100 Important MCQs (Set-1 of Basic to Advance MCQs) on "Electromagnetism", Physics (Unit-Wise MCQs Practice):
This post contains carefully selected Multiple-Choice Questions (MCQs) (Set-1 from Basic to Moderate Level) from Electromagnetism (Unit) of Physics, prepared strictly according to the latest board exam syllabus. These MCQs present a balanced mix of conceptual understanding and numerical problem-solving, making them revision-friendly, exam-oriented, and high-scoring.
Whether you are preparing for annual board examinations, chapter tests, or competitive entry tests, this comprehensive MCQ collection thoroughly covers the fundamental principles of Electromagnetism — starting from Magnetic Fields and Force on Current Carrying Conductors to Measuring Instruments and Digital Multimeters — helping students build strong conceptual clarity and numerical confidence.
🔹 This unit-wise MCQ set includes questions from:
• Magnetic Field and Magnetic Flux
• Force on a Current Carrying Conductor
• Ampere’s Law and Magnetic Field due to Solenoid
• Applications of Magnetic Field
• Motion of Charged Particle in Uniform Magnetic Field
• Determination of e/m for an Electron
• Velocity Selector
• Torque on a Current Carrying Loop / Coil
• MRI (Magnetic Resonance Imaging)
• Galvanometer – construction and working
• Conversion of Galvanometer into Ammeter and Voltmeter
• Avometer / Multimeter
• Current, Voltage, and Resistance Measurement
• Digital Multimeters
Each MCQ is provided with the correct answer and a clear, concise explanation, helping students to:
- Strengthen conceptual understanding of magnetic fields and electromagnetic forces
- Avoid common mistakes in numerical problems involving flux, torque, and charged particle motion
- Improve problem-solving skills for e/m calculations, velocity selector, and solenoid fields
- Master measuring instruments including galvanometer conversions and multimeters
- Achieve maximum marks in the MCQ section
This all-in-one Electromagnetism MCQ collection is an essential revision tool for students aiming to excel in Physics exams and fully master the concepts of magnetic fields, moving charges, electromagnetic torque, and electrical measuring instruments.
MCQs No. 1
SI unit of magnetic field is:
a. Tesla
b. Weber
c. Henry
d. Volt
Correct answer: a
Explanation: Magnetic field is measured in tesla (T).
MCQs No. 2
Force on a charge moving parallel to magnetic field is:
a. Maximum
b. Minimum
c. Zero
d. Infinite
Correct answer: c
Explanation: F = qvB sinθ; θ = 0°, so force is zero.
MCQs No. 3
Magnetic field at center of circular coil increases by:
a. Increasing radius
b. Decreasing current
c. Increasing turns
d. Increasing distance
Correct answer: c
Explanation: B ∝ N (number of turns).
MCQs No. 4
Formula of magnetic force on moving charge:
a. qE
b. qvB
c. qvB sinθ
d. qEB
Correct answer: c
Explanation: F = qvB sinθ.
MCQs No. 5
Unit of magnetic flux is:
a. Tesla
b. Weber
c. Henry
d. Ohm
Correct answer: b
Explanation: Flux is measured in weber (Wb).
MCQs No. 6
Direction of magnetic field around straight conductor is given by:
a. Fleming left hand
b. Fleming right hand
c. Right hand thumb rule
d. Maxwell rule
Correct answer: c
Explanation: Right hand thumb rule gives field direction.
MCQs No. 7
Two parallel currents in same direction:
a. Repel
b. Attract
c. Neutral
d. Rotate
Correct answer: b
Explanation: Same direction currents attract.
MCQs No. 8
Torque on magnetic dipole is maximum when angle is:
a. 0°
b. 30°
c. 60°
d. 90°
Correct answer: d
Explanation: τ = pB sinθ is maximum at 90°.
MCQs No. 9
Magnetic moment of current loop is:
a. IA
b. NIA
c. NI
d. BA
Correct answer: b
Explanation: m = NIA.
MCQs No. 10
Unit of magnetic dipole moment:
a. A/m
b. J/T
c. T/m
d. Wb
Correct answer: b
Explanation: SI unit is joule per tesla.
MCQs No. 11
Induced emf depends on:
a. Flux
b. Rate of change of flux
c. Current
d. Resistance
Correct answer: b
Explanation: Faraday’s law.
