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BECIL MCQs

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

Question 1001
Antenna & Wave PropagationFriis Transmission

In ideal free-space propagation, if the distance between transmitting and receiving antennas is doubled while all other factors remain unchanged, received power becomes?

  • ATwice
  • BHalf
  • COne-fourth
  • DOne-eighth
Report an error
Correct Answer: C. One-fourth
Explanation: The Friis equation gives received power proportional to 1/R², so doubling distance reduces received power to one-fourth.
Reference: Standard antenna and wave propagation: friis transmission
Question 1002
Antenna & Wave PropagationAntenna Arrays

An antenna array is formed by using?

  • AMultiple radiating elements arranged and excited to obtain a desired radiation pattern
  • BA single resistor only
  • COnly one isotropic point with no feed
  • DA capacitor bank with no radiators
Report an error
Correct Answer: A. Multiple radiating elements arranged and excited to obtain a desired radiation pattern
Explanation: Arrays combine fields from multiple antenna elements to shape beam direction, gain and sidelobe behavior.
Reference: Standard antenna and wave propagation: antenna arrays
Question 1003
Antenna & Wave PropagationAntenna Arrays

In a broadside linear array, the principal maximum is ideally directed?

  • AAlong the array axis
  • BPerpendicular to the array axis
  • COnly toward the feed point
  • DRandomly
Report an error
Correct Answer: B. Perpendicular to the array axis
Explanation: A broadside array is phased so that its main beam is normal to the array axis.
Reference: Standard antenna and wave propagation: antenna arrays
Question 1004
Antenna & Wave PropagationAntenna Arrays

In an end-fire array, the principal radiation is directed approximately?

  • AAlong the array axis
  • BPerpendicular to the array axis
  • COnly vertically regardless of orientation
  • DEqually in all directions
Report an error
Correct Answer: A. Along the array axis
Explanation: An end-fire array is phased to produce its main beam along the array axis.
Reference: Standard antenna and wave propagation: antenna arrays
Question 1005
Antenna & Wave PropagationAntenna Arrays

The array factor of an antenna array primarily depends on element?

  • APositions and relative excitation amplitudes/phases
  • BConductor color
  • CMechanical weight only
  • DDielectric breakdown voltage only
Report an error
Correct Answer: A. Positions and relative excitation amplitudes/phases
Explanation: Array factor is determined by the geometry and relative complex excitation of the elements, separate from the individual element pattern.
Reference: Standard antenna and wave propagation: antenna arrays
Question 1006
Antenna & Wave PropagationYagi-Uda Antenna

A Yagi-Uda antenna normally consists of a driven element together with?

  • AA reflector and one or more directors
  • BOnly a parabolic dish
  • COnly a horn aperture
  • DTwo identical ground planes with no parasitic elements
Report an error
Correct Answer: A. A reflector and one or more directors
Explanation: A typical Yagi-Uda uses one driven element, usually a dipole, plus a reflector and one or more parasitic directors.
Reference: Standard antenna and wave propagation: yagi-uda antenna
Question 1007
Antenna & Wave PropagationYagi-Uda Antenna

In a conventional Yagi-Uda antenna, the reflector is generally placed?

  • ABehind the driven element relative to the main radiation direction
  • BIn front of all directors
  • CAt the exact same position as the driven element
  • DOnly inside the feed cable
Report an error
Correct Answer: A. Behind the driven element relative to the main radiation direction
Explanation: The reflector is placed behind the driven element and helps reinforce radiation toward the directors.
Reference: Standard antenna and wave propagation: yagi-uda antenna
Question 1008
Antenna & Wave PropagationYagi-Uda Antenna

Adding suitably designed directors to a Yagi-Uda antenna generally tends to?

  • AIncrease directivity in the forward direction
  • BMake it perfectly isotropic
  • CEliminate all impedance
  • DForce radiation only backward
Report an error
Correct Answer: A. Increase directivity in the forward direction
Explanation: Directors concentrate radiation in the forward direction and can increase Yagi-Uda directivity.
Reference: Standard antenna and wave propagation: yagi-uda antenna
Question 1009
Antenna & Wave PropagationHorn Antenna

A horn antenna is commonly used at?

