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Electromagnetic Theory MCQs

Practice Electromagnetic Theory MCQs from fundamental concepts through intermediate, advanced and application-oriented questions. Each page contains up to 100 questions with answers and explanations where available.

Question 1
Electromagnetic TheoryGauss's Law

Gauss’s law for the electric field in integral form states that the total electric flux of D through a closed surface equals?

  • AEnclosed free charge
  • BTotal current through the surface
  • CMagnetic flux inside the surface
  • DElectric potential on the surface
Report an error
Correct Answer: A. Enclosed free charge
Explanation: Gauss's law states that the closed-surface flux of D equals enclosed free charge.
Reference: Standard electromagnetic theory: gauss's law
Question 3
Electromagnetic TheoryElectrostatics Fundamentals

The SI unit of electric charge is?

  • ACoulomb
  • BVolt
  • CAmpere per metre
  • DWeber
Report an error
Correct Answer: A. Coulomb
Explanation: The coulomb (C) is the SI unit of electric charge.
Reference: Standard electromagnetic theory: electrostatics fundamentals
Question 4
Electromagnetic TheoryCoulomb's Law

According to Coulomb’s law, the magnitude of force between two stationary point charges is proportional to?

  • AProduct of the charges and inversely proportional to the square of their separation
  • BSum of the charges and directly proportional to separation
  • CProduct of the charges and directly proportional to the square of separation
  • DDifference of the charges only
Report an error
Correct Answer: A. Product of the charges and inversely proportional to the square of their separation
Explanation: For point charges, F=(1/(4πε))|q1q2|/r².
Reference: Standard electromagnetic theory: coulomb's law
Question 7
Electromagnetic TheoryElectric Field

The SI unit of electric field intensity E is?

  • AV/m
  • BWb/m²
  • CA/m
  • DC/m² only
Report an error
Correct Answer: A. V/m
Explanation: Electric field intensity is measured in N/C, equivalently V/m.
Reference: Standard electromagnetic theory: electric field
Question 10
Electromagnetic TheoryElectric Potential

The SI unit of electric potential is?

  • AVolt
  • BTesla
  • CHenry
  • DFarad per metre
Report an error
Correct Answer: A. Volt
Explanation: Electric potential is measured in volts.
Reference: Standard electromagnetic theory: electric potential
Question 11
Electromagnetic TheoryElectric Potential

Electric field and electric potential are related by?

  • AE = -grad V
  • BE = grad V without a minus sign
  • CE = V²
  • DE = div V
Report an error
Correct Answer: A. E = -grad V
Explanation: The electric field equals the negative gradient of potential.
Reference: Standard electromagnetic theory: electric potential
Question 12
Electromagnetic TheoryElectric Potential

An equipotential surface is a surface on which?

  • AElectric potential is constant
  • BElectric field is always zero everywhere
  • CCharge density is necessarily zero
  • DMagnetic flux is constant by definition
Report an error
Correct Answer: A. Electric potential is constant
Explanation: Every point on an equipotential surface has the same potential.
Reference: Standard electromagnetic theory: electric potential
Question 15
Electromagnetic TheoryElectric Flux Density

The SI unit of electric flux density D is?

  • AC/m²
  • BV/m
  • CA/m
  • DT
Report an error
Correct Answer: A. C/m²
Explanation: Electric flux density is measured in coulombs per square metre.
Reference: Standard electromagnetic theory: electric flux density
Question 16
Electromagnetic TheoryMaxwell Equations Basics

The divergence form of Gauss’s law is?

  • Adiv D = rho_v
  • Bcurl D = rho_v
  • Cdiv B = rho_v
  • Dcurl E = rho_v
Report an error
Correct Answer: A. div D = rho_v
Explanation: The differential form is ∇·D=ρv.
Reference: Standard electromagnetic theory: maxwell equations basics
Question 17
Electromagnetic TheoryElectrostatics Fundamentals

In electrostatics, the curl of electric field E is?

  • AZero
  • BEqual to charge density
  • CEqual to current density
  • DAlways infinite
Report an error
Correct Answer: A. Zero
Explanation: An electrostatic electric field is conservative, hence ∇×E=0.
Reference: Standard electromagnetic theory: electrostatics fundamentals
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Question 28
Electromagnetic TheoryCurrent Density

The SI unit of current density J is?

