BENG1113PRINCIPLE OF ELECTRICAL AND ELECTRONICS Chapter 1 (week 1) FACULTY OF ELECTRONIC AND COMPUTER ENGINEERING
Learning Outcome • Upon completion of this chapter, student should be able to: • Describe the basic structure of atoms • Define nucleus, proton, neutron and electron • Describe ionization and free electron • Define conductor, semiconductor and insulator • Convert decimal no to standard or engineering notation Chapter 1: Introduction to Electricity
Chapter 1 • Subtopics: • Atomic structure • SI units, Scientific and Engineering notation • Electrical charges • Electrical quantities - voltage, current and resistance • Active and passive components • Basic electrical instruments • Basic circuit measurement • Electrical safety. Chapter 1: Introduction to Electricity
Atomic Structure • ATOM : The smallest particle of an element that possesses the unique characteristics of that element. • PROTON : The basic particle of positive charge. • ELECTRON : The basic particle of negative charge. • NEUTRON : An uncharged particle found in the nucleus of an atom. • NUCLEUS : The central part of an atom containing protons and neutrons.
Balanced Atom • an equal number of electrons and protons. • no electrical charge. Chapter 1: Introduction to Electricity
Valance Electrons • VALANCE SHELL : The outermost shell of an atom. • VALANCE ELECTRONS : Electrons in the valance shell. • The valance electrons contribute to chemical reactions and bonding within the structure of a material and determine its electrical properties.
Ionization • Since electrons are lighter than protons and are outside the nucleus, they can be easily moved from atom to atom to form electrons • When an atom absorbs energy, the valance electrons possess more energy and they can actually escape from the outer shell and becoming free electrons.
Exercises 1. How many electrons contains in the valence shell for the elements below. • Sodium • Chlorine 2. Draw the atomic structure of the copper atom (no.of electrons = 29). Chapter 1: Introduction to Electricity
CONDUCTORS • A material that easily conduct electrical current. • A CONDUCTOR has 1 to 3 valence electrons in the outermost shell. Therefore its electrons tend to move to other atom. • Most metals are good conductors and the best conductors are single-element materials such as copper, silver, gold and aluminium.
INSULATORS • A material that does not conduct electrical current under normal conditions. • Most good insulators are compounds rather than single-element material such as rubber, plastics, glass, mica, and quartz. • An insulator is any material with 5 to 8 valence electrons in the outer ring.
SEMICONDUCTORS • A material that is between conductors and insulators in its ability to conduct electrical current. It has exactly 4 valence electrons. • A semiconductor in its pure (intrinsic) state is neither a good nor a good insulator. • The most common single-element semiconductors are silicon, germanium, and carbon. • The most common compound semiconductor is gallium arsenide.
Quantity Unit Symbol length meter kilogram second ampere Kelvin candela mole m kg s A K cd mol mass time electric current temperature luminous intensity amount of substance SI units  Table 1-1
Quantity Unit Symbol A C V W W ampere coulomb volt ohm watt current charge voltage resistance power • This is the units that are derived from the fundamental units except for current since it is a fundamental unit Table 1-2 Chapter 1: Introduction to Electricity
Quantity Unit Symbol flux density tesla weber ampere-turns/meter ampere-turn webers/ampere-turns-meter ampere-turns/weber T Wb At/m At Wb/Atm At/Wb magnetic flux magnetizing force magnetomotive force permeability reluctance • All magnetic units are derived from the fundamental units . Table 1-3 Chapter 1: Introduction to Electricity
Scientific notation • Provides a convenient method for expressing large and small numbers 1=100 1/10 =0.1 =10-1 10 =101 1/100 =0.01 =10-2 100 =102 1/1000 = 0.001 =10-3 1000 =103 1/10,000 =0.0001 =10-4 Chapter 1: Introduction to Electricity
Mathematical Operation • To perform addition or subtraction using powers of ten, the power of ten must be the same for each term: • Multiplication • Division • Power