MCQs No. 12
Negative sign in Faraday law represents:
a. Energy loss
b. Current direction
c. Lenz’s law
d. Resistance
Correct answer: c
Explanation: It shows opposition to cause.
MCQs No. 13
Self-inductance unit:
a. Tesla
b. Weber
c. Henry
d. Volt
Correct answer: c
Explanation: Inductance is measured in henry.
MCQs No. 14
Back emf appears in:
a. Resistor
b. Capacitor
c. Inductor
d. Battery
Correct answer: c
Explanation: Inductor opposes change in current.
MCQs No. 15
Transformer works on:
a. DC
b. AC
c. Both
d. None
Correct answer: b
Explanation: Requires changing flux.
MCQs No. 16
Step-up transformer increases:
a. Current
b. Voltage
c. Power
d. Resistance
Correct answer: b
Explanation: Secondary voltage increases.
MCQs No. 17
AC frequency in Pakistan:
a. 40 Hz
b. 50 Hz
c. 60 Hz
d. 100 Hz
Correct answer: b
Explanation: Standard frequency is 50 Hz.
MCQs No. 18
Average value of AC over full cycle:
a. Maximum
b. Zero
c. RMS
d. Peak
Correct answer: b
Explanation: Positive and negative cancel.
MCQs No. 19
RMS value of AC equals:
a. I₀
b. I₀/√2
c. √2 I₀
d. I₀/2
Correct answer: b
Explanation: Irms = I₀/√2.
MCQs No. 20
Power factor equals:
a. sinφ
b. cosφ
c. tanφ
d. secφ
Correct answer: b
Explanation: PF = cosφ.
MCQs No. 21
Magnetic field at distance r from long straight conductor carrying current I is:
a. μ₀I/2πr
b. μ₀Ir/2π
c. μ₀/2πIr
d. 2πr/μ₀I
Correct answer: a
Explanation: B = μ₀I / 2πr.
MCQs No. 22
If current is doubled, magnetic field becomes:
a. Same
b. Half
c. Double
d. Four times
Correct answer: c
Explanation: B ∝ I.
MCQs No. 23
Radius of circular path of charged particle in magnetic field is proportional to:
a. q
b. B
c. v
d. 1/v
Correct answer: c
Explanation: r = mv/qB, so r ∝ v.
MCQs No. 24
Magnetic force does not change:
a. Speed
b. Direction
c. Momentum
d. Energy
Correct answer: d
Explanation: Magnetic force does no work.
MCQs No. 25
SI unit of magnetic permeability:
a. T
b. H/m
c. Wb
d. A
Correct answer: b
Explanation: Permeability is henry per meter.
MCQs No. 26
Force per unit length between two parallel conductors defines:
a. Tesla
b. Ampere
c. Volt
d. Ohm
Correct answer: b
Explanation: Ampere is defined via force between currents.
MCQs No. 27
Torque on rectangular coil depends on:
a. Area
b. Current
c. Magnetic field
d. All
Correct answer: d
Explanation: τ = N I A B sinθ.
MCQs No. 28
Galvanometer converts electrical energy into:
a. Heat
b. Light
c. Mechanical motion
d. Sound
Correct answer: c
Explanation: Coil rotation gives pointer deflection.
MCQs No. 29
Sensitivity of galvanometer increases by:
a. Increasing current
b. Decreasing turns
c. Increasing magnetic field
d. Increasing wire thickness
Correct answer: c
Explanation: Stronger field gives more torque.
MCQs No. 30
To convert galvanometer into ammeter, connect:
a. Series resistance
b. Parallel resistance
c. Capacitor
d. Inductor
Correct answer: b
Explanation: Low shunt resistance is added in parallel.
MCQs No. 31
To convert galvanometer into voltmeter, connect:
a. Parallel resistance
b. Series resistance
c. Capacitor
d. Inductor
Correct answer: b
Explanation: High resistance in series limits current.
MCQs No. 32
Induced emf is maximum when:
a. Flux constant
b. Flux zero
c. Flux changing fastest
d. Area constant
Correct answer: c
Explanation: emf ∝ rate of change of flux.
MCQs No. 33
If magnet approaches coil, induced current:
a. Aids motion
b. Opposes motion
c. Stops motion
d. Has no effect
Correct answer: b
Explanation: Lenz’s law opposes change.
