8 Electrical Engineering Objectives Define electrical engineering Explain

8 Electrical Engineering

Objectives • Define electrical engineering. • Explain the secondary and college level education requirements for employment in the electrical engineering profession. • Explain how electrons move on an atomic level. • Describe the characteristics of voltage, current, resistance, and power. • Explain Ohm’s law and use it to solve for values in a circuit. • Identify the operation and application of common electronic components such as resistors, switches, capacitors, diodes, and transistors. © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

About Electrical Engineering • Engineering field that deals with electricity and electronics • Electrical engineers design, build, and test electrical devices and facilities • About 21% of all engineers are electrical engineers © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

Educational Requirements • Bachelor’s degree in electrical engineering • Higher degrees often required for higher level positions • Coursework in electricity, electronics, chemistry, biology, physics, and higher level math and statistics • Associate’s degree required for electrical technicians © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

Professional Organization • Institute of Electrical and Electronics Engineers (IEEE) – Broadest professional society for electrical engineers – Over 375, 000 members – Dedicated to advancing technological innovation and excellence through publications, conferences, standards, and activities © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

Electricity on the Atomic Level • • Electrons, protons, neutrons Valence shell Electron movement Electrically charged atoms are called ions Goodheart-Willcox Publisher © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

Static Electricity • Excess of charge on object’s surface • Many industrial applications • Electrostatic precipitator – Used to remove particles from air – Charged particles stick to collection plates with opposite charge © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

Electricity Through Conductors • Negative to positive flow using electron flow theory • Move slowly, but the effective speed is about the speed of light Goodheart-Willcox Publisher © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

Sources of Electricity • Some form of energy is converted into electrical energy • Three sources of electricity – Magnetism – Chemical action – Solar cells © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

Law of Conservation of Energy • States that energy cannot be created or destroyed • Energy can only be converted from one form to another © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

Magnetism • Generators produce electricity by changing mechanical energy to electrical energy • Voltage induced in wire when magnet passes • Current induced in conductor of generator • Steam, water, or wind turns turbines, creating motion that spins generators © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

Chemical Action • Cells use chemical action to create electricity • Batteries connect multiple cells • Electrodes of different materials has voltage created between them • Two types of cells – Primary cells – Secondary cells © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

Solar Cells • Use light to create electricity • Semiconductors with positive and negative layers absorb some light energy • Energy causes electrons to flow in form of current • Cells can power devices and houses © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

Characteristics and Measurements • Generated electricity has certain characteristics that can be used in different ways • Engineers must understand characteristics and how to measure them – Voltage – Current – Resistance © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

Voltage • Amount of pressure causing flow of electrons • Expressed as electromotive force (EMF) • Also called potential difference because it describes difference in charge from one place to another • Measured in volts © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

Current • • Measure of electrons per unit time Also called amperage Measured in amperes (amps) One ampere is one coulomb of charge passing a point in one second • One coulomb equals 6. 24 1018 electrons © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

Polarity • Refers to positive or negative condition at power supply terminal • Direct current (dc) occurs when polarity is constant and current flows in only one direction • Alternating current (ac) occurs when polarity changes back and forth from positive to negative, causing current to change direction © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

Resistance • Opposition to current flow • Measured in ohms (Ω) • Current flow limited and voltage divided by resistors • Resistant materials are insulators • Inversely proportional to current © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

Power • The rate at which work is done or amount of work done based on period of time • Electrical power is product of voltage and current • Measured in watts • One watt is one volt moving one coulomb of electricity in one second © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

Laws • Ohm’s law – Discovered by George Ohm – Describes relationship between voltage, current, and resistance • Watt’s law – Power equals effort multiplied by rate – Used to find any one of three values when two are known © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

Basic Circuits • Series circuits • Parallel circuits • Series-parallel combination circuits © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

Series Circuits • One path for current flow • Total voltage equals sum of drops across all loads • Total resistance equals sum of resistance of each load • Current remains constant throughout Goodheart-Willcox Publisher © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

Parallel Circuits • Multiple paths for current flow • Total voltage is equal to the voltage across each branch • Total current is equal to the sum of branch currents © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

Series-Parallel Combination Circuits • Circuits with characteristics of both series and parallel • Parallel parts must be broken down and studied as if they were series elements Goodheart-Willcox Publisher © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

Design Schematics • Schematic symbols are used to show components in circuit drawings • Schematic diagrams use symbols and lines to connect components • Often used in building and troubleshooting circuitry © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

Circuit Components • Each component must be understood • Understanding is necessary for design and troubleshooting • Three main types of components – Conductors – Control components – Output components © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

Conductors • Materials have low resistance – Copper – Aluminum – Silver – Gold • Different configurations • American Wire Gauge (AWG) system determines size © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

