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The correct answer is option 2):2000 - 3500 hours

Concept:

• A halogen lamp is an incandescent lamp consisting of a tungsten filament sealed in a compact transparent envelope that is filled with a mixture of inert gas and a small amount of a halogen, such as iodine or bromine.
• This allows the filament to operate at a higher temperature than a standard incandescent lamp of similar power and operating life. this also produces light with higher luminous efficacy and color temperature.
• The small size of halogen lamps permits their use in compact optical systems for projectors and illumination.
• Halogen lamps are used in automotive headlamps, under-cabinet lighting, and work lights.
• The life span of a halogen lamp is 2000 - 3500 hours

The correct  answer is option 1): 0.45 A

Concept:

The current I is given by

I = _{\(Voltage \over R\)}

Calculation:

V = 1.8 V

I = \(1.8 \over 4\)

= 0.45 A

The correct answer is option 2):( 10 Hz)

Concept:

 The synchronous speed is given by

N_s = \(120f\over P\)

Where, f is the supply frequency in Hz or C/s

P is the number of poles

The induction motor rotates at a speed (N_r) close but less than the synchronous speed.

Slip of an induction motor is given by,

\(s = \frac{{{N_s} - {N_r}}}{{{N_s}}}\)

Where,

N_s is the synchronous speed and N_r is the rotor speed

Rotor current frequency

(f_r) = (s)(f)

The slip is negative when the rotor speed is more than the synchronous speed of the rotor field and is in the same direction.

Calculation:

Given 

P = 8

f= 50 Hz

s= 0.2

(fr) = (s)(f)

= 0.2 × 50

= 10 Hz

The correct answer is option 3): (Nichrome)

Concept:

• Nichrome, an Alloy of nickel and chromium
• Nickel 80%-20% chromium
• It is highly resistive, Even heating up for small current
• It is incredibly useful as a heating element in commercial products and home tools. Toasters and hair dryers use coils of nichrome wire to create large amounts of heat
• The most common use for tungsten is in light bulb filaments and is also used in aerospace, military equipment, electronics, and nuclear reactors.

The correct answer is option 3):(Potier's method)

Potier triangle method:

• This method depends on the separation of the leakage reactance of the armature and its effects
• It is used to find the synchronous reactance of a synchronous motor
• It is used to obtain the leakage reactance and field current equivalent of the armature reaction.
• It is the most accurate method of voltage regulation. Calculating the regulation requires open circuit characteristics and zero power factor characteristics.

Additional Information

Synchronous impedance method (EMF Method):

• The synchronous impedance method of calculating the voltage regulation of an alternator is otherwise called the EMF method. The synchronous impedance method or the EMF method is based on the concept of replacing the effect of armature reaction with an imaginary reactance.
• This method is not accurate as it gives a result that is higher than the original value.
• That's why it is called the pessimistic method. For calculating the regulation, the synchronous method requires the armature resistance per phase, the open-circuit characteristic, and the short-circuit characteristic.

Armature turn method:

• It is also known as the MMF method.
• It gives a value that is lower than the original value.
• That's why it is called an optimistic method.
• To calculate the voltage regulation by MMF Method, the following information is required. They are as follows:

          The resistance of the stator winding per phase Open circuit characteristics at synchronous speed Field current at rated short circuit current

The correct answer is option 2):(11 - 33 kV)

Concept:

The cables for operating voltage up to a maximum of 33000 V or 33 kV are said to be super tension cables.

Classification of underground cables on the basis of voltage level is given below

The correct answer is option 4):(resistance will decrease)

Concept:

Effect of temperature on insulator:

• With the increase in the temperature of the insulator, resistance will be decreased
• In insulators, there is a large gap between Valance and conduction band
• When the temperature raised, the electrons moved from the valance band to the conduction band
• The conductance will increase due to the availability of free electrons in the conduction band, so the resistance decreases with an increase in temperature in the insulator.

Additional Information

• Resistance of a conductor increases with an increase in temperature.α is positive.

R=R₀​(1+ α ΔT)

• The resistivity of a semiconductor decreases with temperature.

The Temperature vs Resistivity graph for electrical material is shown below,

The correct answer is option 1):(galvanised steel wire)

Concept:

• Over the bedding, armouring is provided which consists of one or two layers of galvanized steel wire or steel tape.
• Its purpose is to protect the cable from mechanical injury while laying it and during the course of handling.
• Armouring may not be done in the case of some cables.
• Galvanized steel is magnetic because the base steel metal is magnetic.
• Galvanized steel is covered with a thin layer of zinc and this process does not interfere with the magnetic strength of the steel.

The correct answer is option 2): (electronics ballast)

Concept:

• An electronic ballast is a device that controls the starting voltage and the operating currents of lighting devices
• It works on the principle of electrical gas discharge.
• An electronic ballast will convert power frequency to a very high frequency to initialize the gas discharge process in Fluorescent Lamps – by controlling the voltage across the lamp and current through the lamp.

There are some advantages to using electronic ballast instead of electromagnetic ballast.

• It operates in low supply voltage. It produces a high frequency to give a very high output voltage initially to start up the discharge process.
• ​It creates very low noise during operation.
• It does not create any stroboscopic effect or RF interference.
• As it works with a very high frequency, it helps to start the lamp operation instantaneously
• It does not require any starter that is used in electromagnetic ballast
• It never creates flickering.
• No start-up vibration occurs.

The correct answer is option 2):(For uniform stress distribution)

Concept:

• The electrostatic or voltage stress in a single core cable has a maximum value (g_max) at the conductor surface and goes on decreasing as we move towards the sheath.
• The maximum voltage that can be safely applied to a cable depends upon g_max i.e., electrostatic stress at the conductor surface. For the safe working of a cable having a homogeneous dielectric, the strength of the dielectric must be more than g_max.
• If a dielectric of high strength is used for a cable, it is useful only near the conductor where stress is maximum.
• But as we move away from the conductor, the electrostatic stress decreases, so the dielectric will be unnecessarily over-strong.
• The unequal stress distribution in a cable is undesirable for two reasons. Firstly, insulation of greater thickness is required which increases the cable size. Secondly, it may lead to a breakdown of insulation.
• The process of achieving uniform electrostatic stress in the dielectric of cables is known as the grading of cables.
• The reason for using differential coverings in cables,For uniform stress distribution