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Glossary of Terms

 

Anisotropic Magnet- A magnetic material having better magnetic characteristics along the preferred axis than along any other.

C.G.S. System- A system of electromagnetic measurement employing as base units the centimeter, gram, and second

Coercive Force Hc- The demagnetizing force that must be applied to a magnetic material to reduce the induction to zero.

Coercive Force, Intrinsic Hci – The demagnetizing force that must be applied to a magnetic material to reduce the intrinsic induction to zero; the material being in a symmetrically, cyclically magnetized condition.

Coercivity- The relative value of coercive force; i.e., one material is said to have a greater “coercivity” than another.

Curie Point- The elevated temperature, usually expressed in oC, at which a ferromagnetic material becomes paramagnetic.

Demagnetization Curve- That part of the hysteresis loop in the second quadrant between the residual induction point, Br, and the coercive point, Hc. Points on this curve show the relationship of induction to demagnetizing force, and are designated by the coordinates Bd and Hd.

Energy Product Maximum- Peak BdHd max (m.g.o.)-The maximum value shown on the energy product curve.

Flux Density B (See Induction)- The number of lines of maxwells per unit area in a section normal to the direction of flux (expressed in gausses).

Gauss- The c.g.s. unit of flux density.

Gauss =

Total flux (maxwells) or (lines)
Area cm2

Gilbert- Unit of magnemotive force in the c.g.s. system (see Magnemotive Force).

Hysteresis, Magnetic- The property of a magnetic material by virtue of which the magnetic induction for a given magnetizing force depends upon the previous conditions of magnetization.

Hysteresis Loop- A graphic representation of the relationship between the magnetizing force and the resulting induced magnetization or a ferromagnetic material when the magnetizing force is carried through a complete cycle of equal and opposite values under cyclic conditions.

Induction, Intrinsic Bi – The excess of the induction in a magnetic material over the induction in vacuum or air, for a given value of magnetizing force, or (B-H).

Induction, Magnetic B- The magnetic flux per unit area normal to the direction of flux, expressed in gausses in the c.g.s. system (see Flux Density).

Induction, Residual Br – The magnetic induction corresponding to zero magnetizing force in a magnetic material, which is in a symmetrically, cyclically magnetized condition.

Induction, Saturation Bs – The maximum intrinsic induction possible in a material.

Lines- (see Maxwell)

Magnetic Circuit- Usually, in an assembly employing pole pieces, keepers, etc., the closed path of magnetic flux, the path having the direction of the flux at every point.

Open Circuit- A magnet in which no pole pieces are present, although in truth, a magnetic circuit is still generated about the magnet.

Magnetizing Force H- The magnemotive force per unit length. The c.g.s. unit is the oersted and is defined by:

H =

magnemotive force in gilberts
length in centimeters

Magnemotive Force F- Is that force which tends to produce a magnetic field. This force is developed either by an electric current passing through a coil of wire, for example, or by a permanent magnetized body. The unit of Magnemotive Force in the c.g.s. system is the gilbert where

F= 0.4πNI
I= current (in amperes)
N= number of turns of wire

Maxwell Ф- The c.g.s. unit of magnetic flux – used interchangeably with Line.

Oersted- The c.g.s. unit of magnetizing force. A field of one oersted strength is represented by one line/cm2.

Permeability µ - The ratio of magnetic induction in a given medium to the induction which would be produced in a vacuum, or for all practical purposes in air with the same magnetizing force.

Permeability =

magnetic induction in gausses
magnetizing force in oersteds

µ =

B
H

This term is used to describe relative values of permeance; i.e., one material is said to have greater “permeability” than another.

Permeance P (see Reluctance)- The ratio of flux through any cross-section of a tubular portion of a magnetic circuit bounded by lines of force and by two equipotential surfaces, to the magnetic potential difference between the surfaces taken within the portion under consideration.

Permeance =

magnetic flux in maxwells
magnetic flux in maxwells

P =

Ф
F

Reluctance R- Opposition to flux. The reciprocal of permeance.

R =

F
Ф

This represents the magnetic circuit analogy of Ohm’s law, reluctance being analogous to resistance, flux to current, and permeance to conductance.

Remanence Bd – The magnetic induction which remains in a magnetic circuit after the removal of an applied magnemotive force. If there is an air gap in the magnetic circuit, the remanence Bd will be less than the residual induction Br; otherwise they are the same.

 

 

 

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