RRB JE EE CBT 2 Full Test 2

Let the internal resistance of the battery is r.

When load current is zero, output voltage = 100 V
Battery voltage = 100 V
When load current is 2 A, the output voltage is 80 V
⇒ 100 – 2r = 80
⇒ r = 10 Ω

In transformers, voltage transformation ratio is the ratio of secondary induced emf to primary induced emf.

We know that, in a series RLC circuit impedance is given by

Current flowing in the circuit is given by  I = V/Z
Where, Z is impedance
R is resistance
X_L is inductive reactance
X_{C­ ­}is capacitive reactance
At resonance condition, the inductive resistance is equal to capacitive reactance.
At this condition, Z = R which is minimum value of impedance
At minimum impedance, the current flowing in the circuit is maximum
Hence both A and R are true, and R is the correct explanation of A.

As torque/weight ratio is more in PMMC instruments, the accuracy is very high in these instruments. PMMC instruments are used in rectifier type instruments, hence these are also equally accurate.

Moving iron instruments has the least accuracy among all the given instruments.
The order of accuracy in descending order
PMMC > Electrodynamometer > Moving Iron

Spot welding means the joining of two metal sheets and fusing them together between electrode tips at suitably spaced intervals by means of heavy electric current passed through the electrodes.

The electrodes are made up of copper or copper alloy and are water cooled.

The welding current varies widely depending upon the thickness and composition of plates. It varies from 1000 to 10000 A, and voltage between the electrodes is usually less than 2 V.

Thermal instruments are used for the measurement of radio frequency AC signals. They are very useful when used as transfer instruments to calibrate dc instruments by potentiometer and standard cell. These instruments are suitable for both AC and DC.

• The internet is a globally connected network system that transmits data via various types of media; Sometimes it is referred to as a ‘network of networks’
• The World Wide Web, or simply web, is a way of accessing information over the medium of the internet
• A web browser is a software application for accessing information on the World Wide Web

The synchronous motor is a constant speed motor and it always runs as at synchronous speed.

Due to the magnetic locking between stator and rotor poles synchronous motor is not self-starting and there is no starting device to accelerate the rotor to near synchronous speed.

It can be made self-starting by providing damper windings on rotor poles or by using pony motors.

Superposition theorem is valid for only linear bilateral networks. We can apply superposition theorem for both DC and AC circuits.
Hence it is used to obtain current in or voltage across any conductor of the linear network.

We can directly measure voltage, current and frequency by using CRO. We cannot directly measure power by using CRO.

In computing, the Trash (also known as the Recycle Bin in Windows) is the temporary storage for files that have been deleted in a file manager by the user, but not yet permanently erased from the file system.

Typically, a recycle bin is presented as a special file directory to the user, allowing the user to browse deleted files, undelete those that were deleted by mistake, or delete them permanently (either one by one, or by the "Empty Trash" function).

When the quantity of acids in the raining water is more than the average, then such rain is called 'Acid rain'.

We are aware that normally rainwater has a pH of 5.6.  When the pH of the rainwater drops below 5.6, it is called acid rain.

Acid rain refers to the ways in which acid from the atmosphere is deposited on the earth’s surface. Oxides of nitrogen and sulphur which are acidic in nature can be blown by wind along with solid particles in the atmosphere and finally settle down either on the ground as dry deposition or in water, fog and snow as wet deposition.

Acid rain is a byproduct of a variety of human activities that emit the oxides of sulphur and nitrogen in the atmosphere. As mentioned earlier, burning of fossil fuels (which contain sulphur and nitrogenous matter) such as coal and oil in power stations and furnaces or petrol and diesel in motor engines produce sulphur dioxide and nitrogen oxides.

SO₂ and NO₂ after oxidation and reaction with water are major contributors to acid rain because polluted air usually contains particulate matter that catalyses the oxidation.

2SO₂ (g) + O₂ (g) + 2H₂O (l) → 2H₂SO₄ (aq)

4NO₂ (g) + O₂ (g)+ 2H₂O (l) → 4HNO₃ (aq)

The bad effects of acid rain

• When acid rain falls and flows as groundwater to reach rivers, lakes etc, it affects plants and animal life in the aquatic ecosystem
• Acid rain is harmful to agriculture, trees and plants as it dissolves and washes away nutrients needed for their growth
• It causes respiratory ailments in human beings and animal
• It may also cause corrosion in many buildings bridges, monuments, fencing etc
• It causes irritation in the eyes and skin of human beings
• This rain reduces the lustre of the metals too
• Acid rain damages buildings and other structures made of stone or metal
• The Taj Mahal in India has been affected by acid rain

To make the single phase induction motor self-starting, it is temporarily converted into two-phase motor during starting. For this purpose, the stator of a single phase motor is provided with extra winding known as starting winding in addition to the main winding. This is invariably done with a capacitor in series with the second winding.

• Motors with low starting torque have the capacitor left in circuit all the time
• Motors with higher starting torque might need a bigger capacitor, and that will have a centrifugal switch to disconnect it once the motor is running

Shaded pole motor is used to drive the devices which require low starting torque. It doesn’t have any centrifugal switch.

Batten Holder: This type of lamp holder is fitted directly on the wooden board, which itself is fixed on the wall. The lamp is then supported in the batten holder.
Pendant Holder: When the bulb is to be suspended from the ceiling rose, this type of holder has to be used for holding the lamp.
Angle Holder: Angle holders are used when the light of the lamp is needed at a certain angle. These are directly fixed to the walls.
Bracket Holders: These are used where direct light is needed in the room. These are also used on table lamps. Brackets used with such type of holders are made of brass material.
WaterTight Bracket Holder: These are provided with tubular glasses with watertight covers. These are mainly used for street lighting. They are also used for supporting bulbs outside the house premises.

