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(A) the amount or volume of electron flow in a circuit.
(V) the potential difference between electrical charges on either side of an electrical device. The electrical force required to push electrons through a circuit.
The resistance (R) in electrical circuits that oppose the flow of electrons
The measurement of the total amount of electricity needed to operate a component. Measured by multiplying volts by amps.
The flow of electrons under minimal resistance
Control the flow of electrons in a circuit by "resisting" the flow
an electronic device that holds a charge for a period of time
Prevents a circuit from receiving more current than it is designed to hold
materials that easily allow the flow of electrons
materials that resist the flow of electrons
materials with the ability to conduct electrical flow but normally resist the flow
serves as a gateway or switch. Can be "on" or "off".
allows electrical flow in only one direction
electrons have found a second path to flow, normally to ground
electrons can flow from point A to point B directly, switch is closed.
electrons cannot flow from point A to point B because switch is "Open"
AC (Alternating Current)
Provides electrical power to our homes and businesses. In a circuit it can travel in both directions. AC current coming into your home is rated at 110/115 volts Cycles at 60 hertz (60 cycles per second)
DC (Direct Current)
Provides electrical power to computers, radios, etc. In a circuit, electrons flow only in one direction. DC is created by transforming AC to DC by means of a rectifier. A transformer changes the ratio of current to voltage. (Transforms 120 volts to 12 volts)
transforms AC to DC
There is a direct relationship between voltage and current. If voltage increases, amperage increases; if voltage decreases, amperage decreases. There is an inverse relationship between resistance and voltage and current. As resistance decreases, either current or voltage increases. R=E/I R=resistance(Ohms), E=Voltage(V), I=Current(A)
- Receives 100/115 volts input from the wall plug. Uses a rectifier to convert AC to DC.
- Uses a transformer to reduce voltages from 120 to +5, -5, +12, -12 volts. The Power Supply provides voltage for all devices inside the computer. The monitor is not inside the computer case and has a direct plug to an AC outlet. Power Supplies are rated in Watts.(200w, 250w, 300w, etc.)
AT Power Supply
Provides: +5, -5, +12, -12 volts. There are 2 power connectors to the motherboard commonly named P8 and P9.
ATX Power Supply
- Created to support the Pentium CPU. Provides: +3.3, -3.3, +5, -5, +12, and -12 volts.
- There is only 1 power connector to the motherboard, commonly called P1.
Electrostatic Discharge (ESD)
Occurs when electricity is passed from one object to another, not a normal path. When you touch something and get a shock, that is ESD. ESD damage is caused by improper handling of components during installation and/or failure to properly ground the computer and the technician.
occur from small incidents of Electrostatic Discharge (ESD). Evidence of damage is not easily detected and usually appears as a loss of data or program crashes inadvertently.
occurs when Electrostatic Discharge (ESD) causes damage to transistors. These transistors may pass tests during initial installation, but will eventually fail or cause poor system performance. Caused by improper handling of components and failure to maintain a proper ground.
occurs when static shocks are excessive (>3000 volts). They cause immediate problems and are easier to detect because of the complete failure of the component.
Radio Frequency Interference (RFI)
- Occurs when electrons pass through the outer coatings of electrical cables/wires and pass into other cables/wires. Power cords and cords for florescent lighting can cause RFI.
- When installing network cabling in ceilings and cable ways, it is important to prevent the networkcable from coming in contact with electrical wires or to pass over the top of florescent light fixtures. Speakers, electric pencil sharpeners, florescent desk lamps, and even telephones can cause RFI damage.
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