Electrical Measurements and Instrumentation MCQs (Part-9)
What is the purpose of a frequency meter?
A Measure voltage
B Measure frequency
C Measure current
D Measure power
A frequency meter is used to measure the frequency of an alternating current (AC) signal. It counts the number of complete cycles per second (hertz) and is essential in maintaining the correct operating frequency in power systems and communication equipment.
Which device is used to measure the phase difference between two electrical signals?
A Voltmeter
B Ammeter
C Phase meter
D Wattmeter
A phase meter measures the phase difference between two electrical signals, which is important in understanding the timing relationship between voltage and current in AC circuits. Phase measurement is crucial for power factor correction and optimizing the efficiency of electrical systems.
What is the primary use of a current transformer (CT)?
A Step down current
B Step up current
C Measure power
D Measure voltage
A current transformer (CT) is used to reduce high currents to lower, measurable levels, making it safe for instruments to measure. It provides electrical isolation and allows precise monitoring of current in high voltage systems without direct contact.
What does a phase meter primarily measure in an AC circuit?
A Voltage
B Frequency
C Power
D Phase angle
A phase meter measures the phase angle between two AC signals. This is important in understanding the relationship between voltage and current waveforms, ensuring efficient energy transfer and minimizing losses in alternating current (AC) systems.
Which device is used to measure high voltages in power systems?
A Voltmeter
B Current transformer
C Potential transformer
D Frequency meter
A potential transformer (PT) is used to step down high voltages in power systems to a safe, measurable level. It allows accurate voltage measurements and ensures the protection of equipment and personnel by isolating high voltage circuits from the measuring instruments.
What is the function of a frequency meter in a power system?
A Measure current
B Measure resistance
C Measure frequency
D Measure power
A frequency meter measures the frequency of an electrical signal. In power systems, it ensures that the AC signals maintain the correct frequency (typically 50 or 60 Hz). Deviations in frequency can indicate instability or malfunction in the power supply system.
What does a current transformer (CT) provide to electrical measurement systems?
A High voltage
B Accurate current measurement
C Power measurement
D Voltage regulation
A current transformer (CT) provides accurate measurement of high currents by stepping them down to a lower, measurable range. It is used for monitoring, protection, and control purposes, providing data that helps in maintaining and managing electrical systems.
Which of the following instruments measures alternating current (AC)?
A Ammeter
B Voltmeter
C Oscilloscope
D Power meter
An ammeter is used to measure the amount of current flowing through a circuit. It can be used to measure both DC and AC currents, but for AC, it often requires special design features like a moving coil mechanism or shunt resistance.
What is the role of a potential transformer (PT) in electrical measurement systems?
A Step down current
B Measure power
C Step down voltage
D Measure resistance
A potential transformer (PT) reduces high voltage levels to a lower, measurable level, allowing for safe voltage measurements in high voltage power systems. PTs are essential for voltage monitoring, protection, and ensuring safety in electrical power systems.
What does an oscilloscope display?
A Waveforms
B Current
C Power
D Resistance
An oscilloscope displays the waveform of an electrical signal. It allows users to visually analyze how voltage changes over time, which is crucial for diagnosing issues with signals, monitoring signal integrity, and studying waveform characteristics in electrical systems.
Which of the following instruments is used to measure voltage in a circuit?
A Ammeter
B Wattmeter
C Voltmeter
D Galvanometer
A voltmeter is used to measure the electrical potential difference (voltage) across two points in a circuit. It is connected in parallel with the component or circuit being tested and provides accurate voltage readings without affecting the circuit.
What type of signal is typically analyzed with an oscilloscope?
A DC signals
B Both AC and DC signals
C AC signals
D Radio signals
An oscilloscope is capable of analyzing both AC (alternating current) and DC (direct current) signals. It visualizes signal waveforms over time, helping engineers and technicians analyze the behavior of electrical signals, including frequency, amplitude, and waveform shape.
What is the purpose of a bridge circuit like the Wheatstone bridge?
A Measure resistance
B Measure voltage
C Measure current
D Measure power
A bridge circuit, such as the Wheatstone bridge, is used to measure unknown resistances with high accuracy. By balancing the bridge and comparing it with known resistances, the value of the unknown resistance can be calculated precisely.
What is typically measured using a frequency meter?
A Voltage
B Current
C Frequency
D Power
A frequency meter is used to measure the frequency of an alternating signal, typically in hertz (Hz). It helps ensure that systems operate at the correct frequency, which is crucial for maintaining the stability and efficiency of electrical and communication systems.
Which instrument would you use to measure very low resistance values?
A Ohmmeter
B Galvanometer
C Precision ohmmeter
D Multimeter
A precision ohmmeter is specifically designed to measure very low resistance values accurately. It offers higher sensitivity and precision than a standard ohmmeter, making it ideal for tasks like measuring the resistance of fine wires or low resistance components.