals L/R.
MCQ No. 60
Energy stored in 3 H inductor carrying 4 A is:
a) 12 J
b) 18 J
c) 24 J
d) 36 J
Correct answer: c) 24 J
Explanation:
U = ½ LI² = ½ × 3 × 16 = 24 J.
MCQ No. 61
A coil of N turns produces emf ε. If rate of change of flux doubles, emf becomes:
a) Same
b) Half
c) Double
d) Four times
Correct answer: c) Double
Explanation:
ε ∝ dΦ/dt. Doubling rate doubles emf.
MCQ No. 62
If magnetic field increases uniformly, induced emf in closed loop will be:
a) Increasing
b) Constant
c) Zero
d) Decreasing
Correct answer: b) Constant
Explanation:
Uniform increase gives constant rate of change of flux.
MCQ No. 63
A rectangular coil moves into uniform magnetic field region. Induced current is produced when:
a) Completely inside field
b) Completely outside field
c) Entering or leaving field
d) Stationary
Correct answer: c) Entering or leaving field
Explanation:
Flux changes only during entry or exit.
MCQ No. 64
If plane of coil is perpendicular to field and rotates, initial flux is:
a) Maximum
b) Zero
c) Half
d) Negative
Correct answer: a) Maximum
Explanation:
Flux is maximum when θ = 0° (area vector parallel to B).
MCQ No. 65
In AC generator, peak emf is given by:
a) NABω
b) NABA
c) NB/ω
d) Nω/B
Correct answer: a) NABω
Explanation:
Maximum emf formula: E₀ = NABω.
MCQ No. 66
Mutual inductance unit is derived from:
a) Wb/A
b) V/A
c) J/A
d) T/A
Correct answer: a) Wb/A
Explanation:
1 Henry = 1 Weber per ampere.
MCQ No. 67
If two coils are moved farther apart, mutual inductance:
a) Increases
b) Decreases
c) Remains same
d) Becomes zero instantly
Correct answer: b) Decreases
Explanation:
Greater distance reduces magnetic coupling.
MCQ No. 68
Back emf in motor is an application of:
a) Electrostatics
b) Lenz’s law
c) Ohm’s law
d) Kirchhoff’s law
Correct answer: b) Lenz’s law
Explanation:
Back emf opposes applied current as per Lenz’s law.
MCQ No. 69
A copper ring is placed near increasing magnetic field. It will:
a) Attract magnet
b) Repel magnet
c) Remain unaffected
d) Rotate
Correct answer: b) Repel magnet
Explanation:
Induced current creates opposing magnetic field.
MCQ No. 70
If current decreases rapidly, induced emf magnitude will be:
a) Small
b) Large
c) Zero
d) Constant
Correct answer: b) Large
Explanation:
Greater rate of change produces greater emf.
MCQ No. 71
Magnetic energy density in inductor is proportional to:
a) I
b) I²
c) 1/I
d) √I
Correct answer: b) I²
Explanation:
Energy stored is proportional to square of current.
MCQ No. 72
If frequency of AC generator doubles, peak emf becomes:
a) Same
b) Half
c) Double
d) Four times
Correct answer: c) Double
Explanation:
E₀ ∝ ω and ω = 2πf.
MCQ No. 73
Induced emf always acts to:
a) Increase flux
b) Decrease flux
c) Oppose change in flux
d) Stop current
Correct answer: c) Oppose change in flux
Explanation:
This is statement of Lenz’s law.
MCQ No. 74
In ideal inductor, phase difference between voltage and current is:
a) 0°
b) 45°
c) 90°
d) 180°
Correct answer: c) 90°
Explanation:
In pure inductor, current lags voltage by 90°.
MCQ No. 75
If magnetic field is reversed direction completely, flux change equals:
a) Φ
b) 2Φ
c) 0
d) Φ/2
Correct answer: b) 2Φ
Explanation:
Flux changes from +Φ to −Φ; total change = 2Φ.
Electromagnetic Induction MCQs (Set-4: Expert Level, Q76–100)
MCQ No. 76
A conducting loop falls freely under gravity in a uniform magnetic field. After some time, its acceleration becomes:
a) g
b) Zero
c) Less than g
d) Greater than g
Correct answer: c) Less than g
Explanation:
Induced current produces magnetic force opposite to motion (Lenz’s law), reducing acceleration below g.
MCQ No. 77
If magnetic flux through a closed surface changes, induced emf in the surface will be:
a) Always zero
b) Always non-zero
c) Depends on resistance
d) Infinite
Correct answer: a) Always zero
Explanation:
Net magnetic flux through a closed surface is always zero (Gauss’s law for magnetism).
MCQ No. 78
A coil is rotated in uniform magnetic field with constant angular velocity. Instantaneous emf is maximum when flux is:
a) Maximum
b) Zero
c) Minimum
d) Constant
Correct answer: b) Zero
Explanation:
Induced emf is proportional to rate of change of flux, which is maximum when flux is zero.
MCQ No. 79
A superconducting ring placed in changing magnetic field will:
a) Have no current
b) Have finite current
c) Have persistent induced current
d) Break instantly
Correct answer: c) Have persistent induced current
Explanation:
In superconductors (R = 0), induced current persists without decay.
