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RRB MCQs

Practice RRB-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 & InstrumentationMeasurement Errors

The difference between a measured value and the true value is called?

AError
BPrecision
CResolution
DSpan

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Correct Answer: A. Error

Explanation: Measurement error is the deviation of the measured result from the true or accepted reference value.

Reference: Standard measurements and instrumentation: measurement errors

Question 802

Measurements & InstrumentationMeasurement Errors

If the true voltage is 100 V and an instrument reads 98 V, the signed measurement error (measured minus true) is?

A+2 V
B-2 V
C+98 V
D-98 V

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Correct Answer: B. -2 V

Explanation: Error = measured value - true value = 98 - 100 = -2 V.

Reference: Standard measurements and instrumentation: measurement errors

Question 803

Measurements & InstrumentationMeasurement Errors

For a true value of 100 V and a measured value of 98 V, the magnitude of percentage error relative to the true value is?

A1%
B2%
C98%
D102%

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Correct Answer: B. 2%

Explanation: Absolute error magnitude is 2 V, so percentage error = (2/100)×100 = 2%.

Reference: Standard measurements and instrumentation: measurement errors

Question 804

Measurements & InstrumentationMeasurement Errors

An error that remains approximately constant or changes predictably and can often be corrected by calibration is generally classified as?

ASystematic error
BRandom error
CGross error only
DQuantization noise only

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Correct Answer: A. Systematic error

Explanation: Systematic errors have identifiable, repeatable causes such as calibration or environmental effects and can often be compensated.

Reference: Standard measurements and instrumentation: measurement errors

Question 805

Measurements & InstrumentationMeasurement Errors

Unpredictable variations in repeated measurements are commonly called?

ARandom errors
BSystematic errors
CZero errors only
DScale factors

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Correct Answer: A. Random errors

Explanation: Random errors vary irregularly due to uncontrollable or statistical influences.

Reference: Standard measurements and instrumentation: measurement errors

Question 806

Measurements & InstrumentationMeasurement Errors

A gross error in measurement is most commonly associated with?

AHuman mistakes such as incorrect reading or recording
BFundamental thermal noise only
CPerfect calibration
DInfinite resolution

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Correct Answer: A. Human mistakes such as incorrect reading or recording

Explanation: Gross errors typically arise from mistakes in observation, recording, setup or calculation.

Reference: Standard measurements and instrumentation: measurement errors

Question 807

Measurements & InstrumentationCalibration

Calibration of an instrument means comparing its indication with?

AA known reference standard
BAn unknown load
CA random waveform
DOnly its own previous reading

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Correct Answer: A. A known reference standard

Explanation: Calibration establishes the relationship between an instrument's indication and values provided by suitable standards.

Reference: Standard measurements and instrumentation: calibration

Question 808

Measurements & InstrumentationInstrument Characteristics

The range of an instrument refers to?

AThe interval between minimum and maximum measurable input values
BOnly the maximum value
COnly the minimum value
DThe number of internal components

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Correct Answer: A. The interval between minimum and maximum measurable input values

Explanation: Range specifies the limits over which the instrument is intended to measure.

Reference: Standard measurements and instrumentation: instrument characteristics

Question 809

Measurements & InstrumentationMeasurement Fundamentals

Measurement is the process of comparing an unknown quantity with?

AAn accepted standard
BA random signal
COnly a digital display
DA power supply

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Correct Answer: A. An accepted standard

Explanation: Measurement determines the magnitude of a quantity by comparison with an accepted reference or standard.

Reference: Standard measurements and instrumentation: measurement fundamentals

Question 810

Measurements & InstrumentationMeasurement Fundamentals

The closeness of a measured value to the true or accepted value is called?

AAccuracy
BPrecision
CResolution
DSensitivity

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Correct Answer: A. Accuracy

Explanation: Accuracy describes how close a measurement is to the true or accepted reference value.

Reference: Standard measurements and instrumentation: measurement fundamentals

Question 811

Measurements & InstrumentationTemperature Measurement

A thermocouple operates primarily on the?

ASeebeck effect
BHall effect
CPhotoelectric effect only
DPiezoelectric effect

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Correct Answer: A. Seebeck effect

Explanation: A thermocouple generates a thermoelectric emf due to a temperature difference between junctions, known as the Seebeck effect.

Reference: Standard measurements and instrumentation: temperature measurement

Question 812

Measurements & InstrumentationTemperature Measurement

A thermistor is a temperature-sensitive device whose primary electrical property is?