  • AMicrowave frequencies
  • BOnly audio frequencies
  • CDC only
  • DPower-line frequency only
Report an error
Correct Answer: A. Microwave frequencies
Explanation: Horn antennas are practical high-frequency aperture antennas widely used in microwave systems and as feeds for reflectors.
Reference: Standard antenna and wave propagation: horn antenna
Question 1010
Antenna & Wave PropagationHorn Antenna

A major purpose of gradually flaring a waveguide into a horn is to?

  • AProvide a smoother transition from waveguide to free space
  • BCreate a DC short circuit
  • CStop all radiation
  • DIncrease conductor resistance intentionally
Report an error
Correct Answer: A. Provide a smoother transition from waveguide to free space
Explanation: The flare provides a gradual impedance transition and a larger radiating aperture, improving radiation into free space.
Reference: Standard antenna and wave propagation: horn antenna
Question 1012
Antenna & Wave PropagationParabolic Reflector

A parabolic reflector antenna produces high directivity mainly because it?

  • AForms a large effective aperture and converts spherical wavefronts to approximately planar wavefronts
  • BRadiates equally in all directions
  • CUses only a resistive load
  • DHas zero physical aperture
Report an error
Correct Answer: A. Forms a large effective aperture and converts spherical wavefronts to approximately planar wavefronts
Explanation: With a feed near its focus, a paraboloid collimates radiation into a narrow beam, giving high gain/directivity.
Reference: Standard antenna and wave propagation: parabolic reflector
Question 1013
Antenna & Wave PropagationDipole Antennas

The directivity of a half-wave dipole is approximately?

  • A1 or 0 dBi
  • B1.64 or 2.15 dBi
  • C3.28 or 5.16 dBi
  • D10 or 10 dBi
Report an error
Correct Answer: B. 1.64 or 2.15 dBi
Explanation: A half-wave dipole has maximum directivity about 1.64, corresponding to approximately 2.15 dBi.
Reference: Standard antenna and wave propagation: dipole antennas
Question 1014
Antenna & Wave PropagationParabolic Reflector

For a parabolic reflector of fixed efficiency and wavelength, increasing the dish diameter generally?

  • AIncreases gain and narrows the beam
  • BDecreases gain and narrows the beam
  • CLeaves gain unchanged
  • DMakes the antenna isotropic
Report an error
Correct Answer: A. Increases gain and narrows the beam
Explanation: Reflector gain is approximately proportional to (D/lambda)², so a larger diameter gives higher gain and a narrower beam.
Reference: Standard antenna and wave propagation: parabolic reflector
Question 1015
Antenna & Wave PropagationMonopole Antennas

The approximate directivity of a quarter-wave monopole over an ideal infinite conducting ground plane is?

  • A1 or 0 dBi
  • B1.64 or 2.15 dBi
  • C3.28 or 5.15 dBi
  • D10 or 10 dBi
Report an error
Correct Answer: C. 3.28 or 5.15 dBi
Explanation: An ideal quarter-wave monopole radiates into one hemisphere and has about twice the directivity of a half-wave dipole, approximately 3.28 or 5.15 dBi.
Reference: Standard antenna and wave propagation: monopole antennas
Question 1016
Antenna & Wave PropagationEffective Aperture

For a receiving antenna, effective aperture Ae and gain G are related by?

  • AAe = G lambda²/(4 pi)
  • BAe = 4 pi G/lambda²
  • CAe = G/(4 pi lambda²)
  • DAe = lambda/(4 pi G)
Report an error
Correct Answer: A. Ae = G lambda²/(4 pi)
Explanation: For a matched receiving antenna, effective aperture is related to gain by Ae=Gλ²/(4π).
Reference: Standard antenna and wave propagation: effective aperture
Question 1017
Antenna & Wave PropagationSky-Wave Propagation

Sky-wave propagation relies mainly on refraction/return of radio waves by the?