Control Components • • • Insulators Resistors Variable resistors Switches Diodes Zener diodes • Transistors • Capacitors • Integrated circuits (ICs) • Semiconductors • Sensors © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

Insulators • Very high resistance • Do not conduct electricity under normal circumstances • Keep electricity confined to desired path – Plastic – Rubber – Dry wood/paper – Glass/ceramics – Mica © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

Resistors • Limit current flow and divide voltage • Most are made from carbon • Color coding system marks the value of resistors Goodheart-Willcox Publisher © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

Variable Resistors • Vary amount of resistance in dimmer switches and fan speed switches • Two terminals and wiper, which changes amount of resistive material between terminals • Represented by arrow symbol © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

Switches • Open and close circuits • Change direction of flow • Characterized by type of switch, number of poles, and number of throws – SPST switch can turn current on or off to circuit – SPDT switch can direct current in one direction or other © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

Diodes • Standard diodes allow current flow in only one direction • Have two electrodes – Anode is made of positive semiconductor material – Cathode is made of negative semiconductor material • Current flows in forward bias condition only • Can be used as rectifiers © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

Zener Diodes • • Zener diodes are wired in reverse bias Block current until voltage reaches certain level Keep voltage at constant level Used as voltage regulators © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

Transistors • Used as solid state switches and amplifiers • Perform switching function without moving parts • Bipolar transistors have three junction points – Emitter – Base – Collector • Can also be used as amplifiers © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

NPN and PNP Transistors Goodheart-Willcox Publisher © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

Capacitors • Store and discharge electricity very quickly • Smooth out variations in voltage • Two conductive plates separated by thin insulator called dielectric • Ceramic disc and electrolytic • Can maintain charge long after power source is removed © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

Integrated Circuits (ICs) • Multiple electrical circuits etched into thin layer of silicon • Dot or notch on outside of chip is used for orientation • Can be sensitive to static • Common example is 555 timer © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

Semiconductors • Materials with conductive capabilities between that of conductors and insulators • Silicon is most common type • Used in different components – Transistors – Diodes – Solar panels – Integrated circuits © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

Sensors • Create an electrical signal based on environmental conditions • Signal changes as environmental conditions change • Common example is electronic thermostats © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

Output Components • • • Incandescent lamps Gas discharge lamps Fluorescent lamps Compact fluorescent lamps (CFLs) Light-emitting diode (LED) lamps Motors © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

Incandescent Lamps • Creates light when current flow causes tungsten filament to become so hot it glows • All air inside glass globe is evaluated and sometimes replaced with argon • Traditional incandescent bulbs are being phased out © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

Gas Discharge Lamps • Ionized glass and free electrons cause gas to glow and create light • Neon lamps are example, but other gases may be used • Resistor must be placed in series with light to limit current flow © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

Fluorescent Lamps • Long glass tube coated on inside with phosphorous and filled with inert gas and mercury • Electrical current passed through mercury causes ultraviolet light, which causes phosphorous to glow • Use much less electricity than incandescent lamps © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

Compact Fluorescent Lamps (CFLs) • Work on same principle as fluorescent lamps but fit into standard light socket • Use about 75% less energy than incandescent lamps • Last up to ten time longer than incandescent lamps © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

Light-Emitting Diode (LED) Lamps • Create light by wiring semiconductor material in forward biased position • Forward biased direct current passes through semiconductor in LED casing, and light is emitted • Low cost, efficient, and long lasting © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

Motors • Convert electrical energy into mechanical energy • Electromagnet spins until its north pole lines up with south pole of permanent magnet • Polarity of electromagnet reverses, causing it to keep rotating © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

Component Platforms • Circuit boards • Solderless breadboards • Electronic circuit simulation © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

Circuit Boards • Commonly known as printed circuit boards (PCBs) • Copper track laid on fiberglass • Electronic components are soldered to copper track © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

Solderless Breadboards • Ideal for experimentation • Can be used to test circuits before they are constructed • Components and leads can easily be added and removed because no soldering is required © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

Electronic Circuit Simulation • Can be used to simulate performance of circuitry without having to build circuit • Components are laid out on-screen • Software shows how circuits would work • Problems can be identified early on © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

Tools Meters • • • Ammeters Voltmeters Ohmmeters Volt-ohm-milliammeters (VOM) Continuity tester Oscilloscope © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

Troubleshooting • First step may be to test voltage • Continuity tester or ohmmeter may be used to ensure continuity exists • Test to see if diode conducts in forward bias and not reverse • LEDs can be tested by applying voltage directly © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

Electrical Engineering in Action • Hybrid cars – Combine internal combustion engine and batteries – Regenerative braking – Increased fuel mileage Goodheart-Willcox Publisher © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.