  • AA/m²
  • BA/m
  • CC/m²
  • DV/m²
Report an error
Correct Answer: A. A/m²
Explanation: Current density is electric current per unit cross-sectional area, measured in amperes per square metre.
Reference: Standard electromagnetic theory: current density
Question 30
Electromagnetic TheoryContinuity Equation

The general differential form of the charge continuity equation is?

  • A∇·J = -partial rho_v/partial t
  • B∇×J = -partial rho_v/partial t
  • C∇·J = rho_v
  • D∇×E = J
Report an error
Correct Answer: A. ∇·J = -partial rho_v/partial t
Explanation: Charge conservation is expressed locally by ∇·J=-∂ρv/∂t.
Reference: Standard electromagnetic theory: continuity equation
Question 31
Electromagnetic TheoryContinuity Equation

For steady current conditions, the continuity equation reduces to?

  • A∇·J = 0
  • B∇×J = 0 always
  • CJ = 0
  • D∇·D = 0 in every conductor
Report an error
Correct Answer: A. ∇·J = 0
Explanation: Under steady conditions charge density does not change with time, so ∇·J=0.
Reference: Standard electromagnetic theory: continuity equation
Question 32
Electromagnetic TheoryMagnetostatics

The magnetic flux density B is measured in?

  • ATesla
  • BWeber per metre
  • CAmpere per metre
  • DHenry
Report an error
Correct Answer: A. Tesla
Explanation: The SI unit of magnetic flux density is tesla (T), equivalent to Wb/m².
Reference: Standard electromagnetic theory: magnetostatics
Question 33
Electromagnetic TheoryMagnetostatics

The magnetic field intensity H is measured in?

  • AA/m
  • BTesla
  • CWeber
  • DC/m²
Report an error
Correct Answer: A. A/m
Explanation: Magnetic field intensity H has SI unit ampere per metre.
Reference: Standard electromagnetic theory: magnetostatics
Question 35
Electromagnetic TheoryBiot-Savart Law

The Biot-Savart law is used to calculate magnetic field produced by?

  • ACurrent elements
  • BStationary electric charges only
  • CDielectric polarization only
  • DScalar potential without current
Report an error
Correct Answer: A. Current elements
Explanation: Biot-Savart law gives the magnetic field contribution from electric current elements.
Reference: Standard electromagnetic theory: biot-savart law
Question 36
Electromagnetic TheoryPotential Equations

In a charge-free region with uniform permittivity, the electrostatic potential V satisfies?

  • ALaplace's equation
  • BPoisson's equation with nonzero charge density
  • CWave equation only
  • DContinuity equation only
Report an error
Correct Answer: A. Laplace's equation
Explanation: When volume charge density is zero, Poisson's equation reduces to Laplace's equation, ∇²V=0.
Reference: Standard electromagnetic theory: potential equations
Question 38
Electromagnetic TheoryBoundary Conditions

At the boundary between two perfect dielectric media with no free surface charge, which component of electric flux density D is continuous?

  • ANormal component
  • BTangential component only
  • CBoth components must be zero
  • DNeither component
Report an error
Correct Answer: A. Normal component
Explanation: The boundary condition is D1n-D2n=ρs. With no free surface charge, the normal components are equal.
Reference: Standard electromagnetic theory: boundary conditions
Question 45
Electromagnetic TheoryMagnetic Field

The direction of magnetic field around a long straight current-carrying conductor is determined by the?

  • ARight-hand rule
  • BLeft-hand electrostatic rule
  • CLenz law only
  • DGauss electric law only
Report an error
Correct Answer: A. Right-hand rule
Explanation: Curling the fingers of the right hand around the conductor with the thumb along current gives the magnetic-field direction.
Reference: Standard electromagnetic theory: magnetic field
Question 50
Electromagnetic TheoryMaxwell Equations Basics

The differential form of Gauss’s law for magnetism is?