  • AIonosphere
  • BTropospheric ground surface only
  • COcean floor
  • DTransmission-line dielectric
Report an error
Correct Answer: A. Ionosphere
Explanation: In sky-wave communication, ionized atmospheric layers can bend suitable radio waves back toward Earth.
Reference: Standard antenna and wave propagation: sky-wave propagation
Question 1018
Antenna & Wave PropagationSpace-Wave Propagation

Line-of-sight or space-wave propagation is especially important at?

  • AVHF and higher frequencies
  • BOnly very low frequency
  • CDC
  • DAudio frequency
Report an error
Correct Answer: A. VHF and higher frequencies
Explanation: At VHF, UHF and microwave frequencies, propagation is predominantly line-of-sight or space-wave because ionospheric return is generally not the normal mode.
Reference: Standard antenna and wave propagation: space-wave propagation
Question 1019
Antenna & Wave PropagationSpace-Wave Propagation

If transmitting and receiving antenna heights are increased, the radio line-of-sight range generally?

  • AIncreases
  • BDecreases to zero
  • CRemains exactly unchanged
  • DBecomes independent of Earth curvature
Report an error
Correct Answer: A. Increases
Explanation: Increasing antenna heights extends the geometric/radio horizon and therefore generally increases line-of-sight range.
Reference: Standard antenna and wave propagation: space-wave propagation
Question 1020
Antenna & Wave PropagationSpace-Wave Propagation

Which propagation mode is normally most appropriate for a terrestrial microwave point-to-point link?

  • ALine-of-sight space-wave propagation
  • BGround wave around the entire Earth
  • CIonospheric sky wave as the primary mode
  • DConduction through soil
Report an error
Correct Answer: A. Line-of-sight space-wave propagation
Explanation: Terrestrial microwave links generally use highly directional antennas and line-of-sight space-wave propagation.
Reference: Standard antenna and wave propagation: space-wave propagation
Question 1022
Antenna & Wave PropagationWave Propagation

Ground-wave propagation is most useful at relatively?

  • ALow frequencies
  • BOnly optical frequencies
  • COnly millimeter-wave frequencies
  • DX-ray frequencies
Report an error
Correct Answer: A. Low frequencies
Explanation: Ground waves can follow Earth's surface effectively at lower frequencies, with losses increasing as frequency rises.
Reference: Standard antenna and wave propagation: wave propagation
Question 1023
Antenna & Wave PropagationAntenna Pattern Parameters

The front-to-back ratio of a directional antenna compares radiation in the main-beam direction with radiation?

  • AIn the opposite direction
  • BAt the half-power point
  • CAt 90 degrees only
  • DAt the feed terminals
Report an error
Correct Answer: A. In the opposite direction
Explanation: Front-to-back ratio compares forward radiation with radiation approximately 180 degrees behind the main beam.
Reference: Standard antenna and wave propagation: antenna pattern parameters
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Question 1027
Antenna & Wave PropagationParabolic Reflector

The approximate gain of a parabolic reflector is proportional to?

  • A(D/lambda)² times aperture efficiency
  • BD/lambda only
  • Clambda²/D
  • DD²lambda² only
Report an error
Correct Answer: A. (D/lambda)² times aperture efficiency
Explanation: A common reflector relation is G≈eta_a(pi D/lambda)², so gain scales with (D/lambda)² for fixed efficiency.
Reference: Standard antenna and wave propagation: parabolic reflector
Question 1030
Antenna & Wave PropagationIonospheric Propagation

The D layer is particularly associated with significant absorption of?

  • ALower-HF and MF radio waves
  • BVisible light only
  • CAll microwave signals completely
  • DDC current
Report an error
Correct Answer: A. Lower-HF and MF radio waves
Explanation: Collisions in the lower ionosphere cause appreciable absorption, especially at lower radio frequencies.
Reference: Standard antenna and wave propagation: ionospheric propagation
Question 1031
Antenna & Wave PropagationIonospheric Propagation

During daytime, the F region commonly separates into?

  • AF1 and F2 layers
  • BD1 and D2 only
  • CE1 and E2 only
  • DTwo tropospheric layers
Report an error
Correct Answer: A. F1 and F2 layers
Explanation: Under daytime solar ionization, the F region is commonly described as F1 and F2; they tend to merge at night.
Reference: Standard antenna and wave propagation: ionospheric propagation
Question 1032
Antenna & Wave PropagationCritical Frequency

The critical frequency of an ionospheric layer is the highest frequency that is returned to Earth for?

