juliusz b. gajewskifluid.itcmp.pwr.wroc.pl/elektra/l 01.pdfs e m i c o n d u c t o r s —...

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Juliusz B. GajewskiProfessor of Electrical Engineering

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FACULTY OF MECHANICAL AND ELECTRIC POWER ENGINEERING

Process Engineering and Equipment, Electrostaticsand Tribology Research Group

Wybrzeże S. Wyspiańskiego 2750-370 Wrocław, POLAND

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Building A4 „Stara kotłownia”, Room 359Tel.: +48 71 320 3201; Fax: +48 71 328 3218

E-mail: [email protected]: www.itcmp.pwr.wroc.pl/elektra

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Contents

1. Terms. Fundamental Definitions and Units.2. Electrostatics. Electrostatic and Electric Fields.3. Electrodynamics. DC Current.4. Electromagnetism. Magnetic Field of DC Current.5. Electric Circuit Elements.6. Sinusoidal AC Voltage.7. Complex Frequency Concept.8. Electric Filters.9. Electrical Measurements.

10. Three-Phase Circuits.11. Electrical Signals.12. Electric Switches.

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E l e c t r i c a l e n g i n e e r i n g is engineering that deals withpractical applications of e l e c t r i c i t y; generally restricted toapplications involving current flow through conductors, as in motorsand generators.E l e c t r i c a l e n g i n e e r i n g is an engineering discipline thatdeals with the study and practical application of e l e c t r i c i t y ande l e c t r o m a g n e t i s m.

For electrical engineering the science of electricity is fundamental andis the branch of physics. Physics studies, finds, and explains the prin-ciples of electrical phenomena, while electrical engineering explainsthe applications of those phenomena to engineering and technology.

Electrical Engineering

Terms.Fundamental Definitions and Units

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E l e c t r i c c h a r g e or c h a r g e is a basic property ofelementary particles of matter. One does not define charge but takesit as a basic experimental quantity and defines other quantities interms of it.

The early Greek philosophers were aware that rubbing amber withfur produced properties in each that were not possessed before therubbing. For example, the amber attracted the fur after rubbing, butnot before. These new properties were later said to be due to“charge.” The amber was assigned a negative charge and the fur wasassigned a positive charge.

Electric Charge


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Electric Charge


Thales of Miletus(ca. 624–ca. 546 BC)A father of electricity

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Thales of Miletus (ca. 624–ca. 546 BC), a Greek, found that amber attracted different lightobjects when rubbed with silk (fur). He is believed to be a discoverer of static electricity andcould be generally named a father of electricity. The Greek word for amber is ήλεκτρον(élektron) ëelectron (English electron) from which one can get ëelectricity and ëelectronics.The English word electric is based on the Greek amber. Both words derive from the electro-static properties of amber. It is also said that “a first usage of the word e l e c t r i c i t y isascribed to Sir Thomas Browne in his 1646 work Pseudodoxia Epidemica”.Ancient and medieval awareness of electrical effects includes lightning, electric fish, St.Elmo’s fire, the amber effect, and, especially in early China, the lodestone (magnet). Little (oreven nothing) is known about the discoveries or inventions in the field of electricity betweenancient Greece and the Early Modern Times that is times after the development of printing —Gutenberg’s moveable type printing machine — in 1452 and the increasing dispersion ofknowledge in the Renaissance and especially later in the Enlightenment. Those were the Dark(Early) (AD 476–1000) and Middle Ages (AD 1000–1300).

Electric Charge


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A charge can be p o s i t v e or n e g a t i v e, or z e r o. In nature thereoccurs only an integral multiple of a universal basic charge of proton —a positively charged particle that is the nucleus of the lightest chemicalelement, hydrogen.The term „charge” is a primitive notion and an independent quantity(variable) in physics. Its unit is coulomb [C].The charge of e l e c t r o n is conventionally n e g a t i v e, while thatof proton is p o s i t i v e. Both charges are the charged constituents ofordinary matter and the smallest known particles (portions) of charge innature. They are referred to as e l e m e n t a r y and are marked as e ie, where e 1.6021892 0.0000046×1019 C. They are exactly equal toeach other as to their absolute value and are the smallest undivided„amount” of electricity. Each atom has an equal number of electrons andprotons, and therefore is electrically neutral as a whole.

Electric Charge


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Balance of electric charges is one of the most fundamentallaws of nature.The electric charge can be neither c r e a t e d nor d e s t r o y e d.One can only transfer some number of elementary charges, for ex-ample, electrons, from one body to another body which causes thefirst body to be positively charged while the second body has anegative charge of the same absolute value. This process is strictlyrelated to: Charge quantization is the principle that the electric chargeof an object must equal an integral multiple of a universal basiccharge. Conservation of charge is a law which states that the totalcharge or the total algebraic sum of charges of an isolated system isconstant; no violation of this law has been discovered.

