CHAPTER 1 Variables & Circuit Elements School of Computer and Communication Engineering, UniMAP Prepared By: Wan Nur Suryani Firuz bt Wan Ariffin Amir Razif A. b. Jamil Abdullah EET 101 [Electric Circuit I]: V2009

Lecturer : Amir Razif A. Jamil Abdullah amirrazif@unimap.edu.my Office: KKF 8A Textbook: (1) Fundamentals of Electric Circuits – Alexander sadiku (3rd edition) Reference book: (2) Electric Circuits Fundamentals – FLOYD (7Th edition) (3) Basic Engineering Circuit Analysis – J.David Irwin & R.Mark Nelms( 9th edition)

Syllabus - EET 101 Chap 1 : Circuit Elements and Variables Overview of circuit analysis, SI unit, voltage and currents, power, energy, elements on the circuit (passive and active) voltage and current source, Ohm’s Law, Kirchhoff’s Law, circuit model, circuit with dependent source. Chap 2 : Resistive Circuit Series / Parallel circuit, voltage divider circuit, current divider circuit, voltage and current measurement, Wheatstone Bridge, equivalent circuit for delta-wye (Pi-Tee). Chap 3 : Circuit Analysis Methods Introduction to the Node-Voltage Method, the Node-Voltage Method with dependent sources and special cases, introduction to Mesh-Current Method, Mesh-Current Method with dependent sources and special cases, source transformations, Thevenin and Norton equivalent circuit, maximum power transfer and superposition. Chap 4 : Inductance and Capacitance Inductor, relationship between voltage, current, power and energy, capacitor, relationship between voltage, current, power and energy, series-parallel combinations for inductance and capacitance. Syllabus - EET 101

Chap 5 : First-Order and Second-Order Response of RL and RC Circuit Natural response of RL and RC Circuit, Step Response of RL and RC Circuit, general solutions for natural and step response, sequential switching, introduction to the natural and step response of RLC circuit, natural response of series and parallel RLC circuit, Step response of series and parallel RLC circuit. Chap 6: Sinusoidal Steady-State Analysis The sinusoidal source, the sinusoidal response, the phasor and phasor diagram, the passive circuit elements in the frequency domain, impedances and reactance, Kirchhoff’s Laws in frequency domain, techniques of circuit analysis in frequency domain Chap 7 : Sinusoidal Steady-State Power Calculation Instantaneous power, average (active) and reactive power, the rms value power calculation, complex and power triangle , the maximum power transfer Chap 8 : Three Phase System Circuit Single and Three Phase System (Y and Δ circuit), balanced three phase voltage sources, Y – Y circuit analysis, Y - Δ circuit analysis, power calculation in three phase balanced circuit, average power measurement in three phase circuit. Syllabus - EET 101

Course Structure Test 1 – September 2009 Attendance, Quizzes &Tutorial Final Exam = 50% Laboratory = 20% Test (2 test) = 20% Test 1 – September 2009 Test 2 – October 2009 Assignment = 10% Attendance, Quizzes &Tutorial Total : = 100%

Basic Electric Circuit Concepts Review SI Know the definition of basic electrical quantities : voltage, current, and power Know the symbols for and definition of independent and dependent sources Be able to calculate the power absorbed by a circuit element using the passive sign convention

Circuit Elements & Variables Overview of circuit analysis SI unit Voltage, currents, power, energy, elements on the circuit (passive and active) voltage and current source Ohm’s Law and Kirchhoff’s Law circuit model circuit with dependent source.

Thermodynamic temperature SI Unit SI: International System of Unit is used by all the major engineering societies and most engineers throughout the world. Quantity Base unit Symbol Length Meter m Mass Kilogram kg Time second s Electric current Ampere A Thermodynamic temperature Kelvin K Luminous intensity candela cd

Standardized prefixes to signify powers of 10 Symbol 1012 Tera T 109 Giga G 106 Mega M 103 Kilo k 100 10-3 Mili m 10-6 Micro µ 10-9 Nano n 10-12 Pico p 10-15 Femto f 10-18 Atto a

Circuit Elements & Variables Overview of circuit analysis SI unit Voltage, currents, power, energy, elements on the circuit (passive and active) voltage and current source Ohm’s Law and Kirchhoff’s Law circuit model circuit with dependent source.

