Introduction to Electrical...

Introduction to Electrical Engineering(Principles and Applications of Electrical Engineering)

Dong‐Weon Lee at MNTLSchool of Mechanical Systems Engineering

Chonnam National University

Abstraction: 추상

Chapter [email protected]

Principles and Applications of Electrical Engineering


Abstraction: 추상


We could do it the hard way!!!


Apply Maxell’s equation: 전기장과자기장과의관계를기술하는4개의 Equations

1. 체적내부에전하가있을때체적의표면을관통하는전기력선의합은체적내부의전하량과 같다

2. 닫힌체적의표면을관통하는자기력선의합은항상 0이다.

3. 변화하는전기력(electric)이발생하면항상그에수직하는자기력 (magnetic)이발생하고

4. 그역도성립한다




Instead there is an easy way!!!



The easy way!!!

Electrical engineering systems in the automobile



Basic in Electric Engineering


Voltage(電壓) vs Current(電流)

강원도무릉계곡..




차의풍량조절을위해손잡이를돌리면저항값이변화

전동기의전류가바뀌면서풍량이바뀜

이런저항회로를해석하기위하여 KCL, KVL 등의회로이론을도입

모터의저항은?

Car Heater Fan Speed‐Control Application: Control

12 V

? V

? V

폭포?




전기의응용

‐전기밥솥(electric rice cooker)‐전기프라이팬‐토우스터‐전기생선구이‐전기오븐‐전자레인지(??????? oven )‐전기포트‐믹서

Applications

‐식기세척기‐냉장고‐펌프‐환풍기‐에어컨‐세탁기‐청소기

Electric or Electrical

전자사전, 전자수첩, 전자계산기, 전자도서관 …… Microelectronics……




Units

단위계기본단위 : 길이 [meter : m] 질량 [kilogram : kg] 시간 [second : s]

온도 [kelvin : K] 전류 [ampere : A]보조단위 : 각도 [radian : rad]

기계적단위계면적 [m2] 체적 [m3] 속도 [m/s]가속도 [m/s2] 각속도 [rad/s] 각가속도[rad/s2]에너지(일) [Joule : J = N.m] 에너지밀도 [J/m3] Power [watt : W = J/s]힘 [newton : N = kg.m/s2] 압력,응력 [Pascal : Pa = N/m2] 모멘트 [N.m]점도 [Pa.s] 질량밀도 [kg/m3]

전기적단위계전하량 [coulomb : C = A.s] 커패시턴스 [farad : F = C/V]전압 [volt : V = W/A] 전기저항 [ohm : W = V/A]전기전도도 [siemens : S = A/V] 주파수 [hertz : Hz = 1/s]자속 [weber : Wb = V.s] 자속밀도 [tesla : T = Wb/m2]인덕턴스 [henry : H = Wb/A]


Standard Prefixes



Basic in Electrical Engineering


Electronics is the study of the flow of charge through various materials and devices suchas, semiconductors, resistors, inductors, capacitors, nano‐structures, and vacuum tubes. Allapplications of electronics involve the transmission of power and possibly information.Although considered to be a theoretical branch of physics, the design and construction ofelectronic circuits to solve practical problems is an essential technique in the fields ofelectronics engineering and computer engineering.

Electrical engineering = Electrical Eng. + Electronics



Hole과 Electron의차이는?

전기의근원은전자

원자와전자의크기는?

마찰로전기가일어나는이유는?

자유전자의이동은왜발생하는지?

전자의이동과전류의관계는?

전하란? 시간에따라변화하는가?



Prof. Dong‐Weon Lee

Basic in Electrical Engineering (Cont.)


전기전자공학개론

사용하는용어(Terminology), 각 element의역할에관하여이해

RLC의기본개념이해 & 반도체소자의이해신호의필터링 & 증폭

수학적인기법을이용

회로내의임의의위치에서의전류및전압을계산

Power sources건전지, 전압/전류기, 신호발생기등



Basic in Electrical Engineering (Cont.)


Charges: (약 2500년 Amber로부터처음발견)

Charge의중요특성

(1) positive (hole), negative (electron) 극성을가짐

(2) 전자전하의정수배: 1791년정전기에관한논문발표(‐1.6×10‐19C, 전하량을세는기준이되는전자의전하량)

(3) 전기적효과를발생

‐전하가분리되면전압이발생, 전하가흐르면전류발생.‐전하양은전자전하양의정수배로불연속하지만워낙작은양(‐1.6×10‐19 C) 이굉장히많으므로(예: 20。C 구리의경우전자밀도1023개/cm3) 연속적이라고판단




SemiconductorBasic in Electrical Engineering


MOS (Metal Oxide Semiconductor)



전류와전압 (Current and Voltage)

Current: 정의 :임의의단면을단위시간당전하의알짜흐름단위 : C/s = A (amperes)1 A는 1 초에 1 coulomb의전하가흐른다는의미

Voltage:정의 : 전하를분리시키는데드는단위전하당에너지단위 : J/C = V (volts)1 V는 1 Joule의에너지로 1 coulomb의전하를분리시켰다는의미




Example 2.1: 원통형도체의총전하량과흐르는전류는?

