Electrical Measurements Quiz On 06/05/2020

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  • 1/30 Questions

    Operating torques in analogue instruments are---

    • Deflecting and control
    • Deflecting and damping
    • Deflecting, control and damping
    • Vibration and balancing
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About This Quiz

This quiz focuses on electrical measurement techniques and devices used in engineering, covering topics like RLC bridges, high voltage capacitors, and mutual inductance.

Electrical Measurements Quiz On 06/05/2020 - Quiz

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  • 2. 

    Alternating current is measured by---

    • Induction ammeter

    • Permanent magnet type ammeter

    • Electrostatic ammeter

    • Moving iron repulsion type voltmeter

    Correct Answer
    A. Induction ammeter
    Explanation
    An induction ammeter is used to measure alternating current. It works on the principle of electromagnetic induction, where a changing magnetic field induces a current in a nearby conductor. This type of ammeter is specifically designed to measure the magnitude and direction of alternating current accurately. It consists of a coil and a movable iron core, which moves in response to the magnetic field generated by the alternating current. The movement of the iron core is then converted into a reading on the scale, allowing the measurement of alternating current.

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  • 3. 

    In a dynamometer 3-phase power factor meter, the planes of the two moving coils are at--

    • 0°

    • 60°

    • 90°

    • 120°

    Correct Answer
    A. 120°
    Explanation
    In a dynamometer 3-phase power factor meter, the planes of the two moving coils are at 120 degrees. This is because in a 3-phase system, the power factor is determined by the phase angle between the voltage and current waveforms. The two moving coils in the power factor meter are designed to measure the current in two different phases of the system. By placing the planes of these coils at 120 degrees, they are able to accurately measure the phase angle and determine the power factor of the system.

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  • 4. 

    Various adjustments in an energy meter include---

    • Light load or friction

    • Lag and creep

    • Overload and voltage compensation

    • Temperature compensation

    • All of the above

    Correct Answer
    A. All of the above
    Explanation
    The correct answer is "all of the above" because various adjustments in an energy meter include light load or friction, lag and creep, overload and voltage compensation, and temperature compensation. These adjustments are necessary to ensure accurate measurement of energy consumption and to compensate for different factors that can affect the meter's performance, such as variations in load, temperature, and voltage.

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  • 5. 

    Two holes in the disc of energymeter are drilled at the opposite sides of the spindle to---

    • Improve its ventilation

    • Eliminate creeping at no load

    • Increase its deflecting torque

    • Increase its braking torque

    Correct Answer
    A. Eliminate creeping at no load
    Explanation
    The two holes in the disc of the energy meter are drilled at the opposite sides of the spindle to eliminate creeping at no load. Creeping refers to the movement of the disc in the energy meter even when there is no load or power consumption. By drilling holes in the disc, air can flow through and reduce the friction between the disc and the spindle, preventing the disc from moving unnecessarily. This helps to ensure accurate measurement of energy consumption by the meter.

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  • 6. 

    In a ballistic galvanometer, the deflecting torque is proportional to--

    • The current through coil

    • Square of current through coil

    • Square-root of current through coil

    • Sine of measured

    Correct Answer
    A. The current through coil
    Explanation
    In a ballistic galvanometer, the deflecting torque is directly proportional to the current passing through the coil. This means that as the current increases, the deflecting torque also increases. Therefore, the correct answer is "the current through coil".

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  • 7. 

    In a Schering bridge, the potential of the detector above earth potential is----

    • A few volts only

    • 1 kV

    • 5 kV

    • 10 kV

    • Option 5

    Correct Answer
    A. A few volts only
    Explanation
    In a Schering bridge, the potential of the detector above earth potential is only a few volts. This is because the Schering bridge is a type of AC bridge circuit used for measuring capacitance and dissipation factor of high voltage capacitors. The detector in the bridge is typically a high impedance voltmeter, which measures the voltage across the capacitor under test. Since the bridge is designed to work with high voltage capacitors, the potential difference across the detector is kept relatively low, typically in the range of a few volts.

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  • 8. 

    If an inductance is connected in one arm of bridge and resistances in the remaining three arms

    • The bridge can always be balanced

    • The bridge cannot be balanced

    • The bridge can be balanced if the resistances have some specific values

    • None of the above

    Correct Answer
    A. The bridge cannot be balanced
    Explanation
    In order for a bridge to be balanced, the ratio of the resistances in the arms of the bridge must be equal to the ratio of the inductance in the connected arm. However, since there are no resistances in the arm where the inductance is connected, it is not possible to achieve this balance. Therefore, the bridge cannot be balanced in this scenario.

