Test: Utilization of Electrical Energy- 3 - Electrical Engineering (EE) MCQ

Average Speed: It is the mean of the speeds attained by the train from start to stop, i.e. it is defined as the ratio of the distance covered by the train between two stops to the total time of run. It is denoted with V_a

Average speed = distance between stops / actual time of run

V_a = D/T

Where V_a is the average speed of train in kmph

D is the distance between stops in km

T is the actual time in hours

Here the total time of run does not include the duration of the stops. Hence the average speed is independent of the duration of the stops.

Adhesive weight: The total weight to be carried out on the drive in wheels of a locomotive is known as adhesive weight

Accelerating weight: It is the effective weight of train that has angular acceleration due to the rotational inertia including the dead weight of the train.

Tractive effort is the force acting on the wheel of locomotive which is necessary to propel the train. It is a vector quantity always acting tangential to the wheel of a locomotive. It is measured in newton.

The net effective force or the total tractive effort (F_t) on the wheel of a locomotive or a train to run on the track is equals to the sum of tractive effort:

a) Required for linear and angular acceleration (F_a)

b) To overcome the effect of gravity (F_g)

c) To overcome the frictional resistance to the motion of the train (F_r)

F_t = F_a + F_g + F_r

The energy input to the motor is called the energy consumption. This is the energy consumed by various parts of the train for its propulsion. The energy drawn from the distribution system should be equals to the energy consumed by the various parts of the train and the quantity of energy required for lighting, heating, control and braking.

This energy consumption is required for

a) Accelerating the train mass

b) Overcoming the gradient while moving up the gradient

c) Overcoming the train resistance

In the selection of the electric motor for a centrifugal pump, power rating, starting characteristics and Operating speed are most important. Speed control is least significant characteristic for this purpose as most of the time centrifugal pumps operates at constant speed.

Continuous and constant loads: The loads on the motor operate for a long time under the same conditions

Continuous and variable loads: The load on the motor operates repetitively for a longer duration but varies continuously over a period

Pulsating loads: The load on the motor which can be viewed as constant torque superimposed by pulsations

Impact loads: The load on the motor having regular and repetitive load peaks or pulses, i.e. load increases to a maximum level suddenly

Short time loads: The load of the motor occurs periodically remains constant for short time and then remains idle for longer time

Short time intermittent loads: The load on the motor occurs periodically in identical duty cycle, each duty cycle having period of application of load and rest

The load cycle for a motor driving a power press will be intermittent and variable.

The halogen lamp is also known as a quartz halogen and tungsten halogen lamp. It is an advanced form of incandescent lamp. The filament is composed of ductile tungsten and located in a gas filled bulb. This bulb is stronger than standard glass in order to contain the high pressure. This lamp has been an industry standard for work lights and film/television lighting due to compact size and high lumen output.

Advantages:

1) Halogen lamps are small and light weight

2) Low cost to produce

3) Does not use mercury like CFLs (fluorescent) or mercury vapour lights

4) Better colour temperature than standard tungsten (2800-3400 Kelvin)

5) Longer life than a conventional incandescent

6) Instant on to full brightness

Ratings of normal sodium vapour lamp:

1) The efficiency of sodium vapour lamp is lies between 40 and 50 lumens/W

2) Normally these lamps are manufactured in 45 W, 60 W, 85 W and 140 W ratings

3) The normal operating temperatures of these lamps are 300° C

4) The average value life of the sodium vapour lamp is 3000 hr and these are not affected by voltage variations

The fluorescent tube is coated form inside with a thin layer of fluorescent material in the form of powder in order to absorb invisible ultraviolet rays and radiate visible rays.

Fluorescent lamp (electric discharge lamp) is cooler and more efficient than incandescent lamps that produces light by the fluorescence of a phosphor coating. The reason behind this is the tube consumes less power.

The advantages of electric resistance welding are

1) Welding process is rapid and simple

2) Localized heating is possible, if required

3) No need of using filler material

4) Both similar and dissimilar metals can be welded

5) Comparatively lesser skill is required

6) It can be employed for mass production

Flash butt welding is a combination of resistance, arc and pressure welding. This method is mainly used in the production welding.

The advantages of the flash butt welding are

1) Less requirement of power

2) When the surfaces being joined, it requires only less attention

3) Weld obtained is so clean and pure; due to the foreign metals appearing on the surfaces will burn due to flash or arc

Electric arc welding is the process of joining two metallic pieces or melting of metal is obtained due to the heat developed by an arc struck between an electrode and the metal to be welded or between the two electrodes. The basic requirement in this process is high open circuit voltage to form arc between the electrodes.

Hysteresis loss and eddy current loss are used in induction heating of steel

The heating of the conducting materials, such as ferro magnetic and non-ferro-magnetic materials is known as induction heating

In induction heating, high frequency heating is applied to the materials

If the high voltage is applied across an air gap, the air in the gap gets ionized under the influence of electrostatic forces and becomes conducting medium, current flows in the form of a continuous spark, known as arc. The choke is provided to stabilize this arc in arc furnaces.

In radiant heating method, the heat energy is transferred from source (incandescent lamp) and focused upon the body to be heated up in the form of electromagnetic radiations. Normally this method is used for drying clothes in the textile industry and to dry the wet pants on an object.

Refining: It is a process by which the purity of the metal extracted from their ores can be improved

Electrodeposition: It is the process by which one metal is deposited over other metal or non-metal by electrolysis

Electro metallization: It is the process by which the metal can be deposited on a conduction base for decoration and for protective purposes. Any non-conductive base is made as conductive by depositing graphite layer over it

Anodizing: The process of deposition of oxide film on a metal surface is known as anodizing and oxidation

The deposited metal is very much strong and porous. If the rate of current is high, then the nuclei are formed and at low current density, the deposits are coarse and crystalline. The spongy coating of electroplating indicates over current density.

Solid angle is the angle subtended at a point in space by an area, i.e. angle enclosed in the volume formed by numerous lines lying on the surface and meeting at the point. It is usually denoted by symbol ‘ω’ and it is measured in steradian. 

Area of the hemisphere = 2πr²

The solid angle subtended at the centre of a hemisphere of radius r will be