In the oil circuit breaker, oil is used as a dielectric or insulating medium for arc extinction. In oil circuit breaker the contacts of the breaker are made to separate within an insulating oil.

Advantages of oil as an arc quenching:

• The oil has high dielectric strength and provides insulation between the contacts after the arc has been extinguished
• Oil provides a small clearance between the conductors and the earth components
• The hydrogen gas is formed in the tank which has a high diffusion rate and good cooling properties

To determine the polarity of the voltage drop across the resistor, it is necessary to know the direction of the current through the resistor.

The terminal entering the current gives a positive sign of voltage drop.

Ideal voltage source: An ideal voltage source have zero internal resistance.

Practical voltage source: A practical voltage source consists of an ideal voltage source (V_S) in series with internal resistance (R_S) as follows.

An ideal voltage source and a practical voltage source can be represented as shown in the figure.

Ideal current source: An ideal voltage source has infinite resistance. Infinite resistance is equivalent to zero conductance. So, an ideal current source has zero conductance.
Practical current source: A practical current source is equivalent to an ideal current source in parallel with high resistance or low conductance.

Ideal and practical current sources are represented as shown in the below figure.

In HRC (High Rupturing Capacity) fuse, the fuse wire or element can carry short circuit heavy current for a known time period. During this time if the fault gets removed, then it does not blow off. Otherwise, it blows off or melts.

• They do not deteriorate with time
• They have inverse time-current characteristics
• Operation of the fuse is very reliable
• It is required to be replaced after each operation

• Light can travel in a vacuum because the light is electromagnetic in nature which requires no medium as electric fields and magnetic fields constantly generate each other as the wave propagates.
• Sound waves require a medium to travel. The speed of sound is faster in solid materials, slower in liquids and slowest in gases.
• The speed of light in a vacuum is commonly given the symbol c. It is a universal constant that has the value c = 3 x 10⁸ m/second.

Reluctance opposes the passage of magnetic flux lines. Reluctance is analogous to resistance.

We can define the reluctance as,

We know that, 
Where H is field strength
N is the number of turns in a coil
l is mean length of flux in a magnetic circuit
I is current through the coil
The flux in a magnetic circuit is given by


Now, we can define reluctance as 

• Strait of Malacca is a narrow stretch of water which separates the Malay Peninsula and Indonesian Island of Sumatra.
• It was named after the Malacca Sultanate which ruled between 1400 and 1511 over a group of islands.

• A transistor is a device that regulates current or voltage flow and acts as a switch or gate for electronic signals
• It is low voltage and low current device because semiconductors are sensitive to high voltages and current and can be easily destroyed

We know that, in a dc motor

As voltage applied across its armature is increased by 10%, back emf also gets increased by 10%.
As flux is constant and speed is directly proportional to back emf, speed also gets increased by 10%.

The mutual inductance between two magnetically coupled coils is given by

Where μ_r is relative permeability of the core
N is the number of the turns of the coil
A is cross-sectional area of their common core
Hence, the mutual inductance depends on all the above factors.

In an induction motor, stator or the stationary part consists of three-phase winding held in place of slots of a laminated steel core. This steel core is enclosed and supported by closed grained cast iron or a steel frame.

• Vice Admiral G Ashok Kumar, AVSM, VSM assumed charge as Vice Chief of the Naval Staff on 30 Jan 2019.
• Kumar has held various Staff and Command assignments during his distinguished naval career spread over more than three decades.
• He is an alumnus of National Defence Academy, Khadakvasla, Pune and was commissioned into the Executive Branch of the Indian Navy on 01 Jul 1982.

A Threat is any circumstance or event with the potential to cause harm to the system or activity in the form of destruction, disclosure, and modification of data, or denial of service. A threat is a potential for harm. 

Some of the common terms associated with threats and their description are as follows:

• Malware: A collective term for malicious software, such as viruses, worms and trojans; designed to infiltrate systems and information for criminal, commercial or destructive purposes.
• Phishing: A form of social engineering, involving the sending of legitimate-looking emails aimed at fraudulently extracting sensitive information from recipients, usually to gain access to systems or for identity theft.
• Spam: Unsolicited email sent in bulk to many individuals, usually for commercial gain, but increasingly for spreading malware.

Spoofing: A spoofing attack is when a malicious party impersonates another device or user on a network in order to launch attacks against network hosts, steal data, spread malware, or bypass access controls. There are several different types of spoofing attacks that malicious parties can use to accomplish this. They are IP Address Spoofing Attacks, ARP (Address Resolution Protocol) Spoofing Attacks, DNS Server Spoofing Attacks, etc.

A software bug is an error, flaw, failure or fault in a computer program or system that causes it to produce an incorrect or unexpected result, or to behave in unintended ways.

Under dry conditions, the resistance offered by the human body may be as high as one megaohm. Wet or broken skin may drop the body's resistance to 1000 ohms. Adding that, high-voltage electrical energy quickly breaks down human skin, reducing the human body's resistance to 500 ohms.

• 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.

The force experienced by a current carrying conductor lying in a magnetic field is with an angle θ is
F = Bil sinθ

As the conductor is lying parallel to a magnetic field, θ = 0°
Hence the force = zero

An inductor at t = 0⁺ acts as an open circuit and at steady state acts as short circuit
A capacitor at t = 0⁺ acts as short circuit and at steady state acts as an open circuit

Components of Computer
Input Devices
Input devices are used to enter data or instructions into a computer.

• Keyboard
• Mouse
• Digital camera
• Scanner
• Mic
• Barcode reader
• Joystick

Output Devices:
Output unit receives the information from the processing unit and provides the result in a human-readable form.

