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The correct answer is option 1):(Thermal limit)

Concept:

• The power curve of a wind turbine is a graph that indicates how large the electrical power output will be for the turbine at different wind speed
• Power curves are found by field measurements, where an anemometer is placed on a mast reasonably close to the wind turbine (not on the turbine itself or too close to it, since the turbine rotor may create turbulence, and make wind speed
• The cut-in speed (typically between 6 and 9 mph) is when the blades start rotating and generating power. As wind speeds increase, more electricity is generated until it reaches a limit, known as the rated speed. This is the point that the turbine produces its maximum, or rated power.
• The rated wind speed is defined as the wind speed at which the rated power (the maximum output power) of the electrical generator is reached
• The cut-out speed is the point at which the turbine must be shut down to avoid damage to the equipment

so option 1 is wrong.

The correct answer is option 1):(mixture of nitrogen and argon gas)

Concept:

• The glass envelope of an electrical lighting device that contains and protects the light-emitting medium
• The incandescent lamp contains a mixture of nitrogen and argon gas inside the glass envelope to enclose the tungsten filament
• Gases in a light bulb prevent the tungsten from evaporating. otherwise, the bulb would be blackened

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The correct answer is option 1): (commutator brush system)

Concept:

A mechanical rectifier is a device for converting alternating current (AC) to direct current (DC) by means of mechanically operated switches

The commutators function as a mechanical rectifiers in a DC generator, transforming the alternating current from the windings to direct current in the external load circuit.

The commutator in a DC motor switches the direction of the current to deliver electricity to the windings.

The correct answer is option 2):( Murray and Varley loop test)

Concept:

Murray Loop Test :

• Murray loop test is the most common and accurate method for locating earth faults and short-circuit faults
• However, to perform the Murray loop test, it is necessary that a sound (good) cable runs along the faulty cable.
• This test employs the principle of Wheatstone bridge for fault location
• To perform the Murray loop test, the alongside sound cable and the faulty cable is shorted with a jumper conductor at the far end.
• The test side end is connected through a pair of resistors to a voltage source. Also, a null detector or galvanometer is connected between the two conductors at the test end.
• The circuit diagram is shown in the image below.

Varley Loop Test:

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

Additional Information

Directional overcurrent relays respond to excessive current flow in a particular direction in the power system.

The correct answer is option 3): 1.5 mΩ

Concept:

Extension of voltmeter:

For range extension of voltage measurement in moving coil instrument, a resistance is connected in series with internal meter resistance.

For a constant value of current, resistance connected in a series connection has a higher voltage drop compared to a parallel or shunt connection.

The value of the series resistance is given by:

Instrument resistance = \(Potential ; drop :across: the : terminal \over instrument :current \) = R_m

Shunt resistance required for full scale deflection corresponding to

Rsh = \(R_m \over \frac{I}{I_m} -1 \)

Calculation:

Given:

V_m = 75 mV

I_m  = 25 mA

I = 50 A

Resistance of voltmeter (Rm) =  \(75 × 10^{-3} \over 25 × 10^{-3} \)

= 3 Ω

Shunt resistance required for full scale deflection corresponding to

R_sh = \(R_m \over \frac{I}{I_m} -1 \)

= \(3 \over \frac{50}{25× 10^{-3}} -1\)

= \(3 \over 1999\)

= 1.5 × 10^-3 mΩ

The correct answer is option 2): pulsating and unidirectional

Concept:

• If a DC series motor is accidentally connected to single-phase ac supply voltage then the current direction through a series motor is reversed, the polarities of the field poles and the armature conductors are both reversed, resulting in a pushing effort between them in the same direction.
• Because of this, a series motor will operate on AC supply, its direction of rotation is the same for both half cycles.
• The lower the frequency of AC, the greater the torque that can be produced.
• If the frequency is high, the inductive reactance of the coil limits the current that can flow and the torque of the motor.
• An AC supply will exert unidirectional,Pulsating torque because the direction of armature current and field current reverses at the same time and the direction of rotation will as it is.
• Due to the presence of alternating current, eddy currents are induced in the yoke and field cores which causes excessive heating of the yoke and field cores

The correct answer is option 4

The Heat exchanger, nuclear reactor core, Shield, moderator, and control rods are the parts of the nuclear reactor.