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  • 9. 

    Systematic errors are---

    • Instrumental errors

    • Environmental errors

    • Observational errors

    • All of the above

    Correct Answer
    A. All of the above
    Explanation
    Systematic errors refer to consistent errors that occur in a measurement process. These errors can be caused by instrumental factors, such as faulty equipment or calibration issues, as well as environmental factors, such as temperature or humidity fluctuations. Additionally, systematic errors can also arise from observational errors, which include human errors in reading or recording data. Therefore, the correct answer is "all of the above" as systematic errors can result from any of these factors.

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  • 10. 

    The power of a n-phase circuit can be measured by using a minimum of---

    • (n - 1) wattmeter elements

    • N wattmeter elements

    • (n + 1) wattmeter elements

    • 2n wattmeter elements

    Correct Answer
    A. (n - 1) wattmeter elements
    Explanation
    In a n-phase circuit, the power can be measured by using a minimum of (n - 1) wattmeter elements. This is because each wattmeter measures the power in one phase, and since there are n phases, we need n wattmeters to measure the power in each phase. However, one of the phases serves as a reference and does not require a wattmeter, so we only need (n - 1) wattmeter elements to measure the power in the remaining n - 1 phases.

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  • 11. 

    If the current in a capacitor leads the voltage by 80°, the loss angle of the capacitor is---

    • 10°

    • 80°

    • 120°

    • 170°

    Correct Answer
    A. 10°
    Explanation
    If the current in a capacitor leads the voltage by 80°, it means that the current waveform reaches its peak value 80° ahead of the voltage waveform. In an ideal capacitor, the current leads the voltage by 90°. Therefore, the loss angle of the capacitor can be calculated by subtracting the phase angle difference of 80° from the ideal phase angle of 90°. Thus, the loss angle of the capacitor is 10°.

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  • 12. 

    Commonly used instruments in power system measurement are--

    • Induction

    • Moving coil or iron

    • Rectifier

    • Electrostatic

    Correct Answer
    A. Induction
    Explanation
    The commonly used instruments in power system measurement are induction instruments. Induction instruments are widely used due to their simplicity, reliability, and cost-effectiveness. They work on the principle of electromagnetic induction, where the current to be measured induces a magnetic field that interacts with a coil, causing a deflection in the instrument. Induction instruments are suitable for both AC and DC measurements and are commonly used for measuring voltage, current, power, and energy in power systems.

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  • 13. 

    Instrument transformers are----

    • Potential transformers

    • Current transformers

    • Both (a) and (b)

    • Power transformers

    Correct Answer
    A. Both (a) and (b)
    Explanation
    Instrument transformers are devices used to measure and transform high voltage or high current levels into lower, more manageable levels that can be safely measured by instruments. Potential transformers are used to measure high voltage levels, while current transformers are used to measure high current levels. Therefore, instrument transformers can be both potential transformers and current transformers, depending on the specific application and requirements.

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  • 14. 

    In an energymeter braking torque is produced to----

    • Safe guard it against creep

    • Brake the instrument

    • Bring energy meter to stand still

    • Maintain steady speed and equal to driving torque

    Correct Answer
    A. Maintain steady speed and equal to driving torque
    Explanation
    In an energy meter, braking torque is produced to maintain a steady speed and equalize the driving torque. This is important to ensure accurate measurements and prevent the energy meter from creeping or spinning too fast. By applying a braking torque equal to the driving torque, the energy meter can remain stable and provide reliable readings.

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  • 15. 

    In a single-phase power factor meter the phase difference between the currents in the two pressure coils is

    • Exactly 0°

    • Approximately 0°

    • Exactly 90°

    • Approximately 90°

    Correct Answer
    A. Exactly 90°
    Explanation
    In a single-phase power factor meter, the phase difference between the currents in the two pressure coils is exactly 90°. This means that the current in one coil lags behind the voltage by 90°, while the current in the other coil leads the voltage by 90°. This phase difference allows the power factor meter to accurately measure the power factor of the circuit.

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  • 16. 

    The resistance can be measured most accurately by

    • Voltmeter-ammeter method

    • Bridge method

    • Multimeter

    • Megger

    Correct Answer
    A. Bridge method
    Explanation
    The bridge method is the most accurate way to measure resistance. This method uses a bridge circuit, typically a Wheatstone bridge, which balances the resistance being measured with a known resistance. By adjusting the known resistance until the bridge is balanced, the unknown resistance can be accurately determined. This method eliminates errors caused by the internal resistance of the measuring instruments, making it more precise than other methods such as the voltmeter-ammeter method or using a multimeter. Additionally, the bridge method allows for the measurement of very low resistances with high accuracy.

