A microphone is a transducer which converts sound energy to electrical signals. It works opposite to a speaker. Microphones are available in different shape and sizes. Depending on the application, a microphone may use different technologies to convert sound to electrical signals.
Electret Condenser Microphone, as the name suggests is a parallel plate capacitor and works on the principle of a variable capacitance. It consists of two plates, one fixed (called the back plate) and the other moveable (called Diaphragm) with a small gap between them. An electric potential charges the plate. When sound strikes the diaphragm it starts moving, thereby changing the capacitance between the plates which in turn results in a variable electric current to flow.
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