AResistance
BInductance only
CCapacitance only
DFrequency only

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Correct Answer: A. Resistance

Explanation: A thermistor has resistance that changes strongly with temperature.

Reference: Standard measurements and instrumentation: temperature measurement

Question 813

Measurements & InstrumentationDisplacement Measurement

An LVDT is primarily used to measure?

ALinear displacement
BTemperature
CHumidity only
DOptical wavelength

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Correct Answer: A. Linear displacement

Explanation: A Linear Variable Differential Transformer converts linear displacement into an electrical output.

Reference: Standard measurements and instrumentation: displacement measurement

Question 814

Measurements & InstrumentationStrain Measurement

A strain gauge is commonly used to measure strain through a change in?

AElectrical resistance
BMagnetic permeability only
COptical frequency only
DBattery voltage only

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Correct Answer: A. Electrical resistance

Explanation: Mechanical strain changes the gauge's dimensions and therefore its electrical resistance.

Reference: Standard measurements and instrumentation: strain measurement

Question 815

Measurements & InstrumentationStrain Measurement

The gauge factor of a resistive strain gauge is defined as?

AFractional change in resistance divided by strain
BStrain divided by resistance
CResistance multiplied by strain
DVoltage divided by current

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Correct Answer: A. Fractional change in resistance divided by strain

Explanation: Gauge factor GF=(ΔR/R)/ε, where ε is mechanical strain.

Reference: Standard measurements and instrumentation: strain measurement

Question 816

Measurements & InstrumentationBridge Measurements

A Wheatstone bridge is widely used for precise measurement of?

AResistance or small resistance changes
BFrequency only
CInductance only
DOptical power only

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Correct Answer: A. Resistance or small resistance changes

Explanation: The Wheatstone bridge compares resistance ratios and is widely used with resistive sensors such as strain gauges.

Reference: Standard measurements and instrumentation: bridge measurements

Question 817

Measurements & InstrumentationBridge Measurements

For a balanced Wheatstone bridge with arms P, Q, R and S arranged in the standard ratio form, the balance condition is?

AP/Q = R/S
BP+Q = R+S always
CPQ = R+S
DP/R = Q+S

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Correct Answer: A. P/Q = R/S

Explanation: At balance, no detector current flows and the bridge arm ratios satisfy P/Q=R/S (equivalently PS=QR).

Reference: Standard measurements and instrumentation: bridge measurements

Question 818

Measurements & InstrumentationInstrument Characteristics

For an instrument having a measurement range of 0 to 100 V, the span is?

A0 V
B50 V
C100 V
D200 V

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Correct Answer: C. 100 V

Explanation: Span is upper range value minus lower range value: 100-0=100 V.

Reference: Standard measurements and instrumentation: instrument characteristics

Question 819

Measurements & InstrumentationInstrument Characteristics

Hysteresis in an instrument means that, for the same input, the output may depend on?

AWhether the input was approached from increasing or decreasing direction
BOnly the power-supply frequency
COnly the display color
DThe number of terminals

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Correct Answer: A. Whether the input was approached from increasing or decreasing direction

Explanation: Hysteresis causes different indications for the same input depending on the previous direction of input change.

Reference: Standard measurements and instrumentation: instrument characteristics

Question 820

Measurements & InstrumentationInstrument Characteristics

Instrument drift refers to?

AA gradual change in indication with time when the measured quantity is unchanged
BAn instantaneous perfect response
CA deliberate range selection
DA fixed unit conversion

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Correct Answer: A. A gradual change in indication with time when the measured quantity is unchanged

Explanation: Drift is an undesired gradual change in instrument output with time despite an unchanged input.

Reference: Standard measurements and instrumentation: instrument characteristics

Question 821

Measurements & InstrumentationTransducers

A transducer converts?

AA physical quantity from one form into a corresponding usable signal
BAC power directly into mechanical work only
COnly digital data into text
DOnly resistance into heat

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Correct Answer: A. A physical quantity from one form into a corresponding usable signal

Explanation: In instrumentation, a transducer converts a measurand into another form, commonly an electrical signal suitable for measurement or processing.

Reference: Standard measurements and instrumentation: transducers

Question 822

Measurements & InstrumentationTemperature Measurement

Which device is commonly used as a temperature transducer based on resistance change of a metal?

ARTD
BLVDT
CStrain gauge only
DTachogenerator

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Correct Answer: A. RTD

Explanation: An RTD measures temperature through the predictable change of a metal's electrical resistance.

