Chapter Four

Anatomy of a Flashlight

Flashlights are useful for numerous tasks, of which reading under the covers and sending coded messages are only the two most obvious. The common household flashlight can also take center stage in an educational show-and-tell of the ubiquitous stuff known as electricity.

Electricity is an amazing phenomenon, managing to be pervasively useful while remaining largely mysterious, even to people who pretend to know how it works. Fortunately, we need to understand only a few basic concepts to comprehend how electricity is used inside computers.

The flashlight is certainly one of the simpler electrical appliances found in most homes. Disassemble a typical flashlight and you’ll find that it consists of one or more ...

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