Chapter 11 Electrical Engineering Objectives Define electrical engineering

Chapter 11 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. Copyright Goodheart-Willcox Co. , Inc. May not be posted to a publicly accessible website.

Electrical Engineering • Deals with electricity and electronics • Electrical engineers design, build, test electrical devices, facilities • About 21% of engineers are electrical engineers Nesa. Cera/Shutterstock. com Copyright Goodheart-Willcox Co. , Inc. May not be posted to a publicly accessible website.

Professional Aspects • Bachelor’s degree in electrical engineering – Courses in electricity, electronics, sciences, math, statistics – Advanced degrees needed for advanced positions – Associate’s degree required for electrical technicians • Advanced math, science in high school • Institute of Electrical and Electronics Engineers (IEEE) • Ethical conduct, teamwork skills essential Copyright Goodheart-Willcox Co. , Inc. May not be posted to a publicly accessible website.

Electricity on the Atomic Level • Atoms – Electrons, protons, neutrons • Valence shell • Ions • Electron movement critical to understanding electricity Goodheart-Willcox Publisher Copyright Goodheart-Willcox Co. , Inc. May not be posted to a publicly accessible website.

Static Electricity • Excess of charge on object’s surface • Industrial applications – Electrostatic precipitator Goodheart-Willcox Publisher Copyright Goodheart-Willcox Co. , Inc. May not be posted to a publicly accessible website.

Electricity Through a Conductor • Two theories of electrical current flow – Conventional current flow – Electron flow Goodheart-Willcox Publisher Copyright Goodheart-Willcox Co. , Inc. May not be posted to a publicly accessible website.

Sources of Electricity • • Magnetism Chemical action Solar cells Law of conservation of energy – Energy cannot be created or destroyed, only converted from one form to another Copyright Goodheart-Willcox Co. , Inc. May not be posted to a publicly accessible website.

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, wind turns turbines, creating motion that spins generators Goodheart-Willcox Publisher Copyright Goodheart-Willcox Co. , Inc. May not be posted to a publicly accessible website.

Chemical Action • Cells use chemical action to create electricity • Battery connects multiple cells • Electrodes of different materials create voltage between them • Types of cells – Primary cells – Secondary cells Copyright Goodheart-Willcox Co. , Inc. May not be posted to a publicly accessible website.

Solar Cells • Use light to create electricity • Semiconductors with positive, negative layers absorb light energy • Energy causes electrons to flow as current • Cells power devices, houses Spectruminfo/Shutterstock. com Copyright Goodheart-Willcox Co. , Inc. May not be posted to a publicly accessible website.

Characteristics and Measurements • Electricity has characteristics that can be used in different ways – Voltage – Current – Resistance – Power Copyright Goodheart-Willcox Co. , Inc. May not be posted to a publicly accessible website.

Voltage • Amount of pressure causing flow of electrons • Expressed as electromotive force (EMF) • Measured in volts Copyright Goodheart-Willcox Co. , Inc. May not be posted to a publicly accessible website.

Current • Measure of electron flow per unit time • Measured in amperes (amps) • One ampere is one coulomb of charge passing a point in one second • One coulomb equals 6. 24 1018 electrons Copyright Goodheart-Willcox Co. , Inc. May not be posted to a publicly accessible website.

Polarity • Positive or negative condition at power supply terminal • Direct current (dc) constant polarity, current flow in only one direction • Alternating current (ac), polarity reverses from positive to negative, current changes direction Copyright Goodheart-Willcox Co. , Inc. May not be posted to a publicly accessible website.

Polarity Goodheart-Willcox Publisher Copyright Goodheart-Willcox Co. , Inc. May not be posted to a publicly accessible website.

Resistance • Opposition to current flow • Measured in ohms (Ω) • Current flow limited, voltage divided by resistors • Resistant materials are insulators • Inversely proportional to current Copyright Goodheart-Willcox Co. , Inc. May not be posted to a publicly accessible website.

Power • The rate at which work is done or amount of work done based on period of time • Electrical power is product of voltage, current • Measured in watts • One watt is one volt moving one coulomb of electricity in one second Copyright Goodheart-Willcox Co. , Inc. May not be posted to a publicly accessible website.

Ohm’s Law • Relationship between voltage, current, resistance in electrical circuits • Can be used to solve for any of three variables Goodheart-Willcox Publisher Copyright Goodheart-Willcox Co. , Inc. May not be posted to a publicly accessible website.

