Ch 11Magnetic Materials — Class 12 Physics, concept-first.

You have already studied a short bar magnet as a magnetic dipole — a pair of poles of equal and opposite pole strength, separated along an axis, producing a magnetic field at points along that axis an…

When a rectangular current-carrying coil is placed in a uniform magnetic field, it experiences a torque , of magnitude , where is the angle between the coil's magnetic moment and the field .

To understand why some materials are magnetic and others are not, the earlier, purely macroscopic description of a bar magnet (as a pair of poles) is not enough -- the explanation has to start from th…

Model an electron of charge moving with constant speed v in a circular orbit of radius r about the nucleus (Fig. 11.4).

Section 11.3.1 showed that atoms with unpaired electrons carry a net magnetic dipole moment. A bulk material is made of an enormous number of such atoms, each contributing its own moment; but ordinari…

Every material's magnetic behaviour, once an external field is applied, can be classified broadly into one of three categories based purely on the sign and typical magnitude of its susceptibility : di…

A diamagnetic material is one whose atoms/molecules already have a zero net magnetic dipole moment (every electron orbit is paired, as described in section 11.3.1) even before any field is applied.

A paramagnetic material is one whose atoms/molecules DO carry a nonzero net magnetic dipole moment individually (an unpaired-electron atom, as in section 11.3.1), but, in the absence of an external fi…

A ferromagnetic material's atoms/molecules, like a paramagnetic material's, individually possess nonzero magnetic moments; the crucial difference is a strong quantum-mechanical coupling between NEIGHB…

Ferromagnetism is fundamentally a temperature-dependent phenomenon, because it rests entirely on the exchange coupling between neighbouring atomic moments described in section 11.5.3, and that couplin…

The behaviour of a ferromagnetic material subjected to a changing external field is markedly NON-LINEAR, and, unlike a simple linear material, it carries a memory of its past magnetic history -- this…

Sections 11.5.3 and 11.6 showed that a ferromagnetic material retains some magnetization even after an applied field is removed, and that the size of this retained effect -- along with how hard the ma…

A closed shell of soft ferromagnetic material, placed in a region of magnetic field, behaves very differently from an open piece of the same material: because the shell offers the field lines an easy,…

Sample papers and previous-year board questions for this subject.