Below are important multiple choice questions on transducers, including classification, LVDT, strain gauges, piezoelectric sensors, and measurement techniques for pressure, temperature, and flow – frequently asked in SSC JE, RRB JE, and other technical exams.
Classification of Transducers MCQs (Active, Passive, Linear, Non-Linear)
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Which of the following is a passive transducer?
Thermocouple
Strain gauge ✅
Piezoelectric crystal
Photovoltaic cell
Explanation: Passive transducers require external power; strain gauge is a passive type. -
Thermocouples are classified as:
Passive and non-linear
Active and linear ✅
Passive and linear
Active and non-linear
Explanation: Thermocouples generate voltage (active) and are approximately linear over a range. -
Which of the following is a linear transducer?
LVDT ✅
Thermistor
Strain gauge
RTD
Explanation: LVDT gives a linear relationship between displacement and output voltage.
LVDT Based MCQs
-
The output of an LVDT is:
AC voltage ✅
DC voltage
Resistance
Capacitance
Explanation: LVDT works on mutual induction and gives AC output. -
In an LVDT, the secondary voltages are:
Always in phase
180° out of phase ✅
Not related
Same magnitude and phase
Explanation: Secondary coils produce voltages in opposite phase depending on core position. -
Which among the following is not true for LVDT?
It has high sensitivity
It has mechanical contact with core ✅
It is frictionless
It gives differential output
Explanation: LVDT has a free-moving core, hence no mechanical contact.
Strain Gauge MCQs
-
Strain is defined as:
Change in volume/original volume
Change in length/original length ✅
Force per area
Stress per unit strain
Explanation: Strain = ΔL / L. -
The gauge factor is defined as:
Strain / Resistance
(ΔR/R) / strain ✅
Resistance / strain
Voltage / strain
Explanation: Gauge factor measures sensitivity of strain gauge. -
Which bridge circuit is commonly used in strain gauge measurement?
Wheatstone bridge ✅
Maxwell bridge
Schering bridge
Wien bridge
Explanation: Wheatstone bridge provides high accuracy for strain gauge output.
Piezoelectric Transducer MCQs
-
Piezoelectric effect converts:
Mechanical energy into electrical energy ✅
Electrical to magnetic
Heat to electricity
Electrical to mechanical
Explanation: Applied pressure generates voltage in piezoelectric materials. -
Which material is commonly used in piezoelectric sensors?
Quartz ✅
Copper
Iron
Silicon
Explanation: Quartz naturally exhibits piezoelectric properties.
Temperature Measurement MCQs
-
Which of the following is not a temperature transducer?
Thermocouple
Potentiometer ✅
RTD
Thermistor
Explanation: Potentiometer is used for displacement or voltage control. -
RTD stands for:
Resistance Temperature Detector ✅
Reactive Thermo Detector
Resistive Transducer Device
Radiation Temperature Detector
Explanation: RTDs work by measuring change in resistance with temperature.
- Which of the following pressure transducers is suitable for measuring very low pressure (vacuum)?
Bourdon tube
Diaphragm gauge
McLeod gauge ✅
Strain gauge
Explanation: McLeod gauges are used for low-pressure (vacuum) measurements typically in the range of 10⁻³ to 10⁻⁶ torr. - A diaphragm-type pressure transducer works on the principle of:
Magnetic induction
Deflection due to pressure ✅
Change in temperature
Change in capacitance
Explanation: Pressure causes the diaphragm to deflect, which is converted into electrical signal. - A Bourdon tube measures:
Only vacuum
Gauge pressure ✅
Absolute pressure
Atmospheric pressure
Explanation: Bourdon tubes measure gauge pressure, which is pressure above atmospheric pressure. - In a piezoresistive pressure sensor, pressure is converted into:
Capacitance change
Voltage directly
Resistance change ✅
Mechanical displacement
Explanation: Piezoresistive sensors work by converting pressure-induced strain into a change in resistance.
Pressure Measurement MCQs
-
Bourdon tube is used to measure:
Pressure ✅
Temperature
Displacement
Flow
Explanation: Bourdon tube deflects with pressure changes. -
Piezoresistive pressure sensors work on change in:
Capacitance
Inductance
Resistance ✅
Voltage
Explanation: Applied pressure changes resistance of sensor material.
Flow Measurement MCQs
-
Which of the following is used for flow measurement?
Orifice meter ✅
LVDT
Thermistor
RTD
Explanation: Orifice meter measures pressure drop to calculate flow. -
Electromagnetic flow meters can be used for:
Gases only
Conductive fluids ✅
Non-conductive fluids
Steam only
Explanation: They work on Faraday’s law and need conductive media. -
Ultrasonic flow meters operate using:
Heat
Sound waves ✅
Magnetic fields
Radiation
Explanation: Ultrasonic transducers measure transit time differences in sound.
Transducer Numerical MCQs
- An LVDT has a sensitivity of 2 mV/mm. If the output voltage is 8 mV, what is the displacement of the core?
2 mm
6 mm
4 mm ✅
10 mm
Explanation: Displacement = Output Voltage / Sensitivity = 8 mV / 2 mV/mm = 4 mm - An LVDT gives zero output when the core is at the center. When moved to +5 mm, the output is +25 mV. What is the sensitivity of the LVDT?
10 mV/mm
5 mV/mm ✅
25 mV/mm
2.5 mV/mm
Explanation: Sensitivity = Output Voltage / Displacement = 25 mV / 5 mm = 5 mV/mm - An LVDT has a range of ±10 mm and a linearity error of 1%. What is the maximum error in mm?
0.1 mm ✅
1 mm
10 mm
0.01 mm
Explanation: Linearity Error = 1% of Full Range = 1% of 10 mm = 0.1 mm
Conclusion
These MCQs on transducers are handpicked for SSC JE and AE/JE exams. Understanding topics like LVDT, strain gauges, piezoelectric effects, and sensor classifications will boost your technical score significantly.