  • A∇·B = 0
  • B∇×B = 0 always
  • C∇·B = rho_v
  • D∇×B = -partial D/partial t
Report an error
Correct Answer: A. ∇·B = 0
Explanation: The magnetic flux density is divergence-free: ∇·B=0.
Reference: Standard electromagnetic theory: maxwell equations basics
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Question 52
Electromagnetic TheoryFaraday's Law

Faraday’s law states that the induced emf around a closed path is equal to?

  • AThe negative time rate of change of magnetic flux linkage
  • BThe magnetic flux itself
  • CThe electric charge enclosed
  • DThe resistance multiplied by magnetic field
Report an error
Correct Answer: A. The negative time rate of change of magnetic flux linkage
Explanation: Faraday's law gives induced emf as the negative time derivative of magnetic flux linkage.
Reference: Standard electromagnetic theory: faraday's law
Question 53
Electromagnetic TheoryFaraday's Law

The negative sign in Faraday’s law is associated with?

  • ALenz's law
  • BCoulomb's law
  • CGauss's electric law
  • DOhm's law
Report an error
Correct Answer: A. Lenz's law
Explanation: The negative sign expresses Lenz's law: the induced effect opposes the change in magnetic flux that produces it.
Reference: Standard electromagnetic theory: faraday's law
Question 55
Electromagnetic TheoryFaraday's Law

A stationary closed conducting loop is placed in a magnetic field that is constant with time. If the flux through the loop does not change, the transformer-induced emf is?

  • AZero
  • BMaximum
  • CEqual to magnetic flux
  • DAlways 1 V
Report an error
Correct Answer: A. Zero
Explanation: Faraday's law requires a time-varying flux linkage for transformer emf; if flux is constant, induced emf is zero.
Reference: Standard electromagnetic theory: faraday's law
Question 59
Electromagnetic TheoryInductance

The SI unit of inductance is?

  • AHenry
  • BTesla
  • CWeber per square metre
  • DFarad
Report an error
Correct Answer: A. Henry
Explanation: Inductance is measured in henries (H).
Reference: Standard electromagnetic theory: inductance
Question 60
Electromagnetic TheoryInductance

The voltage across an ideal inductor of constant inductance L is?

  • Av = L di/dt
  • Bv = i/L
  • Cv = Li
  • Dv = L/i
Report an error
Correct Answer: A. v = L di/dt
Explanation: For a constant linear inductance, the induced terminal voltage is proportional to the rate of change of current: v=L di/dt.
Reference: Standard electromagnetic theory: inductance
Question 63
Electromagnetic TheoryMutual Inductance

Mutual inductance describes the magnetic coupling between?

  • ATwo circuits or coils
  • BOnly two capacitors
  • CA resistor and a battery only
  • DTwo isolated static charges
Report an error
Correct Answer: A. Two circuits or coils
Explanation: Mutual inductance quantifies how changing current in one circuit induces emf in another magnetically coupled circuit.
Reference: Standard electromagnetic theory: mutual inductance
Question 66
Electromagnetic TheoryMaxwell Equations

Maxwell introduced displacement current primarily to extend which law to time-varying fields?

  • AAmpere's circuital law
  • BCoulomb's law
  • CGauss's magnetic law
  • DBiot-Savart law for static point charges
Report an error
Correct Answer: A. Ampere's circuital law
Explanation: The displacement-current term makes Ampere's law consistent with charge conservation in time-varying electromagnetic fields.
Reference: Standard electromagnetic theory: maxwell equations
Question 68
Electromagnetic TheoryMaxwell Equations

The Maxwell-Ampere equation in differential form is?

  • Acurl H = J + partial D/partial t
  • Bcurl E = J + partial D/partial t
  • Cdiv H = J
  • Ddiv D = J + partial B/partial t
Report an error
Correct Answer: A. curl H = J + partial D/partial t
Explanation: Maxwell-Ampere law is ∇×H=J+∂D/∂t.
Reference: Standard electromagnetic theory: maxwell equations
Question 69
Electromagnetic TheoryMaxwell Equations

Faraday’s law in differential form is?

