Analog Electronics MCQ Questions & Answers | Electrical Engineering

Analog Electronics MCQ Questions & Answers | Electrical Engineering

1.

The action of JFET in its equivalent circuit can best be represented as a

A.Current controlled Current source

B.Current controlled voltage source

C.Voltage controlled voltage source

D.voltage controlled current source

Answer & Solution Discuss in Board Save for Later

2.

In a CB amplifier the maximum efficiency could be

A.99%

B.85%

C.50%

D.25%

Answer & Solution Discuss in Board Save for Later

3.

In a p⁺n junction diode under reverse bias , the magnitude of electric field is maximum at

A.The edge of the depletion region on the p-side

B.The edge of the depletion region on the n-side

C.The p⁺n junction

D.The center of the depletion region on the n-side

Answer & Solution Discuss in Board Save for Later

4.

To prevent a DC return between source and load, it is necessary to use

A.Resistor between source and load

B.Inductor between source and load

C.Capacitor between source and load

D.Either A or B

Answer & Solution Discuss in Board Save for Later

5.

A constant current signal across a parallel RLC circuits gives an o/p of 1.4v at the signal frequency of 3.89KHZ and 4.1KHZ. At the frequency of 4KHZ,the o/p voltage will be

A.1v

B.2v

C.1.4v

D.2.8v

Answer & Solution Discuss

Electrical Engineering Material 75 Mcqs with answers part -2

PKR ELECTRICAL ENGINEERING
Q.1 Materials which can store electrical energy are called
(A) magnetic materials. (B) semi conductors.
(C) dielectric materials. (D) super conductors.
Ans: C

Q.2 ACSR (Aluminium Conductor Steel Reinforced) are used as
(A) over head transmission lines. (B) super conductors.
(C) fuse (D) underground cables.
Ans: A

Q.3 Brass is an alloy of
(A) copper and zinc. (B) copper and iron.
(C) copper and Aluminium. (D) copper and tin.
Ans: A

Q.4 Property of material which allows it to be drawn out into wires is
(A) Ductility. (B) Solder ability.
(C) Super conductivity. (D) Malleability.
Ans: A

Q.5 In n type semi conductor added impurity is
(A) pentavalent. (B) divalent.
(C) tetravalent. (D) trivalent.
Ans: A

Q.6 The covers of electrical machines are made of
(A) soft magnetic materials. (B) hard magnetic materials.
(C) super conductors. (D) semiconductors.
Ans: A

Q.7 The dielectric constant of air is practically taken as
(A) more than unity. (B) unity.
(C) less than unity. (D) zero.
Ans: B

Q.8 n-type semiconductor is an example of
(A) extrinsic semiconductor. (B) intrinsic semiconductor.
(C) super conductor. (D) insulators..
Ans: A

Q.9 Atomic weight of an atom is
(A) sum of the number of protons and neutrons.
(B) sum of the number of protons and electrons.
(C) sum of the number of electrons and neutrons.
(D) sum of the number of electrons, protons and neutrons.
Ans: A

Q.10 Gold and silver are
(A) dielectric materials
(B) low resistivity conducting materials.
(C) magnetic materials.
(D) insulating materials.
Ans: B

Q.11 Phenol and Formaldehyde are polymerised to a resultant product known as
(A) PVC.
(C) polyester.
(B) bakelite.
(D) teflon.
Ans: B

Q.12 Dielectric materials are
(A) Insulating materials.
(B) Semiconducting materials.
(C) Magnetic materials. (D) Ferroelectric materials.
Ans: A

Q.13 Thermocouples are used for the measurement of
(A) humidity. (B) pressure.
(C) temperature. (D) density.
Ans: C

Q.14 Large scale integration chips have between
(A) Less than 10 components. (B) 10 and 100 components.
(C) 100 and 1000 components. (D) More than 1000 components.
Ans: C

Q.15 All semiconductors in their last orbit have
(A) 8 electrons. (B) 2 electrons.
(C) 4 electrons. (D) 6 electrons.
Ans: C

Q.16 The material with lowest resistivity is
(A) constantan. (B) silver.
(C) manganin. (D) nichrome.
Ans: B

Q.17 The property due to which the resistance of some metal or compound vanishes under certain
conditions is
(A) Semi conductivity. (B) Super conductivity.
(C) Curie point. (D) Magnetostriction.
Ans: B

Q.18 Bronze is an alloy of
(A) copper. (B) aluminium.
(C) silver. (D) carbon.
Ans: A

Q.19 Ceramics are good
(A) insulators. (B) conductors.
(C) superconductors. (D) semiconductors.
Ans: A

Q.20 The critical temperature above which the ferromagnetic materials loose their magnetic
property is known as
(A) hysterisis. (B) Curie point.
(C) transition temperature. (D) standard temperature.
Ans: B

