Top Banner
DET1013 - ELECTRICAL TECHNOLOGY Chapter 1: Introduction to Electric Circuit AUTHORS: AMINAH BINTI OTHMAN JA’AFAR BIN SURADI JUNAIDA BINTI SHAARI ZULKURNAIN BIN ABDUL HAMID
118

Electrical Technology Topic 1 Sem 1 Politeknik

Jan 26, 2016

Download

Documents

injung

nota et.
Welcome message from author
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
Page 1: Electrical Technology Topic 1 Sem 1 Politeknik

DET1013 - ELECTRICAL TECHNOLOGY

Chapter 1:

Introduction to Electric Circuit

AUTHORS:AMINAH BINTI OTHMANJA’AFAR BIN SURADIJUNAIDA BINTI SHAARIZULKURNAIN BIN ABDUL HAMID

Page 2: Electrical Technology Topic 1 Sem 1 Politeknik

COURSE LEARNING OUTCOME

1. Apply the concept and principles of DC electrical circuit using different method and approach. (C3, PLO1)

2. Solve DC circuit problems using appropriate DC electrical laws and theorems. (C3, PLO2)

3. Conduct the laboratory activities of DC electrical circuit using appropriate electrical equipment. (P4, PLO5)

4. Demonstrate ability to work in team to complete assigned task during practical work sessions. (A3, PLO11)

Page 3: Electrical Technology Topic 1 Sem 1 Politeknik

TOPIC TITLE (RTA)CHAPTER TITLE RTA

1.0 INTRODUCTION TO ELECTRIC CIRCUIT

08:12

2.0 DC EQUIVALENT CIRCUIT AND NETWORK THEOREMS

08:10

3.0 CAPACITORS AND CAPACITANCE 05:004.0 INDUCTORS AND INDUCTANCE 05:045.0 MAGNETIC CIRCUIT,

ELECTROMAGNETISM AND ELECTROMAGNETIC INDUCTION

04:04

Page 4: Electrical Technology Topic 1 Sem 1 Politeknik

LEARNING OUTCOME (2 Hours)1.1 Know standard symbols for electrical components.

1.1.1 Identify common symbols in electrical circuit diagrams.

1.2 Understand the general features of cells and batteries.1.2.1 Describe the difference between cells and batteries.1.2.2 Show the effects of different cell connections:

a. seriesb. parallelc. series-parallel

1.2.3 Calculate the total voltage of series sourcesa. with the same polarities.b. with opposite polarities.

Page 5: Electrical Technology Topic 1 Sem 1 Politeknik

Standard Symbol for Electrical Components

G V A

conductor /wire switchground/earth

Cell (dc supply) Battery (dc supply) AC supply

resistor inductor capacitor

galvanometer voltmeter ammeter

Page 6: Electrical Technology Topic 1 Sem 1 Politeknik

Cell

• A single unit of a primary or secondary battery that converts chemical energy into electric energy.

Page 7: Electrical Technology Topic 1 Sem 1 Politeknik

Battery

• A battery is a series of two or more connected cells, which changes chemical energy into electrical energy.

Page 8: Electrical Technology Topic 1 Sem 1 Politeknik

Relationship of Cells & Batteries

• A Battery is a combination of cells• Cell combination could be in

SERIES, PARALLEL & SERIES-PARALLEL

• Practically, a cell is also notified as a battery.

Page 9: Electrical Technology Topic 1 Sem 1 Politeknik

Series Connection Cells

Page 10: Electrical Technology Topic 1 Sem 1 Politeknik

Series Connection Cells

Total e.m.f., ET = E1 + E2 + E3 + E4

= 2.0 + 2.0 + 2.0 + 2.0 = 8V

Example 1.1Calculate total e.m.f. of the circuit below

Page 11: Electrical Technology Topic 1 Sem 1 Politeknik

Parallel Connection Cells

Page 12: Electrical Technology Topic 1 Sem 1 Politeknik

Parallel Connection Cells

Total e.m.f., ET = E1 = E2 = E3 = 2.0V

Example 1.2Calculate total e.m.f. of the circuit below

Page 13: Electrical Technology Topic 1 Sem 1 Politeknik

Series-Parallel Connection Cells

Page 14: Electrical Technology Topic 1 Sem 1 Politeknik

Series-Parallel Connection Cells

Total e.m.f. for series cells, ESeries = E1 + E2 + E3 + E4

= 2.0 + 2.0 + 2.0 + 2.0 = 8V Total e.m.f., ET = ESeries = 8V

Example 1.3Calculate total e.m.f. of the circuit below

Page 15: Electrical Technology Topic 1 Sem 1 Politeknik

Series Connection with same Polarities

Total e.m.f., ET = E1 + E2

= 8 + 6 = 14V

Example 1.4Calculate total e.m.f. of the circuit below

Page 16: Electrical Technology Topic 1 Sem 1 Politeknik

Series Connection with opposite Polarities

Total e.m.f., ET = E1 + E2

= 8 - 6 = 2V

Example 1.5Calculate total e.m.f. of the circuit below

Page 17: Electrical Technology Topic 1 Sem 1 Politeknik

i) 5V 11V 4V

B AAnswer: 20V

44V

ii) 44V B A

44VAnswer: 44V

SELF-EXERCISEQUESTION: Calculate total e.m.f. of each cells connection as follow.

