A basic electromagnet consisting of a wire wrapped coil and a magnet can be used to both drive the system (Voice Coil) measure the velocity of the system (Velocimeter).
When the electromagnet is used to drive the system, it is called a Voice Coil. When an external alternating current is introduced into the coil, the varying current in an existing magnetic field induces a force.
When the electromagnet is used to measure the velocity of the coils motion relative to the magnet, it is called a Velocimeter. When the coil moves relative to the magnetic field, a voltage is induced in the coil that is proportional to the relative velocity of the coil's motion within the magnetic field.
This section is divided into three areas: