EE MCQ

SSC JE Electrical 2019 with solution SET-1
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What is the reason behind using a centrifugal switch in a single-phase induction motor?

The centrifugal switch is used to disconnect the starting winding of the motor once the motor approaches its normal operating speed i.e 50% – 70% speed.

Related Question

SSC JE Electrical 2019 with solution SET-1
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Hysteresis loss is NOT a function of

Hysteresis Loss = Kh × BM1.67 × f × v watts

where

Kh = Hysteresis constant depends upon the material

Bm = Maximum flux density

f = frequency

v = Volume of the core

Hence the hysteresis loss does not depend upon the ambient temperature.

SSC JE Electrical 2019 with solution SET-1
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Find H = _____ A/m at the center of a circular coil of diameter 1 m and carrying a current of 2A

Magnetic Field Strength (H) gives the quantitative measure of strongness or weakness of the magnetic field. H = B/μo Where B = Magnetic Flux Density μo = Vacuum Permeability Magnetic Field strength at the center of circular loop carrying current I is given by B = μoI/2r B/μo = I/2r H = I/2r Where r = Radius Now Given Parameters Diameter = 1m Current = 2A ∴ Magnetic field Intensity H = (2 / 2 × 1/2) = 2 A/m

SSC JE Electrical 2019 with solution SET-1
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Which of the following lamps has the shortest/less life span in working hours?

The lifespan of a bulb is referred to as “Average Rated Lifetime Hours” (ARL). Incandescent bulbs generally have the shortest lifespans. The average incandescent bulb light span is approximately 750-2,000 hours. Fluorescent lights generally have a life expectancy of 10,000 to 20,000 hours and other high-intensity lamps, such as high-pressure sodium, have greater than 20,000 hours of life expectancy.

SSC JE Electrical 2019 with solution SET-1
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Reflected Light/Incident Light =

The ratio of luminous flux leaving the surface (Reflected Light) to the luminous flux incident on it (Incident Light) is known as the reflection factor.

Reflection Factor = Reflected light/Incident light

The value of the Reflection factor is always less than 1.