Electrical Engineering

2. 8 Electrical Engineering

3. 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.

4. 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

5. 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

6. 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

7. Electricity on the Atomic Level • Electrons, protons, neutrons • Valence shell • Electron movement • Electrically charged atoms are called ions Goodheart-Willcox Publisher

8. 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

9. 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

10. Sources of Electricity • Some form of energy is converted into electrical energy • Three sources of electricity • Magnetism • Chemical action • Solar cells

11. Law of Conservation of Energy • States that energy cannot be created or destroyed • Energy can only be converted from one form to another

12. 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

13. 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

14. 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

15. 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

16. 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

17. 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

18. 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

19. 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

20. 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

21. 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

22. Basic Circuits • Series circuits • Parallel circuits • Series-parallel combination circuits

23. 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

24. 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

25. 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

26. 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

27. Circuit Components • Each component must be understood • Understanding is necessary for design and troubleshooting • Three main types of components • Conductors • Control components • Output components

28. Conductors • Materials have low resistance • Copper • Aluminum • Silver • Gold • Different configurations • American Wire Gauge (AWG) system determines size

29. Transistors Capacitors Integrated circuits (ICs) Semiconductors Sensors Control Components • Insulators • Resistors • Variable resistors • Switches • Diodes • Zener diodes

30. 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

31. Resistors • Limit current flow and divide voltage • Most are made from carbon • Color coding system marks the value of resistors Goodheart-Willcox Publisher

32. 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

33. 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

34. 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

35. 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

36. 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

37. NPN and PNP Transistors Goodheart-Willcox Publisher

38. 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

39. 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

40. 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

41. Sensors • Create an electrical signal based on environmental conditions • Signal changes as environmental conditions change • Common example is electronic thermostats

42. Output Components • Incandescent lamps • Gas discharge lamps • Fluorescent lamps • Compact fluorescent lamps (CFLs) • Light-emitting diode (LED) lamps • Motors

43. 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

44. 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

45. 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

46. 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

47. 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

48. 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

49. Component Platforms • Circuit boards • Solderless breadboards • Electronic circuit simulation

50. Circuit Boards • Commonly known as printed circuit boards (PCBs) • Copper track laid on fiberglass • Electronic components are soldered to copper track