  • AVertical incidence
  • BHorizontal incidence only
  • CAny angle without limit
  • DGround-wave propagation
Report an error
Correct Answer: A. Vertical incidence
Explanation: Critical frequency is defined for vertical incidence on a particular ionospheric layer.
Reference: Standard antenna and wave propagation: critical frequency
Question 1033
Antenna & Wave PropagationMUF

The maximum usable frequency (MUF) for a given ionospheric path is generally?

  • AAt least as high as the relevant critical frequency and depends on path geometry
  • BAlways zero
  • CAlways lower than every critical frequency
  • DIndependent of ionosphere and path
Report an error
Correct Answer: A. At least as high as the relevant critical frequency and depends on path geometry
Explanation: For oblique incidence, frequencies above the vertical-incidence critical frequency may be returned; MUF depends on layer conditions and geometry.
Reference: Standard antenna and wave propagation: muf
Question 1036
Antenna & Wave PropagationSkip Distance

Skip distance in sky-wave propagation is the minimum distance from the transmitter at which a wave of specified frequency is?

  • AReturned to Earth by the ionosphere
  • BAbsorbed completely by the antenna
  • CConverted to a ground current
  • DGuaranteed to have zero fading
Report an error
Correct Answer: A. Returned to Earth by the ionosphere
Explanation: Skip distance is the shortest ground distance at which a given sky wave returns to Earth under the prevailing ionospheric conditions.
Reference: Standard antenna and wave propagation: skip distance
Question 1038
Antenna & Wave PropagationIonospheric Propagation

Virtual height of an ionospheric layer is the apparent reflection height inferred by assuming the radio wave?

  • ATravels at the speed of light along an equivalent straight path
  • BStops at the ionosphere
  • CTravels through a metallic cable
  • DHas zero propagation time
Report an error
Correct Answer: A. Travels at the speed of light along an equivalent straight path
Explanation: Virtual height is derived from propagation delay using an equivalent straight-line path assumption and is not necessarily the true physical layer height.
Reference: Standard antenna and wave propagation: ionospheric propagation
Question 1041
Antenna & Wave PropagationAntenna Arrays

In a uniform linear array, increasing the number of similarly spaced elements while maintaining a comparable aperture arrangement generally tends to?

  • AIncrease directivity and narrow the main beam
  • BReduce directivity to zero
  • CMake all sidelobes disappear automatically
  • DMake element spacing irrelevant
Report an error
Correct Answer: A. Increase directivity and narrow the main beam
Explanation: More coherently combined elements generally provide a larger effective aperture, higher directivity and narrower main beam.
Reference: Standard antenna and wave propagation: antenna arrays
Question 1043
Antenna & Wave PropagationAntenna Matching

A common purpose of impedance matching at an antenna feed is to reduce?

  • AReflected power
  • BRadiated power intentionally to zero
  • COperating wavelength
  • DSpeed of electromagnetic waves
Report an error
Correct Answer: A. Reflected power
Explanation: A good impedance match reduces the reflection coefficient and improves transfer of available power between feed line and antenna.
Reference: Standard antenna and wave propagation: antenna matching
Question 1045
Antenna & Wave PropagationIonospheric Propagation

The ionosphere is important to HF communication because it contains?

  • AIonized particles capable of refracting radio waves
  • BOnly neutral particles with no electromagnetic effect
  • CA perfect metallic mirror
  • DNo free electrons
Report an error
Correct Answer: A. Ionized particles capable of refracting radio waves
Explanation: Solar radiation ionizes portions of the upper atmosphere, producing electrons and ions that affect radio-wave propagation.
Reference: Standard antenna and wave propagation: ionospheric propagation
Question 1048
Antenna & Wave PropagationGain Units

Antenna gain expressed in dBi is referenced to which ideal antenna?

