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SAIL MCQs

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

Question 801
Measurements & InstrumentationLoading Effect

An ideal voltmeter should have internal resistance of?

  • AZero
  • BInfinite
  • CEqual to source resistance
  • DOne ohm
Report an error
Correct Answer: B. Infinite
Explanation: A voltmeter is connected in parallel and ideally draws no current, requiring infinite input resistance.
Reference: Standard measurements and instrumentation: loading effect
Question 802
Measurements & InstrumentationLoading Effect

A voltmeter with finite input resistance connected across a circuit can cause?

  • ALoading error
  • BZero frequency
  • CInfinite source voltage
  • DNo effect under any condition
Report an error
Correct Answer: A. Loading error
Explanation: The voltmeter draws current and changes the effective circuit resistance, potentially altering the voltage being measured.
Reference: Standard measurements and instrumentation: loading effect
Question 803
Measurements & InstrumentationPotentiometers

A potentiometer is considered a null-type instrument because at balance it?

  • ADraws essentially no current from the source being measured through the detector branch
  • BAlways draws maximum current
  • CUses no reference voltage
  • DMeasures only resistance
Report an error
Correct Answer: A. Draws essentially no current from the source being measured through the detector branch
Explanation: At null balance there is no detector current, enabling accurate comparison without loading the measured source in the ideal case.
Reference: Standard measurements and instrumentation: potentiometers
Question 804
Measurements & InstrumentationPotentiometers

A DC potentiometer can be used to measure an unknown emf by?

  • AComparing it with a known reference under null condition
  • BMeasuring its frequency
  • CConverting it directly to inductance
  • DShort-circuiting the source
Report an error
Correct Answer: A. Comparing it with a known reference under null condition
Explanation: A potentiometer balances the unknown voltage against a calibrated potential drop derived from a reference.
Reference: Standard measurements and instrumentation: potentiometers
Question 806
Measurements & InstrumentationDC Bridges

A Kelvin double bridge is especially suitable for measuring?

  • AVery low resistance
  • BVery high frequency
  • CCapacitance only
  • DTemperature directly
Report an error
Correct Answer: A. Very low resistance
Explanation: The Kelvin double bridge minimizes errors due to lead and contact resistance, making it suitable for low-resistance measurement.
Reference: Standard measurements and instrumentation: dc bridges
Question 807
Measurements & InstrumentationAC Bridges

A Maxwell bridge is commonly used to measure an unknown?

  • AInductance
  • BCapacitance only
  • CFrequency only
  • DDC voltage
Report an error
Correct Answer: A. Inductance
Explanation: The Maxwell bridge determines an unknown inductance by comparison with known resistance and capacitance standards.
Reference: Standard measurements and instrumentation: ac bridges
Question 808
Measurements & InstrumentationAnalog Instruments

The deflecting torque of an ideal PMMC instrument is proportional to?

  • ACurrent through the moving coil
  • BSquare of current
  • CFrequency only
  • DResistance squared
Report an error
Correct Answer: A. Current through the moving coil
Explanation: With a uniform permanent-magnet field, PMMC deflecting torque is directly proportional to coil current.
Reference: Standard measurements and instrumentation: analog instruments
Question 809
Measurements & InstrumentationAC Bridges

A Schering bridge is commonly used for measurement of?

  • ACapacitance and dielectric loss
  • BInductance only
  • CDC current only
  • DMechanical displacement
Report an error
Correct Answer: A. Capacitance and dielectric loss
Explanation: The Schering bridge is widely used for capacitance measurement and evaluation of dielectric loss or dissipation factor.
Reference: Standard measurements and instrumentation: ac bridges
Question 810
Measurements & InstrumentationAnalog Instruments

A moving-iron instrument can normally be used for?