Reference: Standard measurements and instrumentation: temperature measurement

Question 823

Measurements & InstrumentationAnalog Instruments

A PMMC instrument is primarily suitable for direct measurement of?

ADC only
BAC only
CBoth AC and DC without any additional circuit
DMicrowave frequency only

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Correct Answer: A. DC only

Explanation: A PMMC movement responds to the average value and reverses torque with current direction, so it is inherently suited to DC. AC measurement requires rectification.

Reference: Standard measurements and instrumentation: analog instruments

Question 824

Measurements & InstrumentationLoading Effect

An ideal ammeter should have internal resistance of?

AZero
BInfinite
C1 kohm
DEqual to load resistance

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Correct Answer: A. Zero

Explanation: An ammeter is connected in series, so ideally its resistance is zero to avoid altering circuit current.

Reference: Standard measurements and instrumentation: loading effect

Question 825

Measurements & InstrumentationLoading Effect

An ideal voltmeter should have internal resistance of?

AZero
BInfinite
CEqual to source resistance
DOne ohm

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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 826

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

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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 827

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

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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 828

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

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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 829

Measurements & InstrumentationDC Bridges

A Wheatstone bridge has P=100 ohm, Q=200 ohm and R=150 ohm. For balance, S must be?

A75 ohm
B150 ohm
C300 ohm
D450 ohm

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Correct Answer: C. 300 ohm

Explanation: At balance P/Q=R/S. Thus 100/200=150/S, giving S=300 ohm.

Reference: Standard measurements and instrumentation: dc bridges

Question 830

Measurements & InstrumentationDC Bridges

A Kelvin double bridge is especially suitable for measuring?

AVery low resistance
BVery high frequency
CCapacitance only
DTemperature directly

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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 831

Measurements & InstrumentationAC Bridges

A Maxwell bridge is commonly used to measure an unknown?

AInductance
BCapacitance only
CFrequency only
DDC voltage

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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 832

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

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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 833

Measurements & InstrumentationAC Bridges

A Schering bridge is commonly used for measurement of?

ACapacitance and dielectric loss
BInductance only
CDC current only
DMechanical displacement

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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 834

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

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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 835

Measurements & InstrumentationAC Bridges

A Wien bridge is well known for measurement of?

AFrequency
BVery low resistance
CDC current
DMagnetic flux only

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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 836

Measurements & InstrumentationAnalog Instruments

The scale of a PMMC instrument is approximately?

AUniform
BHighly logarithmic
CSquare-law crowded at upper end
DIndependent of current

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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 837

Measurements & InstrumentationAnalog Instruments

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

ANon-uniform
BPerfectly uniform
CDigital
DLinear only at zero frequency

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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 838

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

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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 839

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

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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 840

Measurements & InstrumentationRange Extension

A meter movement has full-scale current 1 mA and internal resistance 100 ohm. What series resistance is required for a 10 V voltmeter range?

A900 ohm
B9.9 kohm
C10 kohm
D100 kohm

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Correct Answer: B. 9.9 kohm

Explanation: Total resistance required is V/I=10/0.001=10 kohm. Subtracting the 100 ohm movement resistance gives 9.9 kohm.

Reference: Standard measurements and instrumentation: range extension

Question 841

Measurements & InstrumentationRange Extension

A 1 mA, 100 ohm meter movement is to measure 1 A full scale. The required shunt resistance is approximately?

A0.100 ohm
B1.00 ohm
C10 ohm
D100 ohm

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Correct Answer: A. 0.100 ohm

Explanation: Meter voltage at full scale is 0.001×100=0.1 V. Shunt current is 0.999 A, so Rsh=0.1/0.999≈0.100 ohm.

Reference: Standard measurements and instrumentation: range extension

Question 842

Measurements & InstrumentationAC Bridges

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

AZero
BMaximum
CEqual to supply current
DAlways 1 A

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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 843

Measurements & InstrumentationMeasurement Errors

An unknown resistance is measured as 50.0 ohm with a possible absolute error of ±0.5 ohm. The maximum relative error is?

A±0.1%
B±1%
C±5%
D±10%

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Correct Answer: B. ±1%

Explanation: Relative error magnitude = 0.5/50=0.01, or 1%.

Reference: Standard measurements and instrumentation: measurement errors

Question 844

Measurements & InstrumentationMeasurement Errors

A voltmeter has an accuracy specification of ±1% of full scale on a 100 V range. The maximum absolute error is?

