EE MCQ

SSC JE Electrical 2019 with solution SET-1
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_______is a tube that brings water to turbines

Penstock

Penstock pipe is used to bring water from the dam to the hydraulic turbine.

Penstock pipes are made up of steel or reinforced concrete.

The turbine is installed at a lower level from the dam.

The penstock is provided with a gate valve at the inlet to completely close the water supply.

It has a control valve to control the water flow rate into the turbine.

Related Question

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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Two decimal coils A and B of 1000 turns each lies in the parallel plane such that 80% of the flux produced by one coil links with the other. If a current of 5A flowing in A produces a flux of 0.05 mWb, then the flux linking with coil B is:

Flux in coil A = 0.05 mWb = 5 × 10−5 wb = φA

No. of turns NA = NB = 1000

Flux linkage in a coil with B = Flux linkage in coil A × 80/100

= 0.8 × 5 × 10−5

= 4 × 10−5 wb =0.04 mwb

SSC JE Electrical 2019 with solution SET-1
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Is it possible to have current in a transmission line, under no-load conditions?

During the no-load condition, the current flowing is only charging current due to line capacitance. It increases the capacitive var in the system. Since the line is under no load the line inductance will be less. Therefore, the capacitive var becomes greater than inductive var during no load or light load condition. Due to this phenomenon, the receiving end voltage becomes greater than the sending end voltage. This effect is also called the Ferranti effect.

In the case of short lines, the effect is negligible, but it increases rapidly with the increase in the length of the line. Therefore, this phenomenon is observable only in medium and long lines. For long high voltage and EHV transmission lines, shunt reactors are provided to absorb a part of the charging current or shunt capacitive VAr of the transmission line under no load or light load conditions, in order to prevent the overvoltage on the line.

SSC JE Electrical 2019 with solution SET-1
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The meter constant of an energy meter will be given in:

Meter constant = No. of revolution/kWh

Hence the number of revolutions made by the disc for 1 kWh of energy consumption is called meter constant.

The meter constant is always written on the name plates of the energy meters installed m homes, commercial and industrial establishments. If the meter constant of an energy meter is 1500 rev/kWh, it means that for the consumption of 1 kWh, the disc will make 1500 revolutions.

SSC JE Electrical 2019 with solution SET-1
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Find the frequency of rotor induced EMF of a 3-phase, 440V, 50 Hz induction motor has a slip of 10%

Given Data

Voltage = 440 V

Frequency = 50 Hz

Slip = 10% =0.1

Now,

Rotor frequency = slip × frequency

= 0.1 × 50 = 5 Hz