Q.21 Permanent magnets are made of
(A) soft magnetic materials. (B) hard magnetic materials.
(C) semi conductors. (D) super conductors.
Ans: B

Q.22 Holes are majority carriers in
(A) P-type semiconductors. (B) N-type semiconductors.
(C) Insulators. (D) Superconductors.
Ans: A

Q.23 Materials, which provide a path to the magnetic flux, are classified as
(A) insulating materials.
(C) magnetic materials.
(B) semi conducting materials.
(D) dielectric materials.
Ans: C

Q.24 Germanium possesses
(A) one valence electrons.
(B) two valence electrons.
(C) three valence electrons. (D) four valence electrons.
Ans: D

Q.25 Dielectric constant of vacuum is
(A) infinity.
(B) 100.
(C) one. (D) zero.
Ans: C

Q.26 Ferrites are
(A) ferromagnetic material.
(B) ferrimagnetic materials.
(C) anti ferromagnetic material. (D) diamagnetic materials.
Ans: A

Q.27 The relative permeability of a paramagnetic substance is
(A) unity. (B) slightly more than unity.
(C) zero. (D) less than unity.
Ans: B

Q.28 Hall effect may be used for which of the following?
(A) determining whether the semiconductor is p or n type.
(B) determining the carrier concentration.
Ans : A

MCQ ABOUT DRAWING TOOLS

How many battens will be there for a Drawing board?
a) 1
b) 2
c) 3
d) 4

Ans : b

The part that doesn’t belong to T-square is ____
a) Working edge
b) Blade
c) Stock
d) Ebony

Ans : d

The angle which we can’t make using a single Set-square is
a) 45o
b) 60o
c) 30o
d) 75o

Ans: d

The angle which we can’t make using both the Set-squares is _
a) 15o
b) 105o
c) 165o
d) 125o

Ans: d

Small bow compass can draw circles less than _ mm radius.
a) 25mm
b) 30mm
c) 35mm
d) 40mm

Ans : a

The areas of the two subsequent sizes of drawing sheet are in the ratio
a) 1:5
b) 1:4
c) 1:2
d) 1:10

Ans: c

The Grade becomes  according to the figure placed in front of the letter B, 2B, 3B, 4B etc.
a) harder
b) lighter
c) darker
d) softer

Ans: d

Which of the following tools is used to draw horizontal lines?
a) Mini – drafter
b) Protractor
c) T – square
d) French curve

Ans: c

Which of the following instrument can be used to draw accurate perpendicular lines, parallel lines and angular lines?

a) Mini – drafter
b) T – square
c) Protractor
d) Set square

Ans: a

According to the Indian Standard Institute (ISI), which among the following designation has the size 1000 x 700 (in mm)?

a) B0
b) B1
c) B2
d) B3

Ans: b

Which is the most common tool used for drawing circles?
a) French curve
b) Mini – drafter
c) Divider
d) Compass

Ans: d

For drawing circles with a large radius, which of the following tool is used?
a) Bow compass
b) Lengthening bar compass
c) Divider
d) Protractors

Ans: b

Which of the following drawing tools is used by architects for making blueprints?

a) Drawing Pencils
b) Dusters
c) Ink Pen
d) Erasers

Ans: c

Which of the following drawing tool is not used to set the drawing sheet onto the drawing board?
a) Drawing clips
b) Drawing pins
c) Divider
d) Adhesive Tape

Ans: c

According to the Indian Standard Institution (ISI), what is the size of the designation A3 in mm?
a) 420 x 297
b) 841 x 594
c) 1189 x 841
d) 297 x 210

Ans:a

For marking angles, which of the following drawing tool is used?
a) Protractor
b) Divider
c) Compass
d) French curve

Ans:a

Using 30˚ – 60˚ – 90˚ and 45˚ – 45˚ – 90˚ set squares, which of the following angle is not possible to draw?
a) 45˚
b) 30˚
c) 10˚
d) 90˚

Ans:c

Which is the instrument used to draw parallel lines fast?
a) Set square
b) Ruler scale
c) Protractor
d) Roll-n-draw

