RRB JE Electrical (CBT II) Mock Test- 6 - Electrical Engineering (EE) MCQ

• A flowchart is the graphical or pictorial representation of an algorithm with the help of different symbols, shapes and arrows in order to demonstrate a process or a program.
• With algorithms, we can easily understand a program.

Cyclo-converters are mainly used for producing low frequency AC voltage.

Other applications of Cyclo-converter include :

HVDC transmission systems, Static Var Generation, Aircraft or shipboard power supplies, Speed control of high power AC drives, Grinding mills, Cement mill drives, Mine winders

By volume, dry air contains 78.09% nitrogen, 20.95% oxygen, 0.93% argon, 0.04% carbon dioxide.

A capacitor is a passive two-terminal electronic component that stores electrical energy in an electric field.

Capacitor acts as short circuit (offers low impedance) for high frequency signals.

Universal motor: It is used in high-speed vacuum cleaners, vacuum cleaners, drink and food mixers, domestic sewing machine, mixer-grinder.

D.C. shunt motor: It is a constant speed motor and is used in centrifugal pumps, fans, blowers

3-phase synchronous motor: It is used for constant speed applications where speed is independent of the load over the operating range of the motor

Induction motor: It is used in a drilling machine, fan, blower printing machines etc.

Transistors were used for second generation computers and integrated circuits in third generation. First generation computers used vacuum tubes and valves as their main electronic component. Vacuum Tubes were invented by Lee De Forest in 1908.

In γ-emission rays ( Gamma rays), no changes occur in the mass/charge.

Gamma rays are electromagnetic waves of short wavelength and high frequency.

They are emitted by most radioactive sources along with alpha or beta particles

Through releasing a gamma photon it reduces to a lower energy state. Hence, Gamma rays have no electrical charge connected with them.

Alpha rays are released by high mass whereas beta has high energy electrons.

In an electromechanical energy conversion device, the developed torque depends upon

Stator field strength

Rotor field strength

Torque angle (δ)

⇒ R = 3/2 = 1.5Ω

Whenever transformer is loaded, the temperature of the transformer insulating oil increases. Consequently, the volume of the oil is increased. As the volume of the oil is increased, the air above the oil level in conservator will come out. At low oil temperature, the volume of the oil is decreased, causes air to enter into conservator tank.

The air consists of moisture in it and this moisture can be mixed up with oil. Hence to filter the air from moisture silica gel breather is used. The drying agent extracts moisture from the in flowing air and ensures that only the dried air will be aspirated into the transformer.

In AC circuits, the power factor is defined as the ratio of the real power flowing to the load to the apparent power in the circuit.

Hence power factor can be defined as watts to volt amperes

Power factor = cosϕ

Where, ϕ is the angle between voltage and current.

If current lags the voltage, power factor will be lagging.

If current leads the voltage, power factor will be leading.

From the options,

1) Ratio of real power to apparent power

2) P/VI represents the ratio of the real power to apparent power, it is known as power factor

3) R/Z also represents power factor from the impedance triangle

• When two or more celestial bodies arrange themselves in a straight line due to their own revolution it is known as a syzygy.
• All eclipses are syzygy but, not all syzygy are eclipses.
• For example, the full moon and new moon are syzygy involving the lining up of the Sun, Earth and Moon so, lunar and solar eclipses are syzygy.

In an AC circuit, power is consumed only in resistor whereas inductor and capacitor act as power sources.

Resistor dissipates the energy whereas inductor and capacitor stores the energy.

Eddy current losses are given by
W e = Kef²B²mt²v
Where, Ke = eddy current constant.
f is frequency
B_m is flux density
t is thickness
v is volume
Here eddy current losses are directly proportional to square of thickness

i(0⁺) = 0 A
i(∞) = V/R = 100/100 = 1
Time constant τ = L/R = 50/100 = 0.5
i(t) = i(∞)+[i(0+)-i(∞)]e^-t/τ
i(t) = 1 - e^-t/0.5
⇒ 0.7 = 1 - e^-t/0.5
⇒ t = 0.6 sec

Controlling torque:

• It is to control the pointer to a definite value which is proportional to the quantity being measured.
• In absence of controlling torque, the pointer will swing beyond its final steady-state position and the deflection will be indefinite.
• After removal of moving mechanism, the pointer has to come back to its initial position, but in absence of controlling torque, the pointer won’t come back to its initial position.
• In a portable instrument, the controlling torque is provided by spring control.

Average energy = 720 MWh
Average power 720 x 10⁶/24 = 30 mW
Load factor = Average power/Maximum demand
Maximum demand = 30 x10⁶/0.6 50MW  

Positive sequence component: It represents three equal phasors with a phase displacement of 120° and has phase sequence same as the original phasors. It specifies that the current is flowing through source to load.

Negative sequence component: It represents three equal phasors with a phase displacement of 120° with each other and has phase sequence opposite to that of the original phasors. It specifies that current is flowing from load to source.

Zero sequence component: It represents three equal and parallel phasors with zero phase displacement. It specifies that current is flowing from source to ground.

In a balanced three phase system operating in normal condition, only positive sequence component exists and hence zero sequence currents are zero.

A printer is an output device that prints characters, images and symbols on paper. On the basis of the printing technique used, printers may be classified as impact or non-impact printers.

Impact printers

Impact printers are like typewriters, as they use some sort of striking/ hammering action to press carbon or fabric ribbon against paper to create a character or a pattern. These devices are noisy and are not capable of producing high-resolution graphics.

The most common impact printers are character printers (e.g. daisy wheel, dot matrix) and line printers (e.g. chain printers, drum printers).

Dot-matrix printers are noisy, slow and produce lower quality output.

Non-impact printers

Non-impact printers overcome the limitations of impact printers. They form characters or images without making print heads strike the paper. They use thermal, electrostatic, chemical or inkjet technology to produce printed output. They are fast and quiet in operation. The most common non-impact printers are inkjet printers and laser printers.

• Uber cup associated with Badminton.
• It is named after a former British women's badminton player, Betty Uber.
• It is often called World Team Championships for Women.
• It is a major international badminton competition contested by women's national badminton teams.
• Thomas Cup is the World Team Championship for Men in Badminton.

Multi-motor drive: Several separate motors are provided for operating different parts of the single machine.

In travelling cranes, three motors are used for hoisting, long travel and cross travel motions.

Multi-motor is used in complicated metal cutting machine tools, rolling mills, paper making machines, etc.

Important Points:

Group drives: Electric drive that is used to drive two or more than two machines from line shaft through belts and pulleys is known as group drive. It is also sometimes called the line shaft drive.

• Varley loop test is used for locating short-circuit and earth faults in underground cables.
• This test also employs the principle of the Wheatstone bridge. However, the difference between Murray loop test and Varley loop test is that, in Varley loop test resistances R₁ and R₂ are fixed, and a variable resistor is inserted in the faulted leg.
• If the fault resistance is high, the sensitivity of Murray loop test is reduced, and Varley loop test may be more suitable.

Appearance: The general appearance of an underground system is better as all the distribution lines are invisible.

Fault location and repairs: In general, there are little chances of faults in an underground system. However, if a fault does occur, it is difficult to locate and repair this system. On an overhead system, the conductors are visible and easily accessible so that fault locations and repairs can be easily made.

Brussels is the capital of Belgium.

A motor meter is Induction type energy meter which consists of the following components

Operating torque system (driving system), moving system, braking system, registering system.

Driving system: the driving system of the meter consists of two electromagnets. The core of these electromagnets is made up of silicon steel lamination.

Moving system: this consist of an aluminium disc mounted on a light alloy shaft. This disc is positioned in the air gap between series and shunt magnets

Braking system: A permanent magnet positioned near the edge of the aluminium disc forms the braking system. The aluminium disc moves in the field of this magnet and thus provides a braking torque.

The transient voltage that appears across the circuit breaker contacts at the instant of arc extinction is called restriking voltage. it is measured in peak value.

According to Gauss law, the electric field inside a conducting sphere is always zero irrespective of how much charge resides on its surface. Due to zero electric field inside a sphere, the electric flux inside a sphere is zero.

Interpole winding

• Interpoles are small narrow commutating poles which are connected in series with armature
• It produces an extra flux to neutralize the reactance MMF produced at the time of commutation process

Compensating winding

• The compensating windings consist of a series of coils embedded in slots in the pole faces
• These coils are connected in series with the armature
• To neutralize the cross-magnetizing effect of armature reaction, a compensating winding is used