  • Acurl E = -partial B/partial t
  • Bdiv E = -partial B/partial t
  • Ccurl H = -partial B/partial t
  • Ddiv B = -partial E/partial t
Report an error
Correct Answer: A. curl E = -partial B/partial t
Explanation: The differential Faraday law is ∇×E=-∂B/∂t.
Reference: Standard electromagnetic theory: maxwell equations
Question 70
Electromagnetic TheoryEM Wave Fundamentals

In a source-free lossless homogeneous medium, electromagnetic waves are?

  • ATransverse, with E and H perpendicular to the direction of propagation
  • BPurely longitudinal with E parallel to propagation
  • CPurely electrostatic
  • DUnable to carry energy
Report an error
Correct Answer: A. Transverse, with E and H perpendicular to the direction of propagation
Explanation: Uniform plane electromagnetic waves in a source-free isotropic medium have mutually perpendicular E, H and propagation directions.
Reference: Standard electromagnetic theory: em wave fundamentals
Question 74
Electromagnetic TheoryEM Wave Fundamentals

The intrinsic impedance of free space is approximately?

  • A50 ohm
  • B75 ohm
  • C120 pi ohm
  • D600 ohm
Report an error
Correct Answer: C. 120 pi ohm
Explanation: η0=sqrt(mu0/epsilon0)=120π ohm, approximately 377 ohm.
Reference: Standard electromagnetic theory: em wave fundamentals
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Question 76
Electromagnetic TheoryPoynting Vector

The Poynting vector represents electromagnetic?

  • APower-flow density
  • BCharge density
  • CMagnetic reluctance
  • DElectric potential
Report an error
Correct Answer: A. Power-flow density
Explanation: The Poynting vector S=E×H gives electromagnetic power flow per unit area.
Reference: Standard electromagnetic theory: poynting vector
Question 79
Electromagnetic TheoryWave Propagation

The complex propagation constant gamma is conventionally written as?

  • Aalpha + j beta
  • Bbeta + j alpha only
  • Calpha beta
  • Dj(alpha + beta)
Report an error
Correct Answer: A. alpha + j beta
Explanation: The propagation constant is γ=α+jβ, where α is attenuation constant and β is phase constant.
Reference: Standard electromagnetic theory: wave propagation
Question 80
Electromagnetic TheoryStanding Waves

A VSWR of 1 corresponds to?

  • APerfect matching with no reflection
  • BTotal reflection
  • CA reflection coefficient magnitude of 1
  • DInfinite attenuation
Report an error
Correct Answer: A. Perfect matching with no reflection
Explanation: VSWR=1 occurs only when |Γ|=0, corresponding to a matched condition.
Reference: Standard electromagnetic theory: standing waves
Question 81
Electromagnetic TheoryWave Propagation

The attenuation constant alpha is commonly measured in?

  • ANp/m
  • Brad/m
  • CHz/m
  • DWb/m
Report an error
Correct Answer: A. Np/m
Explanation: The attenuation constant describes exponential amplitude decay and is measured in nepers per metre.
Reference: Standard electromagnetic theory: wave propagation
Question 82
Electromagnetic TheoryPolarization

The polarization of an electromagnetic wave is specified by the behavior of its?

  • AElectric-field vector
  • BPropagation speed only
  • CMagnetic permeability only
  • DFrequency counter reading
Report an error
Correct Answer: A. Electric-field vector
Explanation: Wave polarization is conventionally defined by the locus and orientation of the electric-field vector at a fixed point.
Reference: Standard electromagnetic theory: polarization
Question 83
Electromagnetic TheoryWave Propagation

The phase constant beta is commonly measured in?

  • Arad/m
  • BNp/m
  • CS/m
  • DC/m
Report an error
Correct Answer: A. rad/m
Explanation: The phase constant describes phase change per unit distance and is measured in radians per metre.
Reference: Standard electromagnetic theory: wave propagation
Question 85
Electromagnetic TheoryWave Propagation

The phase constant beta and wavelength lambda are related by?

  • Abeta = 2 pi/lambda
  • Bbeta = lambda/(2 pi)
  • Cbeta = 2 pi lambda
  • Dbeta = 1/lambda²
Report an error
Correct Answer: A. beta = 2 pi/lambda
Explanation: A phase change of 2π radians occurs over one wavelength, hence β=2π/λ.
Reference: Standard electromagnetic theory: wave propagation
Question 87
Electromagnetic TheorySkin Effect

Skin effect causes high-frequency current in a good conductor to concentrate mainly?

