EE MCQ

SSC JE Electrical 2019 with solution SET-2
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The impedance at resonance offered by a parallel resonant circuit is

A practical parallel resonance circuit is represented by an inductance and a resistance id one branch and a capacitance in other branches.

At resonance in a practical parallel resonance circuit, the impedance is maximum. Hence, it is called a rejector circuit, and it exhibits the property of voltage magnification.

Z = L/CR

Related Question

SSC JE Electrical 2019 with solution SET-2
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The candle power of a lamp placed normal to a working plane is 60 CP. Find the distance if the illumination is 15 lux?

Candle Power of lamp = 60 CP

Illumination of lamp = 15 lux

Distance(D) = ? meters

Illumination of lamp = (candle power)/(distance)2

(D)2 = candle power/Illumination of lamp

(D)2 = 60/15 =4

D = √4

D = 2

SSC JE Electrical 2019 with solution SET-2
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Lower efficiency, lower power factor, are the features of which of the following motors?

The efficiency and power factor of single-phase motors are usually low. Thus at full-load a 186 W motor (1/4 hp) has efficiency and poor factor of about 60 percent. For the same size, the single-phase induction motors develop about 50% of the output as that of three-phase induction motors. The starting torque is also low for asynchronous motors / single phase induction motor.

The low power factor is mainly due to the large magnetizing current, which ranges, between 70 percent and 90 percent of full-load current. Consequently, even at no-load these motors have a substantial temperature rise. The power factor of 3-phase motors is of the order of 0.85 lagging, whereas it is 0.55 to 0.6 for single-phase motors.

The relatively low efficiency and power factor of single-phase induction motors is a consequence of their fractional horsepower ratings. The efficiency of 3-phase motors is quite high of the order of 80 to 90 %, while single-phase motors hardly work with an efficiency of 55 to 60 %.

SSC JE Electrical 2019 with solution SET-2
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The wattage rating of a single-phase induction motor used as a ceiling fan will be in the range of

The wattage rating for a ceiling fan motor is in the range of 50 to 150 W. if the ceiling Fans size ranges from 36 inches to 56 inches then the total wattage use is 55 to 100 watts.. A 48-inch ceiling fan will use 75 watts.