27 real Electrical Measurements & Instrumentation questions from the Electrical Core bank, as asked in Indian campus drives and tech interviews. Every question has a verified answer and an AI-tutor explanation on placd — free to start.
1. What is PMMC instrument?
Junior
A.total VA impedance connected across the current transformer secondary, which must stay within the rated value to preserve accuracy class
B.permanent-magnet moving-coil meter with a uniform scale that reads only the average of DC, extended with shunts and multipliers
C.bridge for low resistances below 1 Ω that removes lead and contact resistance error with a second pair of ratio arms
D.measures total three-phase power as W1 plus W2, with power factor obtained from tan φ equal to √3 (W1 − W2)/(W1 + W2)
2. Which term means: "permanent-magnet moving-coil meter with a uniform scale that reads only the average of DC, extended with shunts and multipliers"?
A.PMMC instrument — total VA impedance connected across the current transformer secondary, which must stay within the rated value to preserve accuracy class
B.PMMC instrument — permanent-magnet moving-coil meter with a uniform scale that reads only the average of DC, extended with shunts and multipliers
C.PMMC instrument — four-arm resistance bridge balanced when the products of opposite arms are equal, used for medium resistances of about 1 Ω to 100 kΩ
D.PMMC instrument — reads rms of AC or DC because deflection is proportional to current squared, which gives a non-uniform cramped scale
A.Moving-iron instrument — measures total three-phase power as W1 plus W2, with power factor obtained from tan φ equal to √3 (W1 − W2)/(W1 + W2)
B.Moving-iron instrument — total VA impedance connected across the current transformer secondary, which must stay within the rated value to preserve accuracy class
C.Moving-iron instrument — reads rms of AC or DC because deflection is proportional to current squared, which gives a non-uniform cramped scale
D.Moving-iron instrument — bridge for low resistances below 1 Ω that removes lead and contact resistance error with a second pair of ratio arms
8. Which term means: "four-arm resistance bridge balanced when the products of opposite arms are equal, used for medium resistances of about 1 Ω to 100 kΩ"?
A.Wheatstone bridge — four-arm resistance bridge balanced when the products of opposite arms are equal, used for medium resistances of about 1 Ω to 100 kΩ
B.Wheatstone bridge — bridge for low resistances below 1 Ω that removes lead and contact resistance error with a second pair of ratio arms
C.Wheatstone bridge — an instrument's maximum error as a percentage of full scale, such as class 0.5 CT for metering and class 5P for protection
D.Wheatstone bridge — permanent-magnet moving-coil meter with a uniform scale that reads only the average of DC, extended with shunts and multipliers
A.Two-wattmeter method — measures total three-phase power as W1 plus W2, with power factor obtained from tan φ equal to √3 (W1 − W2)/(W1 + W2)
B.Two-wattmeter method — slow rotation of an induction meter disc with no load current, prevented by two diametrically opposite holes drilled in the disc
C.Two-wattmeter method — four-arm resistance bridge balanced when the products of opposite arms are equal, used for medium resistances of about 1 Ω to 100 kΩ
D.Two-wattmeter method — AC bridge for measuring capacitance and dissipation factor (tan δ) of high-voltage insulation with a standard capacitor in one arm
A.Accuracy class — four-arm resistance bridge balanced when the products of opposite arms are equal, used for medium resistances of about 1 Ω to 100 kΩ
B.Accuracy class — slow rotation of an induction meter disc with no load current, prevented by two diametrically opposite holes drilled in the disc
C.Accuracy class — reads rms of AC or DC because deflection is proportional to current squared, which gives a non-uniform cramped scale
D.Accuracy class — an instrument's maximum error as a percentage of full scale, such as class 0.5 CT for metering and class 5P for protection
A.Kelvin double bridge — measures total three-phase power as W1 plus W2, with power factor obtained from tan φ equal to √3 (W1 − W2)/(W1 + W2)
B.Kelvin double bridge — four-arm resistance bridge balanced when the products of opposite arms are equal, used for medium resistances of about 1 Ω to 100 kΩ
C.Kelvin double bridge — bridge for low resistances below 1 Ω that removes lead and contact resistance error with a second pair of ratio arms
D.Kelvin double bridge — slow rotation of an induction meter disc with no load current, prevented by two diametrically opposite holes drilled in the disc
20. Which term means: "total VA impedance connected across the current transformer secondary, which must stay within the rated value to preserve accuracy class"?
23. Which term means: "slow rotation of an induction meter disc with no load current, prevented by two diametrically opposite holes drilled in the disc"?
A.Energy meter creep — slow rotation of an induction meter disc with no load current, prevented by two diametrically opposite holes drilled in the disc
B.Energy meter creep — AC bridge for measuring capacitance and dissipation factor (tan δ) of high-voltage insulation with a standard capacitor in one arm
C.Energy meter creep — permanent-magnet moving-coil meter with a uniform scale that reads only the average of DC, extended with shunts and multipliers
D.Energy meter creep — total VA impedance connected across the current transformer secondary, which must stay within the rated value to preserve accuracy class
26. Which term means: "AC bridge for measuring capacitance and dissipation factor (tan δ) of high-voltage insulation with a standard capacitor in one arm"?
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