Maxwell coil
Encyclopedia
A Maxwell coil is a device for producing a large volume of almost constant (or constant-gradient) magnetic field
.
set consists of three coils oriented on the surface of a virtual sphere. According to Maxwell's original 1873 design each of the outer coils should be of radius
and distance 
from the plane of the central coil of radius 
. The number of ampere-turns
of each of the smaller coils should equal exactly
of the middle coil.This arrangement removes variations in magnetic field, up to its 6th-order derivative with respect to position, near the centre of the virtual sphere.
A gradient-field Maxwell coil
is essentially the same geometry of the 3-coil configuration above, with the central coil removed to leave only the smaller two coils . If the current in one of the coils is reversed, a uniform-gradient magnetic field is produced near the centre of the two coils.
Magnetic field
A magnetic field is a mathematical description of the magnetic influence of electric currents and magnetic materials. The magnetic field at any given point is specified by both a direction and a magnitude ; as such it is a vector field.Technically, a magnetic field is a pseudo vector;...
.
Description
A constant-field Maxwell coilCoil
A coil is a series of loops. A coiled coil is a structure in which the coil itself is in turn also looping.-Electromagnetic coils:An electromagnetic coil is formed when a conductor is wound around a core or form to create an inductor or electromagnet...
set consists of three coils oriented on the surface of a virtual sphere. According to Maxwell's original 1873 design each of the outer coils should be of radius
and distance from the plane of the central coil of radius . The number of ampere-turnsAmpere-turn
The ampere-turn was the MKS unit of magnetomotive force , represented by a direct current of one ampere flowing in a single-turn loop in a vacuum...
of each of the smaller coils should equal exactly
of the middle coil.This arrangement removes variations in magnetic field, up to its 6th-order derivative with respect to position, near the centre of the virtual sphere.A gradient-field Maxwell coil
Coil
A coil is a series of loops. A coiled coil is a structure in which the coil itself is in turn also looping.-Electromagnetic coils:An electromagnetic coil is formed when a conductor is wound around a core or form to create an inductor or electromagnet...
is essentially the same geometry of the 3-coil configuration above, with the central coil removed to leave only the smaller two coils . If the current in one of the coils is reversed, a uniform-gradient magnetic field is produced near the centre of the two coils.