One Size Does Not Fit All
Like everything else in our high-tech world, power supplies come in myriad sizes and shapes; witness this table full of different units from Sparkle Power Inc. (www.sparklepower.com).
Laptops use an external power supply, called a "power adapter" or "power brick." It converts AC to a single DC voltage that goes to the laptop's internal power supply, which generates all other required voltages. External adapters are used to reduce the size and weight of the laptop, yet they typically ride along in the laptop case, adding back the weight after all.
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