Exercises 1. Express each number in scientific notation • 200 • 5000 • 85000 • 3,000,000 • 4750 Chapter 1: Introduction to Electricity
2. Express each of the following numbers in scientific notation: • 0.2 • 0.005 • 0.00063 • 0.000015 3. Express each number as a regular decimal number: • 1 x 105 • 2 x 103 • 3.2 x 10-2 • 2.5 x 10-6 Chapter 1: Introduction to Electricity
Engineering notation • Similar to scientific notation • A number can have from one to three digits to the left of the decimal point and the power-of-ten exponent must be a multiple of three  • For example; 33000 = 3.3 x 104 = 33 x 103
1015 10-3 peta P m milli T tera m micro 1012 10-6 giga nano 10-9 109 G n mega 106 p pico 10-12 M 103 f k kilo femto 10-15 • Matrix prefix • Specific powers of ten in engineering notation have been assigned prefixes and symbols 
Metric unit conversions • Larger unit: move the decimal point to the right • Smaller unit: move the decimal point to the left • e.g. 0.15mA = 150µA Chapter 1: Introduction to Electricity
Exercises 1. Perform the mathematical operation; • 6300 + 75000 • 0.0096 – 0.000086 • (0.0002)(0.000007) • (340,000)(0.00061) • 0.00047/0.002 • 690000/0.0000013 • (0.00003)3 • (90800000)2 Chapter 1: Introduction to Electricity
2.Example 1-8 : express the following numbers in engineering notation • 82,000 • 243,000 • 1,956,000 • 0.0022 • 0.000000047 • 0.00033 3. Example 1-10 : Convert the following • 20 kHz to megahertz • 0.01ms to microseconds • 0.002km to millimeters Chapter 1: Introduction to Electricity
Electrical Charges • Charges of opposite signs (one negative and one positive) attract one another. • Charges of the same sign (both positive and both negative) repulse one another. Chapter 1: Introduction to Electricity
Electrical Charges • The unit of charge : • The unit of charge is denoted by Coulomb • One coulomb is the total charge possessed by: 6.25 x 1018 electrons or protons • A single electron has a charge of 1.6 x 10-19 C and a single proton has a charge of +1.6 × 10-19 C. • Total charge;
Exercises • How many Coulombs of charge do 93.8 x 1016 electron represent? • How many electrons does it take to have 3C of charge? Chapter 1: Introduction to Electricity
Electrical Force • Electrical forces act between charges • Q1 and Q2 = charge on the objects (in C) • D = distance between objects (in meters) • k = a constant = 8.99 x 109 N m2/coul2 • The strength of the electrical force decreases as the distance between the charged objects increases
Basic Electrical Components and Instuments • Resistors • Resistors resist, or limits, electrical current in a circuit. • Capacitors • Capasitors store electrical charge; they are used to block direct current (dc) and pass alternating current (ac). • Inductors • Inductors, also known as coils, are used to store energy in an electromagnetic field; they serve many useful functions in an electrical circuit
Transformers • Transformers are used to magnetically couple ac voltages from one point in a circuit to another, or to increase or decrease the ac voltage. Companies such as TNB use huge transformers to change voltages for high-voltage transmission lines. • Electronic Instruments • There are four basic electronic instruments normally found in laboratory and will be use throughout the lab session for this course. These instruments include: • DC power supply - provide current and voltage to power electronic circuits. • Function generator – provide electronic signals. • Multimeter – with its voltmeter, ammeter and ohmmeter functions for measuring voltage, current and resistance, respectively • Oscilloscope – observe and measure ac voltages.
Voltage • Voltage is the electrical force that moves electrons through a conductor. The pressure also known as EMF (Electro Motive Force) that pushes electrons.
Voltage is expressed as; • V = voltage in volts (V) • W = energy in joules (J) • Q = charge in coulombs (C) • One volt is the potential difference (voltage) between two points when one joule of energy is used to move one coulomb of charge from one point to the other.
