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The correc answer is option 2): (Depth of discharge)

Concept:

• Battery's depth of discharge (DoD) indicates the percentage of the battery that has been discharged relative to the overall capacity of the battery.
• Depth of Discharge is defined as the capacity that is discharged from a fully charged battery, divided by battery nominal capacity.
• Depth of discharge is an important parameter appearing in the context of rechargeable battery operation.
• The life of the battery depends on the depth of discharge
• The usable capacity of a battery is known by Depth of discharge
• Depth of Discharge refers to how much energy is cycled into and out of the battery on a given cycle

The correct answer is option 2): Four Wire DC System

Concept:

Four wire system

• The AC power from generating stations is transmitted over long distances through transmission lines to various receiving stations.
• R, Y and B is  3 phase 3 wire, 4^th wire system an additional neutral N is present.
• 4 wire system is mainly used in the distribution side to convert the 3-phase system into a single phase to supply single-phase household loads, where the neutral acts as the current return path.
• It is done by connecting the secondary side of the distribution transformer in star.

Additional InformationDC two-wire:

• In the 2-wire DC system, one is the outgoing wire called the positive wire and the other is the return wire called the negative wire as shown in Figure below.
• The return wire is also connected to the earth.

DC two-wire with mid-point earthed:

• The two-wire DC system with a mid-point earthed is shown in the figure below.
• The maximum voltage between any conductor and the earth is Vm and the maximum voltage between conductors is 2Vm.
• The voltage level is high when compared to two-wire systems.

 (iii) DC three-wire system:

In a 3-wire DC system, there are two outers and a middle wire which is connected to earth.

When the load is balanced, the current in the neutral wire is zero. DC 3- wire system is shown in figure below.

The correct answer is option 2):(3000 RPM)

Concept:

The speed of synchronous generator is given as

N = \(120f\over p\)

where

N is the speed in RPM

f is the frequency in Hz

P is the no of poles

Calculation:

P = 2

f = 50 Hz

N = \(120 \times50 \over 2\)

=3000 RPM

The correct answer is option 4):

Concept:

• In the moving coil instrument type instruments, damping is done  by eddy current
• The deflecting torque is used for deflection
• The controlling torque acts opposite to the deflecting torque. So before coming to rest the pointer always oscillates due to inertia,
• To bring the pointer to rest within a short time by reducing oscillations, we use damping torque without affecting controlling torque. The following mechanism can be used for producing damping torque.

Types of damping

1. Air friction damping
2. Fluid friction damping
3. Eddy current damping

The damping device should be such that it produces a damping torque only while the moving system is in motion. To be effective the damping torque should be proportional to the velocity of the moving current but independent of the operating current.

Eddy current damping:

• When a conductor moves in a magnetic field an emf is induced in it.
• If a closed path is provided, a current (known as eddy current) flows.
• This current interacts with the magnetic field to produce an electromagnet torque that opposes the motion.
• This torque is proportional to the strength of the magnetic field and the current produced.

Additional Information

• Air friction damping  is used in moving iron instrument
• Fluid friction damping is used in Electrostatic voltmeter
• Electromagnetic damping used in flux meter

The correct answer is option 2):(1101)

Concept:

• 8421 is also known as BCD code BCD is a weighted code.
• In weighted codes, each successive digit from right to left represents weights equal to some specified value, and to get the equivalent decimal number to add the products of the weights by the corresponding binary digit.
• The following represents the 4-bit binary representation of decimal values:
• | Decimal | BCD Digits | | --- | --- | | 0 | 0000 | | 1 | 0001 | | 2 | 0010 | | 3 | 0011 | | 4 | 0100 | | 5 | 0101 | | 6 | 0110 | | 7 | 0111 | | 8 | 1000 | | 9 | 1001 |

Explanation :

• A number with an 'n' decimal digit will require 4k bits in BCD.
• Ex- Decimal 396 is represented in BCD with 12 bits as 0011 1001 0110, with each group of 4 bits representing one decimal digit.
• As the decimal digits relating to 1010, 1011, 1100, 1101, 1110, and 1111 do not exist, these are invalid. In BCD valid states are from 0 to 9. So 1101 is invalid state

The correct answer is option 3): (inverter )

Concept:

Inverter An inverter is a device that changes direct current (DC) to alternating current (AC).