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  • 17. 

    The two pressure coils of a single-phase power factor meter have--

    • The same dimensions and the same number of turns

    • The same dimension but different number of turns

    • The same number of turns but different dimensions

    • None of the above

    Correct Answer
    A. The same dimensions and the same number of turns
    Explanation
    The two pressure coils of a single-phase power factor meter have the same dimensions and the same number of turns. This is because the pressure coils are designed to measure the pressure of the current flowing through the circuit. In order to accurately measure the power factor, both coils need to have the same dimensions and number of turns to ensure that they have the same sensitivity and response to the current. If the coils had different dimensions or number of turns, it would result in inaccurate measurements and an unreliable power factor reading.

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  • 18. 

    The standard resistor is made from---

    • Platinum

    • Maganin

    • Silver

    • Nichrome

    Correct Answer
    A. Maganin
    Explanation
    The standard resistor is made from maganin.

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  • 19. 

    In an Anderson bridge, the unknown inductance is measured in terms of---

    • Known inductance and resistance

    • Known capacitance and resistance

    • Known resistance

    • Known inductance

    Correct Answer
    A. Known capacitance and resistance
    Explanation
    In an Anderson bridge, the unknown inductance is measured in terms of known capacitance and resistance. This bridge circuit is specifically designed to measure the value of an unknown inductance by comparing it with a known capacitance and resistance. By adjusting the values of the known capacitance and resistance, the bridge is balanced and the unknown inductance can be determined. The capacitance and resistance values are crucial in establishing the balance condition and accurately measuring the unknown inductance.

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  • 20. 

    For measurement of mutual inductance we can use---

    • Anderson bridge

    • Maxwell's bridge

    • Heaviside bridge

    • Any of the above

    Correct Answer
    A. Heaviside bridge
    Explanation
    The Heaviside bridge can be used for the measurement of mutual inductance. This bridge circuit is specifically designed to measure the mutual inductance between two coils. It consists of a fixed resistor, a variable resistor, and two coils. By adjusting the variable resistor, the bridge can be balanced, and the mutual inductance can be calculated using the known values of the resistors and the inductance of one of the coils. Therefore, the Heaviside bridge is a suitable choice for measuring mutual inductance.

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  • 21. 

    To avoid the effect of the stray magnetic field in A.C. bridges we can use---

    • Magnetic screening

    • Wagner earthing device

    • Wave filters

    • Any of the above

    Correct Answer
    A. Magnetic screening
    Explanation
    To avoid the effect of the stray magnetic field in A.C. bridges, magnetic screening can be used. Magnetic screening involves the use of a material that can block or redirect the magnetic field, preventing it from interfering with the measurements in the A.C. bridge. This can be achieved by using materials with high magnetic permeability, such as mu-metal or ferrite, which can effectively shield the bridge from external magnetic fields. By implementing magnetic screening, the accuracy and reliability of the A.C. bridge measurements can be improved.

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  • 22. 

    A power factor meter has----

    • One current circuit and two pressure circuits

    • One current circuit and one pressure circuit

    • Two current circuits and one pres¬sure circuit

    • None of the above

    Correct Answer
    A. One current circuit and two pressure circuits
    Explanation
    A power factor meter measures the power factor of an electrical system, which is the ratio of the real power (measured in watts) to the apparent power (measured in volt-amperes). In order to accurately measure the power factor, a power factor meter requires both current and voltage measurements. The current circuit measures the current flowing through the system, while the two pressure circuits measure the voltage across the system. Therefore, the correct answer is "one current circuit and two pressure circuits".

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  • 23. 

    Wattmeter cannot be designed on the principle of-----

    • Electrostatic instrument

    • Thermocouple instrument

    • Moving iron instrument

    • Electrodynamic instrument

    Correct Answer
    A. Moving iron instrument
    Explanation
    A wattmeter measures the power in an electrical circuit. It works on the principle of electromagnetic induction, where the movement of a magnetic field induces a current in a conductor. A moving iron instrument, as the name suggests, uses a piece of iron that moves in response to the magnetic field generated by the current in the circuit. This movement is then converted into a measurement of power. On the other hand, electrostatic instruments, thermocouple instruments, and electrodynamic instruments all work on different principles and are not suitable for designing a wattmeter.

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  • 24. 