  • AIsotropic radiator
  • BHalf-wave dipole
  • CQuarter-wave monopole
  • DSmall loop
Report an error
Correct Answer: A. Isotropic radiator
Explanation: dBi expresses antenna gain relative to an ideal isotropic radiator.
Reference: Standard antenna and wave propagation: gain units
Question 1049
Antenna & Wave PropagationGain Units

Antenna gain expressed in dBd is referenced to a?

  • AHalf-wave dipole
  • BIsotropic radiator
  • CParabolic reflector
  • DQuarter-wave transformer
Report an error
Correct Answer: A. Half-wave dipole
Explanation: dBd uses a half-wave dipole as the gain reference.
Reference: Standard antenna and wave propagation: gain units
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Question 1051
Antenna & Wave PropagationEIRP

Effective isotropic radiated power (EIRP) is the product of transmitter power delivered to the antenna and?

  • AAntenna gain relative to isotropic, including applicable feed losses when forming the link budget
  • BAntenna resistance only
  • COperating wavelength only
  • DReceiver sensitivity
Report an error
Correct Answer: A. Antenna gain relative to isotropic, including applicable feed losses when forming the link budget
Explanation: EIRP represents the equivalent power an isotropic radiator would need to produce the same power density in the direction of maximum antenna gain.
Reference: Standard antenna and wave propagation: eirp
Question 1056
Antenna & Wave PropagationLink Budget

A received power of 0 dBm corresponds to?

  • A1 mW
  • B10 mW
  • C100 mW
  • D1 W
Report an error
Correct Answer: A. 1 mW
Explanation: By definition, 0 dBm is 1 milliwatt.
Reference: Standard antenna and wave propagation: link budget
Question 1057
Antenna & Wave PropagationLink Budget

A received power of 30 dBm corresponds to?

  • A30 mW
  • B100 mW
  • C1 W
  • D30 W
Report an error
Correct Answer: C. 1 W
Explanation: 30 dBm=10^(30/10) mW=1000 mW=1 W.
Reference: Standard antenna and wave propagation: link budget
Question 1060
Antenna & Wave PropagationAntenna Noise

The equivalent noise temperature of an antenna is related primarily to?

  • ANoise power received from the environment through its radiation pattern
  • BIts DC resistance only
  • CIts mechanical temperature in every case only
  • DTransmitter output power
Report an error
Correct Answer: A. Noise power received from the environment through its radiation pattern
Explanation: Antenna noise temperature represents environmental noise collected by the antenna, weighted by its directional response.
Reference: Standard antenna and wave propagation: antenna noise
Question 1063
Antenna & Wave PropagationTropospheric Propagation

Tropospheric ducting can allow VHF/UHF/microwave signals to travel?

  • ABeyond the normal radio horizon
  • BOnly through underground conductors
  • COnly vertically upward
  • DOnly within an antenna feed line
Report an error
Correct Answer: A. Beyond the normal radio horizon
Explanation: Strong refractive-index gradients can trap radio waves in atmospheric ducts and extend propagation beyond the normal horizon.
Reference: Standard antenna and wave propagation: tropospheric propagation
Question 1064
Antenna & Wave PropagationTropospheric Propagation

Troposcatter communication relies on?

  • AScattering from irregularities in the troposphere
  • BReflection from the ionospheric F2 layer only
  • CConduction along Earth wires
  • DReflection from a parabolic feed itself
Report an error
Correct Answer: A. Scattering from irregularities in the troposphere
Explanation: Tropospheric scatter uses small-angle scattering from refractive-index irregularities to communicate beyond line of sight.
Reference: Standard antenna and wave propagation: tropospheric propagation
Question 1065
Antenna & Wave PropagationGain Units

A gain of 0 dBd is approximately equal to?

  • A0 dBi
  • B1 dBi
  • C2.15 dBi
  • D3 dBi
Report an error
Correct Answer: C. 2.15 dBi
Explanation: An ideal half-wave dipole has approximately 2.15 dBi gain, so 0 dBd≈2.15 dBi.
Reference: Standard antenna and wave propagation: gain units
Question 1066
Antenna & Wave PropagationDiffraction

Diffraction is especially important in radio propagation when a wave encounters?

