← Things That Run · Lesson 6 of 6
A circuit
A circuit is a loop. Electricity flows from a battery, along a wire, through a bulb and back to the battery. Break the loop anywhere and it stops: that is all a switch does.
Put two bulbs one after another in a single loop and if one breaks, both go out. Give each bulb its own loop from the battery and one can fail while the other stays lit. That is why the lights in a house are wired so that one blown bulb does not put out the rest.
Two bulbs are in one loop, one after the other. One bulb breaks. What happens?
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