L E C T U R E 1 : B A S I C C O N C E P T S

ELECTRIC CIRCUITS I (ELCT 301)

German University in Cairo

Faculty of Information Engineering and Technology (IET)

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COURSE INSTRUCTOR

• Instructor: Prof. Dr. Eng. Yasser G. Hegazy

• Vice President for Student Affairs

• Yasser.hegazy@guc.edu.eg

• Ph.D. (1996) Electrical and computer Engineering Department,

University of Waterloo, Waterloo, Ontario, Canada.

• 31 years of university level teaching experience.

• Vice president for student affairs and dean of the faculty of EMS.

IMPORTANCE OF THE COURSE

• Electric circuits represent the foundation of electrical engineering studies

and practices.

• All electrical systems can be modeled using the electric circuits

approach.

• Learning how to build and analyze electric circuits constitute a milestone

in building our engineering career.

• This course provide students with strong understanding of electric

circuits with emphasis on the problem-solving skills and practical

applications.

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COURSE CONTENTS

• Introduction to Electric Circuits. (one week)

• Basic Laws of Electric Circuits. (3 Weeks)

• Techniques for Solving Electric Circuits. (5 weeks)

• Energy Storing Elements (one week)

• Transient response of First Order Circuits. (2 weeks)

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STUDY PLAN

Week Topic Assignments/

Quizzes Remarks

I Introduction to Electric Circuits

II Circuits Elements and Ohm’s law Start of Tutorials and

Labs

III Kirchhoff's’ Laws

& Voltage and Current Division Rules

IV The Node-Voltage Method Assignment I & Quiz I

V The Mesh-Current Method

VI Superposition method/Source Transformation

VII Thevenin’s and Norton’s Circuits

VIII Midterm Exam – No Lectures

IX Maximum Power Transfer Theorem

X Inductors and Capacitors

XI First Order Transients

XII First Order Transients 5

STUDY RESOURCES

Text Book

• Charles K. Alexander and Matthew Sadiku, “Fundamentals of Electric

Circuits” Second Edition, McGrawHill, 2004.

Reference Book

• . W. Nilsson and S. A. Riedel, “Electric Circuits”, Eights Edition or

later. Upper Saddle River, NJ: Prentice Hall, 2011.

• Chapters 1 – 4 and 6,7. The rest will be covered in Circuits II”.

Webpage

http://eee.guc.edu.eg/ 6

SCHEDULE OF CLASSES

• Lectures: Same lecture repeated at these time slots:

- Mondays 3rd in H14 and Monday 4th in H13 (MECHATRONICS)

Taught by Prof. Tarek Abdelsalam

- Thursdays 1st and 2nd slots in H13. (IET/MET)

Taught by Prof. Yasser Hegazy

Tutorials : according to your schedule.

• Laboratories: according to your schedule.

(The Electric Circuits labs are located in C3 second 209 and lab # 309)

► Instructor office hours:

Every Sunday from 11:00 am to 1:00 p.m. in C7 office # 115

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TUTORIALS

• Every week the instructor will assign problems from the text book.

These problems will be posted on the course webpage

• In the tutorial, some of the assigned problems will be worked out on the

board.

• You will be asked to hand in 3 assignments. Assignments’ grade will be

based on the best 2.

• Three quizzes will be conducted to evaluate your performance and the

quiz mark will be based on the best 2.

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LABORATORIES

• Lab sessions are one slot/week.

• The lab manual is posted on the course webpage before your lab

session.

• It is necessary to go through the lab manual before attending each lab

session.

• The lab instructor will evaluate your performance during the lab and a

lab report has to be submitted to your lab instructor at the end of each

session.

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MARKING SCHEME

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Activity %

Quizzes (Best 2 of 3) 10

Tutorial Assignments 10

Laboratory Performance & Reports 15

Mid Term Examination 25

Final 40

Total 100

INSTRUCTOR RECOMMENDATIONS FOR A SUCCESSFUL SEMESTER

• Try to attend all lectures, laboratories and tutorials for your own

benefits and be on time.

• Make a good plan for your study and manage your time.

• Hand in the assignments, reports and quizzes on time, late reports will

be penalized.

• Try to solve all the end of chapters’ problems to gain better problem

solving skills.

• Update your instructor with any problem that might arise in the tutorial

or in the lab.

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LECTURE HALL RULES

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CHAPTER 1: BASIC CONCEPTS

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WHAT ARE ELECTRIC CIRCUITS?

• Electric circuits are models of electrical systems.

• Circuits are interconnection of electrical elements such as resistors,

inductors, capacitors, and switches.

• Electrical circuit is a network that has a closed loop, giving a return path

for the current.

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SERIES AND PARALLEL CIRCUITS

• Series circuit

• One path for the electric

current

• Failure of one bulb leads to

breaking the circuit

• Parallel circuit

• Many paths for the electric

• Independent light bulbs and

the circuit is not affected by the

failure of one bulb.

WHAT ARE THE MAIN CIRCUIT ELEMENTS?

• There are active elements & passive elements

• Active elements can generate energy

• Voltage and current sources

• Batteries

• Passive elements cannot generate energy

• Resistors

• Capacitors and Inductors (but CAN store energy)

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+

– V I

R capacitor

WHAT ARE THE MAIN CIRCUIT VARIABLES?

• Basic variables are, current (I) , voltage (V) and power (P)

• Current: time rate of change of electric charge I = dq/dt A

1 Amp = 1 Coulomb/sec

• Voltage: electromotive force or potential,

V =dW/dq 1 Volt = 1 Joule/Coulomb = 1 N·m/coulomb

• Power:

1 Watt = 1 Volt·Amp = 1 Joule/sec

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P = dW/dt = I V

Voltage is the difference in energy level of a unit charge located

at each of two points in a circuit, and therefore, represents the

energy required to move the unit charge from one point to the

other.

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Circuit Element(s)

+ – V(t)

Voltage Drop

Voltage Rise

VOLTAGE, V

CURRENT, I

• Current is the flow of charge from a voltage

source

• 1 Ampere (“Amp”) = Flow of 1 Coulomb/sec

• The sign of the current indicates the direction

of flow.

Types of current:

• direct current (dc): batteries and some

special generators

• alternating current (ac): household current

which varies with time +++

+ v

i A

B

PASSIVE SIGN CONVENTION

• When current enters the positive voltage terminal, the element is absorbing

power (positive power).

• When current leaves the positive voltage terminal, the element is supplying

power (negative power).

• Positive (+) Power: element absorbs power

• Negative (-) Power: element supplies power

• In general: (Positive Power) + (Negative Power) = 0 20

Circuit Element

+ –

I

V

P = I V

+ _

+

V

i

EXAMPLE

• Calculate the power delivered or absorbed by each element in the shown

circuit. Show that the sum of the delivered power = sum of the absorbed

power.

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SOLUTION

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Good Luck

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