Electromagnetic coil

<h2 id="windings-and-taps">Windings and taps</h2>

The wire or conductor which constitutes the coil is called the winding.<a class="footnote-ref" id="fnref:8" href="#fn:8">8</a> The hole in the center of the coil is called the core area or magnetic axis.<a class="footnote-ref" id="fnref:9" href="#fn:9">9</a> Each loop of wire is called a turn.<a class="footnote-ref" id="fnref:10" href="#fn:10">10</a> In windings in which the turns touch, the wire must be insulated with a coating of nonconductive <a href="/facts/Insulation_(electric)/SfSXkrh5">insulation</a> such as plastic or <a href="/facts/Magnetic_wire/WhfRIU4T">enamel</a> to prevent the current from passing between the wire turns. The winding is often wrapped around a coil form made of plastic or other material to hold it in place.<a class="footnote-ref" id="fnref:11" href="#fn:11">11</a> The ends of the wire are brought out and attached to an external circuit. Windings may have additional electrical connections along their length; these are called taps.<a class="footnote-ref" id="fnref:12" href="#fn:12">12</a> A winding that has a single tap in the center of its length is called center-tapped.<a class="footnote-ref" id="fnref:13" href="#fn:13">13</a>
Coils can have more than one winding, insulated electrically from each other. When there are two or more windings around a common magnetic axis, the windings are said to be inductively coupled or magnetically coupled.<a class="footnote-ref" id="fnref:14" href="#fn:14">14</a> A time-varying current through one winding will create a time-varying magnetic field that passes through the other winding, which will induce a time-varying voltage in the other windings. This is called a <a href="/facts/Transformer/EYYfXWrF">transformer</a>.<a class="footnote-ref" id="fnref:15" href="#fn:15">15</a> The winding to which current is applied, which creates the magnetic field, is called the <a href="/facts/Primary_winding/EYYfXWrF">primary winding</a>. The other windings are called <a href="/facts/Secondary_winding/EYYfXWrF">secondary windings</a>.

<h2 id="magnetic-core">Magnetic core</h2>
Many electromagnetic coils have a <a href="/facts/Magnetic_core/yojywmuo">magnetic core</a>, a piece of <a href="/facts/Ferromagnetic/fH3HFnSl">ferromagnetic</a> material like <a href="/facts/Iron/QK1JYy8E">iron</a> in the center to increase the magnetic field.<a class="footnote-ref" id="fnref:16" href="#fn:16">16</a> The current through the coil magnetizes the iron, and the field of the magnetized material adds to the field produced by the wire. This is called a ferromagnetic-core or iron-core coil.<a class="footnote-ref" id="fnref:17" href="#fn:17">17</a> A ferromagnetic core can increase the magnetic field and <a href="/facts/Inductance/oIxj7JxX">inductance</a> of a coil by hundreds or thousands of times over what it would be without the core. A ferrite core coil is a variety of coil with a core made of <a href="/facts/Ferrite_core/f60u8q2g">ferrite</a>, a <a href="/facts/Ferrimagnetic/sMcg7RYt">ferrimagnetic</a> ceramic compound.<a class="footnote-ref" id="fnref:18" href="#fn:18">18</a> Ferrite coils have lower <a href="/facts/Core_loss/yojywmuo">core losses</a> at high frequencies.

<ul><li>A coil with a core which forms a closed loop, possibly with some narrow air gaps, is called a closed-core coil. By providing a closed path for the magnetic field lines, this geometry minimizes the <a href="/facts/Magnetic_reluctance/Q3UeLudY">magnetic reluctance</a> and produces the strongest magnetic field. It is often used in transformers.
<ul><li>A common form for closed-core coils is a toroidal core coil, in which the core has the shape of a <a href="/facts/Torus/J9SkaV1W">torus</a> or doughnut, with either a circular or rectangular cross section. This geometry has minimum <a href="/facts/Leakage_flux/NhAPzcne">leakage flux</a> and radiates minimum <a href="/facts/Electromagnetic_interference/gv3DlKNr">electromagnetic interference</a> (EMI).</li></ul></li>
<li>A coil with a core which is a straight bar or other non-loop shape is called an open-core coil. This has lower magnetic field and inductance than a closed core, but is often used to prevent <a href="/facts/Magnetic_saturation/QvhGEldn">magnetic saturation</a> of the core.</li></ul>
A coil without a ferromagnetic core is called an air-core coil.<a class="footnote-ref" id="fnref:19" href="#fn:19">19</a> This includes coils wound on plastic or other nonmagnetic forms, as well as coils which actually have empty air space inside their windings.