Ans: d

Electrical Engineering Material 75 Mcqs with answers part -1

PKR ELECTRICAL ENGINEERING
Q.1 Materials which can store electrical energy are called
(A) magnetic materials. (B) semi conductors.
(C) dielectric materials. (D) super conductors.
Ans: C
Q.2 ACSR (Aluminium Conductor Steel Reinforced) are used as
(A) over head transmission lines. (B) super conductors.
(C) fuse (D) underground cables.
Ans: A
Q.3 Brass is an alloy of
(A) copper and zinc. (B) copper and iron.
(C) copper and Aluminium. (D) copper and tin.
Ans: A
Q.4 Property of material which allows it to be drawn out into wires is
(A) Ductility. (B) Solder ability.
(C) Super conductivity. (D) Malleability.
Ans: A
Q.5 In n type semi conductor added impurity is
(A) pentavalent. (B) divalent.
(C) tetravalent. (D) trivalent.
Ans: A
Q.6 The covers of electrical machines are made of
(A) soft magnetic materials. (B) hard magnetic materials.
(C) super conductors. (D) semiconductors.
Ans: A
Q.7 The dielectric constant of air is practically taken as
(A) more than unity. (B) unity.
(C) less than unity. (D) zero.
Ans: B
Q.8 n-type semiconductor is an example of
(A) extrinsic semiconductor. (B) intrinsic semiconductor.
(C) super conductor. (D) insulators..
Ans: A
Q.9 Atomic weight of an atom is
(A) sum of the number of protons and neutrons.
(B) sum of the number of protons and electrons.
(C) sum of the number of electrons and neutrons.
(D) sum of the number of electrons, protons and neutrons.
Ans: A
Q.10 Gold and silver are
(A) dielectric materials
(B) low resistivity conducting materials.
(C) magnetic materials.
(D) insulating materials.
Ans: B
Q.11 Phenol and Formaldehyde are polymerised to a resultant product known as
(A) PVC.
(C) polyester.
(B) bakelite.
(D) teflon.
Ans: B
Q.12 Dielectric materials are
(A) Insulating materials.
(B) Semiconducting materials.
(C) Magnetic materials. (D) Ferroelectric materials.
Ans: A
Q.13 Thermocouples are used for the measurement of
(A) humidity. (B) pressure.
(C) temperature. (D) density.
Ans: C
Q.14 Large scale integration chips have between
(A) Less than 10 components. (B) 10 and 100 components.
(C) 100 and 1000 components. (D) More than 1000 components.
Ans: C
Q.15 All semiconductors in their last orbit have
(A) 8 electrons. (B) 2 electrons.
(C) 4 electrons. (D) 6 electrons.
Ans: C
Q.16 The material with lowest resistivity is
(A) constantan. (B) silver.
(C) manganin. (D) nichrome.
Ans: B
Q.17 The property due to which the resistance of some metal or compound vanishes under certain
conditions is
(A) Semi conductivity. (B) Super conductivity.
(C) Curie point. (D) Magnetostriction.
Ans: B
Q.18 Bronze is an alloy of
(A) copper. (B) aluminium.
(C) silver. (D) carbon.
Ans: A
Q.19 Ceramics are good
(A) insulators. (B) conductors.
(C) superconductors. (D) semiconductors.
Ans: A
Q.20 The critical temperature above which the ferromagnetic materials loose their magnetic
property is known as
(A) hysterisis. (B) Curie point.
(C) transition temperature. (D) standard temperature.
Ans: B
Q.21 Permanent magnets are made of
(A) soft magnetic materials. (B) hard magnetic materials.
(C) semi conductors. (D) super conductors.
Ans: B
Q.22 Holes are majority carriers in
(A) P-type semiconductors. (B) N-type semiconductors.
(C) Insulators. (D) Superconductors.
Ans: A
Q.23 Materials, which provide a path to the magnetic flux, are classified as
(A) insulating materials.
(C) magnetic materials.
(B) semi conducting materials.
(D) dielectric materials.
Ans: C
Q.24 Germanium possesses
(A) one valence electrons.
(B) two valence electrons.
(C) three valence electrons. (D) four valence electrons.
Ans: D
Q.25 Dielectric constant of vacuum is
(A) infinity.
(B) 100.
(C) one. (D) zero.
Ans: C
Q.26 Ferrites are
(A) ferromagnetic material.
(B) ferrimagnetic materials.
(C) anti ferromagnetic material. (D) diamagnetic materials.
Ans: A
Q.27 The relative permeability of a paramagnetic substance is
(A) unity. (B) slightly more than unity.
(C) zero. (D) less than unity.
Ans: B
Q.28 Hall effect may be used for which of the following?
(A) determining whether the semiconductor is p or n type.
(B) determining the carrier concentration.
(C) calculating the mobility.