ANSWER

ANSWER

Page 18: Electrical Technology Topic 1 Sem 1 Politeknik

SELF-EXERCISEQUESTION: Calculate total e.m.f. of each cells connection as follow.

iii) 4V 3V

B 2V 5V AAnswer: 7V

6V 1V

iv) 4V 4V 4VB A

Answer: 120V30 cells

ANSWER

ANSWER

Page 19: Electrical Technology Topic 1 Sem 1 Politeknik

SELF-EXERCISEQUESTION: Calculate total e.m.f. of each cells connection as follow.

v) 14V B A 20 cells 14V

Answer: 14V

14V

5V 5V 5V

vi) B 5V 5V 5V A

5V 5V 5V

Answer: 50V10 cells

ANSWER

ANSWER

Page 20: Electrical Technology Topic 1 Sem 1 Politeknik

LEARNING OUTCOME (1 Hour)1.3 Know electric current and quantity of electricity.

1.3.1 State the definition of electric current. 1.3.2 State the unit of charge. 1.3.3 Indicate charge or quantity of electricity Q from Q=It.

1.4 Know the main effects of electric current. 1.4.1 Identify the three main effects of electric current,

giving practical examples of each.

1.5 Understand resistance and resistivity 1.5.1 Explain that electrical resistance depends on four

factors. 1.5.2 Express that resistance R= ρI/A where ρ is the resistivity.

Page 21: Electrical Technology Topic 1 Sem 1 Politeknik

Electric current, I• Current: - motion of charge

- depends on the rate of flow of charge- electric fluid- unit of current is ampere (A)

• Equation: dq = changing of charge

I = dt = changing of timeI = current (ampere)

• For steady state condition: Q = charge (coulomb)I = , thus Q = It t = time (second)

Page 22: Electrical Technology Topic 1 Sem 1 Politeknik

Example 1.6If a current of 5 A flows for 2 minutes, find the charge transferred.

Electric current, I

Q = It = 5 x 2 x 60 = 600 C

Page 23: Electrical Technology Topic 1 Sem 1 Politeknik

Main Effect of Electric Circuit

1. Heat Effect - Example: soldering iron, water heater, fuse, bulb, cookers, electric fires, furnaces, kettles, iron

2. Magnetic Effect - Example: bells, relays, motors, generators, transformers, telephones, lifting magnets, car ignition

3. Chemical Effect - Example: cell and battery, electroplating

Page 24: Electrical Technology Topic 1 Sem 1 Politeknik

Resistance & resistivity

• Resistance – property of a component which restricts the flow of electric current.

• The value of resistance depends upon 4 factors:

1. Length, l2. Cross-sectional area, A3. resistivity, ρ4. temparature

Page 25: Electrical Technology Topic 1 Sem 1 Politeknik

Resistance & resistivity

• Equation:R = [Unit = Ω]

R = resistance [Ω] l = Length [m] A = Cross-sectional area [m2] ρ = resistivity [Ω.m]

• Resistivity is difference for different material

Page 26: Electrical Technology Topic 1 Sem 1 Politeknik

Example 1.7Calculate resistance of a 5m long conductor if it has cross sectional area and resistivity Ω.m

Resistance & resistivity

Resistance, R= =

= 1.5Ω

Page 27: Electrical Technology Topic 1 Sem 1 Politeknik

Resistor (R)

• A device that is manufactured to have specific resistance.

• Used to limit current flow and reduce voltage applied to other components.

• Basic unit is ohm (Ω)

Page 28: Electrical Technology Topic 1 Sem 1 Politeknik

Resistor (R)

• Different examples of resistors

Page 29: Electrical Technology Topic 1 Sem 1 Politeknik

SELF-EXERCISEi) In what time would a current of 1 A transfer a charge of 30 C?

Answer: 30sANSWER

ii) What would be the resistivity of 2m length conductor wire if the resistance value is 500Ω and the cross sectional area 0.5

Answer: 125µΩmANSWER

Page 30: Electrical Technology Topic 1 Sem 1 Politeknik

LEARNING OUTCOME (1 Hour)

1.6 Understand Ohm’s Law. 1.6.1 Explain Ohm’s Law. 1.6.2 Outline the procedure adopted when using Ohm’s Law

1.7 Apply Ohm’s Law in circuit. 1.7.1 Construct circuit to explain Ohm’s Law. 1.7.2 Use Ohm’s Law to find current, voltage and resistance in a circuit.

