INC 111 Basic Circuit Analysis
Lecturer
Associate 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.
Course Details
• 3 Credits
• Class time
3 hours / week
• Review + Homework 6 hours/week
• E-learning material (DVD) is provided
Scoring & Grading
Midterm Exam
40%
Final Exam
40%
Assignments
Homework & Quiz (Pop quiz)
20%
Grading follows the faculty of Engineering’s
standard procedure.
Homework & Quiz &
Assignment
Homework takes time.
Allocate 6-12 hours each week for it.
Students need self-study outside class time.
Assignments
3 Assignments
Hand-on circuit design is involved.
Course Webpage
http://www.inc.eng.kmutt.ac.th/inc111
• Lecture Slides
• Homework
• Homework/ Quiz Solutions
• Announcements
Textbook
Engineering Circuit Analysis,
8th edition McGrawHill
William H. Hayt Jr.,
Jack E. Kemmerly,
Steven M. Durbin
5V 800mA
Many things operate using
Electricity. Why?
How to make the electricity?
Faraday’s Law
Practical Electricity Generator
Turbine
Coil Placement
3-phase system
L1
N
S
L2
L3
N
Electric Outlet
N
L1
GND
Alternating Current
AC
5V 800mA
Can this be used?
Why?
Need an AC – DC converter.
How does it look like?
No. 1
Input 120V AC 60Hz 0.1A
Output 24V DC 100mA
No
No. 2
Input 220V AC 50Hz
Output 5V DC 500mA
No
No. 3
Input 120~220V AC 50-60Hz
Output 5V DC 2A
Yes
Electricity
Electricity is a result from the flow of electrons.
electricity
Note: Electricity flows in the opposite direction
of electron flow.
= electron
Electric Current vs. Electron Current
- ++ -
= Atom Structure
- ++ -
- ++ -
- ++ - electricity
++
++
We cannot see electric current.
We need a metaphor.
Which thing has similar property with electricity??
Water
Metaphor
Electricity is similar to water flow.
Water flows from high level
to low level.
Electricity flows from
high voltage to low voltage.
High
Voltage
Low
Voltage
Measurement of Electricity
Since we use electricity to do work for us, how
Can we measure its energy?
How can we measure the water power?
Think about a water gun.
High
Voltage
• strong (fast, high kinetic energy)
• amount of water
Low
Voltage
• Voltage
• Current
Imagine the water power at the outlet
Electric Potential (ศักย์ไฟฟ้า)
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 Point
Normally, 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 (ความต่างศักย์)
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
DC (Direct current)
AC (Alternating current)
Circuits
Constant voltage
Midterm
Constant current
Rules:
Techniques:
Ohm’s law
Kirchoff’s law
Mesh Analysis
Node Analysis
Superposition
Thevenin/ Norton
Voltage
Voltage
Current
Current
Time
Frequency
Phasor
Concept
Transient Response
Topics
Week 1: Introduction to Electricity, Simple DC circuits, Ohm’s law
Week 2: Kirchoff’s voltage law, Kirchoff’s current law
Week 3: Nodal Analysis
Week 4: Mesh Analysis
Week 5: Thevenin’s theorem
Week 6: Norton’s theorem, Maximum power transfer theorem
Week 7: Introduction to AC circuits and components
Week 8: Midterm Exam
Week 9: Transient response of RL circuits
Week 10: Transient response of RC circuits
Week 11: Transient response of RLC circuits
Week 12: Phasor concept
Week 13: Phasor circuit analysis
Week 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
Symbol
Independent
Voltage
Source
Independent
Current
Source
Resistor
1Ω
1V
1A
Electric wire
Ground
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 Measurements
of Electricity
Voltage
Volt (V)
Current
Ampere (A)
Resistance
Ohm (Ω)
Prefix
Giga (G) 109
Mega (M) 106
Kilo (K)
103
Centi (c)
Milli (m)
Micro (μ)
Nano (n)
Pico (p)
10-2
10-3
10-6
10-9
10-12
Simple DC Circuit
Current
1V
1Ω
Metaphor
Current
1V
1Ω
Increasing V is compared to ?
Increasing R is compared to ?
Ohm’s Law
V = IR
for using with a resistor only
Voltage (Volts) =
current (Amperes) x resistance (Ohms)
2A
2Ω
x+4 volts
x volts
Note: Electric wire has a resistance of 0 ohms
Electric Current
1A
1V
1Ω
1A
1A
Every point in the circuit has current = 1A
Electric Voltage
x + 1 Volts
1V
1Ω
x Volts
Ground
Ground = reference point always have voltage = 0 volts
1 Volts
1V
1Ω
0 Volts
Electric Voltage (2)
1 Volts
0 Volts
1V
1Ω
0 Volts
Electric Voltage (3)
1 Volts
1 Volts
1V
1Ω
0 Volts
1 Volts
Negative Voltage and Current
+
2 volts
Same as
-2 volts
-
+
1A
-1 A
Same as
Power
Symbol P
has a unit of Watt
P = VI
+
I
V
Absorb power
V
+
I
Generate power
Passive Sign Convention
Absorb power: Power has a sign +
Generate power: Power has a sign -
Example
2.5mA
10V
4KΩ
DC source generates power = 10V * -2.5mA = - 25mW
Resistor absorbs power = 10V * 2.5mA = 25mW
Note: Resistors always absorb power but DC source can
either generate or absorb power
Direction of Voltage & Current on
Resistors
or
+
-
-
+
Resistor always absorb power.
Therefore, it always have current flow through it from
high voltage pin to low voltage pin.