Helmholtz coils
A pair of flat circular coils with equal numbers of turns and equal diameters, arranged with a common axis, and connected in series to have a common current (see illustration). The purpose of the arrangement is to obtain a magnetic field that is more nearly uniform than that of a single coil without the use of a long solenoid. The optimum arrangement is that in which the distance between the two coils is equal to the radius of one of the coils.
)
Helmholtz coils separated by distance r, resulting in a nearly uniform field of point P
McGraw-Hill Concise Encyclopedia of Physics. © 2002 by The McGraw-Hill Companies, Inc.
Helmholtz coils
[′helm‚hōlts ‚kȯilz] (electromagnetism)
A pair of flat, circular coils having equal numbers of turns and equal diameters, arranged with a common axis, and connected in series; used to obtain a magnetic field more nearly uniform than that of a single coil.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.