EE MCQ

SSC JE Electrical 2019 with solution SET-2
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If the number of poles in an 11 KV transmission line is 80, then how many disc insulators are required?

No of disc required for 11 kV transmission line = 1 disc

Since the transmission line is 3-phase, therefore, the number of discs required for a single-pole will be 3.

Total no. of poles = 80

No of disc = 3 × 80 = 240

Related Question

SSC JE Electrical 2019 with solution SET-2
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Observe the given figure. The maximum power to the load resistor is when Ri is =?

The maximum power transfer theorem states that the DC voltage source will deliver maximum power to the variable-load resistor only when the load resistance is equal to the source resistance. Similarly, this theorem states that the AC voltage source will deliver maximum power to the variable complex load only when the load impedance is equal to the complex conjugate of the source impedance.

Hence when Ri = RL the transfer of power will be maximum.

SSC JE Electrical 2019 with solution SET-2
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If a zero-centered voltmeter has a scale from 5V to − 5V, then the span of it is

Voltage Scale Span of instrument = Vmax − Vmin

Given

Vmax = 5 V

Vmin = −5V

Span = 5 −(−5) = 10 V

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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Observe the figure and find the correct relation from the four given options?

According to Kirchhoff’s law states that the current entering a node is always equal to the current leaving a node.

From the above Diagram

Current Flowing towards the Point: I1, I2, I6

Current Flowing Away from the Point: I3, I4, I5

Hence I1 + I2 + I6 = I3 + I4+ I5

SSC JE Electrical 2019 with solution SET-2
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The input for a condenser in a steam power plant comes from a/an

Condenser – Condenser is a heat exchanger in which cooling water is circulated through the tubes. The exhaust steam from the turbine enters the condenser where it is cooled and converted to condensate (water).