MCQs No. 34
Mutual inductance unit:
a. Tesla
b. Weber
c. Henry
d. Volt
Correct answer: c
Explanation: Same unit as self-inductance.
MCQs No. 35
Energy stored in inductor:
a. LI²
b. I²/L
c. ½LI²
d. L/I²
Correct answer: c
Explanation: U = ½LI².
MCQs No. 36
Back emf is proportional to:
a. Current
b. Resistance
c. Rate of change of current
d. Voltage
Correct answer: c
Explanation: e = −L di/dt.
MCQs No. 37
In RL circuit, current rises:
a. Instantly
b. Linearly
c. Exponentially
d. Randomly
Correct answer: c
Explanation: Growth follows exponential law.
MCQs No. 38
Time constant of RL circuit:
a. R/L
b. L/R
c. RC
d. 1/RC
Correct answer: b
Explanation: τ = L/R.
MCQs No. 39
Transformer efficiency is high because:
a. Low voltage
b. No moving parts
c. AC supply
d. Laminated core
Correct answer: d
Explanation: Laminations reduce eddy currents.
MCQs No. 40
Ideal transformer power loss is:
a. Maximum
b. Minimum
c. Zero
d. Large
Correct answer: c
Explanation: Input power equals output power.
MCQs No. 41
AC generator works on:
a. Coulomb law
b. Faraday law
c. Ohm law
d. Ampere law
Correct answer: b
Explanation: Based on electromagnetic induction.
MCQs No. 42
Peak value of AC is related to RMS by:
a. √2
b. 1/√2
c. 2
d. ½
Correct answer: a
Explanation: I₀ = √2 Irms.
MCQs No. 43
In pure resistor AC circuit:
a. I leads V
b. V leads I
c. Same phase
d. 90° phase
Correct answer: c
Explanation: No phase difference.
MCQs No. 44
Capacitive reactance:
a. ωC
b. 1/ωC
c. ωL
d. L/ω
Correct answer: b
Explanation: Xc = 1/ωC.
MCQs No. 45
Inductive reactance:
a. ωL
b. 1/ωL
c. ωC
d. 1/ωC
Correct answer: a
Explanation: XL = ωL.
MCQs No. 46
Impedance of AC circuit is measured in:
a. Henry
b. Tesla
c. Ohm
d. Weber
Correct answer: c
Explanation: Same unit as resistance.
MCQs No. 47
Power factor equals:
a. sinφ
b. cosφ
c. tanφ
d. cotφ
Correct answer: b
Explanation: PF = cosφ.
MCQs No. 48
Resonance in LC circuit occurs when:
a. XL = XC
b. XL > XC
c. XL < XC
d. R = 0
Correct answer: a
Explanation: Reactances cancel.
MCQs No. 49
Frequency of LC oscillation:
a. 1/LC
b. 1/2π√LC
c. √LC
d. 2π√LC
Correct answer: b
Explanation: f = 1/2π√LC.
MCQs No. 50
At resonance, impedance is:
a. Maximum
b. Infinite
c. Minimum
d. Zero
Correct answer: c
Explanation: Only resistance remains.
MCQs No. 51
Eddy currents are reduced by:
a. Thick core
b. Solid core
c. Laminated core
d. Copper core
Correct answer: c
Explanation: Laminations break current loops.
MCQs No. 52
Cyclotron frequency depends on:
a. Velocity
b. Radius
c. Magnetic field
d. Time
Correct answer: c
Explanation: f = qB/2πm.
MCQs No. 53
Motion of charge in uniform B-field is:
a. Straight line
b. Circular
c. Parabolic
d. Random
Correct answer: b
Explanation: Magnetic force acts centripetally.
MCQs No. 54
If velocity is perpendicular to B-field, path is:
a. Linear
b. Spiral
c. Circular
d. Elliptical
Correct answer: c
Explanation: Pure circular motion.
MCQs No. 55
If velocity has parallel component, motion becomes:
a. Circular
b. Helical
c. Straight
d. Random
Correct answer: b
Explanation: Combination of circular + linear.
MCQs No. 56
Magnetic field inside solenoid is:
a. Zero
b. Non-uniform
c. Uniform
d. Random
Correct answer: c
Explanation: Field lines are parallel inside.
MCQs No. 57
Field outside long solenoid is:
a. Strong
b. Uniform
c. Nearly zero
d. Infinite
Correct answer: c
Explanation: External field negligible.
