RRB JE Electrical (CBT II) Mock Test- 7 - Electrical Engineering (EE) MCQ

Radiation is the transfer of heat energy through space by electromagnetic radiation.

Skin effect is the tendency of an alternating electric current (AC) to become distributed within a conductor such that the current density is largest near the surface of the conductor, and decreases with greater depths in the conductor.

If frequency is increased, skin effect will increases.

Star - delta connection can be used in a transformer to intoduce a phase difference of 30 degrees between its output and corresponding input time voltages.

It can be noted that in a star - delta connection the phase shift of 30° between primary line voltage and secondary line voltage as leading.

A menu bar is a graphical control element which has drop-down menus. Its purpose is to supply a common housing for window-or application-specific menus which provide access to such functions as opening files, interacting with an application, or displaying help documentation or manuals.

minimum ground clearance of 33KV uninsulated electrical conductor is 5.2 meter and 0.3 meter for every 33KV above 33KV.
So, for first 33 kv, 5.2 metres and for next (220-33) = 187kv, 187/33 = 5.66 for which 5.66*0.3mt = 1.7 mt
In total 5.2 + 1.7 = 6.9 metres for 220 kv

A fluorescent lamp tube is filled with a gas containing low-pressure mercury vapor and argon, xenon, neon, or krypton. The pressure inside the lamp is around 0.3% of atmospheric pressure.The inner surface of the lamp is coated with a fluorescent coating made of varying blends of metallic and rare-earth phosphor salts. The lamp's electrodes are typically made of coiled tungsten and usually referred to as cathodes because of their prime function of emitting electrons. For this, they are coated with a mixture of barium, strontium and calcium oxides chosen to have a low thermionic emission. temperature.

Ferrite core is a type of magnetic core made of ferrite on which the windings of electric transformers and other wound components such as inductors are formed.

It is used for its properties of high magnetic permeability coupled with low electrical conductivity (high resistance)

It helps in preventing eddy currents

• The second India-Myanmar bilateral Army exercise named 'IMBEX 2018-19' commenced at Chandimandir military station in Haryana on 14 January 2019.
• The aim of this joint training event is to train the Myanmar delegation for participation in UN peacekeeping operations.
• The exercise includes participation of 15 officers from Myanmar Army and 15 officers from Indian Army

The power dissipated by a transistor is equal to the product (multiplication) of collector current and collector-emitter voltage.
P = V_CE × I_C

A pressure transducer is used to convert a certain value of pressure into its corresponding mechanical or electrical output.

The transducers used for static pressure measurement are

• Semi-conductor strain gauge
• Variable capacitor for transducer
• Piezoelectric transducer

Voltage across resistor (V_R) = 40 V
Voltage across (V_L) = 40 V

R = 10 ohm and X_L = 10 ohm
Impedance of RL circuit is, Z = √R² + X²L
⇒ Z = √10² + 10² = 10√2Ω
Power factor ø = R/Z = 10/10√2 = 0.707
⇒ Phase difference (ϕ) = 45°

According to Faraday's law, the current flowing through a coil produces the magnetic field. Hence the source of a magnetic field is the current loop.

We know that

Band width = resonant frequency/Quality factor = 1000/100 = 10 kHz

Half power point = ω₁ = ω₀ + Δω/2 = 1000 + 10/2 = 1005 kHz

1) Resistance is proportional to length: When wire length becomes half, the resistance becomes half

2) Resistance is inversely proportional to the cross-sectional area: Diameter, becomes half, area reduces by the square of diameter i.e. 1/4 times; Therefore, resistance becomes 4 times more

Ferromagnetism is the phenomenon in which on application of a magnetising force, the domains become aligned to produce a strong magnetic field within the part which is shown in figure

The surface of the earth is a complex zone in which three main components of the environment meet, overlap and interact.

• The solid portion of the earth on which we live is called the Lithosphere
• The gaseous layers that surround the earth, is the Atmosphere, where oxygen, nitrogen, carbon dioxide and other gases are found
• Water covers a very big area of the earth’s surface and this area is called the Hydrosphere; The Hydrosphere comprises water in all its forms, that is, ice, water and water vapour
• The Biosphere is the narrow zone where we find land, water and air together, which contains all forms of life

Lithosphere

The lithosphere is the solid crust or the hard top layer of the earth. It is made up of rocks and minerals and covered by a thin layer of soil. It is an irregular surface with various landforms such as mountains, plateaus, plains, valleys, etc.

The lithosphere is the domain that provides us with forests, grasslands for grazing, land for agriculture and human settlements. It is also a source of mineral wealth.

According to maximum power transfer theorem, in AC circuits the load impedance should be the complex conjugate of the internal impedance of the active network
Z _{L =} Z* _th 

Current drawn from the source
I = 48/20||(12 + 8) 
⇒ I = 4/10 = 4.8A
Current in 8 Ω resistor
I _8 Ω = 4.8/20 + 20 x 20 
I _8 Ω = 2.4 A

Given that, number of turns (N) = 100

Current (I) = 0.2 A

Resistance switching:

• It is a method adopted for dampening the over-voltage transients due to current chopping.
• In this method, a shunt resistance is connected across the contacts of the circuit breaker.
• It reduces the rate of rising of re-striking voltage and the peak value of re-striking voltage.
• It helps to reduce the voltage transient surge during current chopping and capacitive current breaking.

The direction of rotation of a capacitor start motor can be reversed by reversing the connection of the main winding or auxiliary winding.

Z₁ Z₄ =Z₂ Z₃ 


(R + j_wL_x) (1/ 60wC ) = 35/4 (1 + 60²ω²C²)
Rx + 60ω²C L_x+ j(ωL_x- 60R_xωC) = 35/4 (1+60²ω²C²)
Compare real parts of the above equation,
R_x + 60ω²CL_x = 35/4 (1 + 60²ω²C²)
R_x = 35/4 Ω
And, 60ω²CL_x = 35/4 ×60²ω²C²
⇒ Lx = 35/4 × 60 × C = 35/4 × 60 × 25 × 10^-6 = 13.125 mH
Quality factor, Q = ωLx /Rx = 2πfL/Rx = 2π × 50 × 13.125 × 10^-3 / 35/4 = 0.47

Approximate quantities of different gases in the atmosphere in PPM are given below.

• The power losses are very high in the shaded pole induction motor
• The power factor of the motor is low
• The starting torque induces in the induction motor are also very low
• The efficiency is also very low

Important Point:

• The shaded pole induction motor is simply a self-starting single-phase induction motor whose one of the poles is shaded by the copper ring
• The copper ring is also called the shaded ring
• This copper ring act as a secondary winding for the motor
• The shaded pole motor rotates only in one particular direction, and the reverse movement of the motor is not possible
• The direction of rotation of the magnetic field is from nonshaded pole to shaded pole

• Five limb core construction is preferred over three limb construction because in this type of construction magnetic reluctance of the three phase can be balanced.
• 5 limbed transformer core offers low impedance to the flow of unbalanced load between the line and neutral.
• This is because the flux finds its path from 4th and 5th limb. So, tertiary winding will not be needed in a star connected transformer operating in an unbalanced load.