SUBJECT: The Magnetic Field of a Helmholtz Coil (anti-aligned)
DESCRIPTION: This animation shows the magnetic field of a Helmholtz coil when the current in the top and bottom coils flows in opposite directions (ie. their dipole moments are anti-aligned). The fields from the two point in opposite directions, creating a net field that is zero at the center of the coils. Though the coils are fixed, they are repelled from one another, resulting in a pressure in the field between them. This is illustrated by fieldlines as they are compressed along the central horizontal axis between the coils.
VISUALIZATION (MPG - 4 MB)