A system with two Helmholtz coils is a device for producing a large volume of almost constant magnetic field. It is named in honor of the German physicist Hermann von Helmholtz.

Two identical circular magnetic coils are placed on one side and on the opposite side of the experimental area. The two coils are put parallel one to the other and separated by a distance equal to the radius of the coil.

Each coil carries an equal electrical current flowing in the same direction.

In the central part of the experimental zone a magnetic field is produced that is constant in time and attempts to possess a high degree of spatial uniformity. This apparatus creates a magnetic field with small gradient of the magnetic field in the central region of volume.

The calculus of the exact magnetic field has mathematical complexities and involves the study of Bessel functions. An approximate calculation gives the correct value at the center point.

If the radius is R, the number of turns in each coil is n and the current flowing through the coils is I, then the magnetic field, B at the midpoint between the coils will be given by

See also

• Magnetic field

External links

• On-Axis Field of an Ideal Helmholtz Coil
• Axial field of a real Helmholtz coil pair