  • AAn obstacle or sharp edge near the propagation path
  • BA perfectly matched load only
  • CA DC power source
  • DAn ideal isotropic point with no obstacle
Report an error
Correct Answer: A. An obstacle or sharp edge near the propagation path
Explanation: Diffraction bends/spreads waves around edges and obstacles, enabling some reception even when direct line of sight is obstructed.
Reference: Standard antenna and wave propagation: diffraction
Question 1067
Antenna & Wave PropagationFresnel Zone

The first Fresnel zone is important in a point-to-point radio link because excessive obstruction within it can cause?

  • AAdditional diffraction loss
  • BAutomatic gain increase
  • CZero path loss
  • DPerfect impedance matching
Report an error
Correct Answer: A. Additional diffraction loss
Explanation: Keeping much of the first Fresnel zone clear helps minimize diffraction loss and destructive interference.
Reference: Standard antenna and wave propagation: fresnel zone
Question 1069
Antenna & Wave PropagationFresnel Zone

For good practical line-of-sight link clearance, a commonly used planning guideline is to keep at least about what fraction of the first Fresnel zone unobstructed?

  • A20%
  • B40%
  • C60%
  • D100% in every possible situation
Report an error
Correct Answer: C. 60%
Explanation: A widely used engineering guideline is about 60% first-Fresnel-zone clearance to limit diffraction loss.
Reference: Standard antenna and wave propagation: fresnel zone
Question 1070
Antenna & Wave PropagationArray Phase

A two-element array has elements separated by lambda/2. To make their contributions add in phase in the direction along the array axis, the required progressive excitation phase can be chosen as approximately?

  • A0 degrees
  • B90 degrees
  • C180 degrees
  • D360 degrees only
Report an error
Correct Answer: C. 180 degrees
Explanation: A lambda/2 path difference produces 180 degrees propagation phase difference; an opposite 180 degrees excitation progression can compensate it for end-fire addition.
Reference: Standard antenna and wave propagation: array phase
Question 1071
Antenna & Wave PropagationPolarization Matching

Polarization mismatch is minimized when transmitting and receiving antennas have?

  • AMatched polarization
  • BOrthogonal linear polarizations
  • CRandom polarization at all times
  • DZero gain
Report an error
Correct Answer: A. Matched polarization
Explanation: Maximum polarization coupling occurs when the receive antenna polarization matches that of the incident wave.
Reference: Standard antenna and wave propagation: polarization matching
Question 1073
Power ElectronicsSCR

For an SCR, the latching current is generally?

  • AGreater than the holding current
  • BLess than the holding current in every device
  • CExactly zero
  • DAlways equal to gate current
Report an error
Correct Answer: A. Greater than the holding current
Explanation: Typically the latching current is higher than the holding current because stronger current is required just after turn-on to establish conduction.
Reference: Standard power electronics: scr
Question 1074
Power ElectronicsTRIAC

A TRIAC can conduct main current in?

  • ABoth directions
  • BForward direction only
  • CReverse direction only
  • DNeither direction
Report an error
Correct Answer: A. Both directions
Explanation: A TRIAC is a bidirectional thyristor used for AC power control.
Reference: Standard power electronics: triac
Question 1075
Power ElectronicsDIAC & TRIAC

A DIAC is commonly used to?

  • AProvide bidirectional triggering for a TRIAC
  • BRectify high-power three-phase DC
  • CAct as a controlled DC motor
  • DStore magnetic energy
Report an error
Correct Answer: A. Provide bidirectional triggering for a TRIAC
Explanation: A DIAC has bidirectional breakover behavior and is commonly used to produce symmetrical TRIAC gate triggering.
Reference: Standard power electronics: diac & triac
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Question 1076
Power ElectronicsPower Electronics Fundamentals

Power electronics primarily deals with the conversion and control of electrical power using?

  • ASemiconductor switching devices
  • BOnly mechanical switches
  • COnly passive resistors
  • DElectrochemical cells only
Report an error
Correct Answer: A. Semiconductor switching devices
Explanation: Power electronics uses semiconductor devices operated mainly as switches to efficiently convert and control electrical energy.
Reference: Standard power electronics: power electronics fundamentals
Question 1077
Power ElectronicsPower Semiconductor Devices

An ideal power semiconductor switch in the ON state should have?

