lesson 01 - fundamentals of electric circuits

Script Writing Guide: e-Learning Content Development for the 『 Project for Strengthen the CLMV Capacity for the ASEAN-KOREA Cyber University』

Intro > Overview

Opening

Message

This is the first lesson of the first module “Electric circuit” which will equip you with an arsenal of tools necessary to analyze an electrical circuit, especially single-phase and three -phase AC circuits.

1. Electrical Network and its Topology

A : Voice and PPT Overview

B : Text-based Overview

C : Video and PPT Overview

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Lesson topics

1. Electrical Network and its Topology2. Electrical Quantities3. Circuit Elements4. Kirchhoff’s laws

Learning Goals

At the completion of this lesson, you will be able to:

1. Describe an electrical network with its topology and electrical quantities2. Analyze fundamental circuit elements: R, L, C, …3. Formulate equations of the two Kirchhoff ‘s laws


Keywords

Electric chargeDefinite quantity of electricity, either negative or positive

Electric currentFlow of electric charge

A : Voice and PPT Overview

B : Text-based Overview

C : Video and PPT Overview

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VoltageElectrical potential or potential difference expressed in volts

Electric circuit

Interconnection of electrical components (electrical network)consisting of a closed loop

Electrical resistance

Opposition to the passage of an electric current


Lesson > Topic 1 Electrical Network and its Topology

Objectives:

• Describe an electrical network topology

A : Instructor’s video lecture

B : Instructor’s video and PPT

C : Text-based lecture

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1.1 Electrical Network and Circuits

• Electrical network: interconnection of electrical elements




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Closed circuit Open circuit



1.2 Representation

• From conceptual to physical representation




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1.3 Network

• Branch: portion of a circuit with two terminals connected to it




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1.3 Network

• Node: junction of two or more branches




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1.3 Network

• Loop: any closed connection of branches




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1.3 Network

• Mesh: a loop that does not contain other loops




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Mesh 1 Mesh 2


Lesson > Topic 2 Electrical Quantities

Objectives:

• Review the concepts of main electrical quantities: current, voltage and power




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2.1 Current

Time rate of change of charge passing through a predetermined area

dt

dqi




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• 1 ampere = 1 coulomb/second

• Positive direction = Direction of positive charges

dt



2.2 Voltage

• Or potential difference

• Total work per unit charge for motion of charge between 2 points




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i

uAB

A B

coulomb 1

joule 1 volt1



2.3 Electric Power and Sign Convention

• Work done per unit time

Calculated at a branch or element

uiTime

Charge

Charge

Work

Time

Workp




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• Calculated at a branch or element

‒ If u, i chosen with the same direction:• p = ui > 0 receiving energy

• p = ui < 0 generating energy

‒ If u, i chosen with opposite direction:• p = ui > 0 generating energy

• p = ui < 0 receiving energy

i

uA B

i

uA B


Lesson > Topic 3 Circuit Elements

Objectives:

• Analyze fundamental circuit elements: R, L, C, …




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3.1 Sources

• Ideal Voltage Sources

‒ Constant voltage

‒ Current determined by circuit

u(t) = -e(t)

u(t)e




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• Ideal Current Sources

‒ Constant current

‒ Voltage determined by circuitj(t)






3.2 Resistance R

• Resistance to the flow ofelectricity

• Ohm’s law

• Ohms (Ω)

i

uR

R

RiuR

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• Ohms (Ω)

• Conductance (s=1/ Ω)

• Extract work from electric circuit

• Power and energy:

2R Riiup

t

0

t

0

2dtRipdtW

1/Rg



3.2 Resistance

• Resistor




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3.3 Inductance L

• Inductor

‒ Limiting current based on the rise and collapse of a magnetic field

• Ideal inductor




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• Ideal inductor

‒ Zero resistance

‒ Store energy in magnetic field



3.3 Inductance L

• Inductance L of the coil:

• When a time-varying current

wΦψwith i

w

iL

iuL

eL A : Instructor’s video lecture



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• When a time-varying current flowing through:

