RRB JE Electrical (CBT II) Mock Test- 4 - Electrical Engineering (EE) MCQ

Exosphere layer lies above the thermosphere. The exosphere extends beyond the thermosphere around 700-10,000 Km. Exosphere is the uppermost layer where the atmosphere thins out and merges with interplanetary space.

The transformer which changes the magnitude and phase angle at a certain point in the power system is known as the regulating transformer

It is mainly used for controlling the magnitude of the bus voltage and for controlling the power flow, which is controlled by the phase angle of the transformer

Hence these are used to control the load flow

The regulating transformer is of two types; One is used for changing the magnitude of voltage which is called online tap changing transformer and the other is called phase shifting transformer

Kumaun Himalayas, west-central section of the Himalayas in northern India, extending 200 miles (320 km) from the Sutlej River east to the Kali River. The range, comprising part of the Siwalik Range in the south and part of the Great Himalayas in the north.

High rating AC induction motors required protection against

Motor overheating due to either of mechanical overloading, reduced supply voltage, unbalanced supply voltage and single phasing

Short circuit

A motor winding failure such as phase to phase and phase to earth faults

Stalling overload protections

Reverse motor rotation

Motor bearing failure

As superposition principal is applicable for linear,active, bi lateral network.
Current & voltage are linear to each other.
but power = I² x R
Power is direct propositional to square of current , which is non linear.
There for it is applicable only for current & voltage calculation.

Synchronous speed is the speed of rotation of the magnetic field in a rotary machine. An induction motor always runs at a speed less than synchronous speed.

The rotating magnetic field which is produced in the stator will generate flux in the rotor which will make the rotor to rotate. But due to the lagging of rotor flux current with respect to stator flux current, the rotor will never reach to its rotating magnetic field speed i.e. the synchronous speed.

• Jamshedpur is known as the Steel City of India or Pittsburgh of India for being rich in minerals.
• It is a home to many industries like Tata Motors, Tata Steels, Usha Martin Industries, Steel & Wire Products, Tata Pigments, Tayo Rolls Limited, and many other assets.
• This city is also known as the Tatanagar.

Effects of ozone depletion

• It produces a greenhouse effect and also changes the climate
• It results in low production of crops
• It causes damage to the organs of living things
• Ultraviolet rays harm the plants
• It causes to spread the skin cancer disease
• It raises the possibilities of acid rains in urban areas
• It increases the temperature of the environment
• It affects the mental health of man
• It increases the temperature of the atmosphere which has a bad effect on the vegetation
• The UV rays reaching the earth are harmful to the pregnant women and the infant children also

Given that, Magnetic force (H) = 800 AT/m
As it is air, μ_r = 1
We know that,
B = μH = μ₀μ_rH
= 4π x 10^-7 x 1 x 800
= 1 mWb/m²

• Due to the equatorial bulge, i.e. the equator being more bulged towards the outside, the poles are nearer to the Centre of the earth, as compared to the equatorial region.
• And as the acceleration due to gravity is inversely proportional to the distance from the Centre of the earth, as the distance is less on poles, the acceleration due to gravity(g) is more at the poles.

We know that synchronous speed in an alternator is given by
N_s = 120f/P
N_s is synchronous speed in rpm
f is frequency or number of cycles
P is the number of poles
Given that, speed is N rps = 60 N rpm
⇒ 60N = 120f/P ⇒ f = NP/2 

• Novak Djokovic defeated Rafael Nadal to win his 7^th Australian Open Men’s Singles title at Melbourn.
• The resurgent world No. 1 outplayed the second-ranked Nadal 6-3, 6-2, 6-3 in a largely one-sided match.
• In Women’s Singles, Japan’s Naomi Osaka clinched her maiden Australian Open Grand Slam Singles title in Melbourne.

Given that, R = 20 Ω, L = 0.05 H, C = 1 μF

Quality factor of series circuit is,

The faults occurring in cables which are used in lower distribution voltages are:

Ground faults: The insulation of the cable may breakdown causing a flow of current from the core of the cable to the lead sheath or to the earth.

Short circuit faults: If the insulation between two conductors is faulty, a current flow between them.