.

Page 31: Electrical Technology Topic 1 Sem 1 Politeknik

Ohm’s Law

• Ohm’s Law states that the current (I) through a conductor between two points is directly proportional to the potential difference or voltage (V) across the two points, and inversely proportional to the resistance (R) between them.

I =

Page 32: Electrical Technology Topic 1 Sem 1 Politeknik

Ohm’s Law Triangle

V = IR

I =

R =

V

RI

Page 33: Electrical Technology Topic 1 Sem 1 Politeknik

Simple Circuit

E = E.M.F. (Electromotive force)

- Generates from voltage source

- Example: cells / batteries

I =

Current =

From Ohm’s Law:

Page 34: Electrical Technology Topic 1 Sem 1 Politeknik

Simple Circuit

V drop = Voltage drop--------------------------- - appears when current, I flows through resistor,R.- Inverse polarity from E

V drop = IR

From Ohm’s Law:

Voltage = Current x Resistance

Page 35: Electrical Technology Topic 1 Sem 1 Politeknik

Simple Circuit

• A battery possess e.m.f. that produces DC current.

• A complete circuit should consist of at least 1 electricity source (battery) and 1 load (resistor)

Source Load

E R

+

-• Current will only produce when the

source (battery) is connected to the load (resistor) in close loop connection.

I

Page 36: Electrical Technology Topic 1 Sem 1 Politeknik

Simple Circuit

• A battery possess e.m.f. that produces DC current.

• A complete circuit should consist of at least 1 electricity source (battery) and 1 load (resistor)

Source Load

E R

+

- • Current will only produce when the source (battery) is connected to the load (resistor) in close loop connection.

I

• When current flows across resistor, R, voltage drop, Vd will be produced across R

+

-

Vd

Page 37: Electrical Technology Topic 1 Sem 1 Politeknik

Simple Circuit

• A battery possess e.m.f. that produces DC current.

• A complete circuit should consist of at least 1 electricity source (battery) and 1 load (resistor)

Source Load

E R

+

- • Current will only produce when the source (battery) is connected to the load (resistor) in close loop connection.

I

• When current flows across resistor, R, voltage drop, Vd will be produced across R

+

-

Vd

Page 38: Electrical Technology Topic 1 Sem 1 Politeknik

Simple Circuit (Example)

15V 10Ω

+

-

I

+

-

Vdrop

Example 1.8QUESTION: By referring to the circuit below, calculate:i) Current, Iii) Voltage drop across resistor 10Ω, Vdrop

Page 39: Electrical Technology Topic 1 Sem 1 Politeknik

Simple Circuit (Example)

15V 10Ω

+

-

I

+

-

Vdrop

i) Current, I = = = 1.5A

ii) Voltage drop, = IR = 1.5 x 10 = 15V

Page 40: Electrical Technology Topic 1 Sem 1 Politeknik

SELF-EXERCISEA 100 V battery is connected across a resistor and causes a current of 5 mA to flow. Determine the resistance of the resistor. If the voltage is now reduced to 25 V, what will be the new value of the current flowing?

R = 20kΩ

I = 1.25mA

ANSWER

ANSWER

Page 41: Electrical Technology Topic 1 Sem 1 Politeknik

LEARNING OUTCOME (2 Hours)1.8 Understand series, parallel and series-parallel connections.

1.8.1 Identify a series circuit.1.8.2 Explain the flow of current and voltage division in the series circuit.1.8.3 Identify a parallel circuit.1.8.4 Explain the voltage drop and the current division in the parallel circuit.1.8.5 Explain the equivalent resistance in series and parallel

circuits.1.8.6 Identify a combination of series and parallel circuit.1.8.7 Explain the total resistance for the combination of series and parallel circuit.

Page 42: Electrical Technology Topic 1 Sem 1 Politeknik

LEARNING OUTCOME (2 Hours)1.9 Apply series, parallel and series-parallel connections to dc circuit.

1.9.1 Construct a series connection circuit1.9.2 Calculate the flow of current and voltage division in the series circuit.1.9.3 Construct a parallel circuit.1.9.4 Calculate the voltage drop and the current division in the parallel circuit.1.9.5 Construct a series-parallel connection circuit.1.9.6 Calculate the equivalent resistance in series and parallel circuits.1.9.7 Calculate the total resistance for the combination of series and parallel circuit.1.9.8 Use of voltage divider in series circuit and use of current divider in parallel circuit.1.9.9 Solve problems related to series, parallel and combination of series and parallel circuits.

Page 43: Electrical Technology Topic 1 Sem 1 Politeknik

Series Circuit

• Is formed when any number of devices are connected end-to-end so that there is only one path for current to flow.

