WBSETCL Junior Engineer Electrical Grade II 14th March 2022 First Shift Solution PDF
Question : 1
A room of 12 m length and 10 m breadth is lighted by 15 lamps to a fairly uniform illumination of 100 Im/m2. Calculate the utilisation coefficient of the room given that the output of each lamp is 1600 lumens.
Question : 8
How many elements are joined to a principal node?
Question : 10
Find the force (F in Newton) between two point-source charges (Q1 and Q2) in Coulomb) in air when the distance between the charges is d in metre.
Answer-A
Solution:
Coulomb’s law-It states that the magnitude of the electrostatic force F between two point charges D1 and D2 is directly proportional to the product of the magnitudes of charges and inversely proportional to the square of the distance d between them.
Question : 11
Which of the following instruments is used to measure the air gap between the rotor and stator of the starter motor?
Answer-D
Solution:
A feeler gauge is a tool used to measure gap widths.
They consist of a number of small lengths of steel of different thicknesses with measurements marked on each piece.
Feeler gauge is used to measure the air gap between the rotor and stator of the starter motor.
Question : 12
What happens to the diversity factor in the case of an interconnected Grid System?
Answer-D
Solution:
Interconnected grid system-The connection of several generating stations in parallel is known as interconnected grid system.
Interconnected grid Advantages
1.Exchange of peak loads.
2.Ensures economical operation.
3.Increases diversity factor.
4.Reduces plant reserve capacity.
The grid system can improve the diversity factor of each generating station connected to the grid. The diversity factor gets improved because the maximum demand of the grid shared by the generating station is much lesser than the maximum demand imposed on the generating station if it runs individually.
Question : 13
Answer-B
Solution:
A heavily doped semiconductor diode which is designed to operate in reverse direction is known as the Zener diode.
The diode which is specially designed for optimising the breakdown region is known as the Zener diode.
The symbolic representation of Zener diode is shown in the figure below.
Question : 19
What is the function of the shunt reactor in a substation?
Answer-B
Question : 20
Which of the following is true for the earth wire?
Answer-C
Question : 21
Which of the following term is a synonymous term to industrial management?
Answer-C
Solution:
Industrial Engineering is an engineering profession that is concerned with the optimization of complex processes, systems, or organizations by developing, improving and implementing integrated systems of people, money, knowledge, information and equipment.
Industrial engineering term is a synonymous term to industrial management.
Question : 22
Which Type of Lightning Arrester consists of a divided spark gap in series with a resistance element having non-linear characteristics?
Answer-C
Solution:
The lightning arrester protects the electrical equipment from lightning. It is placed very near to the equipment and when the lightning occurs the arrester diverts the high voltage wave of lightning to the ground.
The lightning arrestor is mainly classified into twelve types. These types are
- Road Gap Arrester
- Sphere Gap Arrester
- Horn Gap Arrester
- Multiple-Gap Arrester
- Impulse Protective Gap
- Electrolytic Arrester
- Expulsion Type Lightning Arrester
- Valve Type Lightning Arresters
- Thyrite Lightning Arrester
- Auto valve Arrester
- Oxide Film Arrester
- Metal Oxide Lightning Arresters
Valve Type Lightning Arrester
Such type of resistor is called nonlinear diverter.
It essentially consists a divided spark gap in series with a resistance element having the nonlinear characteristic.
Question : 28
Solution:
Lissajous figure is the pattern which is displayed on the screen, when sinusoidal signals are applied to both horizontal & vertical deflection plates of CRO.
These patterns will vary based on the amplitudes, frequencies and phase differences of the sinusoidal signals, which are applied to both horizontal & vertical deflection plates of CRO.
1.If the Lissajous figure is a straight line with an inclination of 45∘ with positive x-axis, then the phase difference between the two sinusoidal signals will be 0∘. That means, there is no phase difference between those two sinusoidal signals.
2.If the Lissajous figure is a straight line with an inclination of 135∘ with positive x-axis, then the phase difference between the two sinusoidal signals will be 180∘. That means, those two sinusoidal signals are out of phase.
3. If the Lissajous figure is in circular shape, then the phase difference between the two sinusoidal signals will be 90∘ or 270∘.
4. If the Lissajous figure is in elliptical shape, then the phase difference between the two sinusoidal signals will be 30∘ or 330∘.
Question : 29
Which of the following is NOT true for the salient pole rotor when compared to the cylindrical rotor?
Question : 30
What should be the length of the span for the centenary wire on a single route in traction?
Question : 31
A coil of copper wire 200 m long and of cross sectional 0.8mm2 has a resistivity of 0.02 μΩ m at normal working temperature. Calculate the resistance of the coil.
Solution:
Question : 32
Transducer using Hall effect converts ___________.
Question : 33
Which of the following loads can cause a serious frictional error in an induction type single-phase energy meter?
Question : 34
Find the equation for amplification factor (βdc) for the common emitter transistor. Consider dc collector current is IC, dc base current is IB and dc emitter current is IE
Question : 35
What will be the efficiency of a Carnot’s engine, considering the temperature of the source as T1 and the temperature of the sink as T2?
Solution:
Carnot engine- A theoretical thermodynamic cycle proposed by Leonard Carnot.
This engine gives the maximum possible efficiency that a heat engine can have during the conversion process of heat into work or vice-versa, working between two reservoirs.
Question : 38
What is the term used for One complete to and fro motion in Simple harmonic motion?
Question : 39
Which of the following statements is true for a series circuit in below resonant frequency?
Solution:
Question : 43
What is the economic voltage between lines in 3-phase system where V is the line voltage in kV, L is the distance of transmission line in km and P is the maximum power per phase to be delivered in a single circuit?
Solution:
Economical transmission voltage for a 3 phase AC system is given as
Where, V = line voltage in kV
P = maximum power per phase (in kW) to be delivered over single circuit
L = distance of transmission in km
Question : 51
Which of the following is true for the spring control as a controlling force for measuring instruments?
Solution:
Spring Control Method-This is the most common method of providing controlling torque, in electrical instruments. A spiral hairspring made of some non-magnetic material like phosphor bronze is attached to the moving system of the instrument as shown in the figure.
Springs also serve the additional purpose of leading current to the moving system (i.e. operating coil).
With that deflection of the pointer, the spring is twisted in the opposite direction. This twist in the spring provides the controlling torque.
The amount of controlling torque produced will be proportional to the angle of deflection (θ) of the pointer, whereas the deflecting torque (Td) depends upon the current flowing through the coil i.e., Td increases with an increase in current and vice-versa. At steady state
Since current is directly proportional to the deflection angle, uniform scales can be graduated.
The springs used are usually made up of low resistance bronze alloy and consist of a large number of turns to avoid deformation in the spring.
Question : 54
How is the breaking capacity of the circuit breaker calculated?
Question : 56
Identify the DC link configuration for HVDC transmission given in the above figure.