Methods used for localizing ground and short circuit faults are:

• Murray loop test
• Varley loop test

Mass in gms of a compound is given by

mass = molar mass × number of moles

molar mass = 14 +14 = 28 gms

mass = 28 × 0.1

mass = 2.8 gms

Induction generator always works with leading power factor since it will take large amount of reactive power to produce sufficient amount of working flux so that armature reaction is always magnetizing hence it will work always with leading pf

Important Point

• induction generator is basically an induction motor, which runs above the synchronous speed
• when it acts as a generator it will supply the active power back to source, but for this supply of active power it needs reactive power as input to keep its winding excited
• in case if the induction motor is connected to the grid, it will draw the required reactive power for the excitation of windings, but if it is standalone system (ie. not connected to grid) then a capacitor bank will be always connected, and this will provide leading reactive power to keep the winding excited for the process of mechanical to electrical energy conversion
• since the reactive power is supplied by the capacitor, the induction generator is operating in leading power factor

When R_L­ = 0, I = 3 A
⇒ V/R = 3 ⇒ V = 3R
When R_L = 2, I = 1.5
⇒ V/R + R _L = 1.5
⇒ 3R/R + 2 = 1.5
⇒ R = 2 Ω
When, R_L = 1 Ω
I =  V/R + R _L  =  3R/R +  R _L  = ³⁽2)/2 + 1 = 2A

• Keyboard: Most common and popular input device
• Light pen: It is similar to a pen. It is used to select a displayed menu item or draw pictures on the monitor screen
• Joystick: It is used to move cursor position on a monitor screen; Mainly used in computer-aided designing and playing a computer game
• Scanner: Scanner captures images from the source which are then converted into digital form

The natural environment components can be classified into two

1. Abiotic components
2. Biotic components

Abiotic components

These components are not living but can support other living organisms. Some kinds of such organisms are given below:

• Inorganic substances: The elements which are taken up by the plants with the help of sunlight and converted into food. The examples of such inorganic elements are Nitrogen, Calcium, Phosphorus, Hydrogen, Carbon dioxide, and Oxygen.
• Organic substances: The substances which are taken in the form of inorganic materials from the food source and are again sent back to the environment after decomposition by decomposers. E.g. Carbohydrates, proteins, fats etc.
• Physical factors: These factors have a direct effect on living organisms, which are climatic conditions like temperature, rainfall, wind, humidity, soil, and light energy which is used by the plants for the preparation of food.
• Lithosphere: The outermost layer of the earth (i.e.) soil or land.
• Hydrosphere: Part of the earth having water resources like oceans, rivers, ponds, and lakes.
• Atmosphere: It is a cover around the earth composed by a variety of gases which protects the living organisms from various harmful cosmic radiations.

Biotic components

The area in which life is possible is called biosphere. All living organisms in the biosphere depend upon one another and these organisms exist in the biosphere forming the following community.

• Producers: The green plants present on the earth's surface which produce their own food by the process of photosynthesis in sunlight, water, and carbon dioxide forms food for other organisms. E.g. Sugar, carbohydrates etc.
• Consumer: These organisms directly (or) indirectly depend upon green plants for their source of food. E.g. All animals including man.
• Decomposers: These are micro-organisms which decompose the complex compounds in the dead organic matter of plants and animals and again recycle the elements into the environment. E.g. Bacteria and fungi.

Force per unit length of two long current carrying conductors is given by
F/l = µ₀I₁I₂/2πr
Here F = force, I = current, r = distance between two conductors

The electrical circuit breaker is provided on the electric locomotive to protect electrical equipment against excessive overloads automatically.

Important:

• A circuit breaker is a switching device that interrupts the abnormal or fault-current
• It is a mechanical device that disturbs the flow of high magnitude (fault) current and in additions performs the function of a switch
• The circuit breaker is mainly designed for closing or opening of an electrical circuit, thus protects the electrical system from damage
• When the circuit breaker is closed, it acts as a short switch; Thus, before the interruption, the ideal circuit breaker should offer zero impedance
• When the circuit breaker is open, it acts as an open switch; Thus, after an interruption, an ideal circuit breaker should offer infinite impedance

When the resistances are connected in series, the equivalent resistance will be the sum of all the resistances. In series circuit, the current flows through circuit is same.

We know that V = IR

For constant voltage, resistance is inversely proportional to current.

• Emitter resistor is NOT good for A.C. amplification, hence a bypass capacitor is used in parallel to emitter resistor
• Bypass capacitor in the CE amplifier provides a low resistance path for the AC signals

We can use electrostatic instruments to measure voltage and power. These type of wattmeters are used for measurement of a small amount of power, practically when the voltage is high and the power factor is low. It is also used for measurement of dielectric loss of cables on alternating voltage and for calibration of wattmeter and energy meters.

Thermocouple instruments are used to measure current, voltage and power.

We can use the moving iron instrument to measure current and voltage only. It can’t be used to measure power.