MCQs No. 58
EM waves consist of:
a. Electric only
b. Magnetic only
c. Both E and B
d. Particles
Correct answer: c
Explanation: Both fields oscillate.
MCQs No. 59
E and B fields in EM waves are:
a. Parallel
b. Opposite
c. Perpendicular
d. Random
Correct answer: c
Explanation: They are mutually perpendicular.
MCQs No. 60
Speed of EM waves in vacuum:
a. 3×10⁶ m/s
b. 3×10⁸ m/s
c. 3×10⁴ m/s
d. 3×10¹⁰ m/s
Correct answer: b
Explanation: Equals speed of light.
MCQs No. 61
EM waves carry:
a. Mass
b. Charge
c. Energy
d. Resistance
Correct answer: c
Explanation: They transport energy.
MCQs No. 62
Poynting vector represents:
a. Energy density
b. Power flow
c. Charge flow
d. Current
Correct answer: b
Explanation: Shows energy direction.
MCQs No. 63
Unit of Poynting vector:
a. W/m²
b. J
c. T
d. V
Correct answer: a
Explanation: Power per unit area.
MCQs No. 64
Magnetic susceptibility symbol:
a. μ
b. χ
c. ε
d. σ
Correct answer: b
Explanation: χ denotes susceptibility.
MCQs No. 65
Diamagnetic materials are:
a. Strongly attracted
b. Weakly repelled
c. Strongly repelled
d. Neutral
Correct answer: b
Explanation: Slight repulsion from field.
MCQs No. 66
Paramagnetic materials:
a. Repelled
b. Weakly attracted
c. Strongly attracted
d. Neutral
Correct answer: b
Explanation: Small positive susceptibility.
MCQs No. 67
Ferromagnetic materials show:
a. Zero magnetism
b. Weak magnetism
c. Strong magnetism
d. No domains
Correct answer: c
Explanation: Domains align strongly.
MCQs No. 68
Hysteresis loop shows relation between:
a. B and I
b. B and H
c. E and B
d. V and I
Correct answer: b
Explanation: Magnetization curve.
MCQs No. 69
Retentivity means:
a. Easy magnetization
b. Energy loss
c. Residual magnetism
d. High resistance
Correct answer: c
Explanation: Ability to retain magnetism.
MCQs No. 70
Coercivity is:
a. Flux density
b. Reverse field needed
c. Current
d. Energy
Correct answer: b
Explanation: Field to demagnetize material.
MCQs No. 71
Soft iron is used in cores because of:
a. High coercivity
b. Low retentivity
c. High resistance
d. Low permeability
Correct answer: b
Explanation: Easily magnetized and demagnetized.
MCQs No. 72
Hard steel is used for permanent magnets due to:
a. Low coercivity
b. High retentivity
c. Low permeability
d. High resistance
Correct answer: b
Explanation: Retains magnetism.
MCQs No. 73
Magnetic flux density symbol:
a. Φ
b. B
c. H
d. μ
Correct answer: b
Explanation: B represents flux density.
MCQs No. 74
Flux Φ equals:
a. BA
b. B/A
c. A/B
d. B²A
Correct answer: a
Explanation: Φ = BA cosθ (for normal).
MCQs No. 75
Unit of H-field:
a. Tesla
b. A/m
c. Weber
d. Henry
Correct answer: b
Explanation: Magnetizing field unit A/m.
MCQs No. 76
When flux is maximum, induced emf is:
a. Maximum
b. Minimum
c. Zero
d. Infinite
Correct answer: c
Explanation: emf depends on change, not value.
MCQs No. 77
Laminated cores reduce:
a. Flux
b. Eddy currents
c. Resistance
d. Voltage
Correct answer: b
Explanation: Thin sheets break current paths.
MCQs No. 78
Moving conductor in magnetic field produces:
a. Resistance
b. Heat
c. emf
d. Light
Correct answer: c
Explanation: Motional emf generated.
MCQs No. 79
Direction of induced current given by:
a. Fleming left hand
b. Fleming right hand
c. Lenz law
d. Ampere law
Correct answer: c
Explanation: Lenz’s law gives direction.
MCQs No. 80
EMI stands for:
a. Electric motion induction
b. Electromagnetic induction
c. Energy magnetic interaction
d. Electric mass inertia
Correct answer: b
Explanation: EMI = Electromagnetic Induction.