PKR ELECTRICAL ENGINEERING
(D) All the above.
Ans: D Determining whether the semiconductor is p or n type, determining the carrier
concentration, calculating the mobility.
Q.29 Manganin is an alloy of
(A) copper, manganese and nickel. (B) copper and manganese.
(C) manganese and nickel. (D) manganese, aluminium and nickel.
Ans: A
Q.30 Eddy current loss is proportional to the
(A) frequency. (B) square of the frequency.
(C) cube of the frequency. (D) square-root of the frequency.
Ans: B
Q.31 A pure semiconductor under ordinary conditions behaves like
(A) a conductor. (B) an insulator.
(C) a magnetic material. (D) a ferro-electric material.
Ans: B
Q.32 In p-type semiconductor the majority carriers are
(A) holes.
(C) positive ions.
(B) electrons.
(D) negative ions.
Ans: A
Q.33 Copper is completely miscible with
(A) nickel.
(B) gold.
(C) hydrogen. (D) lead.
Ans: B
Q.34 For germanium the forbidden gap is
(A) 0.15ev.
(B) 0.25ev.
(C) 0.5ev. (D) 0.7ev.
Ans: D
Q.35 The dielectric strength of transformer oil should be
(A) 100 V. (B) 5 KV.
(C) 30 KV. (D) 132 KV.
Ans: C
Q.36 Resistivity of conductors is most affected by
(A) composition. (B) temperature.
(C) pressure. (D) current.
Ans: B
Q.37 Copper constantan is used for measuring temperature upto
(A)1400 (B) 750
(C) 400 (D)1100
Ans: C
Q.38 Mica is a
(A) Dielectric material. (B) Insulating material.
(C) Magnetic material. (D) Both insulating and dielectric
material.
Ans: D
Q.39 The conductivity of copper is less than that of silver by
(A) 5 – 10 %. (B) 50 – 60 %.
(C) 80 – 90 %. (D) 20 – 30 %.
Ans: A
Q.40 A ferrite core has less eddy current loss than an iron core because ferrites have
(A) High resistance.
(C) Low permeability.
(B) Low resistance.
(D) High hysteresis.
Ans: A
Q.41 Transformer cores are laminated with
(A) Low carbon steel.
(B) Silicon sheet steel.
(C) Nickel alloy steel. (D) Chromium sheet steel.
Ans: B
Q.42 For silicon the forbidden gap is
(A) 1.1ev.
(B) 0.25ev.
(C) 0.5ev. (D) 0.7ev.
Ans: A
Q.43 Plastics are
(A) Good conductors of heat.
(B) Good conductors of electricity.
(C) Bad conductors of electricity. (D) High density.
Ans: C
Q.44 In order to obtain p-type germanium it should be doped with a
(A) Trivalent impurity. (B) Tetravalent impurity.
(C) Pentavalent impurity. (D) Any of the above will do.
Ans: A
Q.45 Barrier potential in a P-N junction is caused by
(A) Thermally generated electrons and holes.
(B) Diffusion of majority carriers across the junction.
(C) Migration of minority carriers across the junction.
(D) Flow of drift current.
Ans: B
Q.46 The heating elements of electric irons are made of
(A) Copper. (B) Nichrome.
(C) Constantan. (D) Aluminium.
Ans: B
Q.47 The most malleable, ductile low resistivity material is
(A) Copper. (B) Aluminium.
(C) Silver. (D) Iron.
Ans: C
Q.48 The percentage of carbon in mild steel is
(A) 0.08 to 0.3 % (B) 0.5 to 1.4 %
(D) 2.35 % (D) 0.5 %
Ans: A
Q.49 Aluminium is
(A) Silvery white in colour. (B) Yellow in colour.
(C) Reddish in colour. (D) Pale yellow in colour.
Ans: A
Q.50 Hard ferrites are used for making
(A) Transformer cores. (B) Electrical machinery.
(C) High frequency equipment. (D) Light weight permanent magnets.
Ans: D
Q.51 The main constituents of glass is
(A) SiO2 (B) B2O3
(C) Al2O3 (D) Cr2O3
Ans: A
Q.52 Micanite is a form of
(A) Built up mica.
(B) Hydrated potassium aluminium silicate.
(C) Magnesium mica.
(D) Calcium mica.
Q.53
Ans: A
What is the type of bonding in silicon?
(A) Ionic.
(C) Metallic.
(B) Covalent.
(D) Ionic + Metallic
Ans: B
Q.54 P-N junction is
(A) a rectifier. (B) an amplifier.
(C) an Oscillator. (D) a Coupler.
Ans: A
Q.55 The conductivity of an extrinsic semiconductor
(A) decreases with temperature.
(B) increases with temperature.
(C) remains constant with temperature.
(D) decreases and then increases with temperature.
Ans: B
Q.56 When a semiconductor is doped with a P-type impurity, each impurity atom will
(A) acquire negative charge. (B) acquire positive charge.
(C) remain electrically neutral. (D) give away one electron.
Ans: A
Q.57 Number of Terminals in a MOSFET are
(A) Two (B) Three
(C) Four (D) Five
Ans: B

