EE MCQ

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.

Related Question

SSC JE Electrical 2019 with solution SET-2
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For indoor lighting the range of space : height is

In order to achieve uniform illumination over a surface, the number of luminaries must be placed suitably. The space-height ratio plays a vital role in deciding the height of lamps from floor level and their spacing.**Space to height ratio**

It is defined as the ratio of horizontal distance between adjacent lamps to the height of their mountings.

In order to obtain almost uniform illumination over the working plane, the distance between the lamps should not be too much. An ideal scheme could be developed, when there is a large number of small size lamps. But this would increase the installation cost. To have uniform illumination, the ratio of the spacing between the lamps and their height above the working plane (i.e., space-height ratio) should normally lie between 1 and 2.

SSC JE Electrical 2019 with solution SET-2
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For a three-phase induction motor slip at No Load ÷ slip at Full Load

In terms of slip, the actual speed of the motor (N) can be expressed as

N = Ns(1 − s)

At start, the motor is at rest and hence its speed N is zero.

s = 1 ( start)

This is the maximum value of slip s possible for the induction motor which occurs at start. While s = 0 gives us N = N. which is not possible for an induction motor. So slip of the induction motor cannot be zero under any circumstances.

Practically motor operates in the slip range of 0.01 to 0.05 i.e. 1 % to 5 %. The slip corresponding to the full load speed of the motor is called full load slip.

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

SSC JE Electrical 2019 with solution SET-2
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The number of brushes required for a 4 pole, lap wound DC machine is

**Lap Winding:-**In a lap winding the number of parallel paths (a) is always equal to the number of poles (p) and also to the number of brushes. In the given question number of poles is 4 hence the number of brushes will be 4.**Wave Winding:-** In wave windings, the number of parallel paths (a) is always two and there may be two or more brush positions.