• Inductance unit: henrys (H), 1 H = 1 V*s/A

dt

diLeu LL

dt

diL

dt

deL



3.3 Inductance L

• Power and Energy Storage

‒ Power:

dt

diLiiup LL




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‒ Storage of energy in magnetic field:

t

0

2t

0LL Li

2

1LididtpW



3.4 Capacitance C

• Physical capacitor

‒ Store energy in the form of a charge separation




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3.4 Capacitance C

• Ideal capacitor

‒ Open circuit for DC current

‒ Charge separation proportional to voltage

• Capacitance C: iC

CCuq




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• Capacitance C:

‒ Unit: farad (F) = coulomb/volt, µF, pF

• Under varying voltage:

uC

CCuq

dt

duC)Cu(

dt

d

dt

dqi C

C )0(uidtC

1u C

t

0C



3.4 Capacitance C

• Power

dt

duCu

dt

duCuiup C

CC

CCC




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• Energy Storage

u

0

2CC

t

0

CE Cu2

1duCudtpW


Lesson > Topic 4 Kirchhoff’s laws

Objectives:

• Formulate equations for circuit analysis based on the two Kirchhoff’s laws: KCL and KVL




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4.1 Kirchhoff’s Current Law (KCL)

• Charge cannot be created but must be conserved

• Sum of currents at a node is zeroConvention:Currents entering a node are positive and vise versa


k n

kk 1

i 0

i i




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Currents entering a node are positive and vise versa

• KCL equations:

• Write the equation for node C, anything to comment?

0iii- :A Node 521

0iii :B Node 435

R4

e4

e1

R1

L1

R3C2

C3

i4i2

i1

i3

i5A B

C

a b c



4.2 Kirchhoff’s Voltage Law (KVL)

• No energy is lost or created in a circuit

• Net voltage around a closed circuit is zero1 2k n k n

k kk 1 k 1

u e

k n

kk 1

u 0




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• KVL for loop (a):

k 1 k 1

11 1 1 2 1

2

di 1-R i L i dt e

dt C

R4

e4

e1

R1

L1

R3C2

C3

i4i2

i1

i3

i5A B

C

a b c

R5


Practice > Exercise

• Write KVL equations for loop b and c with the direction indicated in the figure

‒ Put correct sign (+ or - ) into the blank

Loop b:

Matching

Fill in the blank

Drag and drop

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R4

e4

e1

R1

L1

R3C2

C3

i4i2

i1

i3

i5A B

C

a b c

R5

3 3 3 4 4 4

3

1i dt R i R i

C= e

Loop c:

5 5 3 32 2

2 3

1i dt R i R i i d =

1

C Ct 0

Loop b:


Outro > Discussion

At high school, did you use any laws similar to Kirchhoff’s laws? Find out some examples!




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Outro > Summary

No Topic Summary

1

Electrical Network and its Topology

You can clearly describe an electrical network now and make it easy to apply later-on analysis methods.

Electrical Quantities You can explain basic electrical quantities in an electrical circuit and ready

A : Text summary

B : Visual summarizer

C : Video and PPT

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2

Electrical Quantities You can explain basic electrical quantities in an electrical circuit and ready to use them in an analysis problem.

3

Circuit Elements From now on, you are able to analyze basic circuit elements and find the relationship between electrical quantities for an element.

4

Kirchhoff’s laws By applying the two laws of Kirchhoff, you can easily write equations relating electrical quantities and parameters elements.


Outro > Next Lesson Guide

Ending Message

We have learnt aboutElectric Circuits

Electrical Quantities

Circuit Elements

Kirchhoff’s laws




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Next Lesson Title AC Network

Next topic

• Sinusoidal Voltages and Currents

• RMS value

• Sinusoidal Signal Representation

• Fundamental AC Circuits

• AC Power

• Power Factor Correction

lesson 01 - fundamentals of electric circuits

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electrical circuit

electrical network topology

circuits electrical

instructors video lecture

electrical quantities2

electrical quantities3

textbased lecture

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