The input voltage, output voltage, and frequency. Inverters power the electric appliances in the event of power failure.

They are also used in uninterruptible power supplies, control of electrical machines, and active power filtering.

The inverter itself does not produce any power – instead, the power is provided by the DC source.

Power inverters are either 100% electronic or they could be a combination of mechanical components such as rotary equipment and electronic circuitry. 

An inverter may take the 12, 24, or 48 volts DC and convert to 230 volts AC.

Additional Information

• A rectifier is an electrical device that converts A.C. to D.C.
• AC Voltage Controller is a thyristor-based device which converts fixed alternating voltage directly to variable alternating voltage without change in frequency
• A DC-to-DC converter is an electronic circuit or electromechanical device that converts a source of direct current (DC) from one voltage level to another

The  correct  answer is option 3): cross field theory

Concept:

• Cross field theory is used to analyze the working of a single-phase induction motor
• Idea behind the cross - field theory is that how the rotor develops torque According to cross field theory, the stator flux can be resolved into two components which are mutually perpendicular One acts along the axis of the stator winding and other acts perpendicular to it
• Assume now that an initial push is given to the rotor in an anticlockwise direction Due to the rotation, rotor physically cuts the stator flux and dynamically e.m.f. gets induced in the rotor
• This e.m.f. circulates current through the rotor
• This current produces its own flux called rotor flux ϕr This axis of ϕr is at 90° to the axis of stator flux hence this rotor flux is called cross-field

The correct answer is option 4): 500 A

Concept:

In a long-shunt compound generator:

Here,

Vt = Terminal Voltage (V)

Il = Line Current (A)

Rsf = Series field resistance (Ω)

Ra = Armature resistance (Ω)

Rshf = Shunt field resistance (Ω)

Ish = Shunt current (A)

Ia = Armature current (A)

Eg = Generated EMF (V)

Vb = Brush voltage drop ( = 2 Vb1 = 2 × voltage drop per brush) Formula:

\({I_{sh}}=\frac{{{V_t}}}{{{R_{shf}}}}\)

E_g = V_t + I_a(R_a + R_sf) + 2 V_b1

P = V × I W

Calculation:

Output Power = P = 100 kW

V_t = 200 V

100 × 10³ = 200 × I

I = 500 A

The correct answer is option 2):  (Partially distributed coil)

Concept:

Distributed winding is a type of coil in electrical machines where all the winding turns are organized in a number of full pitches. These coils are then placed in phase form or the commutator winding in slots spread around the periphery of the air gap. This type of winding is used in stators and rotors of induction motors.

Partially distributed coil type of coil distribution which does not cover all the branches

The correct answer is option 4):(is in a blocked state)

Concept:

• When the rotor of a three-phase induction motor is blocked, the rotor is in stationery.
• The speed of the rotor is zero i.e., Nr = 0.
• Slip speed (N) is equal to the difference between the synchronous speed and rotor speed.
• Slip is equal to
• Slip (s) = (Ns – Nr) / Ns
• As in this case, s = 1  the equivalent circuit of the motor is exactly like a transformer, having a short-circuited secondary.

Additional Information s= 0 (Zero Slip)

• Zero slip means that rotor speed is equal to synchronously rotating magnetic flux.
• Under this condition, there will not be any relative motion between the rotor coils and rotating magnetic flux.
• Therefore, there will not be any flux-cutting action of rotor coils. Hence, no emf will be generated in rotor coils to produce rotor current.
• This means no electromagnetic torque will be produced. The induction motor will not work.
• Therefore, it is very important for induction motors to have a positive value of slip.
• This is the reason; slip is never zero in an induction motor

**s = Negative (Negative Slip)**​

• The negative value of slip in an induction motor can be achieved when the rotor speed is more than the synchronously rotating magnetic flux.
• This is only possible when the rotor is rotated in the direction of rotating magnetic flux by some prime mover.
• Under this condition, the machine operates as an Induction Generator.

​s > 1 (Slip greater than 1)

• Slip more than 1 implies that, the rotor is rotating in a direction opposite to the direction of rotation of magnetic flux.
• This means if magnetic flux is rotating in the clockwise direction, then the rotor is rotating in an anticlockwise direction or vice versa.
• Therefore, the relative speed between them will be (Ns + Nr). In Plugging or Braking the Induction motor, a slip of more than 1 is achieved to quickly bring the rotor to rest.