Microphones can be classified by the method they use to convert acoustical energy in to electrical coil mics, commonly called “dynamic” mics work like speakers, only in reverse. The sound pressure moves the diaphragm, which pushes a coil through a magnetic field and generates mics work more like a guitar string on an electric guitar, in that the vibration of the ribbon itself, over the magnet, generates the mics, usually called “condensers” have two diaphragms, just as capacitors do. The charge on the capacitor is determined by the distance between the diaphragms. As sound pressure deforms the flexible diaphram, the capacitance changes and produces electricity. Since the diaphragm needs electricity to act as a capacitor, these mics all require power to operate.