  • ANear the conductor surface
  • BUniformly throughout the entire cross-section
  • COnly at the conductor axis
  • DOutside the conductor with zero internal current
Report an error
Correct Answer: A. Near the conductor surface
Explanation: At higher frequency, electromagnetic diffusion causes current density to become concentrated near the surface.
Reference: Standard electromagnetic theory: skin effect
Question 88
Electromagnetic TheorySkin Effect

For a good conductor, skin depth decreases when frequency?

  • AIncreases
  • BDecreases
  • CBecomes zero only
  • DHas no effect
Report an error
Correct Answer: A. Increases
Explanation: For a good conductor, δ≈sqrt(2/(omega mu sigma)), so increasing frequency decreases skin depth.
Reference: Standard electromagnetic theory: skin effect
Question 89
Electromagnetic TheorySkin Effect

For a good conductor, the skin depth is approximately?

  • Asqrt(2/(omega mu sigma))
  • Bsqrt(omega mu sigma/2)
  • Comega mu sigma
  • D2 omega/(mu sigma)
Report an error
Correct Answer: A. sqrt(2/(omega mu sigma))
Explanation: The standard good-conductor approximation is δ=sqrt(2/(ωμσ)).
Reference: Standard electromagnetic theory: skin effect
Question 90
Electromagnetic TheoryReflection & Transmission

The reflection coefficient for electric-field amplitude at normal incidence is defined as?

  • AReflected electric-field amplitude divided by incident electric-field amplitude
  • BIncident field divided by reflected field
  • CTransmitted power divided by incident power only
  • DReflected magnetic field multiplied by incident field
Report an error
Correct Answer: A. Reflected electric-field amplitude divided by incident electric-field amplitude
Explanation: The electric-field reflection coefficient is Γ=Er/Ei at the interface.
Reference: Standard electromagnetic theory: reflection & transmission
Question 91
Electromagnetic TheoryReflection & Transmission

If a wave is incident normally from a medium of intrinsic impedance eta1 onto a medium of impedance eta2, the electric-field reflection coefficient is?

  • A(eta2-eta1)/(eta2+eta1)
  • B(eta2+eta1)/(eta2-eta1)
  • Ceta1/eta2
  • Deta1+eta2
Report an error
Correct Answer: A. (eta2-eta1)/(eta2+eta1)
Explanation: Applying tangential E and H boundary conditions gives Γ=(η2-η1)/(η2+η1).
Reference: Standard electromagnetic theory: reflection & transmission
Question 94
Electromagnetic TheoryStanding Waves

A standing wave is produced by the superposition of?

  • AIncident and reflected waves traveling in opposite directions
  • BTwo DC electric fields only
  • COnly one traveling wave
  • DTwo unrelated static magnetic fields
Report an error
Correct Answer: A. Incident and reflected waves traveling in opposite directions
Explanation: Interference between forward and reflected waves of the same frequency creates a standing-wave pattern.
Reference: Standard electromagnetic theory: standing waves
Question 95
Electromagnetic TheoryPoynting Vector

The SI unit of the Poynting vector is?

  • AW/m²
  • BJ/m
  • CV/m
  • DA/m²
Report an error
Correct Answer: A. W/m²
Explanation: Because the Poynting vector is power per unit area, its SI unit is watt per square metre.
Reference: Standard electromagnetic theory: poynting vector
Question 99
Electromagnetic TheoryPolarization

Two orthogonal field components generally produce elliptical polarization when they have?

  • ASuitable unequal amplitudes and/or a phase difference other than the special linear/circular cases
  • BZero frequency only
  • CNo electric field
  • DOnly identical phase and identical direction
Report an error
Correct Answer: A. Suitable unequal amplitudes and/or a phase difference other than the special linear/circular cases
Explanation: Elliptical polarization is the general case for orthogonal components with relative amplitude and phase that do not reduce to linear or circular polarization.
Reference: Standard electromagnetic theory: polarization
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