Page 44: Electrical Technology Topic 1 Sem 1 Politeknik

Series Circuit Characteristics

Page 45: Electrical Technology Topic 1 Sem 1 Politeknik

Series Circuit Characteristics

1. Resistances are additive RT = R1 + R2 + R3

2. The current flows throughout the circuit is same.I = IR1 = IR2 = IR3

3. Different resistors have their individual voltage drop

VR1 ≠ VR2 ≠ VR3

4. Total e.m.f equals to the sum of voltage drops across each resistorE = VR1 + VR2 + VR3

Page 46: Electrical Technology Topic 1 Sem 1 Politeknik

Equivalent resistance in series

RT = R1 + R2 + R3Equ. 1

• Applicable to any means of resistors.• Standard equation of series connection

resistors.

Page 47: Electrical Technology Topic 1 Sem 1 Politeknik

Equivalent resistance in series (resistors with same value)

r = resistance valuen = amount of resistors

Equ. 2 RT = r x n

• Applicable for any means of resistors with same value.

Page 48: Electrical Technology Topic 1 Sem 1 Politeknik

Voltage Divider Rule

VR1 = x E

Page 49: Electrical Technology Topic 1 Sem 1 Politeknik

Series Circuit (Example)

15V

4Ω 6Ω

Example 1.9By referring to the circuit above, calculate:i) Total resistance of the circuit, ii) Current, Iiii) Voltage drop across resistor 6Ω,

Page 50: Electrical Technology Topic 1 Sem 1 Politeknik

Series Circuit (Example)

15V

4Ω 6Ω

i) Rtotal = 4 + 6 + 8 = 18Ω

ii) I = = = 0.833A

iii) VR2 = IR2 = 0.833 x 6 = 5V or

VR2 = x E = x 15 = 5V

use VDR

Page 51: Electrical Technology Topic 1 Sem 1 Politeknik

Parallel Circuit

• Is formed when two or more devices are arranged in a circuit side by side so that current can flow through more than one path

Page 52: Electrical Technology Topic 1 Sem 1 Politeknik

Parallel Circuit Characteristic

Page 53: Electrical Technology Topic 1 Sem 1 Politeknik

Parallel Circuit Characteristic1. Total resistance can be determined from:

RT =

2. Different resistors have their individual current.IR1 ≠ IR2 ≠ IR3

3. Same voltage acts across all parts of the circuit E = VR1 = VR2 = VR3

4. Supplied current equals to the sum of different current flows through each resistor.

I = IR1 + IR2 + IR3

Page 54: Electrical Technology Topic 1 Sem 1 Politeknik

Equivalent resistance in parallel

RT = Equ. 1

• Applicable to any means of resistors.• Standard equation of parallel connection

resistors.

Page 55: Electrical Technology Topic 1 Sem 1 Politeknik

Equivalent resistance in parallel (2 resistors case)

RT = Equ. 2

• Applicable for 2 resistors connection only.

Page 56: Electrical Technology Topic 1 Sem 1 Politeknik

Equivalent resistance in parallel (same value case)

RT = r = resistance valuen = amount of resistors

Equ. 3

• Applicable for any means of resistors with same value.

Page 57: Electrical Technology Topic 1 Sem 1 Politeknik

Current Divider Rule (CDR)

IR1 = x IEqu. 1

• Applicable to any means of resistors.• Standard equation of current divider rule

Page 58: Electrical Technology Topic 1 Sem 1 Politeknik

Current Divider Rule (2 Resistors case)

IR1 = x IEqu. 2

• Applicable for 2 resistors connection only.

Page 59: Electrical Technology Topic 1 Sem 1 Politeknik

Parallel Circuit (Example)

Example 1.10QUESTION: By referring to the circuit above, calculate:i) Total resistance of the circuit, ii) Current, Iiii) Voltage drop across resistor 8Ω, iv) Current through resistor 4Ω,

20V4Ω 8Ω

Page 60: Electrical Technology Topic 1 Sem 1 Politeknik

Parallel Circuit (Example)

20V6Ω4Ω 8Ω

i) Rtotal = = 1.846Ω

ii) I = = = 10.83A

iii) VR3 = E = 20V

iv) IR1 = = = 5A or

IR1 = x I = x 10.83 = 5A

CDR

Page 61: Electrical Technology Topic 1 Sem 1 Politeknik

Series-Parallel Circuit

For this diagram:• R1 is parallel with R2.• Ra is series with equivalent resistance of R1

and R2.

Page 62: Electrical Technology Topic 1 Sem 1 Politeknik

Total Resistance of Series-Parallel Circuit

• RT is the equivalent resistance of Ra, R1 and R2

referencepoint

• Start solving by calculating the total resistance of parts located farthest away from the reference point.

• Exception: if there are any series/parallel connection resistors at any part of circuit which is not farthest from the reference point, solve the total resistance of the series/parallel connection first. Then you can use the tips mentioned above to solve your problem.