Concept:

Nuclear Power Plant:

• A power generating station that converts the heat energy of nuclear fission into electrical energy is called a nuclear power plant.

• The most important characteristic of a nuclear power plant is that a large amount of electrical energy can be produced from a relatively small amount of nuclear fuel.

• Therefore, the running cost of a nuclear power plant is lower than that of thermal and diesel power plants.

• In practice, it has been found that the complete fission of 1 kg of Uranium (U235), which is a radioactive material can produce energy equivalent to that can be produced by the burning of 4500 tons of coal.

• Therefore, nuclear energy can be used for producing low-cost electrical energy at a large scale so that the problem of the energy crisis can be overcome.

• The Schematic diagram of a typical nuclear power plant is shown in the figure.

• In a nuclear power plant, heavy elements such as Uranium (U235) or Thorium (Th232) are subjected to nuclear fission (i.e., breaking up of nuclei of heavy atoms into two nearly equal parts with the release of a large amount of energy) in a piece of equipment called the nuclear reactor.

• The heat energy, released in nuclear fission, is utilized for producing steam at high pressure and temperature.

• This steam runs a steam turbine which converts the heat energy of steam into mechanical energy.

• The steam turbine drives the electric generator which converts the mechanical energy of the turbine into electrical energy.

The correct answer option 2):(Lambert's law of absorption)

Concept:

Lambert's cosine law: This law states that ‘illumination, E at any point on a surface is directly proportional to the cosine of the angle between the normal at that point and the line of flux.

Law of inverse squares: According to the Law of inverse squares, illumination of a surface is inversely proportional to the square of the distance between the surface and the light source.

\(E = \frac{I}{{{d^2}}}\)

Where E is the illuminance, I is the luminous intensity, and D is the distance between the surface and the source

Refraction: When a ray of light passes from one medium to another it suffers a change in direction at the boundary of two media is called refraction.

Interference: The combination of two or more electromagnetic waveforms to form a resultant wave that may have greater, lower, or the same amplitude is called interference.

The correct answer is option 2):  5 slots 

Concept:

• Coil span (also known as coil pitch) is defined as the peripheral distance between two sides of a coil, measured in terms of the number of armature slots between them.
• It means one side of the coil in a particular slot, after how many conjugative slots, the other side of the same coil is placed on the armature. This number is known as the coil span

Pole pitch = \(No:of: slots \over No : of : poles\)

Coil span = pole pitch ,In full pitch coil

Coil span < pole pitch in short pitch coil

Calculation

Given that,

 Number of slot = 22

Number of slot  per pole = 5.5 = 5(round off ) 

Coil span = 5 slot

One side of the coil will be 1^st slot means the next side of the coil will be at the fifth slot (assume that the coil is short pitch)

The correct answer is option 3):(solid bars of conducting material are placed in rotor slots and shorted through end rings on each side)

Concept:

Squirrel Cage Induction Motor:

• The 3 phase squirrel cage induction motor is a type of 3-ϕ induction motor based on the principle of electromagnetism.

• It is called a ‘squirrel cage’ motor because the rotor inside of it looks like a squirrel cage and is known as a squirrel cage rotor.

• This rotor is a cylinder of steel laminations, with highly conductive metal (typically aluminum or copper) embedded into its surface.

• It is also known as short-circuited rotor type motor.

• It doesn't need a slip ring and brush assembly.

• Airgap between the stator and rotor is uniform.

• External resistance cannot be introduced in the rotor circuit.

• In a three-phase induction motor, squirrel cage rotor,solid bars of conducting material are placed in rotor slots and shorted through resistor

• When an alternating current is run through the stator windings, a rotating magnetic field is produced.

• This induces a current in the rotor winding, that produces its own magnetic field.

• The interaction of the magnetic fields produced by the stator and rotor windings produces torque on the squirrel cage rotor.

• One big advantage of a squirrel cage motor is easily it can change its speed-torque characteristics.

• This can be done by simply adjusting the shape of the bars in the rotor.

• Squirrel cage induction motors are mainly used in the industry. Because they are reliable, self-starting, and easy to adjust