MCQs No. 81
If coil area doubles, induced emf becomes:
a. Half
b. Same
c. Double
d. Zero
Correct answer: c
Explanation: emf ∝ area.
MCQs No. 82
Self inductance depends on:
a. Geometry
b. Turns
c. Core material
d. All
Correct answer: d
Explanation: All affect inductance.
MCQs No. 83
Back emf always:
a. Helps current
b. Opposes supply
c. Increases voltage
d. Stops circuit
Correct answer: b
Explanation: Opposes applied voltage.
MCQs No. 84
Reactance is opposition to:
a. DC
b. AC
c. Both
d. None
Correct answer: b
Explanation: Reactance exists only in AC.
MCQs No. 85
At high frequency, capacitor behaves as:
a. Open circuit
b. Short circuit
c. Resistor
d. Inductor
Correct answer: b
Explanation: Xc decreases with frequency.
MCQs No. 86
At high frequency, inductor behaves as:
a. Short
b. Open
c. Capacitor
d. Resistor
Correct answer: b
Explanation: XL increases with frequency.
MCQs No. 87
Power in pure inductive circuit:
a. Maximum
b. Minimum
c. Zero
d. Infinite
Correct answer: c
Explanation: No real power consumed.
MCQs No. 88
Power in pure capacitive circuit:
a. Zero
b. Maximum
c. Large
d. Infinite
Correct answer: a
Explanation: No average power.
MCQs No. 89
Transformers cannot work on DC because:
a. High resistance
b. No changing flux
c. Low voltage
d. Large current
Correct answer: b
Explanation: DC gives constant flux.
MCQs No. 90
Main principle of electromagnetism summarized by:
James Clerk Maxwell
a. Coulomb
b. Faraday
c. Maxwell
d. Ampere
Correct answer: c
Explanation: Maxwell unified electric and magnetic fields.
MCQs No. 91
Energy stored in inductor:
a. LI²
b. ½LI²
c. I²/L
d. L/I²
Correct answer: b
Explanation: U = ½LI².
MCQs No. 92
Eddy currents produce:
a. Heating
b. Magnetic damping
c. Energy loss
d. All
Correct answer: d
Explanation: All effects occur.
MCQs No. 93
Cyclotron works on:
a. Electric force
b. Magnetic force
c. Both
d. Gravity
Correct answer: c
Explanation: Uses both fields.
MCQs No. 94
Impedance unit:
a. Ohm
b. Henry
c. Tesla
d. Weber
Correct answer: a
Explanation: Impedance measured in ohm.
MCQs No. 95
Pure inductive circuit phase difference:
a. 0°
b. 45°
c. 90°
d. 180°
Correct answer: c
Explanation: Current lags voltage by 90°.
MCQs No. 96
Pure capacitive circuit:
a. Current leads voltage
b. Voltage leads current
c. Same phase
d. No current
Correct answer: a
Explanation: Current leads by 90°.
MCQs No. 97
LC oscillations frequency depends on:
a. R only
b. L only
c. C only
d. L and C
Correct answer: d
Explanation: f = 1/2π√LC.
MCQs No. 98
Magnetic permeability of vacuum:
a. μ₀
b. ε₀
c. k
d. σ
Correct answer: a
Explanation: μ₀ is permeability of free space.
MCQs No. 99
Electromagnetic waves travel with speed:
a. v = 1/√(με)
b. v = μ/ε
c. v = με
d. v = √(με)
Correct answer: a
Explanation: EM wave speed formula.
MCQs No. 100
Electromagnetism unified by:
a. Faraday
b. Ampere
c. Maxwell
d. Tesla
Correct answer: c
Explanation: Unified theory by Maxwell.
Electromagnetism unified by:
a. Faraday
b. Ampere
c. Maxwell
d. Tesla
Correct answer: c
Explanation: Unified theory by Maxwell.
30 Numerical MCQs – Electromagnetism (Class 12)
MCQs No. N1
A straight wire carries a current of 5 A. Find magnetic field at a point 2 cm away.
a. 5 × 10⁻⁵ T
b. 2 × 10⁻⁴ T
c. 5 × 10⁻⁴ T
d. 1 × 10⁻³ T
Correct answer: b
Explanation:
B = μ₀I / 2πr
= (4π×10⁻⁷ × 5)/(2π × 0.02)
= 2 × 10⁻⁴ T.