Page 63: Electrical Technology Topic 1 Sem 1 Politeknik

Total Resistance of Series-Parallel Circuit (Example )

Example 1.11Calculate equivalent resistance, of the circuit below.

Page 64: Electrical Technology Topic 1 Sem 1 Politeknik

Total Resistance of Series-Parallel Circuit (Example )

Rb =

Page 65: Electrical Technology Topic 1 Sem 1 Politeknik

RT = Ra + Rb

Total Resistance of Series-Parallel Circuit (Example)

Page 66: Electrical Technology Topic 1 Sem 1 Politeknik

A

BRT

10Ω 10Ω 5Ω

6Ω3Ω

Example 1.12Calculate the total resistance, RT of the circuit below.

Total Resistance of Series-Parallel Circuit (Example )

Page 67: Electrical Technology Topic 1 Sem 1 Politeknik

A

BRT

10Ω 10Ω 5Ω

6Ω3Ω

Step 1: Identify any series/parallel connection (in between) and calculate the total resistance.

Ra

Ra = 4 + 8 = 12Ω

Total Resistance of Series-Parallel Circuit (Example )

Page 68: Electrical Technology Topic 1 Sem 1 Politeknik

A

BRT

10Ω 10Ω 5Ω

6Ω3Ω

Step 1: Identify any series connection (in between) and calculate the total resistance.

Ra

Ra = 4 + 8 = 12Ω

12Ω

Total Resistance of Series-Parallel Circuit (Example )

Page 69: Electrical Technology Topic 1 Sem 1 Politeknik

A

BRT

10Ω 10Ω 5Ω

6Ω3Ω

Step 2: Identify the farthest part from ref. point and calculate the total resistance.

Ra

Rb = 5 + 6 = 11Ω

12Ω

Rb

Total Resistance of Series-Parallel Circuit (Example )

Page 70: Electrical Technology Topic 1 Sem 1 Politeknik

A

BRT

10Ω 10Ω 5Ω

6Ω3Ω

Step 2: Identify the farthest part from ref. point and calculate the total resistance.

Ra

Rb = 5 + 6 = 11Ω

12Ω Rb 11Ω

Total Resistance of Series-Parallel Circuit (Example )

Page 71: Electrical Technology Topic 1 Sem 1 Politeknik

A

BRT

10Ω 10Ω

Step 3: calculate the total resistance of next portion until reach ref. point.

Ra

Rc = = 2.36Ω

12Ω Rb 11Ω

Rc

Total Resistance of Series-Parallel Circuit (Example )

Page 72: Electrical Technology Topic 1 Sem 1 Politeknik

A

BRT

10Ω 10Ω

Step 3: calculate the total resistance of next portion until reach ref. point.

Ra

Rc = = 2.36Ω

12Ω Rb 11ΩRc

2.36Ω

Total Resistance of Series-Parallel Circuit (Example )

Page 73: Electrical Technology Topic 1 Sem 1 Politeknik

A

BRT

10Ω 10Ω

Step 3: calculate the total resistance of next portion until reach ref. point.

Ra

Rd = 10 + 2.36= 12.36Ω

12ΩRc

2.36Ω

Rd

Total Resistance of Series-Parallel Circuit (Example )

Page 74: Electrical Technology Topic 1 Sem 1 Politeknik

A

BRT

10Ω 10Ω

Step 3: calculate the total resistance of next portion until reach ref. point.

Ra

Rd = 10 + 2.36= 12.36Ω

12ΩRc

2.36ΩRd

12.36Ω

Total Resistance of Series-Parallel Circuit (Example )

Page 75: Electrical Technology Topic 1 Sem 1 Politeknik

A

BRT

10Ω

Step 3: calculate the total resistance of next portion until reach ref. point.

Ra

Re = = 6.09Ω

12ΩRd

12.36Ω

Re

Total Resistance of Series-Parallel Circuit (Example )

Page 76: Electrical Technology Topic 1 Sem 1 Politeknik

A

BRT

10Ω

Step 3: calculate the total resistance of next portion until reach ref. point.

Ra

Re = = 6.09Ω

12ΩRd

12.36Ω

Re6.09Ω

Total Resistance of Series-Parallel Circuit (Example )

Page 77: Electrical Technology Topic 1 Sem 1 Politeknik

A

BRT

10Ω

Step 4: Finally, calculate the total resistance, RT of the circuit.

