Ans. At first, the presence of an iron core greatly increases the strength of the field; after a time, however, as the strength of the current flowing in the exciting coils is increased, the conductibility of the iron for the lines of force appears to decrease, until a point is eventually reached when the presence of the iron core appears to have no effect in increasing the strength of the field.
Permeability.—Permeability is a measure of the ease with which magnetism passes through any substance. It is defined as: the ratio between the number of lines of force per unit area passing through a magnetizable substance, and the magnetizing force which produces them.
In other words, it is the ratio of flux density to magnetizing force. Permeability is a measure of the ease with which magnetism passes through any substance. The permeability of good soft wrought iron is sometimes 3000 times that of air, varying with the quality of the iron.
Ques. What is the effect of increasing the magnetization?
Ans. The magnetic permeability decreases as the magnetization increases.
Ques. What is magnetic saturation?
Ans. The state of a magnet which has reached the highest degree of magnetization.
A magnet, just after being magnetized, will appear to have a higher degree of magnetism than it is able to retain permanently; that is, it will appear to be super-saturated, since it will support a greater weight immediately after being magnetized than it will after its armature has been once removed.