<h2 id="types-of-coils">Types of coils</h2>
Coils can be classified by the <a href="/facts/Frequency/QUSbPaW8">frequency</a> of the current they are designed to operate with:

<ul><li>Direct current or DC coils or electromagnets operate with a steady <a href="/facts/Direct_current/r9MNUx84">direct current</a> in their windings</li>
<li>Audio-frequency or AF coils, inductors or transformers operate with <a href="/facts/Alternating_current/qxICS3xa">alternating currents</a> in the <a href="/facts/Audio_frequency/LzHtINcf">audio frequency</a> range, less than 20 kHz</li>
<li>Radio-frequency or RF coils, inductors or transformers operate with alternating currents in the <a href="/facts/Radio_frequency/aWku7h4R">radio frequency</a> range, above 20 kHz</li></ul>
Coils can be classified by their function:

<h3>Electromagnets</h3>
Main article: <a href="/facts/Electromagnet/3YMYtSMX">Electromagnet</a>

Electromagnets are coils that generate a <a href="/facts/Magnetic_field/Ta8Ev588">magnetic field</a> for some external use, often to exert a mechanical force on something.<a class="footnote-ref" id="fnref:20" href="#fn:20">20</a> or remove existing background fields.<a class="footnote-ref" id="fnref:21" href="#fn:21">21</a> A few specific types:

<ul><li><a href="/facts/Solenoid/4aQLSkjp">Solenoid</a> - an electromagnet in the form of a straight hollow helix of wire</li>
<li>Motor and generator windings - iron core electromagnets on the <a href="/facts/Rotor_(electric)/TJegVHtc">rotor</a> or <a href="/facts/Stator/pKBWvIHI">stator</a> of electric motors and generators which act on each other to either turn the shaft (motor) or generate an electric current (generator)
<ul><li><a href="/facts/Field_winding/J0u1X7gd">Field winding</a> - an iron-core coil which generates a steady magnetic field to act on the armature winding.</li>
<li><a href="/facts/Armature_(electrical_engineering)/BvRwHHWn">Armature</a> winding - an iron-core coil which is acted on by the magnetic field of the field winding to either create torque (motor) or induce a voltage to produce power (generator)</li></ul></li>
<li><a href="/facts/Helmholtz_coil/oX40P29d">Helmholtz coil</a>, <a href="/facts/Maxwell_coil/xSKLDtAS">Maxwell coil</a> - air-core coils which serve to cancel an external magnetic field</li>
<li><a href="/facts/Degaussing/ePx3r3ug">Degaussing</a> coil - a coil used to demagnetize parts</li>
<li><a href="/facts/Voice_coil/0Ugf4567">Voice coil</a> - a coil used in a moving-coil <a href="/facts/Loudspeaker/tqEjnJ2z">loudspeaker</a>, suspended between the poles of a magnet. When the <a href="/facts/Audio_signal/rFSTI9IF">audio signal</a> is passed through the coil, it vibrates, moving the attached speaker cone to create sound waves. The reverse is used in a dynamic <a href="/facts/Microphone/7YWGlXCl">microphone</a>, where sound vibrations intercepted by something like a <a href="/facts/Diaphragm_(acoustics)/fYq3PwtC">diaphragm</a> physically transfer to a voice coil immersed in a magnetic field, and the coil's terminal ends then provide an electric analog of those vibrations.</li></ul>
<h3>Inductors</h3>
Main article: <a href="/facts/Inductor/YnfAXB3x">Inductor</a>
<a href="/facts/Inductor/YnfAXB3x">Inductors</a> or reactors are coils which generate a magnetic field which interacts with the coil itself, to induce a back EMF which opposes changes in current through the coil. Inductors are used as <a href="/facts/Circuit_element/CenJ4IkU">circuit elements</a> in electrical circuits, to temporarily store energy or resist changes in current. A few types:

<ul><li>Tank coil - an inductor used in a <a href="/facts/Tuned_circuit/tzEfI7Hf">tuned circuit</a></li>
<li><a href="/facts/Choke_(electronics)/NPh2C02U">Choke</a> - an inductor used to block high frequency AC while allowing through low frequency AC or DC.</li>
<li><a href="/facts/Loading_coil/xeFAC0DW">Loading coil</a> - an inductor used to add inductance to an antenna, to make it resonant, or to a cable to prevent distortion of signals.</li>
<li><a href="/facts/Transformer_types/dtjHg2rD">Variometer</a> - an adjustable inductor consisting of two coils in series, an outer stationary coil and a second one inside it which can be rotated so their magnetic axes are in the same direction or opposed.</li>
<li><a href="/facts/Flyback_transformer/buYWowyk">Flyback transformer</a> - Although called a transformer, this is actually an inductor which serves to store energy in <a href="/facts/Switching_power_supply/YKcyRBtP">switching power supplies</a> and horizontal deflection circuits for CRT televisions and monitors</li>
<li><a href="/facts/Saturable_reactor/Qmw8LTkj">Saturable reactor</a> - an iron-core inductor used to control AC power by varying the saturation of the core using a DC control voltage in an auxiliary winding.</li>
<li><a href="/facts/Electrical_ballast/wI5HEsbh">Inductive ballast</a> - an inductor used in <a href="/facts/Gas-discharge_lamp/SQPgULuM">gas-discharge lamp</a> circuits, such as <a href="/facts/Fluorescent_lamp/R8SlXCyg">fluorescent lamps</a>, to limit the current through the lamp.</li></ul>

<h3>Transformers</h3>

Main article: <a href="/facts/Transformer/EYYfXWrF">Transformer</a>
A transformer is a device with two or more magnetically coupled windings (or sections of a single winding). A time varying current in one coil (called the <a href="/facts/Primary_winding/EYYfXWrF">primary winding</a>) generates a magnetic field which induces a voltage in the other coil (called the <a href="/facts/Secondary_winding/EYYfXWrF">secondary winding</a>). A few types:

<ul><li><a href="/facts/Distribution_transformer/7oSnQy2w">Distribution transformer</a> - A transformer in an <a href="/facts/Electric_power_grid/RkWPqjmG">electric power grid</a> which transforms the high voltage from the electric <a href="/facts/Power_line/jULhrQNv">power line</a> to the lower voltage used by utility customers.</li>
<li><a href="/facts/Autotransformer/uUFUTD0N">Autotransformer</a> - a transformer with only one winding. Different portions of the winding, accessed with taps, act as primary and secondary windings of the transformer.</li>
<li><a href="/facts/Toroidal_transformer/RfElL6kX">Toroidal transformer</a> - the core is in the shape of a <a href="/facts/Toroid/EzsnyLtR">toroid</a>. This is a commonly used shape as it decreases the leakage flux, resulting in less electromagnetic interference.</li>
<li><a href="/facts/Induction_coil/vyAFgQsU">Induction coil</a> or <a href="/facts/Trembler_coil/TEg7wJYk">trembler coil</a> - an early transformer which uses a vibrating interrupter mechanism to break the primary current so it can operate off of DC current.
<ul><li><a href="/facts/Ignition_coil/S67YvhGb">Ignition coil</a> - an induction coil used in <a href="/facts/Internal_combustion_engine/Ju4BXzj0">internal combustion engines</a> to create a pulse of high voltage to fire the <a href="/facts/Spark_plug/Y9lG10hg">spark plug</a> which initiates the fuel burning.</li></ul></li>
<li><a href="/facts/Balun/T4HUHE9C">Balun</a> - a transformer which matches a <a href="/facts/Balanced_transmission_line/cYlqaPo3">balanced transmission line</a> to an unbalanced one.</li>
<li><a href="/facts/Bifilar_coil/87qNc4UH">Bifilar coil</a> - a coil wound with two parallel, closely spaced strands. If AC currents are passed through it in the same direction, the <a href="/facts/Magnetic_flux/jQMVxrnD">magnetic fluxes</a> will add, but if equal currents in opposite directions pass through the windings the opposite fluxes will cancel, resulting in zero flux in the core. So no voltage will be induced in a third winding on the core. These are used in instruments and in devices like <a href="/facts/Ground_Fault_Interrupter/FoylYWEX">Ground Fault Interrupters</a>. They are also used in low inductance wirewound resistors for use at RF frequencies.</li>
<li><a href="/facts/Audio_transformer/dtjHg2rD">Audio transformer</a> - A transformer used with <a href="/facts/Audio_signal/rFSTI9IF">audio signals</a>. They are used for <a href="/facts/Impedance_matching/0mdy9TAp">impedance matching</a>.
<ul><li><a href="/facts/Hybrid_coil/DfnImpU3">Hybrid coil</a> - a specialized audio transformer with 3 windings used in <a href="/facts/Telephony/2GwTTepw">telephony</a> circuits to convert between <a href="/facts/Two-wire_circuit/j0hbjBtD">two-wire</a> and <a href="/facts/Four-wire_circuit/C3InvEMe">four-wire circuits</a></li></ul></li></ul>

