RRB JE Electrical (CBT II) Mock Test- 8 - Electrical Engineering (EE) MCQ

Buchholz relay is used for the protection of transformers from the faults occurring inside the transformer. A Buchholz relay is a safety device mounted on some oil-filled power transformers and reactors, equipped with an external overhead oil reservoir called a "conservator".

Several items need to be considered in order to properly install and wire an electric motor drive and motor circuit.

Special considerations are necessary when installing an electric motor drive and motor circuit. These considerations involve motors, power quality, safety,and engineered applications.

The Scheme will be implemented as a Central Sector Scheme on a pilot basis in 50 districts. With the introduction of the modified scheme, it is expected that an increased number of farmers will be able to manage risk in agriculture production in a better way and will succeed in stabilizing farm income particularly at the times of crop failure on account of natural calamities.

Magnetic susceptibility is a dimensionless proportionality constant that indicates the degree of magnetization of a material in response to an applied magnetic field.

The magnetic susceptibility decreases with an increase in temperature. So, the ferromagnetism decreases with rising temperature. It is maximum at absolute zero temperature and becomes zero at Curie temperature. Above this temperature, the ferromagnetic material behaves as paramagnetic substance.

In diamagnetic materials, susceptibility is independent of temperature.

Field – effect transistor amplifiers provide an excellent voltage gain with the added feature of high input impedance and more temperature stable than BJT. They are also considered low – power consumption configuration with good frequency range and minimal size and weight. FET is a voltage control device.

The frequency of a series RLC circuit at resonance is,

If the value of all the components doubled, the new frequency will be

The name of our planet Earth originates from English language. The name Earth derives from the eighth-century Anglo-Saxon word erda, which means ground or soil. It became eorthe later, and then erthe in Middle English.

Given that, number of turns (N) = 1000
Relative permeability of the iron (μr) = 1400
Cross-sectional area of the core (A) = 5 cm²
Length (l) = 70 cm
Self-inductance of a coil is given by,

Form factor is nothing but ratio between the average value of the entitiy and the RMS valuer of the same.
So, the Form factor of Sinusoidal wave is calculated as:
Form factor = (RMS value/average value) = 0.707I_m/0.637I_m = 1.11.
[Note: crest factor = (peak value)/(RMS value) = I_m/0.707I_m = 1.414

In dynamometer wattmeter, the pressure coil is designed for having a low value of resistance so that the high value of current passes through it. This current produces the deflecting torque on the moving coil.

In a low power circuit, the value of the current is high, and that of the power is low. This high-value current causes the error in the wattmeter reading. To reduce this error, the compensation coil is used in the circuit.

Compensating coil has an equal number of turns of the current coil and is connected in series with a voltage coil or pressure coil. It carries current equal to the sum of two currents i.e. load current plus pressure coil current. The pressure coil is placed such that the field produced by the compensating coil is opposed by the field produced by pressure coil as shown in the above circuit diagram.

Given that, number of turns (N) = 1000
Relative permeability of the iron (μ_r) = 1400
Cross-sectional area of the core (A) = 5 cm²
Length (l) = 70 cm
Self-inductance of a coil is given by,

When a synchronous motor is operating with normal excitation, with the increase in load:

• The motor continues to run at a synchronous speed as it is a constant speed motor
• The torque angle δ increases
• The excitation voltage E_f remains constant
• The armature current I_a drawn from the supply increases due to increase in resultant voltage across the armature
• The phase angle ϕ increases in the lagging direction

The relative permeability (μ_r) of a substance is the ratio of magnetic permeability (μ) of the substance to the permeability of free space (μ₀)
μ_r = μ/μ₀
Hence, it is a dimensionless quantity and is equal to 1 for vacuum

• Windows 10 Mobile was announced on January 21, 2015, as a mobile operating system for smartphones and tablets running on ARM architecture; Its primary focus is unification with Windows 10
• Debian is a Unix-like operating system composed entirely of free software packaged by a team of volunteers
• Microsoft Disk Operating System is an operating system for x-86 based personal computers.
• Android is a mobile operating system developed by Google

The permissible temperature limit at which the insulators may be worked safely without deterioration depends upon the type and class of the insulation as detailed below.