• A visual display unit (Monitor, Screen)
• Printer/Plotter
• Multimedia projector
• Speaker

Storage Devices
Storage devices are the computer hardware used to remember/store data.

• Floppy disks
• Hard disks
• CD/DVD

When single phase AC supply is given to stator winding, it produces alternating flux i.e. which alternates along one space axis only.

It is not synchronously revolving (or rotating) flux, thus it cannot produce any rotation. Hence single phase induction motor is not self-starting.

To overcome this problem and to make the motor self-starting, it is temporarily converted into two-phase motor during starting. For this purpose, the stator of a single phase motor is provided with extra winding known as starting winding in addition to the main winding. These two winding are placed across the single phase supply. It can rotate in both the directions.

Maxwell’s inductance capacitance bridge is used for the measurement of an inductance of medium Q coils.
Hay’s bridge is used to measure for the measurement of an inductance of high Q coils.
Anderson Bridge is the most common and best bridge method for precise measurement of inductance over a wide range.
Wein Bridge is used to measure the frequency.

To convert delta to star,

Given that, emf (E) = 120 V
Magnetizing current (I) = 4 A
Frequency (f) = 60 Hz
Reactance = 120/4 = 30 Ω
We know that, XL = 2πfL

The average value of a sinusoidal wave is zero
The rms value of a sinusoidal wave is 

Invar is an alloy composed of Iron, nickel, and Carbon where Iron is a major component with 63%, nickel with 36% and Carbon with 1%. Invar is an alloy used for making clocks and scientific instruments because of its property of negligible coefficient of expansion.

Given that, line voltage (V_L) = 440 V
Resistance (R) = 4 Ω
Inductive reactance (X_L) = 3 Ω

In delta connection, phase voltage = line voltage
Phase voltage (V_ph) = 440 V

Active power P = 3V_phI_phcosϕ
⇒  P = 3 × 440 × 88 × 0.8 = 92.928kW

• Crooked Glass can cut off the UV rays.
• It is a special type of glass which contains Cerium Oxide [CeO₂].
• It is used in making sunglasses.

Skin Effect: The tendency of alternating current to concentrate near the surface of the conductor is known as skin effect. The skin effect depends on the following factors.
a) Frequency
b) Diameter of the conductor
c) Shape of the conductor

The skin effect increases with the increase of cross section, permeability and supply frequency. It reduces with the increase in resistivity of the conductor material.

Proximity Effect: The alternating flux in a conductor is caused by the current of the other nearby conductor. This flux produces a circulating current or eddy current in the conductor which results in an apparent increase in the resistance of the wire. Thus, more power losses in the windings. This phenomenon is called the proximity effect.

Both skin effect and proximity effect are negligible at small frequencies.

Electroplating is defined as the deposition of a metal over any metallic or non-metallic surfaces. Electroplating is usually employed
1. To protect the metals from corrosion by atmospheric air, moisture and CO₂
2. To give the reflecting properties to reflectors
3. To replace worn out metals
4. To give a shiny appearance to articles

Vaikom Satyagraha was a Satyagraha in Travancore, Kerala against untouchability in Hindu society.

• The movement was cantered at the Shiva temple at Vaikom, near Kottayam.
• The Satyagraha aimed at securing freedom to all sections of society through the public roads leading to the Sri Mahadeva Temple at Vaikom.

Hence, 1 is the correct answer.

• Jamshedpur is known as the Steel City of India or Pittsburgh of India for being rich in minerals.
• It is a home to many industries like Tata Motors, Tata Steels, Usha Martin Industries, Steel & Wire Products, Tata Pigments, Tayo Rolls Limited, and many other assets.
• This city is also known as the Tatanagar.

Schedule Speed: The ratio of the distance covered between two stops to the total time of the run including the time for the stop is known as schedule speed. It is denoted with V_s

Where T_s is the scheduled time in hours

Factors affecting the schedule speed of a train are:

• Crest speed
• The duration of stops
• The distance between the stops
• Acceleration
• Breaking duration

We know that
I_E = I_B + I_C
Here
I_E = Emitter current
I_B = Base current
I_C = Collector current
IE = I_B + I_C = 0.025+4.975=5A

• The Buchholz relay protects the transformer from internal faults
• It is a gas actuated device
• It is placed between the main tank and the conservator
• It is used in the transformer having the rating higher than 500 KVA
• It causes alarm for minor fault and tripping for major fault

• If the two plates are brought closer to each other, the capacitance of the system will increase.
• This can be proved from the expression, C = (ε₀A)/d 
• Where ε0 is the electric constant, A is area of plate and d is distance between the plates.
• Hence the distance is inversely proportional to the capacitance and bringing the plates closer will mean reducing the distance and in effect increasing the capacitance of the system.

For a fixed kVA rating, more the designed frequency of transformer then lesser will be cross sectional area of the core. Hence lesser will be the size and weight of transformer.

All the transformers given in the options have same kVA rating. Hence the transformer with lowest designed frequency has largest size.

The coefficient of adhesion (μ): It is defined as the ratio of the tractive effort (F_t) to propel the wheel of a locomotive to its adhesive weight (W).

The coefficient of the adhesion improves due to the presence of:

• Dry sand on rails
• Rust on rails
• Dust on rails

The coefficient of the adhesion reduces due to the presence of:

• Dew on rails
• Oil and grease on rails

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, so to bring the pointer rest within a short time by reducing oscillations, we use damping torque without effecting controlling torque (or) inertia.

The following mechanism can be used for producing damping torque.
1. Air friction damping
2. Fluid friction damping
3. Eddy current damping

Swamping resistor and condenser are used to reduce the frequency error in MI instruments.

In moving iron instruments, the change in frequency causes an error due to the change in magnitude of eddy currents set up in the metal portion of the instruments.

