Magnetic Circuits Questions and Answers

Answer: D

Such a material is ferromagnetic.

Ferromagnetic materials such as iron, nickel and cobalt and their alloys have magnetic domains that line up readily with an applied field, so they strengthen it enormously. Their relative permeability is much greater than one, from hundreds to many thousands.

Paramagnetic materials (aluminium, platinum) have a relative permeability only slightly greater than one, and diamagnetic materials (copper, bismuth) slightly less than one. A superconductor expels magnetic flux entirely and behaves as a perfect diamagnet, the opposite extreme.

Answer: D

The relative permeability of a ferromagnetic material is very high, from several hundreds to many thousands.

In ferromagnetic materials such as iron, nickel, cobalt and their alloys, the magnetic domains align with an applied field and reinforce it many times over. Soft iron and silicon steel have relative permeabilities in the thousands, and special alloys such as mu-metal reach far higher.

A value slightly higher than unity is typical of paramagnetic materials such as aluminium, and slightly less than unity of diamagnetic materials such as copper. A relative permeability of exactly one belongs to free space and to non-magnetic materials.