Electrical Measurements and Instrumentation MCQs (Part-12)
What effect is utilized by a thermocouple to measure temperature?
A Piezoelectric effect
B Seebeck effect
C Hall effect
D Electrostatic effect
The Seebeck effect is used by thermocouples to measure temperature. When two different metals are joined at two points and exposed to different temperatures, a voltage is generated, which is proportional to the temperature difference.
Which of the following sensors operates based on the piezoelectric effect?
A Piezoelectric sensor
B Strain gauge
C Thermistor
D Thermocouple
Piezoelectric sensors operate on the piezoelectric effect, where certain materials generate an electrical charge when subjected to mechanical stress. These sensors are widely used for vibration, pressure, and force measurements in various applications.
What does a strain gauge measure?
A Displacement
B Temperature
C Force
D Strain
A strain gauge measures strain, or the deformation of a material when subjected to external forces. It works by detecting changes in the resistance of a material as it is stretched or compressed, making it essential for force and load measurements.
Which material is commonly used in a thermocouple for temperature measurement?
A Copper
B Nickel
C Aluminum
D Copper and constantan
A thermocouple typically uses two different metals, such as copper and constantan, to create a voltage proportional to the temperature difference between the two junctions. This combination is commonly used for temperature measurements due to its stability and reliability.
How does a strain gauge work?
A Changes resistance with stress
B Measures pressure directly
C Changes current with temperature
D Changes voltage with strain
A strain gauge operates by changing its resistance when subjected to mechanical stress or strain. This change in resistance can be measured and used to calculate the amount of deformation, making it a valuable tool for testing materials under stress.
What is the primary use of piezoelectric materials in measurements?
A Measure temperature
B Measure displacement
C Measure force or vibration
D Measure pressure
Piezoelectric materials generate an electrical charge when subjected to mechanical stress, making them ideal for measuring force, pressure, or vibrations. These materials are widely used in sensors for industrial, medical, and aerospace applications.
Which type of sensor would you use to measure high pressure in a system?
A Piezoelectric sensor
B Strain gauge
C Thermocouple
D Capacitive sensor
Strain gauges can be used in pressure transducers to measure high pressures. They detect the deformation in a material caused by pressure, and the change in resistance is proportional to the pressure applied. This makes them ideal for accurate pressure measurements.
What causes the piezoelectric effect in materials?
A Temperature change
B Mechanical stress
C Magnetic field
D Electrical charge
The piezoelectric effect occurs in certain materials when mechanical stress is applied, causing the material to generate an electrical charge. This effect is used in sensors, actuators, and transducers to measure pressure, vibration, and acceleration.
What type of material is typically used in strain gauges?
A Insulating materials
B Conductive metals
C Magnetic metals
D Semiconductor materials
Strain gauges typically use conductive materials, such as constantan or metal alloys, for their resistance elements. These materials exhibit a measurable change in resistance when deformed, which is essential for accurate strain measurement.
How are thermocouples connected in a measurement system?
A In series
B In parallel
C In a bridge circuit
D In a differential amplifier
Thermocouples are typically connected in series to form a circuit where the voltage generated by the temperature difference between the two junctions is measured. This allows for precise temperature measurement across a wide range.
What is the main application of a thermistor?
A Pressure measurement
B Temperature sensing
C Vibration detection
D Current measurement
A thermistor is a type of resistor whose resistance varies significantly with temperature. It is commonly used in temperature sensing applications, such as temperature probes, thermostats, and other devices requiring precise temperature control or monitoring.
Which type of measurement is typically done using piezoelectric sensors?
A Voltage
B Vibration or force
C Displacement
D Temperature
Piezoelectric sensors are widely used to measure vibrations, force, and pressure. They convert mechanical stress into an electrical charge, providing high sensitivity and real time data on physical phenomena like vibrations and forces in industrial and scientific applications.
What is a common characteristic of piezoelectric materials?
A They generate electrical charge under stress
B They change resistance with temperature
C They have high conductivity
D They react to magnetic fields
Piezoelectric materials generate an electrical charge when subjected to mechanical stress. This characteristic is utilized in various applications such as sensors for vibration, pressure, and force measurements, as well as actuators and energy harvesting devices.
How does temperature affect the resistance of a thermistor?
A Increases with temperature
B Decreases with temperature
C Remains constant
D Changes randomly
For a Negative Temperature Coefficient (NTC) thermistor, resistance decreases as temperature increases. This property is widely used in temperature sensing applications, where the thermistor’s resistance is measured and correlated to the temperature for precise control or monitoring.
What is the working principle of a strain gauge?
A Change in voltage with strain
B Change in current with strain
C Change in resistance with strain
D Change in temperature with strain
A strain gauge works by detecting changes in resistance that occur when a material undergoes strain. As the material deforms under stress, the strain gauge’s resistance increases or decreases proportionally, providing a measurable indication of the force or pressure applied.