A±0.1 V
B±1 V
C±10 V
D±100 V

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Correct Answer: B. ±1 V

Explanation: One percent of the 100 V full-scale value is 1 V.

Reference: Standard measurements and instrumentation: measurement errors

Question 845

Measurements & InstrumentationMeasurement Errors

On a 100 V range with accuracy ±1% of full scale, a reading of 20 V may have a maximum percentage error relative to the reading of?

A1%
B2%
C5%
D20%

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Correct Answer: C. 5%

Explanation: Maximum absolute error remains 1 V; relative to a 20 V reading this is (1/20)×100=5%.

Reference: Standard measurements and instrumentation: measurement errors

Question 846

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

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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 847

Measurements & InstrumentationDigital Instruments

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

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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 848

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

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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 849

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

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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

Question 850

Measurements & InstrumentationCRO & Oscilloscopes

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

ASawtooth waveform
BPure DC level
CSquare-law current only
DRandom waveform

Show AnswerHide Answer 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 851

Measurements & InstrumentationEnergy Measurement

An induction-type energy meter commonly measures electrical energy in?

AkWh
BkW only
CkVAR only
DHz

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Correct Answer: A. kWh

Explanation: Consumer energy meters integrate power over time and commonly register energy in kilowatt-hours.

Reference: Standard measurements and instrumentation: energy measurement

Question 852

Measurements & InstrumentationCRO & Oscilloscopes

If one cycle of a waveform occupies 4 horizontal divisions at 0.5 ms/div, its period is?

A0.5 ms
B1 ms
C2 ms
D4 ms

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Correct Answer: C. 2 ms

Explanation: T=4 divisions × 0.5 ms/div = 2 ms.

Reference: Standard measurements and instrumentation: cro & oscilloscopes

Question 853

Measurements & InstrumentationEnergy Measurement

A 2 kW load operates for 3 hours. The energy consumed is?

A0.667 kWh
B5 kWh
C6 kWh
D9 kWh

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Correct Answer: C. 6 kWh

Explanation: Energy=P×t=2 kW×3 h=6 kWh.

Reference: Standard measurements and instrumentation: energy measurement

Question 854

Measurements & InstrumentationCRO & Oscilloscopes

A waveform has a period of 2 ms. Its frequency is?

A50 Hz
B200 Hz
C500 Hz
D2 kHz

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Correct Answer: C. 500 Hz

Explanation: f=1/T=1/0.002=500 Hz.

Reference: Standard measurements and instrumentation: cro & oscilloscopes

Question 855

Measurements & InstrumentationTransducer Numericals

An LVDT has sensitivity 2 mV/V/mm and is excited by 5 V. For a displacement of 3 mm, the output magnitude is?

A3 mV
B10 mV
C30 mV
D300 mV

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Correct Answer: C. 30 mV

Explanation: Output=2 mV/V/mm × 5 V × 3 mm=30 mV.

Reference: Standard measurements and instrumentation: transducer numericals

Question 856

Measurements & InstrumentationCRO & Oscilloscopes

A sine wave measures 6 vertical divisions peak-to-peak on a CRO set to 2 V/div. Its peak-to-peak voltage is?

A3 V
B6 V
C12 V
D24 V

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Correct Answer: C. 12 V

Explanation: Vpp=6 divisions × 2 V/div = 12 V.

Reference: Standard measurements and instrumentation: cro & oscilloscopes

Question 857

Measurements & InstrumentationStrain Gauge

A strain gauge has gauge factor 2.0 and is subjected to strain 500 microstrain. The fractional resistance change ΔR/R is?

A0.00025
B0.001
C0.002
D0.01

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Correct Answer: B. 0.001

Explanation: ΔR/R=GF×strain=2×500×10^-6=0.001.

Reference: Standard measurements and instrumentation: strain gauge

Question 858

Measurements & InstrumentationCRO & Oscilloscopes

For a 12 V peak-to-peak sine wave, the peak value is?

A3 V
B6 V
C8.49 V
D12 V

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Correct Answer: B. 6 V

Explanation: For a symmetrical sine wave, Vp=Vpp/2=6 V.

Reference: Standard measurements and instrumentation: cro & oscilloscopes

Question 859

Measurements & InstrumentationCRO & Oscilloscopes

For a sinusoid with peak value 10 V, the RMS value is approximately?

A5 V
B7.07 V
C10 V
D14.14 V

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Correct Answer: B. 7.07 V

Explanation: For a sine wave, Vrms=Vp/√2≈10/1.414=7.07 V.

