How Does an Electric Smoke Detector Beep?
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Basics
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Smoke detectors are made of electrical wiring, an alarm of some type, a speaker, plastic covering and radiation. That's right, there is a small amount of radiation sealed inside a smoke detector. It is stressed that the radiation compartment never be opened. There is approximately 0.1 gram of a radioactive element in the sealed area. It is named americium.
The Connection
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How all of this works together is a good question. The smoke detector is basically a looped circuit, except that there is a gap that can keep the circuit from being complete. The gap has a metal plate on each end. If these two plates could connect in some way, the circuit would close and allow current to flow. When the current flows, the alarm does not sound. It is the absence of the full connection that makes the alarm go off.
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Radiation
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The radiation is what keeps the current moving through the empty space between the two metal plates. The radiation gives off alpha particles, or helium atoms. These particles move into the open space and push electrons away from air molecules that are in the area. The electrons connect together and create a circuit that connects the two metal plates, completing the current. Smoke that makes its way into a smoke detector, neutralizes the electrons and breaks the circuit. Once the current no longer flows, it sets off the alarm, and the speaker sends the blaring beep down as a warning.
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