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 Dirtmeister's Science Lab on Circuits
 What do flashlights, digital clocks, and your portable pocket stereo all have in common? They all run on electricity! But in order for electricity to do its thing, it must travel through a circuit. You can think of a circuit as a pathway through which electricity can travel. Circuits can be as simple as the one that lights your night-light, or as complex as the latest computer chip — but they all work in the same general way. In order for a circuit to function properly, the electricity must leave one end of the power source and return to the opposite end in an unbroken loop, or "circle." In the case of a battery, the electricity leaves the negative (-) end and returns to the positive (+) end. In a wall outlet, there is also a positive end and a negative end — the two holes into which the two prongs of a plug fit. In the early days of electricity, when Thomas Edison was busy working on his lightbulb, all circuits were simple and generally followed a straight-line path. These types of circuits are known as series circuits, and are the same systems used by most holiday tree lights. Many circuits can get really complicated. There are parallel, switched, integrated, and fused circuits. But no matter how you stack it, circuits are still a circle of electricity! To see how a series circuit works — and to discover why you must "know the flow" of your battery to light a lightbulb — try my Science Lab.

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