<h3>Electric machines</h3>
<a href="/facts/Electric_machine/0DvFEdCD">Electric machines</a> such as <a href="/facts/Electric_motor/ArD7BGDa">motors</a> and <a href="/facts/Electric_generator/5sATsUGX">generators</a> have one or more windings which interact with moving magnetic fields to convert electrical energy to mechanical energy. Often a machine will have one winding through which passes most of the power of the machine (the <a href="/facts/Armature_(electrical_engineering)/BvRwHHWn">"armature"</a>), and a second winding which provides the magnetic field of the rotating element ( the "field winding") which may be connected by brushes or slip rings to an external source of electric current. In an <a href="/facts/Induction_motor/DgTnMmJM">induction motor</a>, the "field" winding of the rotor is energized by the slow relative motion between the rotating winding and the rotating magnetic field produced by the stator winding, which induces the necessary exciting current in the rotor.

<h3>Transducer coils</h3>

These are coils used to translate time-varying magnetic fields to electric signals, and vice versa. A few types:

<ul><li>Sensor or pickup coils - these are used to detect external time-varying magnetic fields</li>
<li><a href="/facts/Inductive_sensor/IrqGAK55">Inductive sensor</a> - a coil which senses when a magnet or iron object passes near it</li>
<li><a href="/facts/Recording_head/54Jx7ImE">Recording head</a> - a coil which is used to create a magnetic field to write data to a <a href="/facts/Magnetic_storage/QaK6oArm">magnetic storage</a> medium, such as <a href="/facts/Magnetic_tape/wj6IDTR1">magnetic tape</a>, or a <a href="/facts/Hard_disk/kekLSGSE">hard disk</a>. Conversely it is also used to read the data in the form of changing magnetic fields in the medium.</li>
<li><a href="/facts/Induction_heating/a0MswQ0M">Induction heating coil</a> - an AC coil used to heat an object by inducing <a href="/facts/Eddy_current/KvHNx1v7">eddy currents</a> in it, a process called <a href="/facts/Induction_heating/a0MswQ0M">induction heating</a>.</li>
<li><a href="/facts/Loop_antenna/3NlQUkqD">Loop antenna</a> - a coil which serves as a <a href="/facts/Antenna_(radio)/pGlcXBvc">radio antenna</a>, to convert radio waves to electric currents.</li>
<li><a href="/facts/Rogowski_coil/J4U10EHc">Rogowski coil</a> - a toroidal coil used as an AC measuring device</li>
<li><a href="/facts/Pickup_(music_technology)/Aeuuyvhm">Musical instrument pickup</a> - a coil used to produce the output <a href="/facts/Audio_signal/rFSTI9IF">audio signal</a> in an <a href="/facts/Electric_guitar/yNL6qSw4">electric guitar</a> or <a href="/facts/Electric_bass/lbeoAatH">electric bass</a>.</li>
<li><a href="/facts/Flux-gate_magnetometer/dqX9g1og">Flux gate</a> - a sensor coil used in a <a href="/facts/Magnetometer/dqX9g1og">magnetometer</a></li>
<li><a href="/facts/Magnetic_cartridge/pyfetbvl">Magnetic phonograph cartridge</a> - a sensor in a <a href="/facts/Record_player/VcNQRYVT">record player</a> that uses a coil to translate vibration of a needle to an audio signal in playing vinyl <a href="/facts/Phonograph_record/ccuFV9Af">phonograph records</a>.</li></ul>
There are also types of coil which don't fit into these categories.

