A measure of the quantity of magnetism in a magnetic field.



Related Terms

RED MAGNETISM

The magnetism of the northseeking end of a freely suspended magnet. This is the magnetism of the earth’s south magnetic pole.

ABSOLUTE MAGNETOMETER

An instrument used to measure the intensity of a magnetic field without reference to other magnetic instruments.

ROD

  1. A unit of length equal to 5.5 yards or 16.5 feet. Also called POLE, PERCH. 2. One of the imaginary slender soft iron bars which are assumed to be components or parameters of a craft’s magnetic field caused by magnetism induced in soft iron.

EXCITATION

The production of magnetic flux by supplying electric current to the field poles of a generator to create a variable magnetic field.

GRASSOT FLUXMETER

A type of fluxmeter in which a light coil of wire is suspended in a magnetic field in such a way that it can rotate; the ends of the suspended coil are connected to a search coil of known area penetrated by the magnetic flux to be measured; the flux is determined from the rotation of the suspended coil when the search coil is moved.

SUBPERMANENT MAGNETISM

The magnetism in the intermediate iron of a ship which tends to change as a result of vibration, aging, or cruising in the same direction for a long period, but does not alter immediately so as to be properly termed induced magnetism. This magnetism is the principal cause of deviation changes of a magnetic compass. At any instant this magnetism is recognized as part of the ship’s permanent magnetism, and consequently must be corrected as such by means of permanent magnet correctors.

GAUSSIN ERROR

Deviation of a magnetic compass due to transient magnetism caused by eddy currents set up by a changing number of lines of force through soft iron as the ship changes heading. Due to these eddy currents, the induced magnetism on a given heading does not arrive at its normal value until about 2 minutes after change to the heading. This error should not be confused with RETENTIVE ERROR.

INDUCED MAGNETISM

The magnetism acquired by soft iron while it is in a magnetic field. Soft iron will lose its induced magnetism when it is removed from a magnetic field. The strength and polarity of the induced magnetism will alter immediately as its magnetic latitude, or its orientation in a magnetic field, is changed. The induced mag- netism has an immediate effect upon the magnetic compass as the magnetic latitude or heading of a craft changes.

HALL-PLATE DEVICE

A sensor that uses the Hall effect to measure magnetic field strength.

FLUX

A material used to prevent, dissolve, or facilitate removal of oxides and other undesirable surface substances. Also, the measure of the quantity of magnetism, taking into account the strength and extent of the magnetic field.

Functions Of Fluxes

Continuity of grain structure across a soldered or welded joint can only be obtained if the metals are brought into atomic contact, and this is not possible if the metals are coated with oxide layers, grease, corrosion products or other surface films. Mechanical cleaning can only remove the bulk of such surface films, some form of chemical cleaning being necessary to complete the cleaning operation. Fluxes perform some or all of the following functions:

They chemically clean the surfaces to be joined,

They prevent the formation of new oxide layers during the heating cycle of the joining process,

They assist the filler metal to run freely into the joint, and

They assist the "wetting" process by which surfaces alloying occurs.

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