Watt’s Law • Power equals effort multiplied by rate –P=Ix. E • Use to find any one of three values when two are known Copyright Goodheart-Willcox Co. , Inc. May not be posted to a publicly accessible website.

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 Copyright Goodheart-Willcox Co. , Inc. May not be posted to a publicly accessible website.

Parallel Circuits • Multiple paths for current flow • Total voltage equals voltage across each branch • Total current equals sum of branch currents Goodheart-Willcox Publisher Copyright Goodheart-Willcox Co. , Inc. May not be posted to a publicly accessible website.

Series-Parallel Combination Circuits • Characteristics of both series and parallel • Parallel parts broken down and studied as series elements Goodheart-Willcox Publisher Copyright Goodheart-Willcox Co. , Inc. May not be posted to a publicly accessible website.

Design Schematics • Schematic symbols show components in circuit drawings • Schematic diagrams use symbols, lines to connect components Goodheart-Willcox Publisher Copyright Goodheart-Willcox Co. , Inc. May not be posted to a publicly accessible website.

Conductors • Low-resistance materials – – Copper Aluminum Silver Gold • Configurations vary • American Wire Gauge (AWG) system determines size Goodheart-Willcox Publisher Copyright Goodheart-Willcox Co. , Inc. May not be posted to a publicly accessible website.

Tools Meters urbanbuzz/Shutterstock. com • • Ammeters Voltmeters Ohmmeters Volt-ohmmilliammeters (VOM) • Continuity tester • Oscilloscope science photo/Shutterstock. com Copyright Goodheart-Willcox Co. , Inc. May not be posted to a publicly accessible website.

Control Components • • • Insulators Resistors Variable resistors Switches Diodes Zener diodes • Transistors • Capacitors • Integrated circuits (ICs) • Semiconductors • Sensors Copyright Goodheart-Willcox Co. , Inc. May not be posted to a publicly accessible website.

Insulators • Very high resistance • Do not conduct electricity under normal circumstances • Keep electricity confined to desired path Copyright Goodheart-Willcox Co. , Inc. May not be posted to a publicly accessible website.

Resistors • Limit current flow, divide voltage • Most made from carbon • Color-coding system indicates resistor value Goodheart-Willcox Publisher Copyright Goodheart-Willcox Co. , Inc. May not be posted to a publicly accessible website.

Variable Resistors • Resistance can be changed • Two terminals and wiper – Wiper changes amount of resistive material between terminals • Represented by arrow Goodheart-Willcox Publisher Copyright Goodheart-Willcox Co. , Inc. May not be posted to a publicly accessible website.

Switches • Open, close circuits • Change flow direction • Characterized by type of switch, number of poles, number of throws – SPST switch – SPDT switch Goodheart-Willcox Publisher Copyright Goodheart-Willcox Co. , Inc. May not be posted to a publicly accessible website.

Diodes • Current flows only one direction • Two electrodes – Anode – Cathode • Current flows in forward bias condition only • Can be used as rectifiers Goodheart-Willcox Publisher Copyright Goodheart-Willcox Co. , Inc. May not be posted to a publicly accessible website.

Zener Diodes • • Wired in reverse bias Block current until voltage reaches certain level Keep voltage at constant level Used as voltage regulators Copyright Goodheart-Willcox Co. , Inc. May not be posted to a publicly accessible website.

Transistors • Used as solid state switches, amplifiers • Perform switching function without moving parts • Bipolar transistors have three junction points – Emitter – Base – Collector • Can also be used as amplifiers Copyright Goodheart-Willcox Co. , Inc. May not be posted to a publicly accessible website.

NPN and PNP Transistors Goodheart-Willcox Publisher Copyright Goodheart-Willcox Co. , Inc. May not be posted to a publicly accessible website.

Capacitors • Quickly store, discharge electricity • Smooth out voltage variations • Two conductive plates separated by dielectric • Ceramic disc, electrolytic • Maintain charge long after power source removed Goodheart-Willcox Publisher Copyright Goodheart-Willcox Co. , Inc. May not be posted to a publicly accessible website.

Integrated Circuits (ICs) • Multiple electrical circuits etched into thin layer of silicon • Dot or notch on outside of chip used for orientation • Can be sensitive to static • Common example 555 timer Goodheart-Willcox Publisher Copyright Goodheart-Willcox Co. , Inc. May not be posted to a publicly accessible website.