Electric Units Charge »»» Coulomb (C) Current »»» Ampere (A) Voltage »»» Volt (V) Resistance »»» Ohm () Power »»» Watt (W)

Quantity is CHARGE (Q) Base Unit is COULOMB (C) Charge = 15 Coulombs Electric charge is a property possessed by both electrons and protons. Quantity is CHARGE (Q) Base Unit is COULOMB (C) Examples of correct usage: Charge = 15 Coulombs Q = 15 C

Current is the movement of charge in a specified direction.

Electric Current Terminology An ampere equals a coulomb per second. Quantity is CURRENT (I) Base Unit is AMPERE (A) An ampere equals a coulomb per second. Examples of correct usage: Current = 12 Amperes I = 12 A

Electric Current Relationships Charge Q Current = I = t Time Examples: Q 14 C = 1.4 A I = = t 10 s Q 14 C = 10 s t = = I 1.4 A

Types of Current: DC AC Alternating current (arus ulangalik) ex: Used to run refrigerator, stove, washing machine, and so on… ex batteries – used in automobiles or flashlight DC AC Alternating current (arus ulangalik) Direct current (arus terus) Damped alternating current (arus ulangalik teredam) Exponential current

Voltage Definition of Voltage Voltage is the electric pressure or force that causes current. It is a potential energy difference between two points. It is also known as an electromotive force (emf) or potential.

A volt equals a joule per coulomb. Voltage Terminology Quantity is VOLTAGE (V) Base Unit is VOLT (V) A volt equals a joule per coulomb. Examples of correct usage: Voltage = 32 Volts V = 32 V

Voltage Relationships Energy W Voltage = V = Q Charge Examples: W 56 J = 28 V V = = Q 2 C W 84 J = 4 C Q = = V 21 V

Definition of Resistance Resistance is the opposition a material offers to current. Resistance is determined by: Type of material (resistivity) Temperature of material Cross-sectional area Length of material

Some Factors That Determine Resistance For a specific material and temperature, this block has given amount of resistance. Doubling the length of the block, doubles the resistance. Doubling the cross-sectional area, halves the resistance.

Resistance Terminology An ohm equals a volt per ampere. Quantity is RESISTANCE (R) Base Unit is OHM (W) An ohm equals a volt per ampere. Examples of correct usage: Resistance = 47 ohms R = 47 W

Resistance Relationships Resistivity x length KL Resistance = R = A area Example: KL 1.4 x10-6 W· cm x 2 x104 cm R = = A 0.28 cm2 = 0.1 W

ENERGY Work (W) Energy (W) The joule (J) The amount of work done equals the amount of energy used (converted). consists of a force moving through a distance. Energy (W) is the capacity to do work. Fifty joules of energy are required to do fifty joules of work. The joule (J) is the base unit for both energy and work.

Power is the rate of using energy or doing work. Definition of Power Power is the rate of using energy or doing work. “Using energy” means that energy is being converted to a different form.

A watt equals a joule per second. Power Terminology Quantity is POWER (P) Base Unit is WATT (W) A watt equals a joule per second. Examples of correct usage: Power = 120 Watts P = 120 W

Power Relationships Energy W Power = P = t Time Examples: W 158 J W = Pt = 75 W x 25 s = 1875 J

Circuit Elements & Variables Overview of circuit analysis SI unit voltage and currents, power, energy, elements on the circuit (passive and active) voltage and current source Ohm’s Law and Kirchhoff’s Law circuit model circuit with dependent source.

