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Chapter 22, "The basics of electrical energy," covers electricity and how it relates to the computer. A computer technician does not need to be an electrical engineer, but does need to be able to perform basic tests and to work safely. This chapter provides the reader with background in these issues. | Chapter Overview Electrical power Electrostatic discharge Safety and electrical power Understanding Electricity and Electrical Energy Electricity refers to The form of energy associated with moving electrons and protons The energy made available by the flow of electric charge through a conductor Terminology Terminology (Cont.) Ohm’s Law Ohm’s law states that voltage equals the product of the current times the resistance. Resistance: R=V/I Current: I=V/R Volts: V=IR In these formulas, R = resistance in ohms, V = voltage, and I = current in amperes. Personal Computers and Electrical Power Alternating Current (AC) AC power is man-made, by use of generators. A wire coil inside a generator rotates and produces current that flows from one pole of a magnet to the other, or alternates the direction of the flow. The number of revolutions made by the generator is called its frequency. In the United States, power companies run their systems at 60 turns per second to . | Chapter Overview Electrical power Electrostatic discharge Safety and electrical power Understanding Electricity and Electrical Energy Electricity refers to The form of energy associated with moving electrons and protons The energy made available by the flow of electric charge through a conductor Terminology Terminology (Cont.) Ohm’s Law Ohm’s law states that voltage equals the product of the current times the resistance. Resistance: R=V/I Current: I=V/R Volts: V=IR In these formulas, R = resistance in ohms, V = voltage, and I = current in amperes. Personal Computers and Electrical Power Alternating Current (AC) AC power is man-made, by use of generators. A wire coil inside a generator rotates and produces current that flows from one pole of a magnet to the other, or alternates the direction of the flow. The number of revolutions made by the generator is called its frequency. In the United States, power companies run their systems at 60 turns per second to produce a high voltage of 60 Hz (cycles per second) AC as they rotate. AC Power Uses Three Wires Direct Current (DC) AC is used for transporting low-cost power to users, but a computer’s electronic components require DC power. A PC power supply’s main function is to convert AC into DC. It does this by Using a step-down transformer Using an AC/DC converter DC flows in one direction from one pole (+) to another (-) and thus is said to have polarity. A multimeter is an essential troubleshooting tool for a computer professional. A multimeter measures several aspects of electricity: A multimeter consists of two probes and a multiposition switch to select the type of test. Measuring Electricity AC voltage DC voltage Continuity Resistance Testing AC Power Failure to properly test AC outlets can damage or destroy equipment. When testing an AC power source, check these three things: Is the hot wire sending the correct voltage, and is it wired to the correct pin? Is the neutral wire .
