The Fundamentals of Electricity
Personal Computer systems are powered by the same type of power produced by batteries, which work by generating a voltage at a constant level by means of a controlled chemical reaction. This type of power is known as Direct Current (DC) and is different from the type of power that is supplied to the homes and businesses by electricity suppliers. The type of power supplied to home and business is called Alternating Current (AC). The difference between AC and DC power is that with AC the voltage constantly varies. In order for a computer system to receive the correct type of power and voltage it must be changed from AC to DC by the computer's power supply.
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Next: Alternating Current