 - Magnetic field strength is the intensity of a magnetic field at a given location. Historically, a distinction is made between magnetic field strength H, measured in ampere/meter, and magnetic flux density B, measured in tesla. Magnetic field strength is defined as the mechanical force (newton) on a wire of unit length (m) with unit electric current(A). The unit of the magnetic field, therefore, is newton/ (ampere x meter), which is called tesla.
The magnetic field may be visualized by magnetic field lines. The field strength then corresponds to the density of the field lines. The total number of magnetic field lines penetrating an area is called magnetic flux. The unit of the magnetic flux is tesla x m2 = weber. The older units for the magnetic flux, maxwell = 10-8 weber, and for the magnetic flux density, gauss = maxwell / cm2 = 10-4 tesla, are not to be used any more.
Magnetic flux density diminishes with increasing distance from a straight current-carrying wire or a straight line connecting a pair of magnetic poles around which the magnetic field is stable. At a given location in the vicinity of a current-carrying wire, the magnetic flux density is directly proportional to the current in amperes. If a ferromagnetic object such as a piece of iron is brought into a magnetic field, the "magnetic force" exerted on that object is directly proportional to the gradient of the magnetic field strength where the object is located.
| CONTRIBUTORS: |
Dr. Arnulf Oppelt |
| LAST UPDATED: |
06 Jul 2007
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