Semiconductors • Materials with conductive capabilities between conductors, insulators • Silicon common type • Used in – Transistors – Diodes – Solar panels – Integrated circuits Copyright Goodheart-Willcox Co. , Inc. May not be posted to a publicly accessible website.

Sensors • Create electrical signal based on environmental conditions • Signal changes as environmental condition change • Electronic thermostats Copyright Goodheart-Willcox Co. , Inc. May not be posted to a publicly accessible website.

Control Systems • Open systems – Requires manual adjustment – Dimmer switch • Closed systems – Built-in feedback – Sensor that turns off furnace Copyright Goodheart-Willcox Co. , Inc. May not be posted to a publicly accessible website.

Output Components • Use electricity to perform task • Lamps – Incandescent – Gas discharge – Fluorescent – Compact fluorescent – Light-emitting diode • Motors Copyright Goodheart-Willcox Co. , Inc. May not be posted to a publicly accessible website.

Incandescent Lamps • Current flow causes tungsten filament to become so hot it glows • Air inside glass globe removed, sometimes replaced with argon • Traditional bulbs being phased out Yegor Korzh/Shutterstock. com Copyright Goodheart-Willcox Co. , Inc. May not be posted to a publicly accessible website.

Gas Discharge Lamps • Ionized glass, free electrons cause gas to glow, create light – Neon lamps one example • Resistor placed in series with light to limit current flow Copyright Goodheart-Willcox Co. , Inc. May not be posted to a publicly accessible website.

Fluorescent Lamps • Long glass tube coated on inside with phosphorous, filled with inert gas, mercury • Electrical current passes through mercury causes ultraviolet light, causes phosphorous to glow • Use less electricity than incandescent lamps Copyright Goodheart-Willcox Co. , Inc. May not be posted to a publicly accessible website.

Compact Fluorescent Lamps (CFLs) • Work on same principle as fluorescent lamps • Fit in standard light socket • Use about 75% less energy, last up to ten times longer than incandescent lamps Jonathan Vasata/Shutterstock. com Copyright Goodheart-Willcox Co. , Inc. May not be posted to a publicly accessible website.

Light-Emitting Diode (LED) Lamps • Semiconductor material wired in forward biased position • Forward biased direct current passes through semiconductor in LED casing, light is emitted • Low cost, efficient, long-lasting Goodheart-Willcox Publisher Copyright Goodheart-Willcox Co. , Inc. May not be posted to a publicly accessible website.

Motors • Convert electrical energy into mechanical energy • Electromagnet spins until north pole lines up with south pole of permanent magnet • Polarity of electromagnet reverses, keeps rotating Copyright Goodheart-Willcox Co. , Inc. May not be posted to a publicly accessible website.

Component Platforms • • Link components together Circuit boards Solderless breadboards Electronic circuit simulation Copyright Goodheart-Willcox Co. , Inc. May not be posted to a publicly accessible website.

Circuit Boards • Printed circuit boards (PCBs) • Copper track laid on fiberglass • Components soldered to copper track Trombax/Shutterstock. com Copyright Goodheart-Willcox Co. , Inc. May not be posted to a publicly accessible website.

Solderless Breadboards • Ideal for – Experimentation – Testing circuits before construction • Components, leads can be added, removed as no soldering required Goodheart-Willcox Publisher Copyright Goodheart-Willcox Co. , Inc. May not be posted to a publicly accessible website.

Electronic Circuit Simulation • Simulate circuitry performance without building circuit • Components laid out on screen • Software shows how circuits will work • Problems can be identified early Copyright Goodheart-Willcox Co. , Inc. May not be posted to a publicly accessible website.

Components in Use Goodheart-Willcox Publisher Copyright Goodheart-Willcox Co. , Inc. May not be posted to a publicly accessible website.

Troubleshooting • To troubleshoot – Test voltage – Test for continuity – Test that diode conducts in forward bias, not reverse – Test LEDs by directly applying voltage Goodheart-Willcox Publisher Copyright Goodheart-Willcox Co. , Inc. May not be posted to a publicly accessible website.

Reverse Engineering • Ethical factors – Engineers take apart and study components, ICs, system to repair, recreate, or improve – Engineers must ensure patents on original device not violated or someone else’s work stolen Copyright Goodheart-Willcox Co. , Inc. May not be posted to a publicly accessible website.

Electrical Engineering in Action • Hybrid cars – Combine internal combustion engine, batteries – Regenerative braking – Increased fuel mileage Goodheart-Willcox Publisher Copyright Goodheart-Willcox Co. , Inc. May not be posted to a publicly accessible website.