PKR ELECTRICAL ENGINEERING
Q.58 Which of the following material has the highest melting point
(A) Copper. (B) Aluminium.
(C) Tungsten. (D) Gold.
Ans: C
Q.59 Bronze is an alloy of
(A) Copper and Tin. (B) Copper and Steel.
(C) Copper and Mercury. (D) Copper and Aluminium.
Ans: A
Q.60 A transistor has
(A) One p-n junction. (B) Two p-n junction.
(C) Four p-n junction. (D) Five p-n junction.
Ans: B
Q.61 Example of high resistivity material is
(A) Nichrome (B) Silver
(C) Gold (D) Copper
Ans: A
Q.62 Hard magnetic materials are used for making
(A) Permanent magnets. (B) Temporary magnets.
(C) Conductors. (D) Insulator.
Ans: A
Q.63 Hall effect is associated with
(A) Conductors. (B) Semiconductors.
(C) Thermistors. (D) Solders.
Ans: B
Q.64 Addition of trivalent impurity to a semiconductor creates many
(A) holes. (B) free electrons.
(C) valance electrons. (D) bound electrons.
Ans: B
Q.65 Magnetic materials
(A) provide path to magnetic flux. (B) are good insulators.
(C) are semiconductors. (D) None.
Ans: A
Q.66 In a ferromagnetic material the state of flux density is as follows when external magnetic
field is applied to it.
(A) Increased (B) Decreased
(C) Remains unchanged (D) Becomes zero
Ans: C
Q.67 Paper is hygroscopic and absorbent.
(A) True (B) False
Ans: A
Q.68 Insulators have
(A) A full valence band. (B) An empty conduction band.
(C) A large energy gap. (D) All the above.
Ans: C
Q.69 Hysteresis loss least depends on
(A) Frequency. (B) Magnetic field intensity.
(C) Volume of the material. (D) Grain orientation of material.
Ans: D
Q.70 Atoms with four valence electrons are good conductors.
(A) True (B) False
Ans: B
Q.71 Semi-conductors have temperature coefficient of resistance.
(A) Negative (B) Positive
(C) Both positive and negative (D) None of the above
Ans: A
Q.72 Tick off the material, which is different from the group
(A) Constantan. (B) Manganin.
(C) Nichrome. (D) Brass.
Ans: D
Q.73 Tick of the property, which is different from the group
(A) Ductility. (B) Resistivity.
(C) Tensile strength. (D) Hardness.
Ans: B
Q.74 Ferroelectric materials are characterised by
(A) Very high degree of polarisation.
(B) A sharp dependence of polarisation on temperature.
(C) Non-linear dependence of the charge Q on the applied voltage.
(D) All the above.
Ans: D

Introduction of power plants

Introduction:
The whole world is suffering from energy crisis and the pollution is manifesting itself in the spiraling cost of energy and uncomforted due to increase in pollution as well as the depletion of conventional energy resources and increasing curve of pollution elements.

 

Need of power plant:
               

To meet the challenges one way is to check growing energy demand but that will show down the economic growth as first step and to develop nonpolluting energy conversion system as second step.

It is commonly accepted that the standard of living increases with increasing energy consumption per capita.

Any consideration of energy requirement and supply has to take into account the increasing conservation measures. On the industrial front, emphasis must be placed on the increased with constant effort to reduce energy consumption.

Fundamental changes in the process, production and services are affecting considerable energy saving without affecting the overall economy. It should not be over emphasized that in house hold commercial and industrial use of energy has considerable scope in energy saving.

Attempt at understanding the integrated relationship between environment and energy has given shape due to development ofR-134a, (a non-pollutant refrigent) to emerging discipline of environmental management.

The government of India has laid down the policy “it is important that we carefully utilize our renewal (i.e., non-decaying) resources of soil water, plant and animal live to sustain our economic development” our exploration or exploitation of thesis reflected in soil erosion, salutation, floods and rapid destruction of our forest, floral and wild life resources.

The depletion of these resources such as fuel, fodder, and housing power plant often tends to be irreversible since bulk of our population depends on these natural resources.

relationship

Introduction to Power System:

Introduction to Power System: Thomas A. Edison’s work in 1878 on the electric light led to the concept of a centrally located power station with distributed electric power for lighting in a surrounding area. The opening of the historic Pearl Street Station in New York City on September 4, 1882, with dc generators (dynamos) driven by steam engines, marked the beginning of the electric utility industry. Edison’s dc systems expanded with the development of three-wire 220-V dc systems. But as transmission distances and loads continued to grow, voltage problems were encountered. With the advent of William Stanley’s development of a commercially practical transformer in 1885, alternating current became more attractive than direct current because of the ability to transmit power at high voltage with corresponding lower current and lower line-voltage drops. The first single-phase ac line (21 km at 4 kV) in the United States operated in 1889 between Oregon City and Portland.

Nikola Tesla’s work in 1888 on electric machines made evident the advantages of polyphase over single-phase systems. The first three-phase line (12 km at 2.3 kV) in the United States became operational in California during 1893. The three-phase induction motor conceived by Tesla became the workhorse of the industry.

Today the two standard frequencies for the generation, transmission, and distribution of electric power in the world are 60 Hz (in the United States, Canada, Japan, and Brazil) and 50 Hz (in Europe, the former Soviet Republics, South America except Brazil, India, and also Japan). Relatively speaking, the 60-Hz power-system apparatus is generally smaller in size and lighter in weight than the corresponding 50-Hz equipment with the same ratings. On the other hand,
transmission lines and transformers have lower reactances at 50 Hz than at 60 Hz. Along with increases in load growth, there have been continuing increases in the size of generating units and in steam temperatures and pressure, leading to savings in fuel costs and overall operating costs. Ac transmission voltages in the United States have also been rising steadily: 115, 138, 161, 230, 345, 500, and now 765 kV. Ultrahigh voltages (UHV) above 1000 kV are now being studied. Some of the reasons for increased transmission voltages are:

• Increases in transmission distance and capacity
• Smaller line-voltage drops
• Reduced line losses
• Reduced right-of-way requirements
• Lower capital and operating costs.

In association with ac transmission, there have been other significant developments:

• Suspension insulator
• High-speed relay system
• High-speed, extra-high-voltage (EHV) circuit breakers
• EHV surge arrester to protect from lightning strokes and other surges
• Communications via power-line carrier, microwave, and fiber optics
• Energy control centers with supervisory control and data acquisition (SCADA) and with automatic generation control (AGC)
• Extensive use of microprocessors for various tasks.

Along with ac transmission in the United States, there have been modern high-voltage dc (HVDC) transmission lines: the ±400-kV, 1360-km Pacific Intertie line between Oregon and California in 1970 as well as four other HVDC lines up to 400 kV and five back-to-back ac–dc links as of 1991.Atotal of 30HVDClines up to 533 kV are in place worldwide. For anHVDCline interconnected with an ac system, solid-state converters at both ends of the dc line are needed to operate as rectifiers and inverters. Studies in the United States have shown that overhead HVDC transmission is economical for transmission distances longer than about 600 km. Also, HVDC links seem to improve the overall system stability.

• Better maintenance of continuity of service
• Increase in reliability and improved economy
• Reduction of reserve requirements
• Scheduling power transfers taking advantage of energy-cost differences in respective areas, load diversity, and seasonal conditions
• Shared ownership of larger and more efficient generating units.

Some of the disadvantages of interconnected operations are:

• Increased fault currents during short circuits
• Occasional domino effect leading to a regional blackout (such as the one that occurred in 1965 in the northern United States) due to an initial disturbance in some part of the interconnected grid system.

Voltage and current

Voltage and current:: Voltage attempts to make a current flow, and current will flow if the circuit is complete. Voltage is sometimes described as the 'push' or 'force' of the electricity, it isn't really a force but this may help you to imagine what is happening. It is possible to have voltage without current, but current cannot flow without voltage.

Charge: electric charge, basic property of matter carried by some elementary particles. Electric charge, which can be positive or negative, occurs in discrete natural units and is neither created nor destroyed.

Electric circuits: which are collections of circuit elements connected together, are the most fundamental structures of electrical engineering. A circuit is an interconnection of simple electrical devices that have at least one closed path in which current may flow. However, we may have to clarify to some of our readers what is meant by “current” and “electrical device,” a task that we shall undertake shortly. Circuits are important in electrical engineering because they process electrical signals, which carry energy and information; a signal can be any time varying electrical quantity. Engineering circuit analysis is a mathematical study of some useful interconnection of simple electrical devices.

In describing the operation of electric circuits, one should be familiar with such electrical quantities as charge, current, and voltage.

Charge and Electric Force: The proton has a charge of 1.602 10−19 coulombs (C), while the electron has a charge of −1.602 × 10−19 C. The neutron has zero charge. Electric charge and, more so, its movement are the most basic items of interest in electrical engineering. When many charged particles are collected together, larger charges and charge distributions occur. There may be point charges (C), line charges (C/m), surface charge distributions (C/m2), and volume charge distributions (C/m3).

Coulomb’s law gives an expression to evaluate the electric force in newtons (N) exerted on one point charge by the other:

 

where Q1 and Q2 are the point charges (C); R is the separation in meters (m) between them; ε0

is the permittivity of the free-space medium with units of C2/N.

ELECTRICAL ENGINEERING:

ELECTRICAL ENGINEERING:
The typical curriculum of an undergraduate electrical engineering student includes the subjects listed in Table 1.1.
Although the distinction between some of these subjects is not always clear-cut, the table is sufficiently representative to serve our purposes. The aim of this book is to introduce the non-electrical engineering student to those aspects of electrical engineering that are likely to be most relevant to his or her professional career.
Virtually all of the topics of Table 1.1
will be touched on in the book, with varying degrees of emphasis. The following example illustrates the pervasive presence of electrical, electronic, and electromechanical devices and systems in a very common application: the automobile.
As you read Table 1.1
Electrical through the example, it will be instructive to refer to Table 1.1.

Table 1.1

ELECTRICAL ENGINEERING

Circuit analysis

Electromagnetics

Solid-state electronics

Electric machines

Electric power systems

Digital logic circuits

Computer systems

Communication systems

Electro-optics

Instrumentation systems

Control systems            

Current: 
Current can be defined as the motion of charge through a conducting material. The unit of current is Ampere whilst charge is measured in Coulombs.

Definition of an Ampere: 
“The quantity of total charge that passes through an arbitrary cross section of a conducting material per unit second is defined as an Ampere.”

Mathematically,

where Q is the symbol of charge measured in Coulombs (C), I is the current in amperes (A) and t is the time in seconds (s). The current can also be defined as the rate of charge passing through a point in an electric circuit i.e.

A constant current (also known as direct current or DC) is denoted by the symbol I whereas a timevarying current (also known as alternating current or AC) is represented by the symbol i or i(t).

Voltage or Potential Difference: 
Voltage or potential difference between two points in an electric circuit is 1 V if 1 J (Joule) of energy is expended in transferring 1 C of charge between those points.

It is generally represented by the symbol V and measured in volts (V). Note that the symbol and the unit of voltage are both denoted by the same letter, however, it rarely causes any confusion.

Voltage is always measured across a circuit element as demonstrated in given figure

Circuit Loads: A load generally refers to a component or a piece of equipment connected to the output of an electric circuit.

circuit elements

1. Resistor (R)

2. Inductor (L)

3. Capacitor (C)

Electrical engineering formulas

Volt - unit of electrical potential or motive force - potential is required to send one ampere of current through one ohm of resistance

 

Ohm - unit of resistance - one ohm is the resistance offered to the passage of one ampere when impelled by one volt

 

Ampere - units of current - one ampere is the current which one volt can send through a resistance of one ohm

 

Watt - unit of electrical energy or power - one watt is the product of one ampere and one volt - one ampere of current flowing under the force of one volt gives one watt of energy

 

Volt-ampere (VA) - is a measurement of power in a direct current ( DC ) electrical circuit. The VA specification is also used in alternating current ( AC ) circuits, but it is less precise in this application, because it represents apparent power , which often differs from true power .

 

Kilovolt Ampere - one kilovolt ampere - KVA - is equal to 1000 volt amperes

 

Power Factor - ratio of watts to volt amperes

 

Most important Formulas:

 

Voltage V = I × R = P / I = √(P × R) in volts V         

Current I = V / R = P / V = √(P / R) in amperes A

Resistance R = V / I = P / I2 = V2 / P in ohms Ω    

Power P = V × I = R × I2 = V2 / R in watts W

 

 

Electrical Potential - Ohm's Law

 

Ohm's law can be expressed as:

 

V = R I         (1a)

 

V = P / I         (1b)

 

V = (P R)1/2         (1c)

 

Electric Current - Ohm's Law

 

I = V / R         (2a)

 

I = P / V         (2b)

 

I = (P / R)1/2         (2c)

 

Electric Resistance - Ohm's Law

 

R = V / I         (3a)

 

R = V2/ P         (3b)

 

R = P / I2         (3c)

 

Electric Power

 

P = V I         (4a)

 

P = R I2         (4b)

 

P = V2/ R         (4c)

 

where

 

P = power (watts, W), V = voltage (volts, V)

 

I = current (amperes, A), R = resistance (ohms, Ω)

 

Electric Energy :Electric energy is power multiplied time, or

 

W = P t      (5)

 

where

 

W = energy (Ws, J), t = time (s)

 

Electrical Motors : Electrical Motor Efficiency

 

μ = 746 Php / Pinput_w         (6)

 

where

 

μ = efficiency

 

Php = output horsepower (hp)

 

Pinput_w = input electrical power (watts)

 

or alternatively

 

μ = 746 Php / (1.732 V I PF)         (6b)

 

Electrical Motor - Power

 

P3-phase = (V I PF 1.732) / 1,000         (7)

 

where

 

P3-phase = electrical power 3-phase motor (kW)

 

PF = power factor electrical motor

 

Electrical Motor - Amps

 

I3-phase = (746 Php) / (1.732 V μ PF)         (7)