The reactance of the operating coil changes by the change in frequency.

At high frequencies, the meter will give a reading lower than the actual value and at low frequencies, meter give a reading higher than the actual.

This type of error can be eliminated only if the impedance of the coil is independent of the frequency. This is achieved by having a capacitance in shunt with the swamping resistance of the coil as shown in the figure.

In the above figure, C is condenser and r is swamping resistance, whereas L and R represent the reactance and resistance of operating coil in moving iron instrument.

During the operation of a connecting a busbar in parallel with an incoming alternator, the following condition should be satisfied:

• The phase sequence of the busbar voltages and the incoming machine voltage must be the same
• The busbar voltages and the incoming machine terminal voltage must be in phase
• The terminal voltage of the incoming machine and the alternator which is to be connected in parallel or with the busbar voltage should be equal
• The frequency of the generated voltage of the incoming machine and the frequency of the voltage of the busbar should be equal

By observing V curves,

When excitation of the synchronous motor is increased up to normal excitation from under excitation, armature current decreases

When excitation of the synchronous motor is increased to overexcitation from normal excitation, armature current increases

If two or more components are connected in parallel, they have the same potential difference across their ends but the current flowing through them will be different.

If two or more components are connected in series, the current flowing through them will be different, but they have different voltage drops across them.

Given that, i(t) = 1.25cos(5t − 15^∘)
z = 12∠53^∘Ω


Complex power delivered by the source to the load is

Hydrogen fuel is a zero-emission fuel when burned with oxygen (if one considers water not as an emission) or used in a contained cell (allowing to react galvanically) also capable of 'reversing' the reaction if needed.

An electrical circuit breaker is a switching device which can be operated automatically or manually for protecting and controlling an electrical power system.

The oil used in the oil circuit breaker will absorb arc energy while decomposing.

In double break bulk oil circuit breaker, there are two fixed contact and are bridged by one moving contact. The moving contact is fitted with a driving mechanism of the oil circuit breaker by means of an insulated rod.

• Gujarati poet Sitanshu Yashashchandra was awarded 'Saraswati Samman 2017' on 22 January 2019.
• He was awarded for his poetry collection in Gujarati named 'Vakhar'.
• The award was instituted by K.K.Birla foundation.
• The award is given every year to an outstanding work of an Indian citizen published during the last 10 years in any of the languages mentioned in Schedule 8 of the constitution.

Reciprocity theorem states that in any branch of a network, the current (I) due to a single source of voltage (V) elsewhere in the network is equal to the current through the branch in which the source was originally placed when the source is placed in the branch in which the current (I) was originally obtained.

It is applicable for only single source networks.

In the circuit (a), the value I_a is obtained for a voltage source V. According to reciprocity theorem, this current is equivalent to I_b in circuit B.

Resistance furnace is an electric furnace in which heat is generated by conductors that offer resistance to the passage of a current through them. Resistance furnaces are widely used in heat treatment, for heating prior to pressure shaping, and to dry or melt materials.

Resistance furnaces are readily mechanized and automated, thus alleviating the work of personnel and facilitating the inclusion of such furnaces in automatic transfer lines. In addition, they are compact. Such furnaces provide a secure environment for various processes.

A resistance furnace may be well sealed, in which case the heating is carried out in a vacuum, or it may contain either a gaseous medium that prevents oxidation or a special atmosphere for chemical case hardening. The special atmosphere in these type of furnaces is oxidizing.

Given that, Magnetic force (H) = 800 AT/m
As it is air, μ_r = 1
We know that,

In dynamometer wattmeter, the pressure coil is designed for having a low value of resistance so that the high value of current passes through it. This current produces the deflecting torque on the moving coil.

In a low power circuit, the value of the current is high, and that of the power is low. This high-value current causes the error in the wattmeter reading. To reduce this error, the compensation coil is used in the circuit.

Compensating coil has an equal number of turns of the current coil and is connected in series with a voltage coil or pressure coil. It carries current equal to the sum of two currents i.e. load current plus pressure coil current. The pressure coil is placed such that the field produced by the compensating coil is opposed by the field produced by pressure coil as shown in the above circuit diagram.

The equivalent resistance of the circuit is,


R = 60 Ω
Current (I) = 60/60 = 1 A

Sometimes induction motor refuses to start at all. Sometimes it happens because of the low supply voltage. But the main reason for starting problem in the motor is because of cogging in which the slots of the stator get locked up with the rotor slots.

As we know that there is a series of slots in the stator and rotor of the induction motor. When the slots of the rotor are equal in number with slots in the stator, they align themselves in such way that both face to each other and at this stage the reluctance of the magnetic path is minimum and motor refuse to start. This characteristic of the induction motor is called cogging.

Apart from this, there is one more reason for cogging. If the harmonic frequencies coincide with the slot frequency due to the harmonics present in the supply voltage then it causes torque modulation. As a result of it, cogging occurs. This characteristic is also known as magnetic teeth locking of the induction motor.

This problem can be easily solved by adopting several measures. These solutions are as follows:

1. The number of slots in the rotor should not be equal to the number of slots in the stator.
2. Skewing of the rotor slots, that means the stack of the rotor is arranged in such a way that it angled with the axis of the rotation.

