Magnet keeper

keeper platekeeperkeepers
A magnet keeper, also known historically as an armature, is a bar made from soft iron or steel, which is placed across the poles of a permanent magnet to help preserve the strength of the magnet by completing the magnetic circuit; it is important for magnets that have low magnetic coercivity, such as alnico magnets (0.07T).wikipedia
11 Related Articles

Magnetic circuit

Hopkinson's lawMagnetic Circuitsair gap
A magnet keeper, also known historically as an armature, is a bar made from soft iron or steel, which is placed across the poles of a permanent magnet to help preserve the strength of the magnet by completing the magnetic circuit; it is important for magnets that have low magnetic coercivity, such as alnico magnets (0.07T).

Magnet

permanent magnetmagnetspermanent magnets
A magnet keeper, also known historically as an armature, is a bar made from soft iron or steel, which is placed across the poles of a permanent magnet to help preserve the strength of the magnet by completing the magnetic circuit; it is important for magnets that have low magnetic coercivity, such as alnico magnets (0.07T).

Coercivity

coercive fieldmagnetic coercivitycoercive force
A magnet keeper, also known historically as an armature, is a bar made from soft iron or steel, which is placed across the poles of a permanent magnet to help preserve the strength of the magnet by completing the magnetic circuit; it is important for magnets that have low magnetic coercivity, such as alnico magnets (0.07T).

Alnico

Alnico 5Alnico IIAlnico V
A magnet keeper, also known historically as an armature, is a bar made from soft iron or steel, which is placed across the poles of a permanent magnet to help preserve the strength of the magnet by completing the magnetic circuit; it is important for magnets that have low magnetic coercivity, such as alnico magnets (0.07T).

Neodymium magnet

neodymium magnetsneodymiumSupermagnet
Many magnets do not need a keeper, such as supermagnets, as they have very high coercivities; only those with lower coercivities, meaning that they are more susceptible to stray fields, require keepers.

Earth's magnetic field

geomagnetismgeomagneticgeomagnetic field
In magnets with lower coercivities, the direction in which the magnetic domains are pointing is easily swayed by external fields, such as the Earth's magnetic field or perhaps by the stray fields caused by flowing currents in a nearby electrical circuit.

Bedford Modern School

Bedford Modern School CCFBedford ModernBedford Modern School Boat Club
Clarke was an excellent swimmer and was able to propel himself through the water with a prototype bomb attached to a keeper plate on webbing around his waist.

Cecil Vandepeer Clarke

Major CV ClarkeCecil ClarkeSpigot gun
Clarke was an excellent swimmer and was able to propel himself through the water with a prototype bomb attached to a keeper plate on webbing around his waist.

Pole piece

polepolepiece
A magnet keeper is a specialised pole piece used to temporarily connect the poles of a permanent magnet, to help to preserve the magnetism, and for safety in the case of large and powerful magnets.

Magnetic switchable device

Magnetic basemagnetic clamp
The iron blocks act as keepers by bridging between both poles.