  • AZero voltage drop
  • BInfinite voltage drop
  • CZero current capability
  • DInfinite switching loss
Report an error
Correct Answer: A. Zero voltage drop
Explanation: An ideal closed switch conducts current with zero voltage across it, so its conduction loss is zero.
Reference: Standard power electronics: power semiconductor devices
Question 1078
Power ElectronicsPower Semiconductor Devices

An ideal power semiconductor switch in the OFF state should have?

  • AZero current
  • BMaximum current
  • CZero blocking voltage
  • DInfinite conduction loss
Report an error
Correct Answer: A. Zero current
Explanation: An ideal open switch blocks voltage while carrying zero current.
Reference: Standard power electronics: power semiconductor devices
Question 1079
Power ElectronicsSCR

SCR stands for?

  • ASilicon Controlled Rectifier
  • BSeries Current Regulator
  • CSwitching Capacitor Rectifier
  • DSilicon Current Resistor
Report an error
Correct Answer: A. Silicon Controlled Rectifier
Explanation: SCR is the standard abbreviation for Silicon Controlled Rectifier, a thyristor device.
Reference: Standard power electronics: scr
Question 1081
Power ElectronicsSCR

The three terminals of an SCR are?

  • AAnode, cathode and gate
  • BCollector, base and emitter
  • CDrain, source and gate
  • DAnode, base and drain
Report an error
Correct Answer: A. Anode, cathode and gate
Explanation: The terminals of an SCR are anode (A), cathode (K) and gate (G).
Reference: Standard power electronics: scr
Question 1082
Power ElectronicsSCR

For normal forward turn-on of an SCR by gate triggering, the anode should be?

  • APositive with respect to cathode
  • BNegative with respect to cathode
  • CAt exactly zero potential in every case
  • DDisconnected from the supply
Report an error
Correct Answer: A. Positive with respect to cathode
Explanation: For forward blocking and gate-triggered turn-on, the anode is positive relative to the cathode.
Reference: Standard power electronics: scr
Question 1083
Power ElectronicsSCR

Once a conventional SCR has latched ON, removal of the gate signal normally?

  • ADoes not turn it OFF
  • BImmediately turns it OFF
  • CReverses its anode current
  • DMakes its holding current infinite
Report an error
Correct Answer: A. Does not turn it OFF
Explanation: After latching, the gate loses control over turn-off; anode current must be reduced below the holding current or reverse voltage applied.
Reference: Standard power electronics: scr
Question 1085
Power ElectronicsSCR

The minimum anode current needed immediately after triggering so that an SCR remains ON when the gate pulse is removed is called?

  • ALatching current
  • BReverse leakage current
  • CDisplacement current
  • DLoad current rating
Report an error
Correct Answer: A. Latching current
Explanation: Latching current is the minimum anode current required to establish regenerative conduction after the triggering signal is removed.
Reference: Standard power electronics: scr
Question 1086
Power ElectronicsPower Diode

A power diode is primarily an?

  • AUncontrolled unidirectional power semiconductor device
  • BFully gate-controlled bidirectional device
  • CVoltage-controlled transistor only
  • DMechanical relay
Report an error
Correct Answer: A. Uncontrolled unidirectional power semiconductor device
Explanation: A diode's conduction is determined by circuit voltage/current conditions; it has no control terminal.
Reference: Standard power electronics: power diode
Question 1087
Power ElectronicsPower MOSFET

A power MOSFET is primarily a?

  • AVoltage-controlled device
  • BCurrent-controlled device requiring continuous base current
  • CFour-layer latching thyristor
  • DBidirectional breakover diode
Report an error
Correct Answer: A. Voltage-controlled device
Explanation: The insulated gate of a MOSFET is controlled mainly by gate-to-source voltage, with negligible steady-state gate current ideally.
Reference: Standard power electronics: power mosfet
Question 1089
Power ElectronicsPower MOSFET

Compared with an SCR, a power MOSFET can normally be turned OFF by?