MCQ No. 80
If inductance L is increased while keeping current constant, energy stored becomes:
a) Same
b) Less
c) More
d) Zero
Correct answer: c) More
Explanation:
U = ½ LI². Increasing L increases stored energy.
MCQ No. 81
A metal rod slides on conducting rails in magnetic field. If velocity is constant, net force on rod is:
a) Zero
b) Magnetic only
c) Electric only
d) Infinite
Correct answer: a) Zero
Explanation:
At constant velocity, magnetic force balances applied force.
MCQ No. 82
In an RL circuit connected to DC source, current rises:
a) Instantly
b) Gradually
c) Linearly
d) Sinusoidally
Correct answer: b) Gradually
Explanation:
Due to self-induction, current increases exponentially, not instantly.
MCQ No. 83
If magnetic field is non-uniform but constant in time, induced emf is:
a) Zero
b) Maximum
c) Variable
d) Infinite
Correct answer: a) Zero
Explanation:
Emf depends on change of flux with time, not spatial variation alone.
MCQ No. 84
A square loop rotates such that its plane remains parallel to magnetic field. Induced emf will be:
a) Maximum
b) Zero
c) Constant
d) Increasing
Correct answer: b) Zero
Explanation:
If plane stays parallel, flux does not change; hence no emf.
MCQ No. 85
When current in primary coil decreases, induced current in secondary coil will:
a) Oppose decrease
b) Support decrease
c) Be zero
d) Be constant
Correct answer: a) Oppose decrease
Explanation:
By Lenz’s law, secondary current opposes change in primary current.
MCQ No. 86
If frequency of AC source is very high, inductive reactance becomes:
a) Zero
b) Small
c) Large
d) Constant
Correct answer: c) Large
Explanation:
Inductive reactance XL = 2πfL increases with frequency.
MCQ No. 87
In ideal inductor connected to AC source, average power consumed is:
a) Maximum
b) Zero
c) Constant
d) Infinite
Correct answer: b) Zero
Explanation:
Voltage and current are 90° out of phase; average power is zero.
MCQ No. 88
If magnetic field reverses direction periodically, induced emf will be:
a) DC
b) Constant
c) AC
d) Zero
Correct answer: c) AC
Explanation:
Periodic reversal of flux produces alternating emf.
MCQ No. 89
A conducting ring is cut open and placed in changing magnetic field. Induced current will be:
a) Present
b) Zero
c) Infinite
d) Alternating
Correct answer: b) Zero
Explanation:
Without closed path, no current flows (though emf exists).
MCQ No. 90
The phenomenon of eddy currents is based on:
a) Ohm’s law
b) Electrostatics
c) Electromagnetic induction
d) Capacitance
Correct answer: c) Electromagnetic induction
Explanation:
Changing magnetic flux induces circulating currents in conductors.
MCQ No. 91
If area of coil shrinks uniformly in constant magnetic field, induced current will:
a) Be zero
b) Oppose shrinking
c) Support shrinking
d) Be constant
Correct answer: b) Oppose shrinking
Explanation:
Reduction in flux induces current to oppose decrease.
MCQ No. 92
In a transformer, energy transfer from primary to secondary is due to:
a) Conduction
b) Radiation
c) Mutual induction
d) Resistance
Correct answer: c) Mutual induction
Explanation:
Transformers operate on principle of mutual induction.
MCQ No. 93
If resistance of RL circuit increases, time constant becomes:
a) Larger
b) Smaller
c) Same
d) Zero
Correct answer: b) Smaller
Explanation:
τ = L/R. Increasing R decreases time constant.
MCQ No. 94
Induced emf in a loop is independent of:
a) Rate of change of flux
b) Number of turns
c) Resistance
d) Magnetic field
Correct answer: c) Resistance
Explanation:
Emf depends on flux change; resistance affects current only.
MCQ No. 95
A coil placed in steady magnetic field is suddenly removed. Induced emf will:
a) Be zero
b) Appear momentarily
c) Be constant
d) Increase gradually
Correct answer: b) Appear momentarily
Explanation:
Sudden removal changes flux rapidly, inducing momentary emf.
MCQ No. 96
When switch in RL circuit is opened, spark occurs due to:
a) High resistance
b) High induced emf
c) Low current
d) Capacitance
Correct answer: b) High induced emf
Explanation:
Sudden drop in current produces large back emf.
MCQ No. 97
Magnetic braking in trains works due to:
a) Capacitance
b) Eddy currents
c) Resistance
d) Voltage
Correct answer: b) Eddy currents
Explanation:
Induced eddy currents produce opposing magnetic force.
MCQ No. 98
If permeability of core increases, inductance becomes:
a) Smaller
b) Larger
c) Zero
d) Constant
Correct answer: b) Larger
Explanation:
L ∝ μ. Increasing permeability increases inductance.
MCQ No. 99
For a coil rotating in magnetic field, instantaneous emf is zero when:
a) ω = 0
b) Flux is maximum
c) Flux is zero
d) Speed is high
Correct answer: b) Flux is maximum
Explanation:
At maximum flux, rate of change of flux is zero; hence emf is zero.
MCQ No. 100
Lenz’s law is a direct consequence of:
a) Newton’s law
b) Coulomb’s law
c) Conservation of energy
d) Ohm’s law
Correct answer: c) Conservation of energy
Explanation:
Opposition to change ensures no energy is created from nothing.
