2.02 Magnetic field strength.

Flux distribution.

In the previous section we discovered that magnets possess a property called a magneto motive force (m.m.f.) and that this m.m.f. generates flux, to form a magnetic field surrounding the magnet. The distribution of this flux determines the characteristics of the magnetic field. e.g. The flux can be distributed widely, producing and extended and weak field, or it could be very concentrated, resulting in a strong compact field. There are two measurable parameters that are effected by the flux distribution, these are field strength and flux density.

Field strength

A larger m.m.f. will naturally produce a stronger field. With a fixed magnitude of m.m.f., then as would be logically expected, the more extended the field lines are, then the weaker they will be. (i.e. The field strength is proportional to the m.m.f. and inversely proportional to the length of the magnetic field lines.)

H = m.m.f./l .

Flux density

Flux density is another measure of how concentrated the magnetic field is. However, in this case, we are considering the concentration of field lines, through an area which is perpendicular to their direction. A way of visualising flux density is by thinking of how close, or far apart, the field lines are from each other. Flux density can be calculated from the equation below.

B = I/A .