• Class Y - maximum temperature 90°C
• Class A - maximum temperature 105°C
• Class E - maximum temperature 120°C
• Class B - Maximum temperature 130°C
• Class F - maximum temperature 155°C
• Class H - maximum temperature 180°C
• Class C - maximum temperature above 180°C (limited stability up to 225°C)

Soil Erosion: It is a process in which the top fertile layer of soil is lost by the natural forces. Due to soil erosion, the soil becomes less fertile.

The major cause of soil erosion is deforestation and the different causes of soil erosion are given below.

Causes of soil erosion:

Wind: When strong winds blow, the topsoil along with the organic matter is carried away by the wind. This happens more often when the land is not covered with grass or plants.

Water: When it rains in the hilly areas, the soil gets washed away towards the plains. The running water deposits the mineral-rich soil in the riverbed.

Overgrazing: When cattle are allowed to graze on the same field repeatedly, all the available grass, including the roots are eaten by them. This makes the topsoil vulnerable to wind and flowing water, leading to soil erosion.

Deforestation: Humans have taken land from the forest to cultivate in order to feed the ever-increasing population and to build houses, industries, etc. Cutting down of trees on a large scale for these purposes is known as deforestation.

The roots of trees hold the soil together, thus preventing the soil from getting uprooted. When large areas of the forest are cleared, the topsoil gets eroded by wind and flowing water.

• Any physical quantity which has both magnitude and direction is called a vector quantity. Angular momentum which is the product of the moment of inertia and angular velocity is a vector as it has both magnitude as well as direction.
• Scalar quantities like temperature and time are those quantities which have only magnitude and no direction.
• The dot product of two vectors is always a scalar. Work is the dot product of force and displacement which are both vectors, therefore, work is a scalar quantity.

• River Sutlej originates outside India, at Mount Kailash, Tibet.
• It enters India through Shipki la Pass.
• Yamuna River originates at Yamunotri Glacier, Uttarakhand.
• Ganga River originates at Gaumukh, Gangotri Glacier, Uttarakhand.
• Luni is the only river that flows in Rajasthan.

Time graded protection of a redial feeder can be achieved by definite time relays and Inverse time relays
Definite time relays:

• During relay coordination in electrical power system protection scheme, there is some time intentionally required, to operate some specific relays after some specific time delays.
• Definite time lag relays are those which operate after a specific time.

Inverse time relays:
In this type of relays, the time of operation depends upon the magnitude of actuating quantity (current). If the magnitude of actuating quantity is very high, the relay operation is very fast which is shown in below figure

• A universal motor is referred to AC series motor. It is very similar to a DC series motor in construction but is modified slightly to allow the motor to operate properly on AC power
• It is a commutated series-wound motor where the stator's field coils (armature coils) are connected in series with the rotor windings through a commutator
• These armature coils are connected to commutator through a resistance

Important Point:

Most of the universal motors are designed to operate at higher speeds, exceeding 3500 RPM. They run at lower speed on AC supply than they run on DC supply of same voltage, due to the reactance voltage drop which is present in AC and not in DC.

We know that underdamped galvanometer causes a great waste of time as the coil settles to its final steady position after oscillating about it.

An overdamped galvanometer represents very sluggish behaviour and loss of time.

A critically damped galvanometer represents an arrangement that takes the coil to its final steady position in the minimum time that is possible without overshooting.

The best-operating conditions are attained with a galvanometer that is either critically damped or slightly underdamped which may even give a faster response.

• Nikoloz Basilashvili emerged victorious after a three-set battle with Andrey Rublev to successfully defend his title at the German Tennis Championships.
• The reigning champion claimed his 12th straight win in Hamburg 7-5 4-6 6-3.
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• phagu Chauhan, a six-time member of the Uttar Pradesh Assembly, was sworn in as the 29th Governor of Bihar on 29 July 2019.
• He was administered the oath of office by Chief Justice of Patna High Court Amreshwar Pratap Shahi at the Raj Bhavan in Patna.
• Chief Minister Nitish Kumar, Deputy Chief Minister Sushil Kumar Modi and several other leaders were present during the ceremony.