Uses of solenoid

Electromagnetic solenoids find uses all over the world. They're in hotel door locks, water-pressure valves in air conditioning systems, MRI machines, hard disk drives, speakers, microphones, power plants, and cars. You can hardly swing a bat without hitting a solenoid. Speakers and microphones, for example, both contain solenoids. In fact, a speaker and microphone are pretty much exactly the same thing in reverse of each other. A speaker takes electrical signals and runs it through a solenoid to create motion; that motion drives the speaker and creates a sound. A microphone does the opposite; your voice pushes the solenoid back and forth, and that motion of the solenoid creates an electrical signal that can be used to create the sound elsewhere. Without solenoids, we wouldn't be able to record or reproduce sound at all.