Changes

An '''electromagnet''' is a device that generates a [[magnetic field]] when supplied with an [[electrical current]].<ref name=britannica>[https://www.britannica.com/science/electromagnet Electromagnet] from britannica.com</ref> It is often composed of a core of magnetic material (such as [[iron]]) surrounded by a coil of wire as a [[solenoid]]. The magnetic field created depends on the electrical current flowing through the coil, meaning that the strength of the magnetic field can be varied, the direction reveresed and unlike normal magnets, the magnetic field can be turned off. Electromagnets have a wide variety of uses, ranging from actuators and [[relays]] to [[MRI]] machines.<ref name=universetoday>[https://www.universetoday.com/39295/uses-of-electromagnets/ Uses of electromagnets] from universetoday.com</ref> The strongest electromagnet has a field strength of 45 Tesla.<ref>[https://nationalmaglab.org/about/around-the-lab/meet-the-magnets/meet-the-45-tesla-hybrid-magnet Meet the 45 Tesla Hybrid Magnet] from nationalmaglab.org</ref>

An '''electromagnet''' is a device that generates a [[magnetic field]] when supplied with an [[electrical current]].<ref name=britannica>[https://www.britannica.com/science/electromagnet Electromagnet] from britannica.com</ref> It is often composed of a core of magnetic material (such as [[iron]]) surrounded by a coil of wire as a [[solenoid]]. The magnetic field created depends on the electrical current flowing through the coil, meaning that the strength of the magnetic field can be varied, the direction reversed and unlike normal magnets, the magnetic field can be turned off. Electromagnets have a wide variety of uses, ranging from actuators and [[relays]] to [[MRI]] machines.<ref name=universetoday>[https://www.universetoday.com/39295/uses-of-electromagnets/ Uses of electromagnets] from universetoday.com</ref> The strongest electromagnet has a field strength of 45 Tesla.<ref>[https://nationalmaglab.org/about/around-the-lab/meet-the-magnets/meet-the-45-tesla-hybrid-magnet Meet the 45 Tesla Hybrid Magnet] from nationalmaglab.org</ref>

==History==

==History==

where ''ΔL'' is a length element in the loop, ''μ'' is the permeability and <math display="inline">B_\parallel</math> is the component of the magnetic field parallel to ''ΔL''. In the limit of ''ΔL'' going to 0, this can be rewritten as an [[integral]],

where ''ΔL'' is a length element in the loop, ''μ'' is the permeability and <math display="inline">B_\parallel</math> is the component of the magnetic field parallel to ''ΔL''. In the limit of ''ΔL'' going to 0, this can be rewritten as an [[integral]],

:<math>

:<math>

\int \vec{B} \dot \mathrm{d}\vec{l} = \mu I

\int \vec{B} \cdot \mathrm{d}\vec{l} = \mu I

</math>

</math>

Ampere's law can be used to derive the magnetic field of a straight wire. A straight wire has [[cylinder|cylindrical]] [[symmetry]], so it is expected the magnetic field will reflect this. It will therefore not have any component parallel to the wire. In fact the field will be circular, centred on the wire and parallel to the line element ''ΔL'' at any point. This means the field created is,<ref>[http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/magcur.html#c3 Magnetic Field of Current] from hyperphysics.phy-astr.gsu.edu</ref>

Ampere's law can be used to derive the magnetic field of a straight wire. A straight wire has [[cylinder|cylindrical]] [[symmetry]], so it is expected the magnetic field will reflect this. It will therefore not have any component parallel to the wire. In fact the field will be circular, centred on the wire and parallel to the line element ''ΔL'' at any point. This means the field created is,<ref>[http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/magcur.html#c3 Magnetic Field of Current] from hyperphysics.phy-astr.gsu.edu</ref>

B = \mu nI

B = \mu nI

</math>

</math>

When cooled down to low temperatures, the coil may become [[superconductor|superconductor]] meaning it can carry a very large current. Since a larger current means a larger field, superconducting electromagnets are used when the large magnetic fields are required.  

When cooled down to low temperatures, the coil may become [[superconductor|superconductor]] meaning it can carry a very large current. Since a larger current means a larger field, superconducting electromagnets are used when the large magnetic fields are required.

==Applications==

==Applications==

*[[Magnetic resonance imaging]] (MRI) machines and mass spectrometers

*[[Magnetic resonance imaging]] (MRI) machines and mass spectrometers

*Induction heating

*Induction heating

*[[Particle accelerator]]

*[[Particle accelerator]]s[[File:Superconducting Magnets J-PARC.jpg|thumb|alt=Superconducting magnets used at the LHC at CERN|right|205px|[[Superconductor|Superconducting]] magnets used at the [[Large Hadron Collider|LHC]] at [[CERN]].]]

*Magnetic levitation such as Maglev trains

*Magnetic levitation such as Maglev trains

 

[[Solenoid]]s consist of a coil of wire enveloping a magnetic core, often composed of [[iron]].<ref name=universetoday/> Solenoids generate an almost uniform field in their centre making them useful in certain scientific experiments. They can also be used to control the movement of a component such as in fuel injectors. [[Superconductor|Superconducting]] magnets are able to generate fields on the order of 10-20 [[Tesla]], 150,000 times stronger than the Earth's magnetic field. They are often used in [[particle accelerator]]s such as the [[Large Hadron Collider]] at [[CERN]] which uses magnets that produce 8.3 Tesla using a current of 11,080 [[Amp]]s.<ref>[https://home.cern/about/engineering/pulling-together-superconducting-electromagnets Pulling together: Superconducting electromagnets] from home.cern</ref> Superconducting magnets are also used in [[Magnetic resonance imaging|MRI machine]]s, and typically produce a field between 0.5-2.0 Tesla.<ref>[https://science.howstuffworks.com/mri1.htm How MRI Works] from science.howstuffworks.com</ref> There are also more theoretical applications such as [[ion]] propulsion systems on spacecraft.<ref name=universetoday/>

[[Solenoid]]s consist of a coil of wire enveloping a magnetic core, often composed of [[iron]].<ref name=universetoday/> Solenoids generate an almost uniform field in their centre making them useful in certain scientific experiments. They can also be used to control the movement of a component such as in fuel injectors. [[Superconductor|Superconducting]] magnets are able to generate fields on the order of 10-20 [[Tesla]], 150,000 times stronger than the Earth's magnetic field. They are often used in [[particle accelerator]]s such as the [[Large Hadron Collider]] at [[CERN]] which uses magnets that produce 8.3 Tesla using a current of 11,080 [[Amp]]s.<ref>[https://home.cern/about/engineering/pulling-together-superconducting-electromagnets Pulling together: Superconducting electromagnets] from home.cern</ref> Superconducting magnets are also used in [[Magnetic resonance imaging|MRI machine]]s, and typically produce a field between 0.5-2.0 Tesla.<ref>[https://science.howstuffworks.com/mri1.htm How MRI Works] from science.howstuffworks.com</ref> There are also more theoretical applications such as [[ion]] propulsion systems on spacecraft.<ref name=universetoday/>  

==References==

==References==