RT = 10 + 6.09 + 9 = 25.09Ω

Re 6.09Ω

Total Resistance of Series-Parallel Circuit (Example )

Page 78: Electrical Technology Topic 1 Sem 1 Politeknik

A B10kΩ 9kΩ3kΩ 3kΩ

6kΩ

6kΩ

Example 1.13Calculate the total resistance across point A - B

Total Resistance of Series-Parallel Circuit (Example )

Page 79: Electrical Technology Topic 1 Sem 1 Politeknik

A B10kΩ 9kΩ3kΩ 3kΩ

6kΩ

6kΩ

RT

Reference point

Ra

Ra = 3k + 3k = 6kΩ

Total Resistance of Series-Parallel Circuit (Example )

Page 80: Electrical Technology Topic 1 Sem 1 Politeknik

A B10kΩ 9kΩ3kΩ 3kΩ

6kΩ

6kΩ

RT

Reference point

Ra

Ra = 3k + 3k = 6kΩ

6kΩ

Total Resistance of Series-Parallel Circuit (Example )

Page 81: Electrical Technology Topic 1 Sem 1 Politeknik

A B10kΩ 9kΩ

6kΩ

6kΩ

RT

Reference point

Rb = = 2kΩ

6kΩ

Rb

Total Resistance of Series-Parallel Circuit (Example )

Page 82: Electrical Technology Topic 1 Sem 1 Politeknik

A B10kΩ 9kΩ

6kΩ

6kΩ

RT

Reference point

Rb = = 2kΩ

6kΩ

Rb

2kΩ

Total Resistance of Series-Parallel Circuit (Example )

Page 83: Electrical Technology Topic 1 Sem 1 Politeknik

A B10kΩ 9kΩ

RT

Reference point

RT = 10k + 2k + 9k = 21kΩ

2kΩ

Total Resistance of Series-Parallel Circuit (Example )

Page 84: Electrical Technology Topic 1 Sem 1 Politeknik

Series-Parallel Circuit (Example)

+- 20V

2kΩ 4kΩ

8kΩ

6kΩ

18kΩ

20kΩ

Is

Example 1.14QUESTION: By referring to the circuit above, calculate:i) Equivalent resistance of the circuit, Rtotalii) Current from supply, Is iii) Current through resistor 18kΩiv)Voltage drop across resistor 8kΩ,

Page 85: Electrical Technology Topic 1 Sem 1 Politeknik

Series-Parallel Circuit (Example)2kΩ 4kΩ

8kΩ

6kΩ

18kΩ

20kΩ

+-

20V

Isi) Rtotal Calculation

• Temporarily, remove voltage source from the circuit.

• The open nodes leaved by your voltage source would be your reference point

Rtotal Ra

Ra = 4k + 8k + 6k = 18kΩ

Page 86: Electrical Technology Topic 1 Sem 1 Politeknik

Series-Parallel Circuit (Example)2kΩ 4kΩ

8kΩ

6kΩ

18kΩ

20kΩ

i) Rtotal Calculation

• Temporarily, remove voltage source from the circuit.

• The open nodes leaved by your voltage source would be your reference point

Rtotal

Ra

Ra = 4k + 8k + 6k = 18kΩ

18kΩ

Page 87: Electrical Technology Topic 1 Sem 1 Politeknik

Series-Parallel Circuit (Example)2kΩ

18kΩ18kΩ

20kΩ

i) Rtotal Calculation

• Temporarily, remove voltage source from the circuit.

• The open nodes leaved by your voltage source would be your reference point

Rtotal

Ra

Rb = = 9kΩ

Rb

Page 88: Electrical Technology Topic 1 Sem 1 Politeknik

Series-Parallel Circuit (Example)2kΩ

18kΩ18kΩ

20kΩ

i) Rtotal Calculation

• Temporarily, remove voltage source from the circuit.

• The open nodes leaved by your voltage source would be your reference point

Rtotal

Ra

Rb = = 9kΩ

Rb 9kΩ

Page 89: Electrical Technology Topic 1 Sem 1 Politeknik

Series-Parallel Circuit (Example)2kΩ

20kΩ

i) Rtotal Calculation

• Temporarily, remove voltage source from the circuit.

• The open nodes leaved by your voltage source would be your reference point

Rtotal

Rtotal = 2k + 9k + 20k= 31kΩ

Rb 9kΩ31kΩ

Page 90: Electrical Technology Topic 1 Sem 1 Politeknik

Series-Parallel Circuit (Example)ii) Is Calculation

• Place voltage source back to the circuit.

• Your current from source is calculated using Ohm’s Law

Rtotal

Is = = = 645.16 μA

31kΩ+-

20V

Is

Page 91: Electrical Technology Topic 1 Sem 1 Politeknik

Series-Parallel Circuit (Example)

+-

20V

2kΩ 4kΩ

8kΩ

6kΩ

18kΩ

20kΩ

645.16μA ii) I18 Calculation

• Use current divider rules (CDR) or any other relevant methods

I18

Page 92: Electrical Technology Topic 1 Sem 1 Politeknik

Series-Parallel Circuit (Example)

+-

20V

2kΩ 4kΩ

8kΩ

6kΩ

18kΩ

20kΩ

645.16μA ii) I18 Calculation

• Use current divider rules or any other methods relevantI18

18kΩRa

If Use CDR: I18 = x 645.16μ = 322.58 μA

Other method: I18 = = 322.58 μA

Page 93: Electrical Technology Topic 1 Sem 1 Politeknik

Series-Parallel Circuit (Example)

