basics of electrical circuits ehb 211 e - ituweb.itu.edu.tr/ferhanoglu/edt1.pdf · 2014-09-07 ·...

BASICS OF ELECTRICAL CIRCUITS

EHB 211 E

Introduction

Asst. Prof. Onur Ferhanoğlu

1

BASICS OF ELECTRICAL CIRCUITS

Time: Monday: 09:30 – 12: 30

Place: Room 5301

Grading: Midterm 1 (20%)

Midterm 2 (20%)

HW1-4 (5% * 4 = 20 %)

Final (40%)

Web: http://web.itu.edu.tr/~ferhanoglu/teaching.htm

References:

• Leon O. Chua, Charles A. Desoer, Ernest S. Kuh, ”Linear and

Nonlinear Circuits,” McGraw-Hill, 1987.• Prof. Müştak E. Yalçın’s notes

• Norman Balabanian, “Electric Circuits,” McGraw-Hill, 1993.

• J.W. Nillson, S. Riedel, “Electric Circuits,” Prentice Hall, 2010.

Asst. Prof. Onur Ferhanoğlu Introduction / BASICS OF ELECTRICAL CIRCUITS 2

Lecture 1: Intro & KVL + KCL

Lecture 2: Graph theory

Lecture 3: Two-terminal resistors

Lecture 4: Simple resistive circuits

MIDTERM 1

Lecture 5: Techniques of circuit analysis

Lecture 6: Multiterminal resistors

Lecture 7: Operational amplifiers

Lecture 8: Superposition theorem

MIDTERM 2

Lecture 9: Thevenin & Norton circuits

Lecture 10: First order circuits

Lecture 11: Second order circuits

Lecture 12: State-Space Equations

FINAL

http://web.itu.edu.tr/~ferhanoglu/teaching.htm

Electrical Circuits


Goal is to predict the electrical behavior of circuits, for understanding and improving their design

Voltage & Current


Voltage: Created by separation of chargesis the energy per unit chargev = dw / dq

v: voltage (V)w: energy (J)q: charge (Q)

++--

Current: Created by motion of chargesis the rate of charge flowi = dq / dt

i: current (A)t: time (s)

Power: Energy per unit timep = dw / dt = (dw / dq) * (dq/ dt)p = v.i

Lumped vs. Distributed Circuit


Majority of circuits work with

AC voltages & currents

λ: wavelength

SPACE

wavelength

Lumped vs. Distributed Circuit


Lumped circuit: Dependent variables (voltage & current) are functions of time only: λ >> l

SPACE

wavelength

Distributed circuit: Dependent variables are functions of time and space:

Lumped circuit

λ = c / f

(c: 3*108 m/s)

Example 1: lumped

f = 50 Hz

λ = 6 km!

Much larger than any circuit

Example 2: distributed

f = 100 MHz

λ = 30 cm

Comparable in size

Circu

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Electro

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Physical circuit & Circuit model


Physical circuit is made up of electric

devices (generator, resistor, transistor,

battery, transformer, load etc..)

Circuit model consists of

interconnection of circuit elements

KIRCHHOFF`S LAWS: Reference Directions


• Direction of current flow & voltage polarity may vary with time

• Frame of reference: Assign arbitrary reference directions to current and voltage

Kirchhoff`s Voltage Law (KVL)


Datum / reference node (ground)

• n-node circuit

• n-1 node-datum voltages

(e1,e2,…,en)

• en = 0 V

• + / - : voltage reference

directions

• vk-j = ek – ej = vk-n - vj-n

1

2

3

v3-2 + v2-1 + v1-3 = 0

Example: Analogy

v1-3 = 5 v climb 5 stepsv2-1 = 3 v -> e2 = 8v climb 3 more stepsv3-2 should be -8 V, so that e3=0 get back to original location:

go back 8 steps (-8 steps)

The sum of all node-node voltages = 0

for a closed node sequence (starts and ends at the same node)

Kirchhoff`s Voltage Law (KVL)


v4-5 + v2-4 + v5-2 = 0

v1-2 + v2-3 + v3-4 + v4-5 + v5=1 = 0

Circuit having 2 & 3 terminal elements

Blue closed node sequence: 2-4-5

Red closed node sequence: 1-2-3-4-5

Kirchhoff`s Current Law (KCL)


For all Gaussian (closed) surfaces, sum of all currents leaving the surface = 0-> electric charge is conserved

Circuit with 2 terminal elements (capacitors, batteries, resistors)and a 3 terminal element (operational amplifier)

Gaussian surface

Surface 1:i1 + i2 = 0

Surface 2:-i1 + i12 = 0

Surface 3:i1 + i4 + i5 + i6 = 0

Surface 4:i3 + i11 + i8 + i9 – i6 – i5 – i4 = 0

Surface 5:i11 - i10 – i4 - i7 = 0

Surface 6:-i12 – i3 – i11 – i8 – i9 = 0

KVL


KVL & KCL


Power & energy


basics of electrical circuits ehb 211 e - ituweb.itu.edu.tr/ferhanoglu/edt1.pdf · 2014-09-07 ·...

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