Given that, emf (E) = 2 V
Rate of change of current = 0.5 A/s
We know that, induced emf 
⇒ 2 = L(0.5) ⇒ L = 4H

Applications of different magnetic materials:

• Alnico is used for wide range of permanent magnet applications
• Strontium ferrite is used for the preparation of loud speakers, telephone receiver, various toys, dc motor, and starter motor
• NdFeB is used for a wide range of applications; Small motors (in hand tools), Walkman equipment, DC motors, MRI body scanners, computer applications
• Carbon steel is used for magnets for toys, compass needle, latching relays and certain types of meters
• Tungsten steel is used to prepare DC motor magnets
• Chromium steel is used to prepare the best permanent magnets
• Silicon steel is used for transformer cores

In the given circuit, 50 Ω, 75 Ω and 50 Ω resistors are connected in parallel.
The equivalent resistance of this parallel combination is,


This parallel combination is in series is with 100 Ω.
Equivalent resistance is, R_eq = 18.75 + 100 = 118.75 Ω

• The two liquids that can't dissolve in each other or the two liquids in which diffusion can't takes place are called immiscible liquids. They can’t form homogeneous mixtures.For example- Water and oil.
• When two liquids can be mixed to form homogeneous mixtures they are called miscible liquids.

For example- Alcohol and water.
Extra Information:

• The second India-Myanmar bilateral Army exercise named 'IMBEX 2018-19' commenced at Chandimandir military station in Haryana on 14 January 2019.
• The aim of this joint training event is to train the Myanmar delegation for participation in UN peacekeeping operations.
• The exercise includes participation of 15 officers from Myanmar Army and 15 officers from Indian Army

Ohm’s Law: It states that Voltage across any conducting material is directly proportional to the current flowing through the material at a constant temperature. It gives the relation between voltage and current.

According to Ohm’s law, V = IR

Coulomb’s Law: It states that the magnitude of the electrostatic force of attraction or repulsion between two point charges is directly proportional to the product of the magnitudes of charges and inversely proportional to the square of the distance between them.

An alternator is nothing but the AC generator that converts mechanical energy to electrical energy in the form of alternating current.

Web browser: A browser is a software application used to locate, retrieve and display content of Web pages, images, video and other files. The browser contacts the Web server and requests information and Web server sends the information back to the Web browser which displays the results on the computer.

Some commonly used web browsers are:

• Internet Explorer: Internet Explorer (IE) is a web browser from Microsoft
• Firefox: Firefox is a free, open-source web browser from Mozilla
• Google Chrome: Google Chrome is a free, open source web browser developed by Google
• Opera: Opera is a free, fast, small and standard - compliant web browser developed by the Opera Software company
• Netscape: Netscape was the first commercial web browser

At steady state, the capacitor acts as an open circuit.
Now, the circuit becomes

Equivalent resistance = 20 kΩ

Characteristics of Separately excited DC generator:

Characteristics of DC shunt generator:

Characteristics of DC series generator:

 

Characteristics of DC Compound generator:

The following comments can be made by above load characteristics of different generators.

• Separately excited DC generator – Almost constant voltage
• DC shunt DC generator – Slightly drooping characteristics
• DC series generator – Rising characteristics
• Differentially compounded DC generator – Rapidly falling characteristics

Structure of the atmosphere
The atmosphere is divided into five layers starting from the earth's surface:

1. Troposphere (0 - 18 km): This is the most important layer of the atmosphere. The air breath exists here. All the weather changes like rainfall, fog, and hailstorm occur in this layer.
2. Stratosphere (18 - 50 km): It is free from clouds which makes it the most ideal layer for flying Aeroplanes. It contains a layer of ozone gas which protects from the harmful effect of the sun rays.
3. Mesosphere (50 - 85 km): It is the third layer of the atmosphere. Temperature drops to about -95°C.
4. Thermosphere (85 - 500 km): In this layer, the temperature rises very rapidly with increasing height. The ionosphere is a part of this layer. It helps in radio transmission.
5. Exosphere (500 - 1600 km): The uppermost layer of the atmosphere is called exosphere. It is very thin air. Temperature is very high due to direct solar radiation. Light gases like Helium and Hydrogen float into space from here.

The Exosphere is the uppermost layer of the atmosphere.

Effects of ozone depletion

• It produces a greenhouse effect and also changes the climate
• It results in low production of crops
• It causes damage to the organs of living things
• Ultraviolet rays harm the plants
• It causes to spread the skin cancer disease
• It raises the possibilities of acid rains in urban areas
• It increases the temperature of the environment
• It affects the mental health of man
• It increases the temperature of the atmosphere which has a bad effect on the vegetation
• The UV rays reaching the earth are harmful to the pregnant women and the infant children also

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

The string efficiency is defined as the ratio of voltage across the string to the product of the number of strings and the voltage across the unit adjacent string.
String ef ficiency 
Because of the shunt capacitance effect between insulators and tower, the voltage across each insulator is non-uniformly distributed.

If the shunt capacitance is reduced then the voltage across insulators will get uniformly distributed. Then string efficiency will increase.

The energy loss associated with hysteresis is proportional to the area of the hysteresis loop. As the area of the hysteresis loop for a specimen is found to be large, the hysteresis loss in this specimen is also large.

• The quantum number defines an electron completely in an atom. 
• There are four types of quantum number - Principal Quantum Number, Azimuthal Quantum Number, Magnetic Quantum Number and Spin Quantum Number. 
• Principal Quantum Number describes the size, shape and energy of the shell to which an electron belongs whereas Azimuthal Quantum Number determines the shape of the electron cloud and the number of sub-shells in a shell. 
• Magnetic Quantum Number determines the orientation of sub-shells whereas the spin quantum number represents the direction of the electron spin. 

As the armature core is made of iron and it rotates in a magnetic field, a small current gets induced in the core itself too. Due to this current, some losses occur in the armature iron core. These losses are called as Iron losses. These losses includes eddy current loss and hysteresis loss. Iron losses are also called as Core losses or magnetic losses.

An induction type meter consists of two electromagnets, called shunt magnet and series magnet of laminated construction.