Total charge & current (C/s)?

2r = 210‐3mCharge density(n) = 1029carriers/m3

전하량(q) = 1.6910‐19CDrift velocity() = 19.910‐6m/s

2r

1 m

Vol (V)= 3.1410‐6m3

# of carriers (N) = Vn = 3.14 1023 carriersTotal charges = qN = (1.6910‐19C)(3.141023)=53103C단위길이당 Charge density(Q)는? 53103C/mCurrent(A) : Q = (53103)C/m(19.910‐6)m/s

I = ~1 A(C/s)




Power & Energy1W=1J/s




Ex) 기초개념: 1l의물을데우는데필요한전력은?

가정: 전열기의소비전력 500W, 물의온도는 20ºC, 끓는온도 100ºC(1 cm3의물을 1도올리는데필요한열량 1Cal)

A) 결국 1000 ml (100ºC‐20ºC) = 80,000[Cal]의열이필요

전력량 [Ws] = 열량 [Joule] Cal = 0.24 I2 R t

~ 333333 [Ws]의전력량필요

1초에 500 [Ws]이므로약 666초의시간이필요

; 1l의물을끓이기위해서는약 11분 6초의시간이필요

1 ml = 1 cm3

1 Cal = 4.18605 J1 W = 1 J/s

1500 ~ 2000 W




• Electrical Engineering & Electronics• Electrical Circuit : Energy or signal/information processor• Circuit element : 회로를구성하는전기적인소자–저항, 커패시터, 인덕터, OP‐AMP 등

• 전기공학에서는모든현상을회로로표현하며, 이런현상을수학적으로표현하는것을모델링이라정의

Review




Review: 표현방법Basic in Electrical Engineering (Cont.)

RMS값?



Energy source in Electrical Engineering


Mechanical engineering에서 source란?



Voltage & Current Source: Symbol


Super capacitorDC power supply다이오드 & capacitor 도같음




Voltage Source: Definition

도체의한끝에전자를공급하고, 다른한끝에서전자를제거하는장치(일종의전자펌프)


A voltage source is any device or system that produces an electromotive force between its terminals OR derives a secondary voltage from a primary source of the electromotive force. A primary voltage source can supply energy to a circuit while a secondary voltage source dissipates energy from a circuit. An example of a primary source is a common battery while an example of a secondary source is a voltage regulator.

운동에너지를갖는전자소멸




Different voltage sources(1) 마찰에너지

유리막대를모피나비단조각으로문지를때생기는정전기

(2) 자기에너지구리선을자기장에통과시키면구리선에전류가유도됨발전기의원리교류발전과직류발전교류(DC)와직류(AC)

(3) 화학에너지전지(電池, cell):구리와아연금속전극을전해질(염기, 산, 알칼리)에담그면, 전해질이구리전극으로부터전자를뺏어아연전극에보내어전류가생김배터리(battery):여러개의전지를조합하여필요한전원을만든것

(4) 빛에너지태양전지: 표면이빛에노출되면전자를내보내는감광재료를이용하여전지를제작, 일반적으로고가이나점차가격이내려감





(5) 열에너지서로다른금속선의양단을용접하고, 양단에온도차가생기게하면금속선에전류가생성(Seebeck effect)반대의경우: 금속선에전류를가하면, 양단에온도차가생김(Peltier effect)

(6) 변형에너지(압력)석영, 전기석등의결정을판형으로가공하고이판에인장력이나압축력을가하면판의양단에전압이발생(압전효과)반대의경우: 전압을가하면변형이생김, 교류를가하면진동이발생(crystal microphone, crystal pick‐up, oscillator 등에응용)


Different voltage sources (Cont.)Energy source in Electrical Engineering



회로소자: Independent Sources (전원)

뒤에서다시언급





회로소자: Dependent Sources (전원)


‐ Ideal dependent voltage and current sources회로의다른곳의전압또는전류(Vx, Ix)에의해서변화





증폭의의미?





회로이론의선형모델링Basic in Electrical Engineering




회로소자: 저항 어떻게 & 무슨재료로만드는지?

Details will be introduced on Chap. 4



소스의기울기(+/‐)에의존



회로소자: 저항Basic in Electrical Engineering (Cont.)




Example

The hot resistance of a light bulb is 120 ohm. Find the current through and the power absorbed by the bulb if it is connected across a constant 90 V source.



백열등과형광등의차이



저항율 (Resistivity)Basic in Electrical Engineering




직렬및병렬저항회로Basic in Electrical Engineering




분압회로Basic in Electrical Engineering




분류회로Basic in Electrical Engineering




이상적전원의 RepresentationBasic in Electrical Engineering


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