  • ABoth AC and DC
  • BDC only
  • CAC only above 1 MHz
  • DTemperature only
Report an error
Correct Answer: A. Both AC and DC
Explanation: Moving-iron torque depends approximately on the square of current, so its direction is independent of current polarity and it can measure AC or DC.
Reference: Standard measurements and instrumentation: analog instruments
Question 811
Measurements & InstrumentationAC Bridges

A Wien bridge is well known for measurement of?

  • AFrequency
  • BVery low resistance
  • CDC current
  • DMagnetic flux only
Report an error
Correct Answer: A. Frequency
Explanation: The Wien bridge uses frequency-dependent RC arms and is commonly used for audio-frequency measurement and oscillator circuits.
Reference: Standard measurements and instrumentation: ac bridges
Question 812
Measurements & InstrumentationAnalog Instruments

The scale of a PMMC instrument is approximately?

  • AUniform
  • BHighly logarithmic
  • CSquare-law crowded at upper end
  • DIndependent of current
Report an error
Correct Answer: A. Uniform
Explanation: Because deflection is proportional to current, a PMMC instrument has an approximately uniform scale.
Reference: Standard measurements and instrumentation: analog instruments
Question 813
Measurements & InstrumentationAnalog Instruments

The scale of a basic moving-iron instrument is generally?

  • ANon-uniform
  • BPerfectly uniform
  • CDigital
  • DLinear only at zero frequency
Report an error
Correct Answer: A. Non-uniform
Explanation: Moving-iron deflecting torque is nonlinear with current, so its scale is generally non-uniform and crowded near the lower end.
Reference: Standard measurements and instrumentation: analog instruments
Question 814
Measurements & InstrumentationRange Extension

To convert a sensitive galvanometer or meter movement into a higher-range ammeter, a low resistance is connected?

  • AIn parallel as a shunt
  • BIn series as a multiplier
  • CAcross the power supply only
  • DIn series with the load and meter separately
Report an error
Correct Answer: A. In parallel as a shunt
Explanation: A low-value shunt bypasses most of the measured current around the sensitive meter movement.
Reference: Standard measurements and instrumentation: range extension
Question 815
Measurements & InstrumentationRange Extension

To extend the voltage range of a voltmeter movement, a high resistance is connected?

  • AIn series with the movement
  • BIn parallel with the movement
  • CAcross the current source only
  • DIn parallel with a short circuit
Report an error
Correct Answer: A. In series with the movement
Explanation: A series multiplier resistance limits current through the meter movement at higher applied voltages.
Reference: Standard measurements and instrumentation: range extension
Question 817
Measurements & InstrumentationDigital Instruments

A 4-bit ideal ADC provides how many quantization levels?

  • A4
  • B8
  • C16
  • D32
Report an error
Correct Answer: C. 16
Explanation: An N-bit ADC provides 2^N ideal quantization codes; for N=4 this is 16 levels.
Reference: Standard measurements and instrumentation: digital instruments
Question 818
Measurements & InstrumentationAC Bridges

In an AC bridge at balance, the detector current is ideally?

  • AZero
  • BMaximum
  • CEqual to supply current
  • DAlways 1 A
Report an error
Correct Answer: A. Zero
Explanation: At bridge balance the detector terminals are at equal potential, so ideally no detector current flows.
Reference: Standard measurements and instrumentation: ac bridges
Question 822
Measurements & InstrumentationDigital Instruments

A 3.5-digit digital meter is commonly capable of displaying up to approximately?

  • A1999 counts
  • B999 counts
  • C9999 counts
  • D65535 counts
Report an error
Correct Answer: A. 1999 counts
Explanation: A conventional 3.5-digit display has three full digits plus a leading half digit that is typically 0 or 1, giving a maximum display around 1999.
Reference: Standard measurements and instrumentation: digital instruments
Question 823
Measurements & InstrumentationCRO & Oscilloscopes

In a conventional CRO, the vertical deflection system is primarily used to represent?