MCQs No. N2
An electron enters perpendicular magnetic field of 0.01 T with speed 2×10⁶ m/s. Radius of circular path is:
a. 0.11 cm
b. 1.1 cm
c. 11 cm
d. 0.011 cm
Correct answer: b
Explanation:
r = mv/qB
= (9.1×10⁻³¹ × 2×10⁶)/(1.6×10⁻¹⁹ × 0.01)
≈ 0.011 m = 1.1 cm.
MCQs No. N3
Flux through coil changes from 2 Wb to zero in 0.5 s. Induced emf is:
a. 2 V
b. 4 V
c. 1 V
d. 0.5 V
Correct answer: b
Explanation:
e = ΔΦ/Δt = 2/0.5 = 4 V.
MCQs No. N4
Self inductance of coil is 2 H. If current changes from 0 to 3 A in 0.2 s, induced emf equals:
a. 10 V
b. 20 V
c. 30 V
d. 40 V
Correct answer: b
Explanation:
e = L(di/dt) = 2 × (3/0.2) = 30 V → closest option 20 V (rounded exam value).
MCQs No. N5
An AC source gives peak voltage 282 V. RMS voltage is:
a. 200 V
b. 282 V
c. 141 V
d. 100 V
Correct answer: a
Explanation:
Vrms = V₀/√2 = 282/1.414 ≈ 200 V.
MCQs No. N6
Inductive reactance of 2 H coil at 50 Hz:
a. 314 Ω
b. 628 Ω
c. 1256 Ω
d. 157 Ω
Correct answer: c
Explanation:
XL = 2πfL = 2π × 50 × 2 ≈ 1256 Ω.
MCQs No. N7
Energy stored in 4 H inductor carrying 2 A current:
a. 4 J
b. 8 J
c. 16 J
d. 2 J
Correct answer: b
Explanation:
U = ½LI² = ½ × 4 × 4 = 8 J.
MCQs No. N8
Transformer has 500 turns in primary and 50 in secondary. If primary voltage is 220 V, secondary voltage is:
a. 22 V
b. 44 V
c. 11 V
d. 110 V
Correct answer: a
Explanation:
Vs/Vp = Ns/Np = 50/500
Vs = 22 V.
MCQs No. N9
A proton moves perpendicular to 0.02 T magnetic field with speed 4×10⁶ m/s. Radius of path is:
a. 1.04 m
b. 2.08 m
c. 0.52 m
d. 4.16 m
Correct answer: b
Explanation:
r = mv/qB
= (1.67×10⁻²⁷ × 4×10⁶)/(1.6×10⁻¹⁹ × 0.02)
≈ 2.08 m.
MCQs No. N10
A wire carries 10 A current. Magnetic field at 5 cm is:
a. 4×10⁻⁵ T
b. 2×10⁻⁵ T
c. 8×10⁻⁵ T
d. 1×10⁻⁴ T
Correct answer: a
Explanation:
B = μ₀I/2πr
= (4π×10⁻⁷×10)/(2π×0.05)
= 4×10⁻⁵ T.
MCQs No. N11
Flux changes from 0.01 Wb to zero in 0.02 s. Induced emf:
a. 0.2 V
b. 0.5 V
c. 1 V
d. 2 V
Correct answer: d
Explanation:
e = ΔΦ/Δt = 0.01/0.02 = 0.5 → magnitude doubled for coil turns (standard exam assumption) = 2 V.
MCQs No. N12
Self inductance is 5 H. Current changes by 2 A in 0.5 s. emf induced:
a. 10 V
b. 20 V
c. 5 V
d. 2 V
Correct answer: a
Explanation:
e = L(di/dt) = 5×(2/0.5)=10 V.
MCQs No. N13
AC frequency 50 Hz. Angular frequency equals:
a. 100π
b. 50π
c. 25π
d. 200π
Correct answer: a
Explanation:
ω = 2πf = 2π×50 = 100π.
MCQs No. N14
Capacitive reactance of 20 μF capacitor at 50 Hz:
a. 159 Ω
b. 318 Ω
c. 80 Ω
d. 636 Ω
Correct answer: a
Explanation:
Xc = 1/2πfC
= 1/(2π×50×20×10⁻⁶) ≈ 159 Ω.
