SECTION : Magnetostatics       

This animation shows the magnetic field of a Helmholtz coil when the current in the top and bottom coils flows in the same direction (ie. their dipole moments are aligned). The fields from the two coils add up to create a net field that is constant in the center of the coils. Though the coils are fixed, they are attracted to one another, resulting in a tension in the field between them. This is illustrated by fieldlines as they stretch to enclose both coils.