Basic Electrical Engineering interview questions

1. A.cosine of the angle between voltage and current, equal to real power divided by apparent power, lagging for inductive loads and leading for capacitive
2. B.real power √3·VL·IL·cos φ for a balanced load regardless of star or delta connection, with reactive power using sin φ instead
3. C.magnitude of an alternating current that produces the same heating as an equal direct current, 0.707 of the peak for a sinusoid
4. D.occurs at the load where variable copper loss equals constant iron loss, so distribution transformers are designed to peak at about 50–75% load

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1. A.RMS value
2. B.Star-delta relations
3. C.Three-phase power
4. D.Power factor correction

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1. A.RMS value — in star the line voltage is √3 times phase voltage with equal currents; in delta the line current is √3 times phase current with equal voltages
2. B.RMS value — cosine of the angle between voltage and current, equal to real power divided by apparent power, lagging for inductive loads and leading for capacitive
3. C.RMS value — magnitude of an alternating current that produces the same heating as an equal direct current, 0.707 of the peak for a sinusoid
4. D.RMS value — occurs at the load where variable copper loss equals constant iron loss, so distribution transformers are designed to peak at about 50–75% load

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1. A.voltage induced in the rotating armature, Eb = V − Ia·Ra, proportional to speed and flux, which self-regulates armature current against load changes
2. B.in star the line voltage is √3 times phase voltage with equal currents; in delta the line current is √3 times phase current with equal voltages
3. C.ratio of rms to average value of a waveform, 1.11 for a sinusoid, distinct from peak factor which is peak to rms at 1.414
4. D.instantaneous magnetic trip thresholds B at 3–5×In for resistive loads, C at 5–10×In for general inductive loads, D at 10–20×In for motors and transformers

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1. A.Power factor
2. B.Form factor
3. C.RMS value
4. D.MCB tripping curves

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1. A.Form factor — instantaneous magnetic trip thresholds B at 3–5×In for resistive loads, C at 5–10×In for general inductive loads, D at 10–20×In for motors and transformers
2. B.Form factor — ratio of rms to average value of a waveform, 1.11 for a sinusoid, distinct from peak factor which is peak to rms at 1.414
3. C.Form factor — parallel capacitor supplying leading reactive power kVAR = P(tan φ1 − tan φ2), cutting line current, losses and utility penalties
4. D.Form factor — in star the line voltage is √3 times phase voltage with equal currents; in delta the line current is √3 times phase current with equal voltages

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1. A.cosine of the angle between voltage and current, equal to real power divided by apparent power, lagging for inductive loads and leading for capacitive
2. B.instantaneous magnetic trip thresholds B at 3–5×In for resistive loads, C at 5–10×In for general inductive loads, D at 10–20×In for motors and transformers
3. C.magnitude of an alternating current that produces the same heating as an equal direct current, 0.707 of the peak for a sinusoid
4. D.voltage induced in the rotating armature, Eb = V − Ia·Ra, proportional to speed and flux, which self-regulates armature current against load changes

Answer + AI explanation with Pro

1. A.MCB tripping curves
2. B.Three-phase power
3. C.Power factor
4. D.Form factor

Answer + AI explanation with Pro

1. A.Power factor — ratio of rms to average value of a waveform, 1.11 for a sinusoid, distinct from peak factor which is peak to rms at 1.414
2. B.Power factor — instantaneous magnetic trip thresholds B at 3–5×In for resistive loads, C at 5–10×In for general inductive loads, D at 10–20×In for motors and transformers
3. C.Power factor — cosine of the angle between voltage and current, equal to real power divided by apparent power, lagging for inductive loads and leading for capacitive
4. D.Power factor — real power √3·VL·IL·cos φ for a balanced load regardless of star or delta connection, with reactive power using sin φ instead