<h2 id="winding-technology">Winding technology</h2>
Main article: <a href="/facts/Coil_winding_technology/73rEaMnW">Coil winding technology</a>
<h2 id="see-also">See also</h2>
<ul><li><a href="/facts/Hanna_curve/gQygWJvQ">Hanna curve</a></li></ul>

<h2 id="further-reading">Further reading</h2>
<ul><li>Querfurth, William, "Coil winding; a description of coil winding procedures, winding machines and associated equipment for the electronic industry" (2d ed.). Chicago, G. Stevens Mfg. Co., 1958.</li>
<li>Weymouth, F. Marten, "Drum armatures and commutators (theory and practice) : a complete treatise on the theory and construction of drum winding, and of commutators for closed-coil armatures, together with a full résumé of some of the principal points involved in their design; and an exposition of armature reactions and sparking". London, "The Electrician" Printing and Publishing Co., 1893.</li>
<li>"Coil winding proceedings". International Coil Winding Association.</li>
<li>Chandler, R. H., "Coil coating review, 1970–76". Braintree, R. H. Chandler Ltd, 1977.</li></ul>
<h2 id="external-links">External links</h2>

Look up coil or winding in Wiktionary, the free dictionary.

Wikimedia Commons has media related to Electromagnetic coils.

<ul><li><a href="http://www.66pacific.com/calculators/coil_calc.aspx">Coil Inductance Calculator</a> Online calculator for determining the inductance of single-layer and multilayer coils</li>
<li>R. Clarke, "<a href="http://www.ee.surrey.ac.uk/Workshop/advice/coils/">Producing wound components</a> <a href="https://web.archive.org/web/20070707141302/http://www.ee.surrey.ac.uk/Workshop/advice/coils/">Archived</a> 2007-07-07 at the <a href="/facts/Wayback_Machine/nmQ3a6JC">Wayback Machine</a>". Surrey.ac.uk, 2005 October 9</li></ul>

