Electrical Measurements and Instrumentation MCQs (Part-9)
What is the primary function of a dynamometer-type wattmeter?
A Measure energy
B Measure average power in AC and DC circuits
C Measure instantaneous power
D Measure voltage
Dynamometer wattmeters measure average power in AC and DC circuits by utilizing the interaction of magnetic fields produced by fixed and moving coils.
What is the working principle of an energy meter?
A Piezoelectric effect
B Electromagnetic induction
C Magnetic deflection
D Electrostatic attraction
Energy meters use electromagnetic induction to drive a rotating disk proportional to power consumption, measuring total energy over time.
Which type of transducer converts pressure into an electrical signal?
A Thermocouple
B Piezoelectric transducer
C LVDT
D Strain gauge
Piezoelectric transducers generate electrical signals when subjected to mechanical pressure, using the piezoelectric effect.
What is the typical range of a household energy meter?
A 0–100 kWh
B 0–1,000 kWh
C 0–10,000 kWh
D 0–50,000 kWh
Energy meters in households typically measure energy consumption up to 10,000 kWh or more.
Which instrument measures the angular velocity of a rotating shaft?
A Tachometer
B Multimeter
C Frequency meter
D Galvanometer
Tachometers measure the rotational speed or angular velocity of a rotating object, usually in revolutions per minute (RPM).
What is the purpose of an Anderson bridge?
A Measure capacitance
B Measure inductance
C Measure resistance
D Measure voltage
Anderson bridge is a type of AC bridge used for precise measurement of inductance in electrical systems.
What type of error arises due to drift in the components of an instrument?
A Random error
B Systematic error
C Gross error
D Instrumental error
Instrumental errors occur due to issues like drift, aging, or manufacturing defects in the instrument components.
Which transducer is best for displacement measurement?
A Strain gauge
B Thermistor
C LVDT
D Tachometer
Linear Variable Differential Transformers (LVDTs) are precise transducers used for measuring linear displacement based on changes in inductance.
What does a phase meter measure?
A Voltage
B Frequency
C Phase angle between two AC signals
D Current
Phase meters measure the angular phase difference between two AC signals, typically expressed in degrees.
What is the principle of operation of a Hall-effect sensor?
A Electromagnetic induction
B Voltage induced by magnetic field
C Current-induced magnetic field
D Resistance change due to strain
Hall-effect sensors operate on the principle of generating a voltage when a current-carrying conductor is placed in a perpendicular magnetic field.
What does a Kelvin bridge measure?
A Low resistance
B High resistance
C Inductance
D Capacitance
Kelvin bridges are designed to measure very low resistances accurately by compensating for lead and contact resistances.
What does a potentiometer measure?
A Voltage
B Current
C Resistance
D Capacitance
Potentiometers measure an unknown voltage by comparing it to a known reference voltage.
Which sensor uses the Seebeck effect?
A Thermistor
B Thermocouple
C Piezoelectric sensor
D Strain gauge
Thermocouples use the Seebeck effect, generating an electrical voltage based on the temperature difference between their junctions.
What is the typical unit of frequency measured by a frequency meter?
A Joules
B Ohms
C Hertz
D Watts
Frequency meters measure the number of cycles per second of an alternating current signal, expressed in Hertz (Hz).
What type of error occurs due to external electromagnetic interference?
A Gross error
B Systematic error
C Environmental error
D Random error
Environmental errors arise due to external factors like electromagnetic interference or temperature variations.
What is the primary purpose of a signal conditioner?
A Store data
B Amplify and filter signals
C Measure resistance
D Display data
Signal conditioners process the raw data from transducers by amplifying, filtering, or converting it into usable forms for further measurement or analysis.
What is the purpose of a Schering bridge?
A Measure resistance
B Measure capacitance
C Measure inductance
D Measure voltage
Schering bridges are used to measure capacitance and dielectric loss in electrical systems, especially in capacitors.
What does an oscilloscope primarily measure?
A Displacement
B Voltage waveform over time
C Pressure changes
D Temperature variations
Oscilloscopes visually display the shape and characteristics of voltage signals over time, allowing for detailed analysis.
What is the purpose of damping in measuring instruments?
A Reduce sensitivity
B Stabilize the pointer and reduce oscillations
C Amplify the signal
D Increase range
Damping minimizes oscillations in the instrument pointer, allowing it to settle quickly and provide accurate readings.
Which type of transformer is used in metering systems?
A Distribution transformer
B Power transformer
C Instrument transformer
D Auto transformer
Instrument transformers, such as current transformers (CTs) and potential transformers (PTs), are used in metering and protection systems to step down high values for safe measurement.