  • ARemoving or appropriately changing its gate-to-source drive
  • BReducing load current below holding current only
  • CApplying a DIAC pulse only
  • DWaiting for AC current zero in every application
Report an error
Correct Answer: A. Removing or appropriately changing its gate-to-source drive
Explanation: A MOSFET is a fully controlled switch: its channel can be turned on and off by controlling gate voltage.
Reference: Standard power electronics: power mosfet
Question 1090
Power ElectronicsRectifiers

A rectifier converts electrical power from?

  • AAC to DC
  • BDC to AC
  • CDC to DC only
  • DAC to AC only
Report an error
Correct Answer: A. AC to DC
Explanation: A rectifier converts alternating input power into a unidirectional/DC output.
Reference: Standard power electronics: rectifiers
Question 1091
Power ElectronicsInverters

An inverter converts electrical power from?

  • ADC to AC
  • BAC to DC
  • CAC to AC only
  • DMechanical to electrical
Report an error
Correct Answer: A. DC to AC
Explanation: An inverter synthesizes an AC output from a DC source.
Reference: Standard power electronics: inverters
Question 1092
Power ElectronicsDC Choppers

A DC chopper is principally a?

  • ADC-to-DC converter
  • BAC-to-DC converter
  • CDC-to-AC converter
  • DAC-to-AC transformer only
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Correct Answer: A. DC-to-DC converter
Explanation: A chopper controls the average DC output obtained from a DC input through high-frequency switching.
Reference: Standard power electronics: dc choppers
Question 1093
Power ElectronicsAC Voltage Controllers

An AC voltage controller converts?

  • AFixed-frequency AC to variable-magnitude AC at the same basic frequency
  • BDC to AC
  • CAC directly to pure DC only
  • DDC to DC
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Correct Answer: A. Fixed-frequency AC to variable-magnitude AC at the same basic frequency
Explanation: An AC voltage controller regulates the RMS AC output, commonly by phase or integral-cycle control, while retaining the supply's fundamental frequency.
Reference: Standard power electronics: ac voltage controllers
Question 1094
Power ElectronicsCycloconverters

A cycloconverter directly converts?

  • AAC at one frequency to AC at another frequency
  • BDC to AC only
  • CAC to DC only
  • DDC to DC only
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Correct Answer: A. AC at one frequency to AC at another frequency
Explanation: A cycloconverter performs direct AC-to-AC frequency conversion without an intermediate DC link.
Reference: Standard power electronics: cycloconverters
Question 1095
Power ElectronicsFreewheeling Diode

A freewheeling diode connected across an inductive DC load mainly provides?

  • AA path for load current when the main switch or rectifier device stops supplying it
  • BA permanent short circuit across the source
  • CGate current for an SCR
  • DVoltage amplification
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Correct Answer: A. A path for load current when the main switch or rectifier device stops supplying it
Explanation: Inductive current cannot change instantaneously, so the freewheeling diode provides a path for continuing current and helps limit load voltage excursions.
Reference: Standard power electronics: freewheeling diode
Question 1096
Power ElectronicsControlled Rectifiers

In phase-controlled rectifiers, firing angle alpha is measured from?

  • AThe reference point where the device would naturally become forward-biased in the supply cycle
  • BThe instant of maximum load current only
  • CThe end of every negative half-cycle only
  • DThe gate-current peak regardless of supply waveform
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Correct Answer: A. The reference point where the device would naturally become forward-biased in the supply cycle
Explanation: The firing delay angle alpha specifies how long triggering is delayed from the natural forward-bias reference in each applicable cycle.
Reference: Standard power electronics: controlled rectifiers
Question 1097
Power ElectronicsControlled Rectifiers

For a single-phase half-wave controlled rectifier with a purely resistive load, increasing firing angle from 0 toward 180 degrees generally causes the average output voltage to?

  • ADecrease
  • BIncrease
  • CRemain constant
  • DBecome independent of the supply
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Correct Answer: A. Decrease
Explanation: Delaying SCR turn-on shortens the conduction interval, reducing the average output voltage for a resistive load.
Reference: Standard power electronics: controlled rectifiers
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