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JTO MCQs

Practice JTO-oriented Electronics & Telecommunication Engineering MCQs with answers and explanations for technical exam preparation. Questions are arranged in pages of up to 100.

Question 901
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 903
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 904
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 905
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 906
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 908
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 909
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 911
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 918
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 923
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
Question 925
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
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Question 926
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 928
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 932
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 933
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 937
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 940
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 942
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 943
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 944
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 948
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
Question 950
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
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Question 951
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 952
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 953
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 954
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 955
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 957
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 959
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 960
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 961
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 962
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 963
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 966
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 967
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 973
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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Question 976
Antenna & Wave PropagationDirectivity & Gain

A power gain of 10 corresponds to approximately?

  • A3 dB
  • B10 dB
  • C20 dB
  • D100 dB
Report an error
Correct Answer: B. 10 dB
Explanation: Gain in decibels is 10log10(10)=10 dB.
Reference: Standard antenna and wave propagation: directivity & gain
Question 978
Antenna & Wave PropagationAntenna Fundamentals

The primary function of a transmitting antenna is to convert?

  • AGuided electromagnetic energy into radiated electromagnetic waves
  • BDC power directly into mechanical energy
  • CSound waves into heat only
  • DDigital data into resistance
Report an error
Correct Answer: A. Guided electromagnetic energy into radiated electromagnetic waves
Explanation: A transmitting antenna couples guided RF energy from a transmission system into electromagnetic waves that propagate through space.
Reference: Standard antenna and wave propagation: antenna fundamentals
Question 979
Antenna & Wave PropagationAntenna Fundamentals

A receiving antenna primarily converts incident electromagnetic waves into?

  • AElectrical signals available at its terminals
  • BMechanical rotation only
  • CDC resistance only
  • DOptical energy only
Report an error
Correct Answer: A. Electrical signals available at its terminals
Explanation: A receiving antenna intercepts electromagnetic energy and produces a corresponding electrical signal at its terminals.
Reference: Standard antenna and wave propagation: antenna fundamentals
Question 980
Antenna & Wave PropagationRadiation Pattern

The radiation pattern of an antenna describes the variation of its radiation properties with?

  • ADirection in space
  • BSupply voltage only
  • CConductor resistance only
  • DTime of day
Report an error
Correct Answer: A. Direction in space
Explanation: An antenna radiation pattern shows how radiation intensity, field strength or related quantities vary with direction.
Reference: Standard antenna and wave propagation: radiation pattern
Question 983
Antenna & Wave PropagationRadiation Pattern

A lobe other than the major lobe is generally called a?

  • AMinor lobe
  • BIsotropic lobe
  • CFeed lobe
  • DImpedance lobe
Report an error
Correct Answer: A. Minor lobe
Explanation: Side lobes and back lobes are collectively minor lobes because they are not the principal radiation lobe.
Reference: Standard antenna and wave propagation: radiation pattern
Question 984
Antenna & Wave PropagationIsotropic Radiator

An isotropic radiator is a hypothetical antenna that radiates?

  • AEqually in all directions
  • BOnly along one axis
  • COnly in the horizontal plane
  • DNo power
Report an error
Correct Answer: A. Equally in all directions
Explanation: An isotropic radiator is an ideal reference source with uniform radiation intensity in every direction.
Reference: Standard antenna and wave propagation: isotropic radiator
Question 985
Antenna & Wave PropagationDirectivity & Gain

The directivity of an isotropic radiator is?

  • A1 or 0 dBi
  • B2 or 3 dBi
  • C1.64 or 2.15 dBi
  • DInfinite
Report an error
Correct Answer: A. 1 or 0 dBi
Explanation: By definition, an isotropic radiator has directivity 1, corresponding to 0 dBi.
Reference: Standard antenna and wave propagation: directivity & gain
Question 986
Antenna & Wave PropagationDirectivity & Gain

Antenna directivity is the ratio of radiation intensity in a specified direction to?