    A universal RLC bridge uses-----

    • Maxwell bridge configuration for measurement of inductance and De Santas bridge for measurement of capacitance

    • Maxwell Wein bridge for measurement of inductance and modified De Sauty's bridge for measurement of capacitance

    • Maxwell Wein bridge for measurement of inductance and Wein bridge for measurement of capacitance

    • Any of the above.

    Correct Answer
    A. Maxwell Wein bridge for measurement of inductance and modified De Sauty's bridge for measurement of capacitance
    Explanation
    A universal RLC bridge is a type of electronic instrument used for measuring the values of resistance (R), inductance (L), and capacitance (C) components in a circuit. The Maxwell Wein bridge configuration is commonly used for measuring inductance, while the modified De Sauty's bridge is used for measuring capacitance. Therefore, the correct answer states that a universal RLC bridge uses the Maxwell Wein bridge for measurement of inductance and the modified De Sauty's bridge for measurement of capacitance.

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  • 25. 

    For measurement of inductance having a high value, we should use---

    • Maxwell's bridge

    • Maxwell Wein bridge

    • Hay's bridge

    • Any of the above

    Correct Answer
    A. Hay's bridge
    Explanation
    Hay's bridge is the most suitable option for measuring inductance with a high value. Maxwell's bridge and Maxwell Wein bridge are not specifically designed for measuring inductance and may not provide accurate results for high inductance values. Hay's bridge, on the other hand, is specifically designed for measuring inductance and is more suitable for high inductance values. Therefore, Hay's bridge is the correct choice for measuring inductance with a high value.

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  • 26. 

    The commonly used standard capacitor is----

    • Spherical type

    • Concentric cylindrical type

    • Electrostatic type

    • Multilayer parallel plate type

    Correct Answer
    A. Concentric cylindrical type
    Explanation
    The commonly used standard capacitor is the concentric cylindrical type. This type of capacitor consists of two cylindrical conductors, one inside the other, with an insulating material between them. The cylindrical shape allows for a larger surface area, which increases the capacitance of the capacitor. This type of capacitor is commonly used in various electronic circuits and applications due to its compact size and high capacitance values.

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  • 27. 

    Volt box is a component to---

    • Extend voltage range

    • Measure voltage

    • Compare voltage in a box

    • None of the above

    Correct Answer
    A. Extend voltage range
    Explanation
    The Volt box is a component that is used to extend the voltage range. It allows for the expansion of the voltage range beyond what is initially provided by the power source. This can be useful in various applications where a wider voltage range is required, such as in electrical testing or experimentation.

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  • 28. 

    For measurements on high voltage capacitors, the suitable bridge is----

    • Wein bridge

    • Modified De Sauty's bridge

    • Schering bridge

    • Any of the above

    • None of the above

    Correct Answer
    A. Schering bridge
    Explanation
    The Schering bridge is the suitable bridge for measurements on high voltage capacitors. The Schering bridge is specifically designed for measuring the capacitance of high voltage capacitors accurately. It is a type of AC bridge circuit that is used to measure the capacitance of unknown capacitors. The Schering bridge is preferred for high voltage capacitors because it provides a balanced condition for accurate measurements and minimizes the effect of stray capacitance and inductance.

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  • 29. 

    Wagner earthing device is used to eliminate errors due to---

    • Electrostatic coupling

    • Electromagnetic coupling

    • Both (a) and (b)

    • None of the above

    Correct Answer
    A. Electrostatic coupling
    Explanation
    The Wagner earthing device is used to eliminate errors caused by electrostatic coupling. Electrostatic coupling refers to the transfer of electric charge between two objects through their electric fields. This can cause interference and errors in electrical systems. The Wagner earthing device helps to divert and dissipate these electrostatic charges, ensuring accurate and reliable operation of the system.

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  • 30. 

    The power factor of a single-phase load can be calculated if the instruments available are---

    • One voltmeter and one ammeter

    • One voltmeter, one ammeter and one wattmeter

    • One voltmeter, one ammeter and one energy meter

    • Any of the above

    Correct Answer
    A. One voltmeter, one ammeter and one wattmeter
    Explanation
    The power factor of a single-phase load can be calculated using one voltmeter, one ammeter, and one wattmeter. The voltmeter measures the voltage, the ammeter measures the current, and the wattmeter measures the power consumed by the load. By using these three instruments, the power factor can be determined by calculating the ratio of the real power (measured by the wattmeter) to the product of the voltage and current (measured by the voltmeter and ammeter). The power factor is an important parameter in electrical systems as it indicates the efficiency of power consumption.

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  • Mar 15, 2023
    Quiz Edited by
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  • May 06, 2020
    Quiz Created by
    Ramu1632
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