Exercises • Determine the voltage • 10J / 1C • 5J / 2C • 100J / 25C • If 50J of energy are available for every 10C of charge, what is the voltage? • 500J of energy are used to move 100C of charge through a resistor. What is the voltage across the resistor?
- + Porous separator Electrolyte Negative electrode Positive electrode Voltage Source • Battery: A battery is a type of voltage source that convert chemical energy into electrical energy. A battery consists of one or more electrochemical cells that are electrically connected. • four basic components: a positive electrode, a negative electrode, electrolyte and a porous separator.
Solar cells: The operation of solar cells is based on the photovoltaic effect (light energy is converted directly into electrical energy). It has 2 layers of different types of semiconductive materials joined together to form a junction. When one layer is exposed to light, many electrons acquire enough energy to break away from their parent atoms and cross the junction, and thus a voltage is developed.
Generator: Electrical generators convert mechanical energy into electrical energy using a principle called electromagnetic induction. A conductor rotated through a magnetic field, and a voltage is produced across the conductor. • Electronic power supply: Electronic power supply does not produce electrical energy from some other from energy. They simply convert the ac voltage from wall outlet to a constant (dc) voltage. • Measuring instrument: A VOLTMETER
Current • Current is the movement or flow of charge (electrons) from the negative end of the conductor to the positive end • Current in a conductor material is measured by the number of electrons (amount of charge) that flow past a point in a unit of time I = current in Ampere (A) Q = charge of the electrons in coulombs (C) t = time in seconds (s)
One ampere (1A) is the amount of current that exists when a number of electrons having a total charge (1C) move through a given cross-sectional area in one second. • Electricity with electrons flowing in only one direction is called Direct Current (DC). It flows in one direction, positive to negative, steadily. A graph of a DC voltage or current would look like a flat horizontal line.
Electricity with electrons flowing back and forth, negative - positive- negative, is called Alternating Current, or AC. It literally changes direction at a certain rate, called its frequency, measured in Hertz. • Ordinary household electricity in Malaysia is 240 VAC, 50 Hz. A graph of 240 VAC is a sine wave. AC can be used at it is in light bulbs and motors, but for electronic devices, it must be stepped down to a lower voltage and then converted to DC. For example, the CPU in many computers typically takes 3.6 volts DC. • Measuring instrument: Ammeter
Exercises • 10C of charge flow past a given point in a wire in 2s. What is the current in amperes? • If there are 8A of direct current through the filament of a light bulb, how many coulombs have moved through the fillament in 1.5s?
Resistance • Resistance, R, is the force that reduces or stops the flow of electrons. • Opposite to current and measured in Ohms () • The schematic symbol is shown below • Conductance, G, is the reciprocal of resistance. • The unit is in Siemens (S) • Measuring instrument: Ohmmeter
Alphanumeric Labeling • Two or three digits, and one of the letters R, K, or M are used to identify a resistance value. • The letter is used to indicate the multiplier, and its position is used to indicate decimal point position.
Power • When current is forced through a resistance, work is said have been done. Power is the rate of working, represented by "P". Energy is the capacity to do work. • Power is energy per time or the rate of working, represented by "P". The standard unit used in electricity is the Watt (W) = 1 Joule / second. • The amount of power consumed by an electrical device is the rate at which it dissipates energy.
Basic Circuit Measurement • Multimeter Analog Multimeter Digital Multimeters (DMM)
Most analog ammeters have a number of possible settings for the maximum possible current that can be measured; for example: 2 A, 200 mA, 20 mA, 2 mA. You should always start by turning the setting to the highest possible rating (for example, 2 A). If the ammeter reading is too small from the selected scale, then you can reduce the scale to get the reading. It is important not to overshoot the maximum value that can be read. • For example, if the current is about 75 mA, then the ammeter would be set to the 200 mA scale for the most accurate reading. Setting to the 20 mA scale would overload the ammeter and most likely open its internal fuse.