EE MCQ

SSC JE Electrical 2019 with solution SET-2
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Voltage regulation is considered to be the best for transmission lines?

Voltage Regulation: When the transmission line is energized, the current is flowing in the line. Due to this current, a voltage drop occurs because of the resistance and inductance of the line. So, the receiving-end voltage (VR) is always less than the sending-end voltage (Vs).

The difference produced in the voltage at the receiving end of the transmission line from no load to full load conditions is known as voltage regulation of the line and it is expressed as a percentage of the receiving-end voltage (VR).

It is always desirable that the voltage regulation of the line should be low, or in other words, the increase in the load current should lead to a small difference in the receiving-end voltage.

Related Question

SSC JE Electrical 2019 with solution SET-2
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In a 4 pole. 20 kW, 200 V wave wound DC shunt generator, the current in each parallel path will be

Given

Power (P) = 20 kW = 20 × 103 W

Voltage (V) = 200 V

P = VI = I = P/V

I = (20 × 103)/200

I = 100A

For wave wound No. of Parallel Path = 2

Current in Each parallel Path for wave wound

I = 100/2 = 50 A

SSC JE Electrical 2019 with solution SET-2
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While estimating domestic wiring cost, if the length of the PVC conduit required is 62 meters, then what is the length of the cable required?

The size of the conduit is 62 meters. In conduit, there is a 2-phase wire and 1 neutral wire. Therefore the total number of conducting wire is 3 in a conduit

Total length of cable = 62 × 3 = 186 meters.

SSC JE Electrical 2019 with solution SET-2
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The names of the four materials have been given, select the one which has the least resistivity at 20°C?

The resistivity of iron at 20°C is 9.71 × 108

The resistivity of silver at 20°C is 1.59 × 108

The resistivity of Glass at 20°C is 1.10 × 109

The resistivity of nichrome at 20°C is 100 × 108

Hence silver is the least resistive material in the given option.

SSC JE Electrical 2019 with solution SET-2
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The combined inductance of two coils connected in a series is 0.6H and 0.1H, depending on the relative directions of the currents to the coils. If one of the coils when isolated has a self-inductance of 0.2 H, then calculate the natural inductance?

The combined inductance of two coils connected in series

L = L1 + L2 + 2M

In series adding case

L1 + L2 + 2M = 0.6 H ——–(1)

In series opposing case

L1 + L2 − 2M = 0.1 H ——–(2)

Subtracting eqn (2) from eqn (1) we get

4M = 0.5 H

M = 0.125 H

Let L1 = 0.2 H (since the coil when isolated, its self-inductance is 0.2 H)

Putting the value of M & L1 in equation (2)

0.2 + L2 + 2 ×0.125 = 0.06

0.2 + L2 = 0.35

L2 = 0.15 H