1. A+ Computer Repair Lesson 9 Problems Causing Power Events

2. Do Now List all the items you use that require the use of electricity.

3. Objectives List and define common external power problems Describe electrostatic discharge Define line noise and explain the problems that this can cause

4. Common External Power Problems Improper grounding Power surges Power spikes or transients Power sags or brownouts OscillationsBlackouts

5. Electrostatic Discharge An electrostatic discharge (ESD) occurs when one material carrying an electrostatic charge transfers [because of the force of attraction] that charge to another material across a potential voltage difference.

6. ESD! An electrostatic discharge can also occur between you and a computer if your body is carrying an electrostatic charge and comes into contact with a computer's motherboard or components. Electrostatic discharge can affect a computer immediately or cause long term system degradation.

7. Electromagnetic Interference (EMI) Electromagnetic Interference (EMI ) occurs when magnetic fields generated by [electric] current-conducting wires in one circuit influence neighboring magnetic fields.

8. Radio Frequency Interference (RFI) Radio frequency line noise (RFI) occurs in a computer and begins operating erratically because it is picking up radio transmissions from nearby electrical wires or devices. RFI coming from a video monitor or hard disk drive can be enough to create computer system errors.

9. Improper Grounding Proper grounding affects voltage, stability, and is critical to personal safety. Any time that a computer is not properly grounded—an outlet is not providing a wire connection to a ground—the computer poses an electrical hazard and could shock a user. When a user is shocked by a computer, the user has become the ground.

10. Power Surges A power surge is a large, unexpected, and sudden increase in electric voltage. A surge can last for up to several seconds. Consequences of electrical surges can be severe and consist of lockups, a loss of memory, problems in retrieving data, altered data, garbling, damaged or destroyed equipment.

11. Power Spikes Also called transients, a spike is a sudden, high-powered, voltage overload. Spikes last briefly—between.5 and 100 microseconds. When a spike occurs, a power line is hit with anywhere from 240 to several thousand volts. A spike is the equivalent of an electric tidal wave entering equipment through AC wiring and network, serial, or telephone lines.

12. Power Sags Also called brownouts, sags occur when voltage falls 80% below normal capacity. Sags commonly occur during hours of peak use: when consumer power use is high, circuits become overloaded, and voltage decreases. Usually, when your lamps flicker faintly, a brownout or sag has occurred.

13. Consequences of Oscillations More commonly called harmonic distortion, oscillations are secondary signals that occur on top of the 60-Hz waveform. Severe harmonic distortion can disrupt the operation of a computer system.

14. What are the potential consequences of blackouts?

15. Also called a power outage, a blackout is a complete loss of electrical power. Blackouts usually result from storms or power company equipment failure. A power outage during computer operations can lead to data loss or corruption.