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

In State of Madras Vs. Champakam Dorairajan case, the Supreme Court decisions stated that the Directive Principles of State policy cannot override fundamental rights.

Electric currents represent the flow of particles (electrons) and carry power, part or all of which is dissipated as heat in resistances. Magnetic fields don't represent a "flow" of anything, and no power is dissipated in reluctances.

Noise is defined as unwanted sound. Sound which pleases the listeners is music and that which causes pain and annoyance is noise. Anything above this (40-45 dB) threshold limit is considered to be noise.

A circuit breaker should be rated with short circuit making capacity. As the rated short circuit making current of the circuit breaker is expressed in peak value, it is always more than rated short circuit breaking current of the circuit breaker.

Making capacity of a circuit breaker is equal to 2.55 times symmetrical breaking current.

Breaking capacity is always expressed in rms value.

Both breaking and making capacity are generally expressed MVA.

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.

A fuse is an electrical safety device that operates to provide overcurrent protection of an electrical circuit. Its essential component is a metal wire or strip that melts when too much current flows through it, thereby interrupting the current.

The fuse wire should have low melting point so that it can get melt when current more than rated flows in the circuit

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.

Reluctance = length of wire/area x permeability
Reluctance, therefore reluctance varies as length/ Area.

• Nitrogen is the most electronegative among Arsenic, Nitrogen and Phosphorus.
• As per the periodic table, Nitrogen has an atomic number of 7 and hence its electron configuration is 1s2 2s2 2p3.
• Amongst all the others nitrogen has the highest tendency to attract a shared pair of electrons towards itself.

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.

The field winding of an alternator is placed on the rotor and is connected to DC supply through two slip rings.

The 3-phase armature winding is placed on the stator. This arrangement has the following advantages:

• It is easier to insulate stationary winding for high voltages for which the alternators are usually designed
• The stationary 3-phase armature can be directly connected to load without going through large, unreliable slip rings and brushes
• Only two slip rings are required for DC supply to the field winding on the rotor. Since the exciting current is small, the slip rings and brush gear required are of light construction
• Due to the simple and robust construction of the rotor, higher speed of rotating DC field is possible. This increases the output obtainable for a machine of given size

Ubuntu, Linux, Unix, Microsoft Windows and macOS all fall under the category of operating systems.

An Operating system is basically a low-level system software and an important program that runs on every computer. Its basic function is to perform basic tasks such as controlling peripherals, managing computer software and hardware resources, keeping track of directories and files in the storage drive, sending output to the display and more.

The superposition theorem can be applied to solve networks when the network contains two or more than two sources of anyone, or both types.

The superposition theorem for electrical circuits states that for a linear system the response (voltage or current) in any branch of a bilateral linear circuit having more than one independent source equals the algebraic sum of the responses caused by each independent source acting alone, where all the other independent sources are replaced by their internal impedances. This theorem is essentially based on linearity.

Let's first find the current for each heater

P = V × I

I = P/V = 1000/250 = 4 Amp.

Now we need to find resistance of each heater.

V = I × R or R = V/I

I.e. R = 250/4 = 62.5 ohms.

∴ resistance of 2 heaters = 125 ohms.

Now we need to find the total power

P = 4 × 125 = 500 watts = ½ kW

A principal node is a junction where branch current can combine or divide

Important:

Node:

A point or junction where two or more circuit’s elements (resistor, capacitor, inductor etc.) meet is called Node. In other words, a point of connection between two or more branches is known as a Node.

Branch:

That part or section of a circuit which locate between two junctions is called the branch. In a branch, one or more elements can be connected, and they have two terminals.

Loop:

A closed path in a circuit where more than two meshes can occur is known as Loop i.e. there may be many meshes in a loop, but a mesh does not contain on one loop.

Mesh:

A closed loop which contains no other loop within it or a path which does not contain on other paths is called Mesh

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

Concept
When the LCR circuit is set to resonance, the resonant frequency is 
Quality factor is 
At resonance current is Maximum i.e. I₀
I _O = V₀/R
Calculation:
At resonance current is maximum i.e. I₀
I _O = V₀/R = 200/20 = 10A

The sag is given by
S = w L ²/8T
Where w is the weight per unit length of the conductor
T is the tension of the conductor
L is the length of the span
If sag on the transmission is increased, the tension will decrease

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.

By Charter Act of 1833 Governor of the state of Bengal designated as Governor-General of India.

An ideal rectifier should have:

• Efficiency = 100%
• AC components (V_ac) = 0
• Transformer Utilization Factor = 1
• Power Factor = 1

According to the operating voltage, the substations may be categorized as:

• High voltage substations – involving voltages between 11 kV and 66 kV
• Extra high voltage substations – involving voltages between 132 kV and 400 kV
• Ultra-high voltage – operating voltage above 400 kV

Important Points:

By nature of duties, the substations may be categorized as:

• Step-up or primary substations
• Primary grid substations
• Step-down or distribution substations

By service rendered, the substations may be categorised as:

• Transformer substations
• Switching substations
• Converting substations

By design, the substations may be categorised as:

• Indoor type substations
• Outdoor substations
• Pole mounted substations
• Foundation mounted substations

Power consumed in case of balanced delta connection  P = V² ph/Req
Equivalent resistance in this case: Req 2R/3
Now, the power will be P₁ = 3V ph/2R
If one resistor is removed from a 3 - phase delta connected circuit, then the circuit will be converted into single phase circuit having two resistors in series.
Equivalent resistance in this case: Req = 2R
Now, the power will be P₂ V ph/2R
⇒ P₂ = P₁/3