  • AAverage radiation intensity over all directions
  • BInput current only
  • COhmic resistance
  • DWavelength squared only
Report an error
Correct Answer: A. Average radiation intensity over all directions
Explanation: Directivity compares radiation intensity in a given direction, usually its maximum, with the average radiation intensity.
Reference: Standard antenna and wave propagation: directivity & gain
Question 987
Antenna & Wave PropagationDirectivity & Gain

Antenna gain differs from directivity because gain also accounts for?

  • AAntenna efficiency
  • BOnly operating frequency
  • COnly polarization direction
  • DSpeed of light
Report an error
Correct Answer: A. Antenna efficiency
Explanation: Gain includes the effect of radiation efficiency, whereas directivity is based on the shape of the radiation pattern.
Reference: Standard antenna and wave propagation: directivity & gain
Question 989
Antenna & Wave PropagationBeamwidth

A narrower main beam generally indicates?

  • AHigher directivity
  • BLower directivity in every case
  • CZero gain
  • DNo radiation
Report an error
Correct Answer: A. Higher directivity
Explanation: Concentrating radiation into a narrower angular region generally increases antenna directivity.
Reference: Standard antenna and wave propagation: beamwidth
Question 990
Antenna & Wave PropagationAntenna Resistance

Radiation resistance is a fictitious resistance that represents?

  • APower radiated by the antenna
  • BOnly conductor heating loss
  • CDielectric breakdown
  • DFeed-line reactance only
Report an error
Correct Answer: A. Power radiated by the antenna
Explanation: Radiation resistance is defined so that the power attributed to it equals the antenna's radiated power for the specified current convention.
Reference: Standard antenna and wave propagation: antenna resistance
Question 991
Antenna & Wave PropagationAntenna Efficiency

Antenna radiation efficiency is commonly defined as radiated power divided by?

  • AAccepted input power
  • BIncident power density only
  • CReactive power only
  • DReflected power only
Report an error
Correct Answer: A. Accepted input power
Explanation: Radiation efficiency is the fraction of power accepted by the antenna that is actually radiated rather than dissipated as loss.
Reference: Standard antenna and wave propagation: antenna efficiency
Question 993
Antenna & Wave PropagationAntenna Impedance

For maximum power transfer between a transmission line and an antenna at a single frequency, the antenna input impedance should ideally be?

  • AMatched to the line impedance
  • BZero
  • CInfinite
  • DPurely capacitive regardless of the line
Report an error
Correct Answer: A. Matched to the line impedance
Explanation: Impedance matching minimizes reflection and permits efficient transfer of power from the line to the antenna.
Reference: Standard antenna and wave propagation: antenna impedance
Question 994
Antenna & Wave PropagationPolarization

The polarization of an antenna is normally defined by the polarization of the wave it?

  • ARadiates in a specified direction
  • BAbsorbs as heat only
  • CReflects from the ground only
  • DCarries inside a DC cable
Report an error
Correct Answer: A. Radiates in a specified direction
Explanation: Antenna polarization is described by the electric-field polarization of its radiated wave in the direction considered.
Reference: Standard antenna and wave propagation: polarization
Question 995
Antenna & Wave PropagationDipole Antennas

A vertically oriented half-wave dipole ideally produces what polarization in its broadside direction?

  • AVertical linear polarization
  • BHorizontal linear polarization
  • CCircular polarization automatically
  • DUnpolarized radiation
Report an error
Correct Answer: A. Vertical linear polarization
Explanation: The electric field of a thin dipole is oriented parallel to the dipole axis, giving vertical linear polarization for a vertical dipole.
Reference: Standard antenna and wave propagation: dipole antennas
Question 1000
Antenna & Wave PropagationDipole Antennas

The radiation pattern of an ideal half-wave dipole has maximum radiation in directions?

  • AAlong the dipole axis
  • BPerpendicular to the dipole axis
  • COnly at 45 degrees to the axis
  • DEqually in every direction
Report an error
Correct Answer: B. Perpendicular to the dipole axis
Explanation: A thin half-wave dipole has maximum radiation broadside to its axis and nulls along the axis.
Reference: Standard antenna and wave propagation: dipole antennas
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