A coil having a large number of turns of fine wire is wound on the middle limb of shunt magnet. This coil is known as voltage coil or pressure coil and it is connected across the supply mains. It has many turns and is arranged to be as highly inductive as possible. This causes the current and therefore the flux, to lag the supply voltage by nearly 90°.

An adjustable copper shading rings are provided on the central limb of the shunt magnet to make the phase angle displacement between the magnetic field set up by shunt magnet and the supply voltage is approximately 90°.

The series electromagnet is energized by a coil which is known as current coil and it is connected in series with the load so that it carries the load current. The flux produced by this magnet proportional to and in phase with the load current.

The moving system essentially consists of a light rotating aluminium disk mounted on a vertical spindle or shaft. The fluxes produced by shunt and series magnet induce eddy currents in the aluminium disc. The interaction between these two magnetic fields and eddy currents set up a driving torque in the disc.

As in energy meter instrument, we have two fluxes and two eddy currents and therefore two torques are produced by

(i) First flux interacting with eddy current produced by second flux and

(ii) Second flux interacting with eddy currents generated by the first flux

Maximum torque is produced when the phase angle between these two fluxes is 90°

The Zeroth law of thermodynamics defines temperature. It states that “If two systems are in thermal equilibrium with the third system, then they are in thermal equilibrium with each other.”
Zeroth law – concept of temperature
First law – concept of internal energy
Second law – concept of entropy

Peak factor is defined as the ratio of peak value to rms value
Peak value of sinusoidal value = √2 × rms value
Peak factor of a sinusoidal value = √2 = 1.414

• The SI unit of angular frequency is rad/sec.
• It refers to the angular displacement of an object per unit time and is given by: ω = ν × 2π
  where, ν is the frequency.

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.

If the motor is running at synchronous speed, then the torque generated by the motor equal to zero. If rotor runs at synchronous speed as the field of the stator, this will cause the slip to become zero, then there will be no torque generated in rotor.

• Silicon and germanium both have four valence electrons, but germanium will at a given temperature have more free electrons and a higher conductivity
• Silicon is a widely used semiconductor for electronics because it can be used at much higher temperatures than germanium
• As the temperature increase, more electrons will be moved out from below the Fermi level to above the Fermi level
• If we the temperature the conductivity will increase due to thermal ionisation but the position of Fermi level will not change

Belted Cables: The conductors (usually three) are bunched together and then bounded with an insulating paper ‘belt’. In such cables, each conductor is insulated using paper impregnated with a suitable dielectric. The gaps between the conductors and the insulating paper belt are filled with a fibrous dielectric material such as Jute or Hessian.

• The chemical formula of Hematite is Fe₂O₃, called as ferric oxide. It is a reddish black mineral and an ore of Iron.
• FeO(OH).nH₂O is also an ore of Iron and is the chemical formula of Limonite.
• FeS₂ is the chemical formula of Pyrite.

The common causes of brush sparking in the universal motor (AC series motor) are:

• Open armature winding
• Shorted armature winding
• Shorted field winding
• High commutator mica
• Brushes are not in a properly working state

Compensating winding is used to reduce sparking of brushes.

In AC circuits, the power factor is defined as the ratio of the real power flowing to the load to the apparent power in the circuit.
Hence power factor can be defined as watts to volt amperes
Power factor = cosϕ
Where, ϕ is the angle between voltage and current.
If current lags the voltage, power factor will be lagging.
If current leads the voltage, power factor will be leading.

From the options,
1) Ratio of real power to apparent power
2) P/VI represents the ratio of the real power to apparent power, it is known as power factor
3) R/Z also represents power factor from the impedance triangle
4) V/I represents resistance but not power factor

The Man Booker Prize for Fiction is a literary prize awarded each year for the best original novel written in the English language and published in the UK.

A voltage source having an open circuit voltage of 100 V and internal resistance of 50 ohms can be represented as 100 V voltage source in series with a resistance of 50 ohms as shown in the below figure.

By source transformation, we can represent this circuit as a current source with resistance in parallel.

Whenever transformer is loaded, the temperature of the transformer insulating oil increases. Consequently, the volume of the oil is increased. As the volume of the oil is increased, the air above the oil level in conservator will come out. At low oil temperature, the volume of the oil is decreased, causes air to enter into conservator tank.

The air consists of moisture in it and this moisture can be mixed up with oil. Hence to filter the air from moisture silica gel breather is used. The drying agent extracts moisture from the in flowing air and ensures that only the dried air will be aspirated into the transformer.

In series resonance,

• At the frequencies below resonant frequency, impedance is capacitive
• At resonant frequency, impedance is resistive
• At the frequencies above resonant frequency, impedance is inductive

The impedance - frequency curve is shown below

In the given question, resonant frequency (f_r) = 150 Hz
Operating frequency (f) = 50 Hz
As operating frequency is less than the resonant frequency, impedance is capacitive.

When the distributor is connected to a substation on one end only with the help of feeder, then the system is called a radial distribution system.

The feeders, distributors and service mains are radiating away from the substation hence name given as radial system.

There are combinations of one distributor and one feeder, connecting that distributor to the substation.

In the above diagram, one end of distributors are connected to the substation with the help of feeders and the other end will be connected to the service mains.

In this distribution system, electricity is distributed from a single point in a radial distribution system. The fluctuation in the supply is less at the consumer’s terminal.

Both the given statements are true, but B is not the correct explanation of A.

Given that, voltage across resistor R₁ (V_R1) = 6 V
Current flows through resistor R₁ (I_R1) = 4 A
Resistance (R₁) = 6/4 = 1.5 Ω

‘Agha Khan Cup’ is associated with the game of Hockey whereas Agha Khan Gold Cup is associated with Football.