 

where

 

I3-phase = electrical current 3-phase motor (amps)

 

PF = power factor electrical motor

Electrical measurements

Quantity

Name

Definition

frequency f

hertz (Hz)

1/s

force F

newton (N)

kg•m/s²

pressure p

pascal (Pa) = N/m²

kg/m•s²

energy E

work joule (J) = N•m

kg•m²/s²

power P

watt (W) = J/s

kg•m²/s³

electric charge Q

coulomb (C) = A•s

A•s

voltage V

volt (V)= W/A

kg•m²/A•s³

current I

ampere (A) = Q/s

A

capacitance C

farad (F) = C/V = A•s/V = s/Ω

A²•s4/kg•m²

Test 5 General Electrical Engineering

Test 5 General Electrical Engineering

1_______ is used to measure the flow of air around aeroplane 

A. Anemometer. 
B. Venturimeter. 
C. Orifice. 
D. nucleus.Answer

2 Relative permittivity can be measured by _______ bridge 

A. Wheatstone. 
B. Hays. 
C. Desauty. 
D. Schering.Answer

3 There is a ________ between two nodes of signal flow graph 

A. link. 
B. branch. 
C. tree. 
D. none of the abovAnswer

4 What is the phase difference between two windings of A.C servomotor ? 

A. 30°. 
B. 60°. 
C. 90°. 
D. 120°.Answer

5 Which of the following logic circuits is the fastest? 

A. RTL. 
B. DTL. 
C. TTL. 
D. All have same speed.Answer

6 Which of the following is not a transmission medium? 

A. Telephone lines. 
B. Coaxial cables. 
C. Modem. 
D. Microwave systems.Answer

7 In a RC phase shift oscillator, the minimum number of R-C networks to be connected in cascade will be 

A. one. 
B. two. 
C. three. 
D. four.Answer

8 A three phase 400 V, 6 pole, 50 Hz, squirrel cage induction motor is running at a slip of 5%. The speed of stator magnetic field with respect to rotor magnetic field and speed of rotor w.r.t stator magnetic field are

A. zero , - 50 rpm. 
B. zero, 950 rpm. 
C. 1000 rpm, - 50 rpm. 
D. 1000 rpm, 950 rpm.Answer

9 A 400 V, 50 Hz, 30 Hp, three phase IM is drawing 50 A current at 0.8 p.f lagging. The stator and rotor copper losses are 1.5 KW and 900 W respectively. The friction and windage losses are 1050 W and core losses are 1200 W. The air gap power of the motor will be 

A. 23.06 kW. 
B. 24.11 kW. 
C. 25 kW. 
D. 26.21 kW.Answer

10 What is the rms value of the voltage waveform shown in Figure ?
diagram-for-mcq

A. 200 /p V. 
B. 100 /p V. 
C. 200 V. 
D. 100 V.Answer

Test 4 General Electrical Engineering

Test 4 General Electrical Engineering

1 Inside a hollow conducting sphere 

A. electric field is zero. 
B. electric field is a non zero constant. 
C. electric field changes with magnitude of the charge given to the conductor. 
D. electric field changes with distance from the center of the sphere.Answer

2 Two infinite parallel metal plates are charged with equal surface charge density of the same polarity. The electric field in the gap between the plates is 

A. same as that produced by one plate. 
B. double the field produced by one plate. 
C. dependent on coordinates of field points. 
D. zero.Answer

3 As a result of reflection from a a plane conducting wall, electromagnetic waves acquire an apparent velocity greater than the velocity of light in space. This is called the 

A. velocity of propagation. 
B. normal velocity. 
C. group velocity. 
D. phase velocity.Answer

4 Length of the cable is doubled, its capacitance C will be 

A. one-fourth. 
B. one-half. 
C. double. 
D. unchanged.Answer

5————- is the most detrimental impurity in the magnetic materials 

A. Carbon. 
B. Sulphur. 
C. Oxygen. 
D. Nitrogen.Answer

6 The chemical effect of current is used in

A. D.C ammeter hour meter. 
B. D.C ammeter. 
C. D.C energy meter. 
D. none of the above.Answer

7 Swamping resistance is used to compensate 

A. error due to temperature true variations. 
B. compensate error due to strong magnetic field. 
C. both A and B. 
D. none of these.Answer

8———– was the first city in India to adopt electric traction. 

A. Delhi. 
B. Madras. 
C. Calcutta. 
D. Bombay.Answer

9 Unit of deflection sensitivity of a CRO is 
A. V / mm. 
B. meter / volt. 
C. mm per mV. 
D. mm / V.Answer

10 Null type recorders are 

A. bridge recorders. 
B. LVDT recorders. 
C. potentiometric recorder. 
D. any one of the above.Answer