Answer + AI explanation with Pro

1. A.ratio of rms to average value of a waveform, 1.11 for a sinusoid, distinct from peak factor which is peak to rms at 1.414
2. B.cosine of the angle between voltage and current, equal to real power divided by apparent power, lagging for inductive loads and leading for capacitive
3. C.parallel capacitor supplying leading reactive power kVAR = P(tan φ1 − tan φ2), cutting line current, losses and utility penalties
4. D.in star the line voltage is √3 times phase voltage with equal currents; in delta the line current is √3 times phase current with equal voltages

Answer + AI explanation with Pro

1. A.Power factor
2. B.RMS value
3. C.Star-delta relations
4. D.Form factor

Answer + AI explanation with Pro

1. A.Star-delta relations — instantaneous magnetic trip thresholds B at 3–5×In for resistive loads, C at 5–10×In for general inductive loads, D at 10–20×In for motors and transformers
2. B.Star-delta relations — in star the line voltage is √3 times phase voltage with equal currents; in delta the line current is √3 times phase current with equal voltages
3. C.Star-delta relations — occurs at the load where variable copper loss equals constant iron loss, so distribution transformers are designed to peak at about 50–75% load
4. D.Star-delta relations — cosine of the angle between voltage and current, equal to real power divided by apparent power, lagging for inductive loads and leading for capacitive

Answer + AI explanation with Pro

1. A.ratio of rms to average value of a waveform, 1.11 for a sinusoid, distinct from peak factor which is peak to rms at 1.414
2. B.voltage induced in the rotating armature, Eb = V − Ia·Ra, proportional to speed and flux, which self-regulates armature current against load changes
3. C.real power √3·VL·IL·cos φ for a balanced load regardless of star or delta connection, with reactive power using sin φ instead
4. D.occurs at the load where variable copper loss equals constant iron loss, so distribution transformers are designed to peak at about 50–75% load

Answer + AI explanation with Pro

1. A.Power factor
2. B.Star-delta relations
3. C.Three-phase power
4. D.Maximum transformer efficiency

Answer + AI explanation with Pro

1. A.Three-phase power — cosine of the angle between voltage and current, equal to real power divided by apparent power, lagging for inductive loads and leading for capacitive
2. B.Three-phase power — voltage induced in the rotating armature, Eb = V − Ia·Ra, proportional to speed and flux, which self-regulates armature current against load changes
3. C.Three-phase power — occurs at the load where variable copper loss equals constant iron loss, so distribution transformers are designed to peak at about 50–75% load
4. D.Three-phase power — real power √3·VL·IL·cos φ for a balanced load regardless of star or delta connection, with reactive power using sin φ instead

Answer + AI explanation with Pro

1. A.magnitude of an alternating current that produces the same heating as an equal direct current, 0.707 of the peak for a sinusoid
2. B.instantaneous magnetic trip thresholds B at 3–5×In for resistive loads, C at 5–10×In for general inductive loads, D at 10–20×In for motors and transformers
3. C.ratio of rms to average value of a waveform, 1.11 for a sinusoid, distinct from peak factor which is peak to rms at 1.414
4. D.parallel capacitor supplying leading reactive power kVAR = P(tan φ1 − tan φ2), cutting line current, losses and utility penalties

Answer + AI explanation with Pro

1. A.MCB tripping curves
2. B.Maximum transformer efficiency
3. C.RMS value
4. D.Power factor correction

Answer + AI explanation with Pro

1. A.Power factor correction — occurs at the load where variable copper loss equals constant iron loss, so distribution transformers are designed to peak at about 50–75% load
2. B.Power factor correction — cosine of the angle between voltage and current, equal to real power divided by apparent power, lagging for inductive loads and leading for capacitive
3. C.Power factor correction — real power √3·VL·IL·cos φ for a balanced load regardless of star or delta connection, with reactive power using sin φ instead
4. D.Power factor correction — parallel capacitor supplying leading reactive power kVAR = P(tan φ1 − tan φ2), cutting line current, losses and utility penalties