Electric Charge — Laws and Principles


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Isolated system is s u c h a system through which boundariesn o charges can pass

or

is a system which is s o i s o l a t e d that it c a n n o t exchangecharges with its surroundings and therefore the total charge insidethe system is p r e s e r v e d.

Therefore the charge is indestructible: never can be c r e a t e d ord e s t r o y e d. The charges then can transfer from one place toanother one, but never come from nowhere. We therefore say thatthe charge is p r e s e r v e d.



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Transfer of electrons from one body to the other causes the bodiesto be charged as a result of an e x c e s s or a d e f i c i e n c y ofcharges.

Such a process is called e l e c t r i f i c a t i o n or c h a r g i n gand is a physical proof of the law of charge conservation.



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Atomic Structure

N

N

nucleusorbit

orbital electron

Helium atom

N

electron

proton

neutron


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Atomic Structure

82 +125 N2-

8-

18-

32-

18-

4-

Lead atom

valence electrons


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Atom Ionization

N

N

0q

Unionized atom

0q

hN

N

Ionized atom – positive ion

1q

free electron


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Atom Ionization

N

N


1q


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Atom Ionization

N

N


1q


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Atom Ionization

N

N


1q


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Atom Ionization

N

N


1q


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Atom Ionization

N

N


1q


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Atom Ionization

N

N


1q


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Charge Properties There are negative charges as e l e c t r o n s or n e g a t i v ei o n s and positive charges as p o s i t i v e i o n s which alwaysare the integral multiples of the smallest charge, that is an electronor a proton.

Opposite charges a t t r a c t and like charges r e p e l.

Charges can be s t a t i c, i m m o b i l e and i n v a r i a b l eor they can be in m o t i o n, or can v a r y with time.


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Current

c o n d u c t o r s: class I — metals and coal; class II —electrolytes (water solutions of acids, salts and bases);

i n s u l a t o r s (dielectrics, or non-conductors) — gases,insulating liquids (water without additives, distilled water), insulat-ing oil, glass, porcelain, paper, cotton, silk, isinglass, plastics, etc.;

s e m i c o n d u c t o r s — germanium, silicon, oxides of dif-ferent metals and other bodies of complex structure.

E l e c t r i c c u r r e n t is connected with the motion or time-variations of electric charges; it is strictly related to the classifica-tion (division) of bodies which is as follows:


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Current conduction current in conductors — in a crystal lattice free

electrons are loosely bound with atomic nuclei (positive ions)located in the lattice points and can move about in the space of alattice between at very high velocities of about 105 m/s at roomtemperature and at almost as twice as great velocity at atemperature of 1000 K;

displacement current in insulators — there are few or no freeelectrons at all and hence the insulator (dielectric) ability tocarry electric current is minimal or it does not conduct thecurrent; electrons are strongly bound with the atomic nuclei andcan move only within a given atom. In an ideal (perfect)dielectric charges can move in its interior without disturbing itsstructure, and the so-called dielectric polarization occurs.


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Current

E 0

E 0

non-polarized insulator (dielectric) polarized insulator (dielectric)


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International System of Units SISI base units

length l, s metre mmass m kilogram kgtime t, second scurrent I, i amper Athermodynamic temperature T kelvin K, degluminous intensity j candela cd

Derived unitsangle , , radian rad

solid angle , steradian sr


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Standard Prefixes for the SI Units of MeasureMultiples Subdivisions

Name Symbol Factor Name Symbol Factoryottazettaexapetateragigamegakilohectodeca

YZEPTGMkhda

1024

1021

1018

1015

1012

109

106

103

102

10

decicentimillimicronanopicofemtoattozeptoyocto

dcnnpfazy

101

102

103

106

109

1012

1015

1018

1021

1024


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Physical Quantities

]W[WW

]W[]W[]W[ 332211 WWWW


5 m/s; m 130 kg; I 2.5 A; U 230 V; W 360 J…

F 10 kG 9806650 dyne 98.1 N;

l 12 inch 30.48 cm 0.3048 m = 30.48 102 m…

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Selected Quantities in Electrical Engineeringelectric charge Q coulomb Cpotential, its difference V, , volt Vvoltage, SEM U, E volt Velectric field strength E volt per metre V/melectric displacement D coulomb per square metre C/m2permittivity farad per metre F/mcapacitance C farad Fresistance R ohm resistivity ohm metre ·mconductance G siemens Sconductivity siemens per metre S/mmagnetic flux density B tesla Tmagnetic flux weber Wbmagnetic field strength H ampere per metre A/m


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Selected Quantities in Electrical Engineeringmagnetic permeability henry per metre H/minductance L henry Hmagnetic resistance R turns per henry 1/Hfrequency f hertz Hzangular velocity radian per second rad/swork, energy A, W joule Jactive power P watt Wreactive power Q volt ampere reactive (var) varapparent power S volt ampere VAvelocity metre per second m/sacceleration a metre per second squared m/s2force F newton Ntorque, moment of force M newton metre N·mother … … …


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