A non-magnetic discontinuity in a magnetic circuit (i.e. the distance between two magnetic poles), this gap often includes other materials such as brass, aluminium or paint.

The second/left quadrant of the hysteresis loop, generally describing the behaviour of magnetic characteristics in actual use. Also known as the B-H curve.

Leakage flux particularly associated with edge effects and leakage patterns in a magnetic circuit.

This is the magnetic flux per unit area of section in the applied magnetic direction of flux. This is measured in Gauss.

This is the partial demagnetisation of a magnet material when introduced to external factors such as high/low temperatures and demagnetising fields. Losses can only by rectified by remagnetisation. However, magnets can be stabilised to prevent the variation of performance caused by irreversible losses.

A magnetic material which does not have a preferred direction of magnetic orientation and therefore can be magnetised in any direction without the loss of magnetic characteristics.

A magnet is an object made of certain materials which create a magnetic field. Every magnet has at least one north pole and one south pole. By convention, we say that the magnetic field lines leave the North end of a magnet and enter the South end of a magnet. This is an example of a magnetic dipole (“di” means two, thus two poles). If you take a bar magnet and break it into two pieces, each piece will again have a North pole and a South pole. If you take one of those pieces and break it into two, each of the smaller pieces will have a North pole and a South pole. No matter how small the pieces of the magnet become, each piece will have a North pole and a South pole. It has not been shown to be possible to end up with a single North pole or a single South pole which is a monopole (“mono” means one or single, thus one pole).

The point at which the B-H curve ceases to be linear. If the operating point of the magnet falls below the knee, the magnet will not be able to recover full magnetic potential without the application of a magnetising force.

This is the loss of magnetic flux which occurs through leakage caused by saturation or air gaps introduced into the magnetic circuit. This induces a loss of efficiency in the circuit which cannot be recovered.

Indicates the length of the central flux path across an air gap.

An assembly consisting of some or all of the following: permanent magnets, ferromagnetic conduction elements, air gaps, electrical currents.

The total magnetic induction over a given area.

The magnetomotive force per unit length at any point in a magnetic circuit. This is measured in Oersteds.

Ratio of the magnetic induction to self demagnetising force. This is also known as the ‘load line’ or operating point of the magnet.

Usually illustrated in graph format, these curves are a representation of the relationship between the attractive force exerted by a magnet on a soft magnetic workpiece and the distance between them. Pull Gap curve diagrams are useful when selecting a magnet for a particular tractive or holding application.

Reluctance is the resistance in a magnetic circuit and is related to the magnetomotive force, F and magnetic flux (R =F/ magnetic flux) where F is the magnetomotive force.

Remenance is the magnetic induction which remains in a magnetic circuit after the removal of an applied magnetising force. If there is an air gap in the circuit, the remenance will be less than the residual induction Br.

This represents the maximum flux output from a given magnet material measured at the point where the Hysteresis Loop crosses the B axis at zero magnetising force.

A magnetic circuit which provides a low reluctance path for the magnetic flux. Reversible Temperature Coefficient A measure of the reversible changes in flux caused by temperature variations.

This is the condition whereby a magnet or ferromagnetic material has reached a maximum value and an increase in the appliance of magnetising force produces no increase in induction i.e. saturation flux densities for steels range from 16,000 to 20,000 Gauss.

The process where a magnet is exposed to demagnetising influences expected to be encountered in operation. The exposure to these demagnetising influences such as high or low temperatures or external magnetic fields prevents irreversible losses during actual operation.

The material has a preferred direction of magnetic orientation.

That magnetic pole which attracts the geographic North Pole.

Flux density, measured in gauss, of a magnetic material after being fully magnetized in a closed circuit.