Answer + AI explanation with Pro

1. A.ratio of rms to average value of a waveform, 1.11 for a sinusoid, distinct from peak factor which is peak to rms at 1.414
2. B.voltage induced in the rotating armature, Eb = V − Ia·Ra, proportional to speed and flux, which self-regulates armature current against load changes
3. C.in star the line voltage is √3 times phase voltage with equal currents; in delta the line current is √3 times phase current with equal voltages
4. D.instantaneous magnetic trip thresholds B at 3–5×In for resistive loads, C at 5–10×In for general inductive loads, D at 10–20×In for motors and transformers

Answer + AI explanation with Pro

1. A.Back emf of DC motor
2. B.MCB tripping curves
3. C.RMS value
4. D.Maximum transformer efficiency

Answer + AI explanation with Pro

1. A.Back emf of DC motor — occurs at the load where variable copper loss equals constant iron loss, so distribution transformers are designed to peak at about 50–75% load
2. B.Back emf of DC motor — voltage induced in the rotating armature, Eb = V − Ia·Ra, proportional to speed and flux, which self-regulates armature current against load changes
3. C.Back emf of DC motor — in star the line voltage is √3 times phase voltage with equal currents; in delta the line current is √3 times phase current with equal voltages
4. D.Back emf of DC motor — cosine of the angle between voltage and current, equal to real power divided by apparent power, lagging for inductive loads and leading for capacitive

Answer + AI explanation with Pro

1. A.in star the line voltage is √3 times phase voltage with equal currents; in delta the line current is √3 times phase current with equal voltages
2. B.magnitude of an alternating current that produces the same heating as an equal direct current, 0.707 of the peak for a sinusoid
3. C.cosine of the angle between voltage and current, equal to real power divided by apparent power, lagging for inductive loads and leading for capacitive
4. D.instantaneous magnetic trip thresholds B at 3–5×In for resistive loads, C at 5–10×In for general inductive loads, D at 10–20×In for motors and transformers

Answer + AI explanation with Pro

1. A.Form factor
2. B.RMS value
3. C.Power factor correction
4. D.MCB tripping curves

Answer + AI explanation with Pro

1. A.MCB tripping curves — cosine of the angle between voltage and current, equal to real power divided by apparent power, lagging for inductive loads and leading for capacitive
2. B.MCB tripping curves — instantaneous magnetic trip thresholds B at 3–5×In for resistive loads, C at 5–10×In for general inductive loads, D at 10–20×In for motors and transformers
3. C.MCB tripping curves — voltage induced in the rotating armature, Eb = V − Ia·Ra, proportional to speed and flux, which self-regulates armature current against load changes
4. D.MCB tripping curves — real power √3·VL·IL·cos φ for a balanced load regardless of star or delta connection, with reactive power using sin φ instead

Answer + AI explanation with Pro

1. A.parallel capacitor supplying leading reactive power kVAR = P(tan φ1 − tan φ2), cutting line current, losses and utility penalties
2. B.voltage induced in the rotating armature, Eb = V − Ia·Ra, proportional to speed and flux, which self-regulates armature current against load changes
3. C.occurs at the load where variable copper loss equals constant iron loss, so distribution transformers are designed to peak at about 50–75% load
4. D.in star the line voltage is √3 times phase voltage with equal currents; in delta the line current is √3 times phase current with equal voltages

Answer + AI explanation with Pro

1. A.RMS value
2. B.Maximum transformer efficiency
3. C.Star-delta relations
4. D.Back emf of DC motor

Answer + AI explanation with Pro

1. A.Maximum transformer efficiency — instantaneous magnetic trip thresholds B at 3–5×In for resistive loads, C at 5–10×In for general inductive loads, D at 10–20×In for motors and transformers
2. B.Maximum transformer efficiency — ratio of rms to average value of a waveform, 1.11 for a sinusoid, distinct from peak factor which is peak to rms at 1.414
3. C.Maximum transformer efficiency — parallel capacitor supplying leading reactive power kVAR = P(tan φ1 − tan φ2), cutting line current, losses and utility penalties
4. D.Maximum transformer efficiency — occurs at the load where variable copper loss equals constant iron loss, so distribution transformers are designed to peak at about 50–75% load

Answer + AI explanation with Pro