Incineration is a waste treatment process that involves the combustion of organic substances contained in waste materials. Incineration and other high-temperature waste treatment systems are described as "thermal treatment". Incineration of waste materials converts the waste into ash, flue gas and heat means in the presence of air.

• The IUPAC name of sec-Butyl chloride is 2-Chlorobutane.

In symmetrical or balanced three-phase faults, all three phases are simultaneously short-circuited.

LLLG fault is a symmetrical fault. LG, LL, LLG faults are asymmetrical faults.

So, three-phase faults give symmetrical fault currents.

An indifference curve is a graph showing combination of two goods that give the consumer equal satisfaction and utility. Each point on an indifference curve indicates that a consumer is indifferent between the two and all points give him the same utility.

• Fundamental rights in the Indian constitution has been taken from the US constitution.
• The other features that have been borrowed from the US Constitution are:

1. Impeachment of the president
2. Functions of president and vice-president
3. Removal of Supreme Court and High court judges
4. Judicial review
5. Independence of judiciary
6. The preamble of the constitution

Web browser

• A browser is a software application used to enable computers users to locate and access web pages
• Browser translates the basic HTML code that allows us to see image, text video and listen to audios on the website, along with hyperlinks that let us travel to different web pages
• The Web utilizes browsers, such as Internet Explorer or Firefox, to access web documents called web pages that are linked to each other via hyperlinks

Some commonly used web browsers are:

• Internet Explorer: Internet Explorer (IE) is a web browser from Microsoft
• Firefox: Firefox is a free, open-source web browser from Mozilla
• Google Chrome: Google Chrome is a free, open source web browser developed by Google
• Opera: Opera is a free, fast, small and standard - compliant web browser developed by the Opera Software company
• Netscape: Netscape was the first commercial web browser

• The electric field formed in the depletion region acts as a barrier
• This barrier is formed when some of the free electrons in the n-region diffuse across the junction and combine with holes to form negative ions
• The development of barrier potential in the depletion zone of a PN junction is consequent to diffusion of majority carriers across the junction

A fractional-horsepower motor (FHP) is an electric motor with a rated output power of 746 Watts or less.

There is no defined minimum output. However, it is generally accepted that a motor with a frame size of less than 35 mm square can be referred to as a micro-motor.

The synchronous motor is not a fractional horsepower motor.

Helsinki is the capital of Finland.

Shaded pole motor is used to drive the devices which require low starting torque. It has the following advantages.

• No commutator, brushes, collector rings, contactors and capacitors
• It is relatively cheaper, simpler and extremely rugged in construction and reliable
• Low initial as well as maintenance cost
• Comparatively small starting current

Asthma is a condition in which a person's airways become inflamed, narrow and swell and produce extra mucus, which makes it difficult to breathe. It is caused due to air pollution.

• The World Earth Day is celebrated on 22^nd April annually to support the environmental protection.
• It was first celebrated in 1970, by United State Senator Gaylord Nelson.

Quality factor is defined as the ratio of the maximum energy stored to maximum energy dissipated in a cycle

In a series RLC, Quality factor 
In a parallel RLC, 
It is defined as, resistance to reactance of reactive element.

• In the US Open Tennis, Novak Djokovic of Serbia won the Men's singles final.
• He defeated Juan Martin del Potro of Argentina. It was Djokovic's 14th Grand Slam title and the third US Open title.
• With this win, he has equaled Pete Sampras's mark of 14 Grand Slams.

As a result of the greenhouse effect, the average temperature of the earth’s atmosphere is gradually increasing. This is called Global warming. The exchange of incoming and outgoing radiation that warms the surface of Earth is known as the greenhouse effect. The greenhouse gases include carbon dioxide, methane, water vapors, nitrous oxide, and other gases.

Greenhouse effect

• It occurs due to the increase in the percentage of carbon dioxide in the atmosphere
• It absorbs the solar rays and energy of the sun due to which the temperature on the earth increases and natures balance gets disturbed
• Our vehicles and industries are continuously increasing the amount of carbon dioxide in the atmosphere

Global Warming

• Increase in average temperature of the earth surface due to the greenhouse effect is called global warming
• It also refers to the increase in average temperature of the air and sea at earth's surface

Green House Gases (GHG):
The major greenhouse gases are

• Water vapour - causes about 36% - 70% of the greenhouse effect
• Carbon dioxide (CO₂) which causes 9 - 26%
• Methane (CH₄) causes 4 - 9% and ozone (O₃)

So Ethane is not a greenhouse gas

If two resistances are connected in parallel, they have the same potential difference across their ends but the current flowing through them will be different.

If two resistances are connected in series, the current flowing through them will be different, but they have different voltage drops across them.

Currents are additive in parallel circuits whereas voltages are additive in series circuits.

Powers are additive in both series and parallel.

Noise pollution may cause or contribute to the following adverse effects:

• anxiety, stress, nervousness, nausea, headache,
• emotional instability,
• argumentativeness,
• increase in social conflicts
• depression and fatigue
• Insomnia as a result of lack of undisturbed and refreshing sleep

The voltage across 1 Ω resistor is 5 V
Current flows through 1 Ω resistor = 5/1 = 5 A

In plate earthing, the earthing plate is placed deep into a pit (usually dug up to 2-3 meters), along with wood coal (absorbs and retains moisture) and salt (creates an ionic solution for faster dissipation of current). The plate is connected via a Copper conductor, or GI Conductor or concealed copper cable to the respective electrical set-up.

The synchronous motor is a constant speed motor and it always runs as at synchronous speed.

Due to the magnetic locking between stator and rotor poles synchronous motor is not self-starting and there is no starting device to accelerate the rotor to near synchronous speed.

It can be made self-starting by providing damper windings on rotor poles or by using pony motors.

