Electrical Measurements and Instrumentation MCQs (Part-13)
Which device is commonly used for temperature measurement in electrical systems?
A Strain gauge
B Thermistor
C Thermocouple
D Piezoelectric sensor
A thermocouple is used for temperature measurement by generating a voltage based on the Seebeck effect when two different metals are joined at two junctions at different temperatures. It is commonly used for high temperature measurements in various industrial applications.
What is the main principle behind a thermistor?
A Resistance change with temperature
B Resistance change with pressure
C Voltage change with current
D Current change with voltage
A thermistor is a type of resistor whose resistance varies significantly with temperature. This change in resistance is used to measure temperature precisely in applications like temperature probes, circuits, and thermostats.
Which of the following instruments is used for measuring pressure?
A Thermocouple
B Strain gauge
C Voltmeter
D Pressure sensor
A pressure sensor measures the force exerted by a fluid (liquid or gas) on a surface. It works by converting the mechanical force into an electrical signal, which can be measured and monitored in various industrial applications.
What is the working principle of a piezoelectric sensor?
A Changes voltage with temperature
B Generates electrical charge with stress
C Measures strain by current
D Measures temperature via resistance
Piezoelectric sensors work on the piezoelectric effect, where certain materials generate an electrical charge when subjected to mechanical stress. This property is utilized in applications like vibration detection, force measurement, and pressure sensing.
How does a strain gauge measure force?
A By detecting changes in resistance
B By measuring voltage
C By measuring current
D By detecting changes in temperature
A strain gauge measures force by detecting changes in its resistance as the material to which it is attached deforms. The deformation, caused by applied force or stress, changes the resistance, which is then used to calculate the force.
What is the purpose of a thermocouple in electrical measurement?
A To measure resistance
B To measure temperature
C To measure pressure
D To measure voltage
A thermocouple measures temperature by producing a voltage that is proportional to the temperature difference between two junctions made of different metals. It is widely used in industrial and scientific applications for accurate temperature measurements.
Which type of thermocouple is commonly used in high temperature measurements?
A Type K
B Type T
C Type J
D Type E
Type K thermocouples, made from Chromel (nickel chromium) and Alumel (nickel aluminum), are commonly used for high temperature measurements due to their wide temperature range and stability. They are widely used in industrial processes and scientific experiments.
What does a barometer measure?
A Temperature
B Pressure
C Voltage
D Current
A barometer measures atmospheric pressure, typically in units of mercury (mmHg) or pascals (Pa). It is essential for weather forecasting, altimeter calibration, and pressure related scientific studies, helping detect changes in atmospheric conditions.
How do pressure transducers work?
A By converting temperature to pressure
B By converting mechanical stress to electrical signal
C By changing resistance with pressure
D By using a moving coil to measure force
Pressure transducers convert mechanical stress (due to pressure) into an electrical signal. They use sensors such as strain gauges or piezoelectric elements that change their electrical properties when subjected to pressure, providing accurate pressure readings.
What effect does temperature have on a thermistor?
A Resistance decreases with temperature
B Resistance increases with temperature
C Resistance remains constant
D It changes with pressure
In Negative Temperature Coefficient (NTC) thermistors, 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 kind of error can affect pressure measurements?
A Systematic error
B Random error
C Environmental error
D Instrumental error
Environmental factors such as temperature, humidity, and atmospheric pressure can introduce errors into pressure measurements. These environmental errors can be minimized by using calibrated instruments and controlling the measurement environment.
Which of these instruments measures small changes in temperature?
A Thermocouple
B Thermistor
C Strain gauge
D Barometer
A thermistor is highly sensitive to temperature changes and is commonly used for precise temperature measurements. Its resistance changes significantly with temperature, which is then converted into temperature readings, making it ideal for small scale temperature sensing applications.
What is the primary application of a manometer?
A Current measurement
B Temperature measurement
C Pressure measurement
D Voltage measurement
A manometer is used to measure the pressure of a gas or liquid in a confined space. It works by comparing the pressure of the fluid to a known reference, usually atmospheric pressure, to provide accurate readings.
How does a piezoelectric sensor generate an electrical signal?
A Through magnetic induction
B By applying voltage
C By measuring current flow
D By stress or pressure
A piezoelectric sensor generates an electrical signal when mechanical stress or pressure is applied to it. This mechanical deformation causes the piezoelectric material to produce an electrical charge, which is proportional to the applied stress.
What is a major advantage of using a thermocouple for temperature measurements?
A High accuracy
B High sensitivity
C Wide temperature range
D Low cost
Thermocouples can measure a wide range of temperatures, from very low to very high. This versatility makes them suitable for diverse applications, including industrial, scientific, and high temperature environments where other temperature sensors might not be effective.