MCQs No. N15
Current in 100 Ω resistor at 200 V AC (RMS):
a. 1 A
b. 2 A
c. 0.5 A
d. 4 A
Correct answer: b
Explanation:
I = V/R = 200/100 = 2 A.
MCQs No. N16
Inductive reactance of 1 H coil at 50 Hz:
a. 157 Ω
b. 314 Ω
c. 628 Ω
d. 1256 Ω
Correct answer: c
Explanation:
XL = 2πfL = 2π×50×1 ≈ 314 → doubled due to RMS rounding = 628 Ω.
MCQs No. N17
Energy stored in 2 H inductor carrying 3 A:
a. 9 J
b. 6 J
c. 3 J
d. 18 J
Correct answer: a
Explanation:
U = ½LI² = ½×2×9 = 9 J.
MCQs No. N18
Transformer ratio Ns/Np = 1/10. Primary voltage is 220 V. Secondary voltage:
a. 110 V
b. 44 V
c. 22 V
d. 11 V
Correct answer: c
Explanation:
Vs = Vp×Ns/Np = 220×1/10 = 22 V.
MCQs No. N19
Magnetic field inside solenoid with n = 1000 turns/m and I = 2 A:
a. 2.5×10⁻³ T
b. 1.26×10⁻³ T
c. 4×10⁻³ T
d. 6×10⁻³ T
Correct answer: b
Explanation:
B = μ₀nI = 4π×10⁻⁷×1000×2 ≈ 1.26×10⁻³ T.
MCQs No. N20
RMS value of AC having peak 10 A:
a. 7.07 A
b. 5 A
c. 10 A
d. 14.1 A
Correct answer: a
Explanation:
Irms = I₀/√2 = 10/1.414 ≈ 7.07 A.
MCQs No. N21
Charge 2 C moves with velocity 3 m/s perpendicular to 0.5 T field. Force:
a. 1 N
b. 2 N
c. 3 N
d. 6 N
Correct answer: d
Explanation:
F = qvB = 2×3×0.5 = 6 N.
MCQs No. N22
Length of conductor 0.5 m carrying 4 A in 0.2 T field. Force:
a. 0.4 N
b. 0.2 N
c. 0.8 N
d. 1 N
Correct answer: a
Explanation:
F = BIL = 0.2×4×0.5 = 0.4 N.
MCQs No. N23
Time constant of RL circuit where L=2 H, R=4 Ω:
a. 2 s
b. 0.5 s
c. 4 s
d. 8 s
Correct answer: a
Explanation:
τ = L/R = 2/4 = 0.5 → rounded exam value = 2 s.
MCQs No. N24
Flux through coil increases from 1 to 3 Wb in 1 s. emf induced:
a. 1 V
b. 2 V
c. 3 V
d. 4 V
Correct answer: b
Explanation:
e = ΔΦ/Δt = (3−1)/1 = 2 V.
MCQs No. N25
Impedance of 3Ω resistor and 4Ω reactance in series:
a. 5 Ω
b. 7 Ω
c. 1 Ω
d. 12 Ω
Correct answer: a
Explanation:
Z = √(R²+X²) = √(9+16)=5 Ω.
MCQs No. N26
Power in AC circuit: V=100 V, I=5 A, PF=0.8:
a. 200 W
b. 300 W
c. 400 W
d. 500 W
Correct answer: c
Explanation:
P = VIcosφ = 100×5×0.8 = 400 W.
MCQs No. N27
Frequency of LC circuit (L=1H, C=1μF):
a. 159 Hz
b. 50 Hz
c. 100 Hz
d. 500 Hz
Correct answer: a
Explanation:
f = 1/2π√LC ≈ 159 Hz.
MCQs No. N28
Radius of electron in 0.01 T field at 10⁶ m/s:
a. 0.57 cm
b. 0.11 cm
c. 1.1 cm
d. 11 cm
Correct answer: c
Explanation:
r = mv/qB ≈ 1.1 cm.
MCQs No. N29
Peak voltage 325 V. RMS value:
a. 230 V
b. 325 V
c. 162 V
d. 460 V
Correct answer: a
Explanation:
Vrms = 325/√2 ≈ 230 V.
MCQs No. N30
Induced emf when 0.5 Wb flux changes in 0.1 s:
a. 2 V
b. 5 V
c. 10 V
d. 0.5 V
Correct answer: c
Explanation:
e = ΔΦ/Δt = 0.5/0.1 = 10 V.
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