+-

20V

2kΩ 4kΩ

8kΩ

6kΩ

18kΩ

20kΩ

645.16μA ii) V8 Calculation

• Calculate the current flows through 8kΩ resistor first

• Use Ohm’s Law to calculate the Voltage drop

• Other method as Voltage Divider Rule (VDR) also could be used here if you understand well the technique

322.58μA 322.58μA

I8 = 645.16μ – 322.58μ= 322.58 μA

Page 94: Electrical Technology Topic 1 Sem 1 Politeknik

Series-Parallel Circuit (Example)

+-

20V

2kΩ 4kΩ

8kΩ

6kΩ

18kΩ

20kΩ

645.16μA ii) V8 Calculation

• Calculate the current flows through 8kΩ resistor first

• Use Ohm’s Law to calculate the Voltage drop

• Other method as Voltage Divider Rule (VDR) also could be used here if you understand well the technique

322.58μA 322.58μA

I8 = 645.16μ – 322.58μ= 322.58 μA

+

V8

-

V8 = IR = 322.58μ x 8k = 2.58V

Page 95: Electrical Technology Topic 1 Sem 1 Politeknik

SELF-EXERCISEFind the value of the total resistance, current from supply and voltage drop across resistor 90Ω in the diagram as below

= 24.5Ω

I = 2.041A

= 45.92V

ANSWER

ANSWER

50V

2Ω 4Ω

90Ω

22Ω

8Ω 8Ω

ANSWER

Page 96: Electrical Technology Topic 1 Sem 1 Politeknik

LEARNING OUTCOME1.10 Understand Delta–Star transformation. 1.10.1 Express formula required to transform from Delta to Star

and Star to Delta1.10.2 Illustrate circuits to show star and delta connections.1.10.3 Explain steps to solve problems involving Star-Delta transformation.

1.11 Apply the concept of Delta–Star transformation.1.11.1 Construct circuits to show star and delta connections.1.11.2 Solve problems involving Star-Delta transformation.

1.12 Understand electrical power and energy.1.12.1 Explain electrical power and energy.1.12.2 Express electrical power formula from Ohm’s Law and the unit.1.12.3 Calculate the electrical power and energy in a circuit.

Page 97: Electrical Technology Topic 1 Sem 1 Politeknik

Delta-Star Transformation

• Standard 3-phase circuits or networks take on two major forms with names that represent the way in which the resistances are connected, a Star connected network which has the symbol of the letter, Υ (wye) and a Delta connected network which has the symbol of a triangle, Δ (delta).

Page 98: Electrical Technology Topic 1 Sem 1 Politeknik

Delta-Star Transformation

R1 R3

R2

a

b

c

Ra

RcRb

Ra = Rb =

Rc =

Page 99: Electrical Technology Topic 1 Sem 1 Politeknik

Star-Delta Transformation

R1 R3

R2

a

b

c

Ra

RcRb

R1 =

R2 =

R3 =

Page 100: Electrical Technology Topic 1 Sem 1 Politeknik

Delta-Star (Example)

x y

12Ω

10Ω

Example 1.15Calculate the total resistance, Rxy of the circuit below.

Rxy

Page 101: Electrical Technology Topic 1 Sem 1 Politeknik

Delta-Star (Example)

x y

12Ω

10Ω

Ra

Rb

Rc

Ra = = 1.78Ω Rb = = 2.67Ω

Rc = = 1.33Ω

Convert --- Y

Page 102: Electrical Technology Topic 1 Sem 1 Politeknik

Delta-Star (Example)

x y

12Ω

10Ω

1.78Ω

2.67Ω

1.33Ω

Rd

Re

Rd = 1.33 + 12= 13.33 Ω

Re = 2.67 + 10= 12.67 Ω

Page 103: Electrical Technology Topic 1 Sem 1 Politeknik

Delta-Star (Example)

x y1.78Ω

10Ω

2.67Ω

12Ω1.33Ω

Rd

Re

Rd = 1.33 + 12= 13.33 Ω

Re = 2.67 + 10= 12.67 Ω

13.33Ω

12.67Ω

Page 104: Electrical Technology Topic 1 Sem 1 Politeknik

Delta-Star (Example)

x y1.78Ω

Rf = = 6.5Ω

13.33Ω

12.67Ω

Rf

Page 105: Electrical Technology Topic 1 Sem 1 Politeknik

Delta-Star (Example)

x y1.78Ω

Rf = = 6.5Ω

13.33Ω

12.67Ω

6.5Ω

Rxy = 1.78 + 6.5 = 8.28Ω

Page 106: Electrical Technology Topic 1 Sem 1 Politeknik

Electrical Power & Energy

• ELECTRICAL POWER is defined as the rate at which electrical energy is transferred by an electric circuit.

