page_title: Electromagnetic coil
section_title: Transducer coils
hierarchical_section_title: Electromagnetic coil / Types of coils / Transducer coils
caption_attribution_description: English: Metal detecting in progress on a Time Team dig This was added from the site called flickr.com under the name portableantiquities. See source for details.
context_page_description: An electromagnetic coil is an electrical conductor such as a wire in the shape of a coil, spiral or helix. Electromagnetic coils are used in electrical engineering, in applications where electric currents interact with magnetic fields, in devices such as electric motors, generators, inductors, electromagnets, transformers, and sensor coils. Either an electric current is passed through the wire of the coil to generate a magnetic field, or conversely an external time-varying magnetic field through the interior of the coil generates an EMF in the conductor.
  A current through any conductor creates a circular magnetic field around the conductor due to Ampere's law. The advantage of using the coil shape is that it increases the strength of magnetic field produced by a given current. The magnetic fields generated by the separate turns of wire all pass through the center of the coil and add to produce a strong field there. The more turns of wire, the stronger the field produced. Conversely, a changing external magnetic flux induces a voltage in a conductor such as a wire, due to Faraday's law of induction.
context_section_description: These are coils used to translate time-varying magnetic fields to electric signals, and vice versa. A few types:
  Sensor or pickup coils - these are used to detect external time-varying magnetic fields
  Inductive sensor - a coil which senses when a magnet or iron object passes near it
  Recording head - a coil which is used to create a magnetic field to write data to a magnetic storage medium, such as magnetic tape, or a hard disk. Conversely it is also used to read the data in the form of changing magnetic fields in the medium.
  Induction heating coil - an AC coil used to heat an object by inducing eddy currents in it, a process called induction heating.
  Loop antenna - a coil which serves as a radio antenna, to convert radio waves to electric currents.
  Rogowski coil - a toroidal coil used as an AC measuring device
  Musical instrument pickup - a coil used to produce the output audio signal in an electric guitar or electric bass.
  Flux gate - a sensor coil used in a magnetometer
  Magnetic phonograph cartridge - a sensor in a record player that uses a coil to translate vibration of a needle to an audio signal in playing vinyl phonograph records.
  There are also types of coil which don't fit into these categories.
caption: The sensor coil of a metal detector.
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