  • ASignal amplitude
  • BTime only
  • CPower factor only
  • DFrequency counter output only
Report an error
Correct Answer: A. Signal amplitude
Explanation: The input signal is normally applied to the vertical channel, so vertical displacement represents instantaneous signal voltage.
Reference: Standard measurements and instrumentation: cro & oscilloscopes
Question 825
Measurements & InstrumentationThree-Phase Measurement

For a balanced three-phase load at unity power factor, the two wattmeters in the two-wattmeter method ideally read?

  • AEqual positive values
  • BEqual and opposite values
  • COne zero and one negative
  • DBoth zero
Report an error
Correct Answer: A. Equal positive values
Explanation: At φ=0, W1=VLIL cos30° and W2=VLIL cos30°, so the readings are equal and positive.
Reference: Standard measurements and instrumentation: three-phase measurement
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Question 826
Measurements & InstrumentationCRO & Oscilloscopes

The time-base generator of a CRO normally produces a?

  • ASawtooth waveform
  • BPure DC level
  • CSquare-law current only
  • DRandom waveform
Report an error
Correct Answer: A. Sawtooth waveform
Explanation: A sawtooth or ramp voltage sweeps the electron beam horizontally at an approximately uniform rate.
Reference: Standard measurements and instrumentation: cro & oscilloscopes
Question 836
Measurements & InstrumentationDigital Oscilloscopes

A digital storage oscilloscope differs from a basic analog CRO mainly because it can?

  • ADigitize and store acquired waveforms
  • BMeasure only DC
  • COperate without any sampling
  • DDisplay no transient signals
Report an error
Correct Answer: A. Digitize and store acquired waveforms
Explanation: A DSO samples the input, converts it to digital data and stores the waveform for processing and display.
Reference: Standard measurements and instrumentation: digital oscilloscopes
Question 837
Measurements & InstrumentationInstrument Transformers

A current transformer is primarily used to?

  • AScale large AC current to a smaller measurable current
  • BIncrease DC voltage
  • CMeasure temperature
  • DGenerate radio frequency
Report an error
Correct Answer: A. Scale large AC current to a smaller measurable current
Explanation: A CT reproduces a scaled version of primary AC current for metering and protection.
Reference: Standard measurements and instrumentation: instrument transformers
Question 838
Measurements & InstrumentationInstrument Transformers

The secondary of an energized current transformer should generally not be?

  • AOpen-circuited
  • BConnected to its rated burden
  • CShorted through an ammeter of low impedance
  • DGrounded at one designated point where required
Report an error
Correct Answer: A. Open-circuited
Explanation: Opening an energized CT secondary can produce dangerously high secondary voltage and excessive core flux.
Reference: Standard measurements and instrumentation: instrument transformers
Question 839
Measurements & InstrumentationInstrument Transformers

A potential transformer is used mainly to?

  • AStep down high AC voltage for measurement and protection
  • BMeasure only resistance
  • CConvert DC current to AC
  • DIncrease current for welding
Report an error
Correct Answer: A. Step down high AC voltage for measurement and protection
Explanation: A PT/VT provides an accurately scaled lower voltage for instruments and protective relays.
Reference: Standard measurements and instrumentation: instrument transformers
Question 841
Measurements & InstrumentationPower Measurement

A single-phase electrodynamometer wattmeter measures?

  • AReal power
  • BReactive power only
  • CFrequency only
  • DResistance only
Report an error
Correct Answer: A. Real power
Explanation: A wattmeter's average deflecting torque is proportional to the average product of voltage and current, corresponding to real power.
Reference: Standard measurements and instrumentation: power measurement
Question 845
Measurements & InstrumentationSignal Conditioning

An instrumentation amplifier is especially useful for sensor signals because it typically provides?

  • AHigh input impedance and high common-mode rejection
  • BVery low input impedance and zero gain
  • COnly digital output
  • DNo differential amplification
Report an error
Correct Answer: A. High input impedance and high common-mode rejection
Explanation: Instrumentation amplifiers are designed for accurate amplification of small differential signals in the presence of common-mode voltage.
Reference: Standard measurements and instrumentation: signal conditioning
Question 846
Measurements & InstrumentationData Acquisition

A low-pass anti-aliasing filter is placed before an ADC mainly to?

  • ALimit input bandwidth before sampling
  • BIncrease aliasing
  • CConvert digital data to analog
  • DGenerate quantization levels
Report an error
Correct Answer: A. Limit input bandwidth before sampling
Explanation: The filter attenuates frequency components that could fold into the sampled baseband and cause aliasing.
Reference: Standard measurements and instrumentation: data acquisition
Question 847
Measurements & InstrumentationData Acquisition

An ideal 10-bit ADC has how many output codes?

  • A256
  • B512
  • C1024
  • D2048
Report an error
Correct Answer: C. 1024
Explanation: An N-bit ADC provides 2^N codes, so 2^10=1024.
Reference: Standard measurements and instrumentation: data acquisition
Question 848
Measurements & InstrumentationData Acquisition

A sample-and-hold circuit in a data-acquisition system is used to?

  • AHold the analog input approximately constant during conversion
  • BGenerate random samples
  • CEliminate the ADC
  • DConvert digital output to AC power
Report an error
Correct Answer: A. Hold the analog input approximately constant during conversion
Explanation: The hold capacitor maintains the sampled input level while the ADC completes conversion.
Reference: Standard measurements and instrumentation: data acquisition
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Question 855
Measurements & InstrumentationADC & Data Acquisition

A successive-approximation ADC determines the digital code primarily by?

  • ABinary search
  • BCounting down from infinity
  • CFrequency multiplication only
  • DAnalog integration without comparison
Report an error
Correct Answer: A. Binary search
Explanation: A SAR ADC tests bits from MSB to LSB using a comparator and internal DAC, effectively performing a binary search.
Reference: Standard measurements and instrumentation: adc & data acquisition
Question 856
Measurements & InstrumentationADC & Data Acquisition

A flash ADC is known for high conversion speed because it uses?

  • AMany comparators operating in parallel
  • BOne comparator in a long serial search
  • CA mechanical pointer
  • DA Wheatstone bridge only
Report an error
Correct Answer: A. Many comparators operating in parallel
Explanation: A flash ADC compares the input against many reference levels simultaneously, giving very fast conversion.
Reference: Standard measurements and instrumentation: adc & data acquisition
Question 857
Measurements & InstrumentationSignal Conditioning

A CMRR of 10000 expressed in decibels is?

  • A40 dB
  • B60 dB
  • C80 dB
  • D100 dB
Report an error
Correct Answer: C. 80 dB
Explanation: CMRR(dB)=20log10(10000)=20×4=80 dB.
Reference: Standard measurements and instrumentation: signal conditioning
Question 858
Measurements & InstrumentationAdvanced Measurement

A true-RMS voltmeter is valuable for nonsinusoidal waveforms because it measures a quantity related to?

  • AHeating or power-equivalent value
  • BPeak value only
  • CAverage value with no waveform dependence
  • DFrequency only
Report an error
Correct Answer: A. Heating or power-equivalent value
Explanation: RMS is the effective value that produces the same heating effect in a resistor as an equivalent DC value.
Reference: Standard measurements and instrumentation: advanced measurement
Question 860
Measurements & InstrumentationDynamic Characteristics

A smaller time constant in a first-order measuring instrument generally means?

  • AFaster response
  • BSlower response
  • CLower static sensitivity necessarily
  • DInfinite hysteresis
Report an error
Correct Answer: A. Faster response
Explanation: A smaller time constant causes the exponential transient to decay more quickly, producing a faster response.
Reference: Standard measurements and instrumentation: dynamic characteristics
Question 861
Measurements & InstrumentationDynamic Characteristics

The term dead time in an instrument refers to?

