EE MCQ

SSC JE Electrical 2019 with solution SET-1
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Lamp efficiency is measured in

The luminous efficiency of an electric lamp is the ratio of the luminous flux (in lumen) emitted by the lamp to the electric power (watt) given to it i.e.

Luminous efficiency η = Luminous flux/Watt

Note:- Lumens is the unit of measurement for luminous flux, which is the total amount of visible light emitted by a source.

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Related Question

SSC JE Electrical 2019 with solution SET-1
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In the two wattmeter method, the readings of the two wattmeters are 500W, 500W respectively. The load power factor in a balanced 3-phase 3-wire circuit is:

In two wattmeter method the phase angle is tanφ = √3(W1 − W2)/(W1 + W2) tanφ = √3(500 − 500)/(500 + 500) tanφ = 0° φ = tan−10° = 0° Power factor = cosφ PF = cos0° = 1

SSC JE Electrical 2019 with solution SET-1
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Which motor is referred to as a universal motor?

Universal motors may be powered by either AC or DC power sources.

The universal motor is constructed in the same way as a series-wound DC motor. However, it is designed to operate with either AC or DC applied.

The series-wound motor is the only type of DC motor that will operate with AC applied.

The windings of shunt-wound motors have inductance values that are too high to allow the motor to function with AC applied.

The series-wound motors have windings that have low inductances (few turns of large diameter wire), and they, therefore, offer a low impedance to the flow of AC.

The universal motor is one type of AC motor that has concentrated or salient field windings. These field windings are similar to those of all DC motors.