Active and Passive Elements Circuit Elements Active elements capable of generating electric energy Example : voltage and current sources Passive elements incapable of generating electric energy Example : resistore, inductor, capacitor, diode and etc

Independent Source Current Voltage

Dependent Source Voltage Current

Ideal Voltage Source Connected in Series

Ideal Current Source Connected in Parallel

Symbol of Circuit Elements Resistor R UNIT: Ohm (Ω)

Resistor Color Code

Resistor Color Code Yellow 4 7 Violet 00 Red ±10 % Silver

Resistor Color Code 56 x 103 ± 5 % = 56,000 ± 5 % = 56 KW ± 5 % Green = 5 Blue = 6 Orange = 3 Gold = ± 5 % 56 x 103 ± 5 % = 56,000 ± 5 % = 56 KW ± 5 %

Resistor Color Code = 464 kW ± 2% 4 6 4 0 0 0 ± 2%

Conductance Conductance is a measure of the ability of an element to conduct electric current Inverse of resistance The units is Siemens (S) or mhos

Capacitor Inductor C UNIT: Farad (F) L UNIT: Henry (H)

Circuit Elements & Variables Overview of circuit analysis SI unit voltage and currents, power, energy, elements on the circuit (passive and active) voltage and current source Ohm’s Law and Kirchhoff’s Law circuit model circuit with dependent source.

Short Circuit R = 0  no voltage difference exists all points on the wire are at the same potential. Current can flow, as determined by the circuit

Open circuit R =   no current flows Voltage difference can exist, as determined by the circuit

Circuit Nodes and Loops A node is a point where two or more circuit elements are connected. A loop is formed by tracing a closed path in a circuit through selected basic circuit elements without passing through any intermediate node more than once

Example: Find the Nodes + - Vs node

Example: Find the loops

Ohm’s Law George Simon Ohm (1787-1854) formulated the relationships among voltage, current, and resistance as follows: The current in a circuit is directly proportional to the applied voltage and inversely proportional to the resistance of the circuit.

Kirchhoff Law Gustav Robert Kirchhoff (1824–1887) Models relationship between: circuit element currents (KCL) circuit element voltages (KVL) Introduce two laws: Kirchhoff Current Law (KCL) Kirchhoff Voltage Law (KVL)

Kirchhoff’s Current Law (KCL) Current entering node = current exiting (What goes in, must come out) Convention: +i is exiting, -i is entering For any circuit node:

Kirchhoff’s Current Law (KCL) No matter how many paths into and out of a single point all the current leaving that point must equal the current arriving at that point.

Kirchhoff’s Voltage Law (KVL) voltage increases = voltage decreases (What goes up, must come down) Convention: hit minus (-) side first, write negative For any circuit loop:

Kirchhoff’s Voltage Law (KVL) The voltage drops around any closed loop must equal the applied voltages

Circuit Elements & Variables Overview of circuit analysis SI unit voltage and currents, power, energy, elements on the circuit (passive and active) voltage and current source Ohm’s Law and Kirchhoff’s Law circuit model circuit with dependent source.

Circuit Model SERIES PARALLEL PARALLEL-SERIES

An energy or power source This complete circuit uses the following: An energy or power source A control device A load Conductors Insulation (not shown)

Calculating Current V R = 36 V 1800 W I = = 0.02 A = 20 mA SPST S1 B1 1.8 kW B1 36 V V R = 36 V 1800 W I = = 0.02 A = 20 mA

Calculating Resistance B1 24 V A 0.03 A V I = 24 V 0.03 A R = = 800 W = 0.8 k W

Calculating Voltage A V = IR = 0.15 A * 270 W = 40.5 V 0.15 A B1 R

Calculating Power A V IV = P = 0.2 A * 54 V = 10.8 W P = I2R = 0.2 A * 0.2 A * 270 W = 10.8 W P = V2/R = (54 V * 54 V) / 270 W = 10.8 W

Circuit Elements & Variables Overview of circuit analysis SI unit voltage and currents, power, energy, elements on the circuit (passive and active) voltage and current source Ohm’s Law and Kirchhoff’s Law circuit model circuit with dependent source.

Circuit With Dependent Source

Solve the equations, Using KCL on the second loop, Using KVL on the first loop, Using KCL on the second loop, Solve the equations,

Using Ohm law for the resistor,