What makes a speaker a microphone and does this mean that a microphone works as a speaker?
In: Technology
Speakers DO in fact work as microphones. And the othe way around. Just as electric motors can be spun by hand and they’ll output electricity at the other end (working as a dynamo).
It all has to do with electromagnetism. If you have a magnet and a coil of wire around it, if you put electric current through the wire then the wire itself becomes magnetic according to the current you put through it (this is where the electromagnetism comes in) and the two magnets start to move relative to each other, since now we’re dealing with magnetic polarity. Since the sound signal comes as a wave and not a constant electric signal, these two magnets are going to start vibrating in relation to the sound wave (which comes as current and changes the magnetic strength and polarity). That vibration of the two elements moves the speaker’s membrane and air is moved. That movement of air is what we hear. This is what sound is.
BUT! Electromagnetism also works in reverse. If you mechanically move those two elements (the magnet and the wire), this will actually produce current. Current that would otherwise be coming from the other direction. But this time, you’re the one creating the air waves that move the membrane and you reverse the process.
And the same goes for electric motors, except the magnets and the type of current (which in this case is direct current and constant) are set up in such a way that the movement they create provides rotation rather than vibration.
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