  • AA delay before the output begins responding to an input change
  • BThe final steady-state error only
  • CThe calibration interval
  • DThe full-scale value
Report an error
Correct Answer: A. A delay before the output begins responding to an input change
Explanation: Dead time is the interval between an input change and the beginning of the observable output response.
Reference: Standard measurements and instrumentation: dynamic characteristics
Question 862
Measurements & InstrumentationDynamic Characteristics

A zero-order instrument ideally produces an output that is?

  • AInstantaneously proportional to the input
  • BAlways delayed by one time constant
  • CAlways oscillatory
  • DIndependent of input
Report an error
Correct Answer: A. Instantaneously proportional to the input
Explanation: An ideal zero-order instrument has no dynamic energy-storage effect and follows the input proportionally without dynamic lag.
Reference: Standard measurements and instrumentation: dynamic characteristics
Question 863
Measurements & InstrumentationDynamic Characteristics

For a first-order instrument described by T dy/dt + y = Kx, K represents the?

  • AStatic sensitivity or gain
  • BTime constant
  • CDamping ratio
  • DNatural frequency
Report an error
Correct Answer: A. Static sensitivity or gain
Explanation: At steady state dy/dt=0, so y=Kx; therefore K is the static gain or sensitivity.
Reference: Standard measurements and instrumentation: dynamic characteristics
Question 864
Measurements & InstrumentationTransducers

A piezoelectric transducer is particularly suitable for measurement of?

  • ADynamic force, pressure or vibration
  • BTrue static displacement over indefinitely long periods
  • CDC resistance only
  • DHumidity only
Report an error
Correct Answer: A. Dynamic force, pressure or vibration
Explanation: Piezoelectric sensors generate charge under mechanical stress and are especially suited to dynamic measurements; charge leakage limits true static measurement.
Reference: Standard measurements and instrumentation: transducers
Question 865
Measurements & InstrumentationTransducers

A Hall-effect sensor is commonly used to sense?

  • AMagnetic field
  • BHumidity only
  • CAcoustic pressure only
  • DChemical pH only
Report an error
Correct Answer: A. Magnetic field
Explanation: The Hall effect produces a transverse voltage in a current-carrying material subjected to a magnetic field.
Reference: Standard measurements and instrumentation: transducers
Question 867
Measurements & InstrumentationTransducers

An inductive proximity sensor is commonly used for detecting?

  • AMetallic objects
  • BOnly transparent liquids
  • COnly temperature
  • DOnly light intensity
Report an error
Correct Answer: A. Metallic objects
Explanation: Inductive proximity sensors generate electromagnetic fields and detect changes caused primarily by nearby conductive metallic targets.
Reference: Standard measurements and instrumentation: transducers
Question 868
Measurements & InstrumentationIndustrial Instrumentation

In a 4-20 mA industrial current loop, the value 4 mA commonly represents?

  • ALive zero or lower-range value
  • BFull-scale value
  • CPower failure by definition
  • DExactly 25% of every physical quantity
Report an error
Correct Answer: A. Live zero or lower-range value
Explanation: The 4 mA lower endpoint is a live zero, helping distinguish a valid minimum reading from certain fault conditions such as an open loop.
Reference: Standard measurements and instrumentation: industrial instrumentation
Question 871
Measurements & InstrumentationSignal Conditioning

Common-mode rejection ratio of an instrumentation amplifier is the ratio of?

  • ADifferential gain to common-mode gain
  • BCommon-mode gain to differential gain
  • COutput resistance to input resistance
  • DBandwidth to gain
Report an error
Correct Answer: A. Differential gain to common-mode gain
Explanation: CMRR=Ad/Acm and indicates how strongly the amplifier rejects signals common to both inputs.
Reference: Standard measurements and instrumentation: signal conditioning
Question 873
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 875
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
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Question 876
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 879
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 882
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 883
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 884
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 887
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 888
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 889
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
Question 900
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
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