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



Related Terms

LENARD SPIRAL

A type of magnetometer consisting of a spiral of bismuth wire and a Wheatstone bridge to measure changes in the resistance of the wire produced by magnetic fields and as a result of the transverse magnetoresistance of bismuth.

MAGNETIC FLUX QUANTUM

A fundamental unit of magnetic flux, the total magnetic flux in a fluxoid in a type II superconductor, equal to h/(2e), where h is Planck's constant and e is the magnitude of the electron charge, or approxiiron, nickel, or titanium, or nonmagnetic deposits which either contain magnetic gangue minerals or are associated with magnetic structures.

B-H METER

A device used to measure the intrinsic hysteresis loop of a sample of magnetic material.

EXCITATION

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

ELECTROKINETOGRAPH

An instrument used to measure ocean current velocities based on their electrical effects in the magnetic field of the earth.

DIP NEEDLE

A magnetic needle suspended so as to be free to rotate about a horizontal axis. An instrument using such a needle to measure magnetic dip is called a DIP CIRCLE. A dip needle with a sliding weight that can be moved along one of its arms to balance the magnetic force is called a HEELING ADJUSTER.

WEBER

A derived unit of magnetic flux in the International System of Units; it is that magnetic flux which, linking a circuit of one turn, would produce in it an electromotive force of 1 volt if it were reduced to zero at a uniform rate in 1 second.

HALL-PLATE DEVICE

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

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.

RETENTIVE ERROR

Deviation of a magnetic compass due to the tendency of a vessel’s structure to retain some of the induced magnetic effects for short periods of time. For example, a vessel on a northerly course for several days, especially if pounding in heavy seas, will tend to retain some fore-and-aft magnetism gained through induction. Although this effect is not large and generally decays within a few hours, it may cause incorrect observations or adjustments, if neglected. This error should not be confused with GAUSSIN ERROR.

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