• Kirchhoff's second law is called loop law.
• According to Kirchhoff's first law, the sum of currents which are meeting at a point (junction) in a circuit is always 0. It is therefore also called junction law.
• According to the sign convention adopted for this law, the current flowing towards the junction is taken as positive and the current leaving the junction is taken as negative.
• These two laws were given by Kirchhoff in 1842.

According to nature, pollutants can be classified into Non-degradable pollutants and Bio - degradable pollutants.

Non-degradable pollutants

Those pollutants which cannot be broken down into simpler, harmless substances in nature.

DDT, plastics, polythene, bags, insecticides, pesticides, mercury, lead, arsenic, metal articles like aluminium cans, synthetic fibres, glass objects, iron products and silver foils are nonbiodegradable pollutants. (Tables)

Bio-degradable pollutants

Those pollutants which can be broken down into simpler, harmless substances in nature.

Sewage waste, domestic waste, etc. are the bio-degradable waste.

A computer mouse is an input device that is most often used with a personal computer. Moving a mouse along a flat surface can move the on-screen cursor to different items on the screen. Items can be moved or selected by pressing the mouse buttons (called clicking). The mouse has two buttons, the left button, and right button, with a scroll wheel in between the two.

Use of a mouse:

• Move the mouse cursor - The primary function is to move the mouse pointer on the screen.
• Open or execute a program - Once you've moved the pointer to an icon, folder, or other object clicking or double-clicking that object opens the document or executes the program.
• Select - A mouse also allows you to select text or a file or highlight and select multiple files at once.
• Drag-and-drop - Once something is selected, it can also be moved using the drag-and-drop method.
• Hover - Moving the mouse cursor over objects with additional hover information can help discover the function of each object on the screen. For example, hover the mouse over the hover link to see an example.
• Scroll - When working with a long document, or viewing a long web page, you may need to scroll up or down. To scroll, use the mouse wheel, or click and drag the scroll bar.

Ward-Leonard method of speed control is achieved by varying the applied voltage to the armature. Hence it is basically a voltage control method. The connection diagram is shown below.

In the above system, M is the main DC motor whose speed is to be controlled, and G is a separately excited DC generator. The generator G is driven by a 3-phase driving motor.

The voltage of the generator is changed by changing the generator field current. This voltage when directly applied to the armature of the main DC motor, the speed of the motor M changes.

The Bhil are an indigenous tribe in the Kolarian group and were the earliest settlers in India. According to the 2011 Census of India, Bhil is the most populous tribe in Madhya Pradesh with a total population of 4,618,068, constituting 37.7 per cent of the total ST population.

As all three resistors are connected in parallel, the voltage across all the resistors will be the same.
Voltage across 3 ohm resistor = 30 V
Current flows through 3-ohm resistor = 30/3 = 10 A

By applying KVL,

−36 + 4i₀ + 5i₀ = 0
⇒ i₀ = 4A

Fleming's Right-hand Rule shows the direction of induced current when a conductor attached to a circuit moves in a magnetic field. It can be used to determine the direction of current in a generator's windings.

 

As shown on the above figure, if the thumb, the forefinger, and the middle finger of the right hand are bent at right angles to one another with the thumb pointed in the direction of motion of a conductor relative to a magnetic field and the forefinger in the direction of the field, then the middle finger will point in the direction of the induced electromotive force.

Lenz's law: When a voltage is generated by a change in magnetic flux according to Faraday's law, the polarity of the induced voltage is such that it produces a current whose magnetic field opposes the change which produces it.

When the voltage of a circuit is measured by a voltmeter whose input impedance is low as compared to the output impedance of the circuit, the instrument gives less accurate results. This is known as the error due to the loading effect.

To reduce this effect, we need to use high impedance voltmeter compared to the load impedance.

An ideal transformer a transformer which has no copper losses, no iron loss in core and no leakage flux. In other words, an ideal transformer gives output power exactly equal to the input power.

Characteristics of an ideal transformer:

• The resistances of primary and secondary winding are zero
• The core of the ideal transformer has infinite permeability
• The leakage flux in the transformer core is zero
• The ideal transformer has 100 percent efficiency

Given that, q(t) = 0.50 (1 – e^-5t)

• Avalanche breakdown occurs when we apply a high reverse voltage across the PN junction
• When we increase the applied reverse voltage across the PN junction, the electric field across the junction will keep increasing
• This electric field exerts a force on the electrons at the junction and it frees them from covalent bonds

In the given image,

• A and D represent isolators
• B represents the current transformer (CT)
• C represents circuit breaker

Eddy currents (also called Foucault currents) are loops of electrical current induced within conductors by a changing magnetic field in the conductor according to Faraday's law of induction. Eddy currents flow in closed loops within conductors, in planes perpendicular to the magnetic field.

The generations of computers are characterized by a major technological development that fundamentally changed the way computers operate, resulting in smaller, cheaper, more powerful and more efficient and reliable devices.

The various generations of computers are listed below:

To measure insulation resistance of equipment’s of voltage rating up to 440 V the megger generator must generate the voltage more than the voltage rating of equipment. Hence the answer should be 500 V.

When warm air rises up and cold air from the surrounding areas rushes in to fill its place then this sets up convection in air.

• When warm air rises, the air pressure at that place gets lowered. The cold air from the surrounding areas rushes in to fill its place. This sets up convection currents in the air.
• Wind currents are generated due to uneven heating on the earth.
• Convection is the process by which the transmission of heat takes place through a substance from one point to another due to actual bodily movement of heated particles of the substance

• Annealing is one of the major processes in the manufacture of glass.
• It is a controlled slow cooling process of heat treatment of glass.
• It helps in strengthening the glass and relieving the stress.