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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…

  5. Measures of Electricity

  6. Voltage • Electrical force created by the potential difference in charge • Measured in units called volts

  7. Voltage

  8. Amps • Ampere = unit of measurement for electrical current

  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

  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) • 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) • 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

  14. Computer Power Supply

  15. Hot, Neutral, and Ground

  16. Hot, Neutral, and Ground • 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

  17. Hot, Neutral, and Ground

  18. Hot, Neutral, and Ground

  19. Some Common Electronic Components

  20. Materials Used to Make Electronic Components • Conductors • Insulators • Semiconductors

  21. 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

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

  23. 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

  24. Using a Ground Bracelet

  25. Using a Ground Bracelet and a Ground Mat

  26. Using Static Shielding Bags

  27. 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

  28. Surge Protection andBattery Backup • Devices that filter AC input • Surge suppressors (or surge protectors) • Power conditioners • Uninterruptible power supply (UPS) • Also provides backup power

  29. 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

  30. Uninterruptible Power Supply

  31. 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

  32. UPS Manufacturers

  33. 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

  34. 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

  35. AT Form Factor

  36. ATX Form Factor

  37. NLX Form Factor

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

  39. Desktop Cases

  40. Minitower Cases

  41. Tower and Desktop Cases

  42. Case and Power Supply Vendors

  43. 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

  44. 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

  45. A Multimeter

  46. 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

  47. Measuring Voltage on an AT Motherboard

  48. Measuring Voltage Output to an AT Motherboard

  49. Measuring Voltage Output to an AT Motherboard

  50. Measuring Voltage Output to an ATX Motherboard

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