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Chapter 4

Chapter 4. Electricity and Power Supplies. You Will Learn…. How electricity is measured How to protect your computer system against damaging changes in electrical power About different form factors and computer cases How to detect and correct power supply problems

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Chapter 4

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  1. Chapter 4 Electricity and Power Supplies

  2. You Will Learn… • How electricity is measured • How to protect your computer system against damaging changes in electrical power • About different form factors and computer cases • How to detect and correct power supply problems • About Energy Star specifications

  3. Electricity: Basic Introduction

  4. Measures of Electricity continued… Page 121

  5. Measures of Electricity

  6. Voltage • Measures potential differences • Electrical force created by the potential difference in electron charge flowing between 2 points • Measured in units called volts • Negative to positive flow • Measures when power is on Voltmeter: Page 122

  7. Voltage

  8. Amps • Ampere = unit of measurement for electrical current • Amps remain constant throughout electrical system • Current: volumn of electrons flowing through an electrical system Ammeter

  9. Relationship Between Voltage and Current • Direct relationship • As the electrical potential difference (voltage) increases, the electrical current increases • As the voltage decreases, the current decreases

  10. Ohms • Standard unit of measurement for electrical resistance • Resistors are devices used in electrical circuits to resist the flow of electricity • As resistance decreases, electricity increases Paragraph Page 124

  11. Relationship Among Voltage, Current, and Resistance • Voltage and current have a direct relationship • When voltage increases, current increases • Resistance has an inverse relationship with voltage and current • As resistance increases, either current or voltage decreases • As resistance decreases, either current or voltage increases (Ohm’s Law) V=I/R or Volts = Amps/Ohms • One volt drives a current of one amp through a resistance of one ohm

  12. Wattage • Total amount of power needed to operate an electrical device • Measured in watts • Calculated by multiplying volts by amps in a system (W = V x A)

  13. AC and DC • AC (alternating current) • Means of sending power over extended distances • Cycles back and forth rather than traveling in only one direction • Most economical way to transmit electricity • DC (direct current) • Travels in only one direction • Type of current required by most electronic devices, including computers • Computer power supplies function as both a transformer and a rectifier Device that changes ratio of current to voltage (reduces voltage to a usable level) Device that converts AC to DC

  14. Computer Power Supply Hertz (Hz):

  15. Power Supply Function Rectifier Chapter questions 2-6

  16. Hot, Neutral, and Ground

  17. Hot, Neutral, and Ground • Hot: inbound current • Neutral: outbound current • Ground: protection for neutral line against short circuits • Short circuit • Occurs when electricity is allowed to flow uncontrolled from hot line to neutral line or from hot line to the ground • Fuse • Designed to prevent too much current from flowing through the circuit • Rated in amps Paragraph 127

  18. Hot, Neutral, and Ground 128

  19. Hot, Neutral, and Ground Receptacle tester

  20. Materials Used to Make Electronic Components • Conductors: easily conducts electricity (gold or copper) • Insulators: resists flow of electricity (glass or ceramic) • Semiconductors: falls between conductors & insulators—ability to conduct electricity when charge is applied (silicon) 129

  21. Some Common Electronic Components Device that can hold electrical charge for period of time & smooth the uneven flow through a circuit Device serves as a gate or switch for electrical signal & can amplify the flow 130

  22. Protecting Your Computer System • General safety precautions • Protecting against electricity • Protecting against electrostatic discharge (ESD or static electricity) and electromagnetic interference (EMI) • Surge protection and battery backup

  23. Protecting Against Electricity • When working inside a computer • Turn off the power • Unplug the computer • Use a ground bracelet 131

  24. Static Electricity • Ground yourself and computer parts, using static control devices or methods • Ground bracelet or static strap • Ground mats • Static shielding bags • Caution: Don’t wear a ground bracelet when working inside a monitor or with high-voltage equipment such as a laser printer

  25. Using a Ground Bracelet

  26. Using a Ground Bracelet and a Ground Mat

  27. Using Static Shielding Bags

  28. Electromagnetic Interference • Caused by the magnetic field produced as a side effect when electricity flows • Radio frequency interference (RFI) can cause problems with radio and TV reception • Use a line conditioner to filter electrical noise causing the EMI 135

  29. Surge Protection andBattery Backup • Devices that filter AC input • Surge suppressors (or surge protectors): protect against sudden changes in power level • Power conditioners • Uninterruptible power supply (UPS) • Also provides backup power Alters power to provide continuous voltage Tips on 136

  30. Uninterruptible Power Supply • Benefits • Condition line for brownouts and spikes • Provide backup power during a blackout • Protect against very high spikes that could damage equipment Spikes: temporary voltage surges Brownouts: temporary voltage reductions

  31. Uninterruptible Power Supply

  32. What to Consider WhenBuying a UPS • Cost • Rating should exceed your total VA or wattage output by at least 25% • Degree of line conditioning • Warranty, service policies, and guarantee

  33. UPS Manufacturers 138

  34. Computer Case and Form Factors • Form factor • Describes the size, shape, and general makeup of a hardware component • Must match for motherboard, power supply, and case

  35. AT ATX (most popular) LPX NLX Backplane systems Most common form factors used on PCs: AT Baby AT ATX Mini-ATX Case, Power Supply, and Motherboard Form Factors

  36. AT Form Factor

  37. ATX Form Factor

  38. NLX Form Factor

  39. Types of Cases • Desktop cases • Tower cases • Minitower • Midsize (most popular) • Full-size • Laptop cases

  40. Desktop Cases

  41. Minitower Cases

  42. Tower and Desktop Cases

  43. Case and Power Supply Vendors

  44. Detecting and Correcting Power Supply Problems • Measuring the voltage of a power supply • Upgrading and installing power supplies • Troubleshooting the power system and power supply

  45. Measuring the Voltage of a Power Supply • Use a multimeter • Before using, tell it three things • Whether to measure voltage, current, or resistance • Whether the current is AC or DC • What range of values it should expect • How to measure voltage • How to measure current • How to measure continuity

  46. A Multimeter

  47. How to Measure the Voltage of a Power Supply • How to measure the power output for AT and ATX motherboards • Procedure for a secondary storage device

  48. Measuring Voltage on an AT Motherboard

  49. Measuring Voltage Output to an AT Motherboard

  50. Measuring Voltage Output to an AT Motherboard

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