Even though a Helmholtz coil is used most often to cancel out the Earth's magnetic field, the Earth's and Helmholtz coil's magnetic field components may not cancel out uniformly over all space. This is of significance if you wish to know how a finite magnetic object might react and align itself with such a field. This Demonstration enables you to clearly see the non-uniformity and off-axis magnetic field components, thus allowing you to determine how such an object might react. The symmetry axis of the Helmholtz coil is aligned with the Earth's horizontal magnetic field. The coils are in the
plane with one centered at
and the other separated by the radius
of the coils centered at
. The number of turns for the coils
is initially set to 25 and the vacuum permeability
is included in the equations as well. You can vary the radius of the coils, the current supplied to them, the number of turns in the coils, and the Earth's field. All units are in the MKS system.