Electrical Measurements and Instrumentation MCQs (Part-1)
What is the primary purpose of an electrical measuring instrument?
A Generate power
B Display voltage
C Store data
D Measure electrical quantities
Electrical measuring instruments are used to measure various electrical quantities such as voltage, current, resistance, power, and energy. These instruments help in analyzing electrical circuits, ensuring safety, and diagnosing faults. Their primary function is to provide accurate readings of electrical parameters, which are crucial in designing and maintaining electrical systems.
Which device is used to measure electric current in a circuit?
A Wattmeter
B Ammeter
C Voltmeter
D Ohmmeter
An ammeter is specifically designed to measure electric current in a circuit. It is connected in series with the load to allow current to flow through it. Ammeter readings help in analyzing circuit performance and detecting faults. To measure high currents, shunt resistors or current transformers are often used with ammeters.
What type of measuring instrument is a voltmeter?
A Voltage measuring
B Energy measuring
C Current measuring
D Power measuring
A voltmeter is used to measure the electrical potential difference (voltage) between two points in a circuit. It is connected in parallel with the component whose voltage needs to be measured. A high internal resistance ensures that the voltmeter does not draw significant current from the circuit, preventing measurement errors.
Which instrument is used to measure electrical power in a circuit?
A Ammeter
B Voltmeter
C Ohmmeter
D Wattmeter
A wattmeter measures electrical power in a circuit, which is the product of voltage and current. It consists of two coils: a voltage coil connected in parallel and a current coil connected in series. This configuration allows it to measure real power accurately, making it essential for power analysis in electrical systems.
What does an ohmmeter measure?
A Power
B Voltage
C Resistance
D Current
An ohmmeter is used to measure electrical resistance, which opposes current flow in a circuit. It applies a small voltage and measures the resulting current to determine resistance using Ohm’s Law. Digital ohmmeters provide precise readings and are commonly used for troubleshooting electrical components.
What is the function of a multimeter?
A Measure voltage, current, and resistance
B Amplify signals
C Measure resistance only
D Store electrical energy
A multimeter is a versatile measuring instrument capable of measuring voltage, current, and resistance. It is available in analog and digital versions, with digital multimeters (DMMs) being more accurate and widely used. Multimeters are essential for diagnosing circuit issues, checking battery levels, and verifying electrical connections.
Which instrument is used to measure electrical energy consumption?
A Oscilloscope
B Ammeter
C Voltmeter
D Energy meter
An energy meter measures electrical energy consumption over time, typically in kilowatt-hours (kWh). It is used in homes and industries to monitor electricity usage. Modern digital energy meters provide accurate readings and additional features like remote monitoring and real time consumption data.
What does a galvanometer measure?
A Frequency
B High voltage
C Small electric current
D Electrical power
A galvanometer is a highly sensitive instrument designed to detect and measure small electric currents. It operates on the principle of electromagnetic deflection, where current passing through a coil generates a magnetic field, causing needle movement. Galvanometers are commonly used in bridge circuits and laboratory experiments.
What is the main function of an oscilloscope?
A Display waveforms
B Convert AC to DC
C Generate voltage
D Measure frequency only
An oscilloscope is an essential tool for visualizing electrical signals over time. It provides a graphical representation of voltage variations, allowing engineers to analyze signal characteristics such as frequency, amplitude, and phase. It is widely used in electronics, communication, and research applications.
Which device measures the frequency of an AC signal?
A Ohmmeter
B Frequency meter
C Ammeter
D Wattmeter
A frequency meter is used to measure the frequency of an alternating current (AC) signal. It helps in determining the number of cycles per second (Hertz) of an electrical waveform. Frequency measurement is crucial in power systems, signal processing, and communication applications to ensure correct operation.
What is the function of a current transformer (CT)?
A Step down current
B Convert DC to AC
C Measure resistance
D Step up voltage
A current transformer (CT) is used to step down high current levels to a safer, measurable value for instruments and protection relays. It is widely used in power systems for monitoring and protection purposes. CTs ensure accurate current measurement while isolating instruments from high voltage circuits.
What is the role of a potential transformer (PT)?
A Convert AC to DC
B Measure power
C Store electrical energy
D Step down voltage
A potential transformer (PT) reduces high voltages to lower, measurable levels for meters and relays. It ensures the safe and accurate measurement of high voltage systems while protecting measuring instruments from excessive voltage exposure. PTs are commonly used in power distribution networks.
What type of error is caused by aging and wear of measuring instruments?
A Gross error
B Instrumental error
C Random error
D Environmental error
Instrumental errors arise due to imperfections, aging, or calibration issues in measuring instruments. These errors can be minimized through regular maintenance, calibration, and using high precision instruments. They affect measurement accuracy and should be accounted for in scientific and industrial applications.
What is the principle of strain gauge measurement?
A Magnetic field
B Capacitance change
C Resistance change
D Inductance change
A strain gauge measures strain (deformation) in a material by detecting changes in electrical resistance. When a material is stretched or compressed, its resistance changes proportionally. Strain gauges are widely used in structural engineering, load monitoring, and mechanical testing.
What is the main purpose of signal conditioning in measurements?
A Convert signals into usable form
B Increase voltage
C Store data
D Reduce resistance
Signal conditioning processes raw sensor signals into a form suitable for measurement and analysis. This includes amplification, filtering, and conversion. It is essential in data acquisition systems to improve signal accuracy and reliability, making measurements more precise and meaningful.