INC 112 Basic Circuit Analysis

Lecturer

Assistant Prof. Dr. Poj Tangamchit

About the Instructor

Office: CB40603 (CB4 6th floor)Control System and Instrumentation Eng. (INC)

Tel: x-9094

E-mail: poj.tan@kmutt.ac.th

Research Interest: Robotics, Artificial Intelligence (AI)

Lecture: Self-lecture. Reading material before coming to class is encouraged.

Freshmen’s Requirements

• Computer INC160

• Software INC151

• Circuit INC112

Course Details

• 3 Credits

• Class time 3 hours / week

• Review + Homework 6 hours/week

• E-learning material (DVD) is provided

Scoring & Grading

Midterm Exam 35%Final Exam 35%Homework, assignment 20%Quiz (Pop quiz) 10%

Grading follows the faculty of Engineering’sstandard procedure.

Homework & Quiz

Homework takes time.Allocate 6-12 hours each week for it.

Students need self-study outside class time.

Assignment

Course Webpage

http://www.inc.eng.kmutt.ac.th/inc112

• Lecture Slides• Homework• Homework/ Quiz Solutions• Announcements

Textbook

Engineering Circuit Analysis,7th edition McGrawHillWilliam H. Hayt Jr.,Jack E. Kemmerly,Steven M. Durbin

How to read a Textbook

Book Overview• Read Index• Think about what should be in each chapter• Think about what each chapter relate to each other

Chapter Focus• Read the title of each section, Guess what it will say• Look at pictures and description• Read equations and Math parts• Reread the section that you want to know more

Electricity

Electricity is a result from the flow of electrons.

= electron

electricity

Note: Electricity flows in the opposite directionof electron flow.

Electric Current vs. Electron Current

+ +- -= Atom Structure

+ +- -+ +- -

+ +- -+ +

--

+ +electricity

MetaphorElectricity is similar to water flow.

Water flows from high levelto low level.

Electricity flows fromhigh voltage to low voltage.

HighVoltage

LowVoltage

Measurement of ElectricitySince we use electricity to do work for us, howCan we measure its energy?

How can we measure the water power?Think about a water gun.

• strong (fast, high kinetic energy)• amount of water

• Voltage• Current

HighVoltage

LowVoltage

Imagine the water power at the outlet

Electric Potential (ศกยไฟฟา) Which water drop has more impact force at the ground?

Potential Energy (Height)

transform

Kinetic Energy (Velocity)

Electric potential can be compared with the height of the water drop from the reference ground

Ground: Reference PointNormally, we measure height compared to the sea level.

Also, electric potential at a point can be measured compared to the electric potential at the ground.

Unit: Volt (V)

Electric potential,or voltage has a unit “volt”.

Ground always has 0 volts.

Voltage (ความตางศกย)Voltage is a difference of electric potential between 2 points

Unit: Volt

Compare to the height of 2 water drops

Electric Current (กระแส)

Low current High current

Electric Current Unit

Unit: Ampere, Amp (A)

Note: Both current and voltage have directions

What is Circuit Analysis about?

To calculate voltage or current at some points

and some time in electric circuits

Course Overview

Constant voltage

Constant current

Mid

termRules:Ohm’s lawKirchoff’s law

Techniques:Mesh AnalysisNode AnalysisSuperpositionThevenin/ Norton

Circuits

Time

Voltage

Current

Voltage

Current

DC (Direct current) AC (Alternating current)

Frequency

Transient Response

Phasor Concept

Topics

Week 1: Introduction to Electricity, Simple DC circuits, Ohm’s lawWeek 2: Kirchoff’s voltage law, Kirchoff’s current lawWeek 3: Nodal AnalysisWeek 4: Mesh AnalysisWeek 5: Thevenin’s theoremWeek 6: Norton’s theorem, Maximum power transfer theoremWeek 7: Introduction to AC circuits and components

Week 8: Midterm ExamWeek 9: Transient response of RL circuitsWeek 10: Transient response of RC circuitsWeek 11: Transient response of RLC circuitsWeek 12: Phasor conceptWeek 13: Phasor circuit analysisWeek 14: AC Power, Frequency response

Week 15: Final Exam

Components

• Electric sources• Independent Sources – voltage, current• Dependent Sources – voltage, current

• Resistors• Measurement Devices

• Ammeters: measure current• Voltmeters: measure voltage

• Ground – reference point• Electric Wire

1V 1A1Ω

IndependentVoltageSource

IndependentCurrentSource

Resistor Ground

Symbol

Electric wire

General Rules

• All points on a same electric wire have the same voltage.

• A voltage source always have voltage difference of its pins equal to its value.

• A current source always have current pass through it equal to its value.

• Ground always has zero voltage. (0 volts)

Electric Flow Rule• Electric current flows from high voltage to low voltage when there is a path.

• Electric current can freely pass through electric wire.

• Electric current can flow through a resistor with the amount according to Ohm’s law.

• Electric current can flow through a voltage source with the amount depended on other components in the circuit.

• Electric current can flow pass a current source according to its value.

Three Measurementsof Electricity

Voltage Volt (V)

Current Ampere (A)

Resistance Ohm (Ω)

Prefix

Giga (G) 109

Mega (M) 106

Kilo (K) 103

Centi (c) 10-2

Milli (m) 10-3

Micro (μ) 10-6

Nano (n) 10-9

Pico (p) 10-12

Simple DC Circuit

1V 1Ω

Current

Metaphor

1V 1Ω

Current

Increasing V is compared to ?Increasing R is compared to ?

Ohm’s Law

V = IR

Voltage (Volts) = current (Amperes) x resistance (Ohms)

2A

x voltsx+4 volts2Ω

for using with a resistor only

Note: Electric wire has a resistance of 0 ohms

Electric Current

1V 1Ω

1A

1A

1A

Every point in the circuit has current = 1A

Electric Voltage

1V 1Ω

x + 1 Volts

x Volts

Ground

Ground = reference point always have voltage = 0 volts

1V 1Ω

1 Volts

0 Volts

1V 1Ω

Electric Voltage (2)

1 Volts

0 Volts

0 Volts

1V 1Ω

Electric Voltage (3)

1 Volts

0 Volts

1 Volts

1 Volts

Negative Voltage and Current

+

2 volts

-

-

-2 volts

+

Same as

Same as

1 A -1 A

PowerSymbol P has a unit of Watt

P = VI

+

V

-

I

Absorb power

-

V

+

I

Generate power

Passive Sign Convention

Absorb power: Power has a sign +

Generate power: Power has a sign -

Example

10V 4KΩ

2.5mA

DC source generates power = 10V * -2.5mA = - 25mW

Resistor absorbs power = 10V * 2.5mA = 25mW

Note: Resistors always absorb power but DC source caneither generate or absorb power

Direction of Voltage & Current on Resistors

+ -

Resistor always absorb power.Therefore, it always have current flow through it fromhigh voltage pin to low voltage pin.

- +or