1. CHAPTER 7 ELECTRICITY AND MULTIMETERS Suraya Alias

2. Understanding Concept Electricity is energy UnitDefinition and MeasurementComputer Example Volt (measures potential difference) - Known as V (110V), are measured by finding the potential difference between the electrical charges on either side of an electrical device in an electrical system An AT power supply provides four separate voltages: +12V, -12V, +5V and -5V. An ATX or BTX power supply provides these voltages and +3.3V as well Amp or amperes (measures electrical current) -Known as A (1.5A). Amps are measured by placing an ammeter in the flow of current and measuring the current 17 inch monitor requires less than 2 A to operate. A small laser printer uses about 1 A. A CD-ROM dives uses about 1 A.

3. Understanding Concept UnitDefinition and MeasurementComputer Example Ohm (measures resistance) - Known with symbol Ω (20Ω). Devices are rated according to how much resistance to electrical current they offer. Current can flow in typical computer cables and wires with a resistance of near zero Ω Watt (measures power) -Known as W (20W).Watts are calculated by multiplying volts by amps A computer power supply is rated at 200 to 600 W

4. Understanding Concept VOLTAGE ◦electric potential: the difference in electrical charge between two points in a circuit expressed in volts ◦For example the potential difference between the two points on either side of a bulb ◦Voltage is measured in units called Volts (V)

5. Understanding Concept AMPS ◦Current is the volume of electrons (electricity) that flows through an electrical system ◦It is measured using Amperes (A) or amps

6. Understanding Concept OHMS ◦Electrical resistance is measured in ohms ◦Resistance in an electrical system is a property that opposes the flow of electricity for example a resistor ◦As electrical resistance increases, the flow of electrons decreases and vice versa

7. Understanding Concept WATTAGE ◦Total amount of power needed to operate an electrical device ◦It is measured in watts (W) ◦Can be calculated using formula (W = V x A) ◦For example 120v X 5 amps is 600 watts