Reference: Standard measurements and instrumentation: cro & oscilloscopes

Question 860

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

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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 861

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

Show AnswerHide Answer 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 862

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

Show AnswerHide Answer 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 863

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

Show AnswerHide Answer 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 864

Measurements & InstrumentationInstrument Transformers

A CT has a ratio of 200/5 A. If its secondary current is 4 A, the corresponding ideal primary current is?

A40 A
B80 A
C160 A
D200 A

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Correct Answer: C. 160 A

Explanation: The ratio is 200/5=40, so primary current=40×4=160 A.

Reference: Standard measurements and instrumentation: instrument transformers

Question 865

Measurements & InstrumentationPower Measurement

A single-phase electrodynamometer wattmeter measures?

AReal power
BReactive power only
CFrequency only
DResistance only

Show AnswerHide Answer 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 866

Measurements & InstrumentationPower Measurement

For a single-phase sinusoidal circuit, real power is?

AVI cosφ
BVI sinφ
CV/I
DI²/V

Show AnswerHide Answer Report an error

Correct Answer: A. VI cosφ

Explanation: Real power is P=Vrms Irms cosφ.

Reference: Standard measurements and instrumentation: power measurement

Question 867

Measurements & InstrumentationPower Measurement

A 230 V load draws 10 A at power factor 0.8. Its real power is?

A1.84 kW
B2.30 kW
C2.875 kW
D18.4 kW

Show AnswerHide Answer Report an error

Correct Answer: A. 1.84 kW

Explanation: P=230×10×0.8=1840 W=1.84 kW.

Reference: Standard measurements and instrumentation: power measurement

Question 868

Measurements & InstrumentationThree-Phase Measurement

In the two-wattmeter method for a balanced three-phase load, total real power equals?

AW1+W2
BW1-W2 always
CW1×W2
D(W1+W2)/2

Show AnswerHide Answer Report an error

Correct Answer: A. W1+W2

Explanation: The algebraic sum of the two wattmeter readings gives total three-phase real power.

Reference: Standard measurements and instrumentation: three-phase measurement

Question 869

Measurements & InstrumentationStrain Gauge

For a 120 ohm strain gauge with gauge factor 2 and strain 500 microstrain, the resistance change is?

A0.012 ohm
B0.12 ohm
C1.2 ohm
D12 ohm

Show AnswerHide Answer Report an error

Correct Answer: B. 0.12 ohm

Explanation: ΔR=R×GF×strain=120×2×500×10^-6=0.12 ohm.

Reference: Standard measurements and instrumentation: strain gauge

Question 870

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

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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 871

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

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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 872

Measurements & InstrumentationData Acquisition

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

A256
B512
C1024
D2048

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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 873

Measurements & InstrumentationData Acquisition

According to the sampling theorem, a signal band-limited to 4 kHz requires a sampling frequency of at least?

A2 kHz
B4 kHz
C8 kHz
D16 kHz

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Correct Answer: C. 8 kHz

Explanation: The Nyquist rate is twice the highest signal frequency, so at least 8 kHz is required ideally.

Reference: Standard measurements and instrumentation: data acquisition

Question 874

Measurements & InstrumentationDynamic Characteristics

A first-order low-pass sensor has a time constant of 0.2 s. After a step input, it reaches about 63.2% of its final change after?

A0.1 s
B0.2 s
C0.4 s
D1 s

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Correct Answer: B. 0.2 s

Explanation: A first-order system reaches 1-e^-1≈63.2% of its final change after one time constant.

Reference: Standard measurements and instrumentation: dynamic characteristics

Question 875

Measurements & InstrumentationADC & Data Acquisition

For an ideal 8-bit ADC with a 0 to 5.12 V input range, the nominal LSB step size using 5.12/256 is?

A10 mV
B20 mV
C40 mV
D50 mV

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Correct Answer: B. 20 mV

Explanation: An 8-bit ADC has 256 code intervals in the common idealized calculation, so 5.12/256=0.02 V=20 mV.

Reference: Standard measurements and instrumentation: adc & data acquisition

Question 876

Measurements & InstrumentationADC & Data Acquisition

For an ideal 12-bit ADC, the number of possible digital output codes is?

A1024
B2048
C4096
D8192

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Correct Answer: C. 4096

Explanation: A 12-bit converter has 2^12=4096 possible output codes.