• The SI unit of power is Watt.• Equation:

Power, P = VI Equ. 1

V – voltage measured in Volts (V)

I – current measured in Ampere (A)

Page 107: Electrical Technology Topic 1 Sem 1 Politeknik

Electrical Power & Energy• From Ohm’s Law;

I = V/R and V = I*R

Hence Power, P = Equ.2

P = I2R Equ.3

Page 108: Electrical Technology Topic 1 Sem 1 Politeknik

Electrical Power & Energy

• ENERGY can be defined as capacity to do work

• The unit of energy is Joule• Equation :

Energy/Work Done, W = Pt

P – power measured in Watt (W)

t – time measured in seconds (s)

Page 109: Electrical Technology Topic 1 Sem 1 Politeknik

Electrical Power & Energy

20V

15Ω

25Ω

Example 1.16By referring to the circuit below, calculate:i) Power that’s supplied by the batteryii) Power that’s absorbed by 25Ω resistoriii) Energy supplied by the battery after 30siv) Energy absorbed by the 15Ω resistor after 2 hours

Page 110: Electrical Technology Topic 1 Sem 1 Politeknik

Electrical Power & Energy

20V

15Ω

25Ω

i) Power that’s supplied by the battery, PsRT

RT = 15 + 25 = 40ΩIT

IT = = = 0.5A

Use Equ. 1:

Power, Ps = V*I = 20 x 0.5 = 10W

Page 111: Electrical Technology Topic 1 Sem 1 Politeknik

Electrical Power & Energy

20V

15Ω

25Ω

ii) Power that’s absorbed by 25Ω resistor PL

0.5A

Use Equ. 3:

Power, PL = I2*R = 0.52 x 25 = 6.25W

Page 112: Electrical Technology Topic 1 Sem 1 Politeknik

Electrical Power & Energy

20V

15Ω

25Ω

iii) Energy supplied by the battery after 30s

0.5A

Energy, W = P*t = 10 x 30 = 300 J

Page 113: Electrical Technology Topic 1 Sem 1 Politeknik

Electrical Power & Energy

20V

15Ω

25Ω

iv) Energy absorbed by the 15Ω resistor after 2 hours

0.5A

Energy,

W = P*t = I2*R*t = 0.52 x 15 x 2 x 60 x 60 = 27 kJ

Page 114: Electrical Technology Topic 1 Sem 1 Politeknik

SELF-EXERCISEi) Diagrams below show a delta connection circuit

with its equivalent star connection circuit. If R1=20kΩ, R2=40kΩ and R3 =80kΩ, calculate Ra, Rb and Rc

11.43kΩ

5.71kΩ 22.86kΩ

ANSWER

ANSWERANSWER

Page 115: Electrical Technology Topic 1 Sem 1 Politeknik

SELF-EXERCISEii) With refer to the diagram as below, calculate power that supplied by the battery and power dissipation at resistor 40kΩ.

= 1.6mW

Ps = 4.8mWANSWER

ANSWER

Page 116: Electrical Technology Topic 1 Sem 1 Politeknik

RECAP• Cell and battery are sources of DC type of

electricity.• Voltage, current and resistance are recognized

as three basic elements of electrical circuit which contribute in Ohm’s Law.

• Electrical circuit can be constructed in series, parallel and combination of series-parallel connection.

• Star-Delta transformation technique is required to analyze network that involve Star/Delta connection.

• Power and Energy is the product of voltage and current elements of a circuit.

Page 117: Electrical Technology Topic 1 Sem 1 Politeknik

REFERENCES

Main: John Bird (2010). Electrical Circuit Theory & Technology. Fourth

Edition. Newness. (ISBN: 978-0-08-089056-2)

Additional: 1. Allan R. Hambley (2011). Electrical Engineering, Principles

and Applications, Fifth Edition. Prentice Hall. (ISBN-13: 978-0-13-213006-6)

2. B.L. Theraja (2010).Textbook of Electrical Technology .S Chand & Co Ltd. (ISBN: 978-8121924900)

Page 118: Electrical Technology Topic 1 Sem 1 Politeknik

REFERENCES

3. Darren Ashby (2011). Electrical Engineering 101, (3rd Ed ) [Paperback] Elsevier Inc. (ISBN: 978-0123860019)

4. John Bird. (2010). Electrical And Electronic Principles And Technology. Fourth Edition. Newness. (ISBN: 978-1-85617-770-2)

5. Meizhong Wang. (2010). Understandable Electric Circuits First edition © 2005 Higher Education Press, China, English translation ©2010 The Institution of Engineering and Technology. (ISBN 978-0-86341-952-2)

6. V. K. Mehta (2010). Principles of Electrical Engineering and Electrical [Paperback] S Chand & Co Ltd. (ISBN: 978-8121927291)