Power Supply
A power supply is a device that provides electricity which then goes to an electrical load. The power supply is mainly used to convert one form of electricity to another form because of this power supplies are sometimes refereed to as electric power converters. Some are used for separate devices and are more discrete whereas others are put into larger devices, e.g. latter include power supplies that are found in desktop PC's and other devices.
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Wattage is the amount of power that the power supply can actually output to different components and devices. The power supply converts a 220 -230 volt alternating current into a steady low voltage direct current which is only usable and rated by the number of watts that are generated. There are many different power supplies that have different wattage. Depending on how much power each component needs makes it depend on what wattage of a power supply is needed to be added to a PC build.
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Power supply efficiency is the amount of power that is given out to each internal component, which is divide by the amount drawn from the mains. For example a 50% efficient power supply unit that has to give out 50 watts of power to a PC that will receive 100 watts from the mains and the national grid, but the extra 50 watts is lost as a type of waste energy known as heat.
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Modularisation is a method that is used to reduce the complexity of a system, this is done by taking the system apart into separate parts to make it easier to manage and use, e.g. a business system.