Reference: Standard measurements and instrumentation: adc & data acquisition

Question 877

Measurements & InstrumentationADC & Data Acquisition

Increasing ADC resolution from 8 bits to 10 bits increases the number of output codes by a factor of?

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Correct Answer: B. 4

Explanation: 2^10/2^8=4, so the number of codes becomes four times larger.

Reference: Standard measurements and instrumentation: adc & data acquisition

Question 878

Measurements & InstrumentationADC & Data Acquisition

The maximum ideal quantization error magnitude for a uniform ADC is commonly approximately?

A1 LSB
B1/2 LSB
C2 LSB
DZero for every input

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Correct Answer: B. 1/2 LSB

Explanation: For ideal rounding quantization, the error is bounded approximately by ±0.5 LSB.

Reference: Standard measurements and instrumentation: adc & data acquisition

Question 879

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

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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 880

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

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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 881

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

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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

Question 882

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

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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 883

Measurements & InstrumentationAdvanced Measurement

For a symmetrical square wave alternating between +10 V and -10 V, the RMS voltage is?

A5 V
B7.07 V
C10 V
D20 V

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Correct Answer: C. 10 V

Explanation: The square of the waveform is constantly 100 V², so its mean square is 100 and Vrms=10 V.

Reference: Standard measurements and instrumentation: advanced measurement

Question 884

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

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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 885

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

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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 886

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

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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 887

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

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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 888

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

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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 889

Measurements & InstrumentationTransducers

A Hall-effect sensor is commonly used to sense?

AMagnetic field
BHumidity only
CAcoustic pressure only
DChemical pH only

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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 890

Measurements & InstrumentationTransducers

A capacitive transducer can measure displacement by converting motion into a change in?

ACapacitance
BOnly resistance
COnly frequency independent of circuitry
DMagnetic flux only

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Correct Answer: A. Capacitance

Explanation: Displacement can change plate area, separation or dielectric properties, thereby changing capacitance.

Reference: Standard measurements and instrumentation: transducers

Question 891

Measurements & InstrumentationTransducers

An inductive proximity sensor is commonly used for detecting?

AMetallic objects
BOnly transparent liquids
COnly temperature
DOnly light intensity

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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 892

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

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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 893

Measurements & InstrumentationIndustrial Instrumentation

For a linear 4-20 mA transmitter calibrated for 0-100 °C, an output of 12 mA corresponds to?

A25 °C
B50 °C
C75 °C
D100 °C

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Correct Answer: B. 50 °C

Explanation: 12 mA is halfway between 4 and 20 mA, so it represents 50% of span, or 50 °C.

Reference: Standard measurements and instrumentation: industrial instrumentation

Question 894

Measurements & InstrumentationIndustrial Instrumentation

A 4-20 mA pressure transmitter covers 0-200 kPa. What current ideally represents 150 kPa?

A8 mA
B12 mA
C16 mA
D20 mA

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Correct Answer: C. 16 mA

Explanation: 150/200=0.75 of span. Current=4 mA+0.75×16 mA=16 mA.

Reference: Standard measurements and instrumentation: industrial instrumentation

Question 895

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

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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 896

Measurements & InstrumentationSignal Conditioning

If an instrumentation amplifier has differential gain 1000 and common-mode gain 0.1, its CMRR is?

A100
B1000
C10000
D100000

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Correct Answer: C. 10000

Explanation: CMRR=Ad/Acm=1000/0.1=10000.

Reference: Standard measurements and instrumentation: signal conditioning

Question 897

Measurements & InstrumentationSignal Conditioning

A CMRR of 10000 expressed in decibels is?

A40 dB
B60 dB
C80 dB
D100 dB

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Correct Answer: C. 80 dB

Explanation: CMRR(dB)=20log10(10000)=20×4=80 dB.

Reference: Standard measurements and instrumentation: signal conditioning

Question 898

Electromagnetic TheoryGauss's Law

A closed Gaussian surface encloses no net charge. The net electric flux of D through the surface is?

AZero
BAlways positive
CAlways negative
DInfinite

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Correct Answer: A. Zero

Explanation: By Gauss's law, zero enclosed net charge gives zero net flux.

Reference: Standard electromagnetic theory: gauss's law

Question 899

Electromagnetic TheoryElectrostatics Fundamentals

The SI unit of electric charge is?

ACoulomb
BVolt
CAmpere per metre
DWeber

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Correct Answer: A. Coulomb

Explanation: The coulomb (C) is the SI unit of electric charge.

Reference: Standard electromagnetic theory: electrostatics fundamentals

Question 900

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

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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