<h2 id="references">References</h2>

<ol>
<li id="fn:1">Stauffer, H. Brooke (2002). NFPA's Pocket Dictionary of Electrical Terms. Jones and Hymel Tucker. p. 36. ISBN 978-0877655992. <a href="978-0877655992" target="_blank">978-0877655992</a> <a href="#fnref:1" class="footnote-back-ref">↩</a></li>
<li id="fn:2">Laplante, Phillip A. (1999). Comprehensive Dictionary of Electrical Engineering. Springer. pp. 114–115. ISBN 978-3540648352. <a href="978-3540648352" target="_blank">978-3540648352</a> <a href="#fnref:2" class="footnote-back-ref">↩</a></li>
<li id="fn:3">Arun, P. (2006). Electronics. Alpha Sciences International Ltd. pp. 73–77. ISBN 978-1842652176. <a href="978-1842652176" target="_blank">978-1842652176</a> <a href="#fnref:3" class="footnote-back-ref">↩</a></li>
<li id="fn:4">Arun, P. (2006). Electronics. Alpha Sciences International Ltd. pp. 73–77. ISBN 978-1842652176. <a href="978-1842652176" target="_blank">978-1842652176</a> <a href="#fnref:4" class="footnote-back-ref">↩</a></li>
<li id="fn:5">Arun, P. (2006). Electronics. Alpha Sciences International Ltd. pp. 73–77. ISBN 978-1842652176. <a href="978-1842652176" target="_blank">978-1842652176</a> <a href="#fnref:5" class="footnote-back-ref">↩</a></li>
<li id="fn:6">Amos, S. W.; Amos, Roger (4 March 2002). Newnes 2002, p. 129. Elsevier. ISBN 9780080524054. <a href="9780080524054" target="_blank">9780080524054</a> <a href="#fnref:6" class="footnote-back-ref">↩</a></li>
<li id="fn:7">Arun, P. (2006). Electronics. Alpha Sciences International Ltd. pp. 73–77. ISBN 978-1842652176. <a href="978-1842652176" target="_blank">978-1842652176</a> <a href="#fnref:7" class="footnote-back-ref">↩</a></li>
<li id="fn:8">Stauffer, H.B. (2005). NFPA's Pocket Dictionary of Electrical Terms. Jones & Bartlett Learning, LLC. p. 273. ISBN 9780877655992. Retrieved 2017-01-07. <a href="9780877655992" target="_blank">9780877655992</a> <a href="#fnref:8" class="footnote-back-ref">↩</a></li>
<li id="fn:9">Amos, S W; Roger Amos (2002). Newnes Dictionary of Electronics. Newnes. p. 191. ISBN 978-0080524054. <a href="978-0080524054" target="_blank">978-0080524054</a> <a href="#fnref:9" class="footnote-back-ref">↩</a></li>
<li id="fn:10">Laplante, Phillip A. (1999). Comprehensive Dictionary of Electrical Engineering. Springer. pp. 114–115. ISBN 978-3540648352. <a href="978-3540648352" target="_blank">978-3540648352</a> <a href="#fnref:10" class="footnote-back-ref">↩</a></li>
<li id="fn:11">Laplante, Phillip A. (1999). Comprehensive Dictionary of Electrical Engineering. Springer. pp. 114–115. ISBN 978-3540648352. <a href="978-3540648352" target="_blank">978-3540648352</a> <a href="#fnref:11" class="footnote-back-ref">↩</a></li>
<li id="fn:12">Laplante, P.A. (1999). Comprehensive Dictionary of Electrical Engineering. Springer Berlin Heidelberg. p. 633. ISBN 9783540648352. Retrieved 2017-01-07. <a href="9783540648352" target="_blank">9783540648352</a> <a href="#fnref:12" class="footnote-back-ref">↩</a></li>
<li id="fn:13">Stauffer, H.B. (2005). NFPA's Pocket Dictionary of Electrical Terms. Jones & Bartlett Learning, LLC. p. 29. ISBN 9780877655992. Retrieved 2017-01-07. <a href="9780877655992" target="_blank">9780877655992</a> <a href="#fnref:13" class="footnote-back-ref">↩</a></li>
<li id="fn:14">Amos, S.W.; Amos, R. (2002). Newnes Dictionary of Electronics. Elsevier Science. p. 167. ISBN 9780080524054. Retrieved 2017-01-07. <a href="9780080524054" target="_blank">9780080524054</a> <a href="#fnref:14" class="footnote-back-ref">↩</a></li>
<li id="fn:15">Amos, S.W.; Amos, R. (2002). Newnes Dictionary of Electronics. Elsevier Science. p. 326. ISBN 9780080524054. Retrieved 2017-01-07. <a href="9780080524054" target="_blank">9780080524054</a> <a href="#fnref:15" class="footnote-back-ref">↩</a></li>
<li id="fn:16">Laplante, Phillip A. (1998). Comprehensive Dictionary of Electrical Engineering. Springer. p. 143. ISBN 978-3540648352. <a href="978-3540648352" target="_blank">978-3540648352</a> <a href="#fnref:16" class="footnote-back-ref">↩</a></li>
<li id="fn:17">Laplante, P.A. (1999). Comprehensive Dictionary of Electrical Engineering. Springer Berlin Heidelberg. p. 346. ISBN 9783540648352. Retrieved 2017-01-07. <a href="9783540648352" target="_blank">9783540648352</a> <a href="#fnref:17" class="footnote-back-ref">↩</a></li>
<li id="fn:18">Laplante, P.A. (1999). Comprehensive Dictionary of Electrical Engineering. Springer Berlin Heidelberg. p. 243. ISBN 9783540648352. Retrieved 2017-01-07. <a href="9783540648352" target="_blank">9783540648352</a> <a href="#fnref:18" class="footnote-back-ref">↩</a></li>
<li id="fn:19">Laplante, P.A. (1999). Comprehensive Dictionary of Electrical Engineering. Springer Berlin Heidelberg. p. 19. ISBN 9783540648352. Retrieved 2017-01-07. <a href="9783540648352" target="_blank">9783540648352</a> <a href="#fnref:19" class="footnote-back-ref">↩</a></li>
<li id="fn:20">Amos, S.W.; Amos, R. (2002). Newnes Dictionary of Electronics. Elsevier Science. p. 113. ISBN 9780080524054. Retrieved 2017-01-07. <a href="9780080524054" target="_blank">9780080524054</a> <a href="#fnref:20" class="footnote-back-ref">↩</a></li>
<li id="fn:21">Hobson, P. J.; et al. (2022). "Bespoke magnetic field design for a magnetically shielded cold atom interferometer". Sci. Rep. 12 (1): 10520. arXiv:2110.04498. Bibcode:2022NatSR..1210520H. doi:10.1038/s41598-022-13979-4. PMC 9217970. PMID 35732872. S2CID 238583775. <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9217970" target="_blank">https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9217970</a> <a href="#fnref:21" class="footnote-back-ref">↩</a></li>
</ol>

Electromagnetic coil open-in-new

Electromagnetic coil