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

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.

Peroxy Acetyl Nitrate is a secondary air pollutant whereas, Suspended Particulate Matter, SO₂ and NO₂ are primary air pollutants.

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.

Cobalt is a chemical element with symbol Co and atomic number 27.

By observing V curves,
When excitation of the synchronous motor is increased up to normal excitation from under excitation, armature current decreases
When excitation of the synchronous motor is increased to overexcitation from normal excitation, armature current increases

To convert delta to star,

Electroplating is defined as the deposition of a metal over any metallic or non-metallic surfaces. Electroplating is usually employed

1. To protect the metals from corrosion by atmospheric air, moisture and CO₂

2. To give the reflecting properties to reflectors

3. To replace worn out metals

Given that, (t) = 1.25 cos (5t – 15°)

Complex power delivered by the source to the load is

• Vice Admiral G Ashok Kumar, AVSM, VSM assumed charge as Vice Chief of the Naval Staff on 30 Jan 2019.
• Kumar has held various Staff and Command assignments during his distinguished naval career spread over more than three decades.
• He is an alumnus of National Defence Academy, Khadakvasla, Pune and was commissioned into the Executive Branch of the Indian Navy on 01 Jul 1982.

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

During the operation of a connecting a busbar in parallel with an incoming alternator, the following condition should be satisfied:

• The phase sequence of the busbar voltages and the incoming machine voltage must be the same
• The busbar voltages and the incoming machine terminal voltage must be in phase
• The terminal voltage of the incoming machine and the alternator which is to be connected in parallel or with the busbar voltage should be equal
• The frequency of the generated voltage of the incoming machine and the frequency of the voltage of the busbar should be equal

The frequency of a series RLC circuit at resonance is,

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

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.

Energy resources can be classified into two categories:

1. Renewable source (Non-conventional energy)
2. Non-Renewable source (Conventional energy)

Renewable energy resources are natural resources which can be regenerated continuously and are inexhaustible. They can be used again and again in an endless manner. Examples are Wood, Solar energy, wind energy, hydropower, tidal energy, geothermal energy, Biomass Energy etc.

• Biomass Energy: Energy produced by organic matter like plants and animals are called Biomass Energy
• Examples of biomass are wood, crop residues, seeds, cattle dung, sewage, agricultural wastes etc
• Biogas and biofuel are examples of biomass energy

Non-Renewable energy resources are natural resources which cannot be regenerated once they are exhausted. They cannot be used again. Examples are Oil, Coal, petroleum, natural gas, nuclear fuels etc.

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

• Hima Das won her second international gold in women's 200m with a top finish at the Kutno Athletics Meet in Poland.
• Hima took 23.97 seconds to clinch the gold while VK Vismaya bagged the silver in 24.06 seconds.
• This was Hima's second competitive 200m race of 2019. She has a personal best of 23.10s, which she clocked in 2018.

• 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.

Advantages of carbon arc welding:

• The heat developed during the welding can be easily controlled by adjusting the length of the arc
• It is quite clean, simple, and less expensive when compared to other welding processes
• Both the ferrous and non-ferrous metals can be welded
• Easily adaptable to automation

Disadvantages of carbon arc welding:

• Input current required in this welding, for the workpiece to raise its temperature to welding temperature, is more
• In case of ferrous metal, there is a chance of disintegrating the carbon at high temperature and transfer to the weld, which causes weld deposit to be harder and brittle
• A separate filler rod has to be used if any filler metal is required

Curie temperature: It is the temperature above which ferromagnetic materials lose their permanent magnetic field and the magnetism completely disappears.

When four 90-ohm resistors are connected in series, the equivalent resistance becomes:

R_eq = 4 × 90 = 360 Ω

Voltage (V) = 18 V

Wooden poles, steel poles, RCC and PCC poles and steel towers are used for transmission line.

Wooden poles:

Wooden poles are used for temporary electrical line. The length of wooden pole is kept 6-9 meters out of which 1-2 meter length buried in the ground. The diameter of the pole is kept 15-25 cm so as to have safety factor of 3.5. Maximum permissible span for wooden poles is 75 meter.

Steel poles:

• Steel poles possess greater mechanical strength and thus permit the use of longer spans (60 to 80 metres).
• These poles have the longer life (more than 40 years) which can further be increased by regular painting.
• These poles need protection against corrosion. Hence at the bottom (the portion which is buried underground), these poles are set in concrete muffs in order to protect them from chemical reactions.

RCC and PCC poles:

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.