Helmholtz coils

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 enlarge picture
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.
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References in periodicals archive ?
In particular, with six coils type magnetometer three Helmholtz coils may be used, located in the center of the magnetic field shielding region [10] or six magnetometers disposed in respective planes and orthogonally oriented with respect to the control windings.
The feedback loop was disconnected, and the transducer was placed into the Helmholtz coils to estimate sensitivities and factors of compensation coils.
The initial background static MF inside the incubators (Binder CB 150, Germany) used for the HUVEC cells varied from 10 to 40 [micro]T, so triaxial single-wound Helmholtz coils were used to establish a uniform static MF and vertical or horizontal ELF MFs (Figure 1).
The Helmholtz coils used to generate a uniform applied field [B.sub.a] have a radius of 180 mm and are aligned and separated by a distance of 180 mm.
ANSI/IEEE standard [6], [7] defines two magnetic sensor calibration methods: single-layer square loop and round Helmholtz coils.
At low frequencies, large Helmholtz coils driven by power amplifiers are used to establish a uniform field.
Key words: Helmholtz coils, uniform magnetic field, COMSOL simulation, magnetic measurements
Kilaneh, an Iranian scientist, investigated the thermal behavior of magnetic nanofluid exposed to magnetic field and published the results at Journal of Computational and Theoretical Nanoscience, volume 7, pages 1425-1435, 2010.Imparting the advantage of the aforementioned research as the type of applied magnetic field, he said, "The properties of cooling nanofluids are improved under this field so they could be applied more efficiently in active laser environment, high power machines, power plant industry etc."Kilaneh first computed and verified the magnetic field distribution caused by Helmholtz coils through numerical methods.
Equipment--Two Neodymium magnets (each with diameter of 1.2 cm, combined mass of 18.5 g, and combined length of 1.2 cm), a stop-watch timer, a thin string, a DC low voltage source, a set of Helmholtz coils of radius of 14.8 cm with 130 turns each, and a fluke digital multi-meter to measure coil current.
The system comprises a dedicated controller with automated calibration and self-test features, an AC and DC magnetic sensor, and Helmholtz coils in a structural casing.