Test: Magnetic Properties - JEE MCQ

In electromagnetism the magnetic susceptibility (Latin: susceptibilis, “receptive”; denoted X) is a measure of how much a material will become magnetized in an applied magnetic field. Mathematically, it is the ratio of magnetization M(magnetic moment per unit volume) to  the applied magnetizing field intensity H.

Remanence or remanent magnetization or residual magnetism is the magnetization left behind in a ferromagnetic material (such as iron) after an external magnetic field is removed. It is also the measure of that magnetization. Colloquially, when a magnet is "magnetized" it has remanence.The remanence of magnetic materials provides the magnetic memory in magnetic storage devices, and is used as a source of information on the past Earth's magnetic field in paleomagnetism.The equivalent term residual magnetization is generally used in engineering applications. In transformers, electric motors and generators a large residual magnetization is not desirable (see also electrical steel) as it is an unwanted contamination, for example a magnetization remaining in an electromagnet after the current in the coil is turned off. Where it is unwanted, it can be removed by degaussing.Sometimes the term retentivity is used for remanence measured in units of magnetic flux density.

Magnetic declination is the angle on the horizontal plane between magnetic north (the direction the north end of a compass needle points, corresponding to the direction of the Earth's magnetic field lines) and true north (the direction along a meridian towards the geographic North Pole).
 

Such materials are called ferromagnetic, after the Latin word for iron, ferrum. Not only do ferromagnetic materials respond strongly to magnets (the way iron is attracted to magnets), they can also be magnetized themselves—that is, they can be induced to be magnetic or made into permanent magnets.

Ceramics are used for coating magnetic tapes in a cassette player or for building memory stores in a modern computer. Ceramics are specially treated barium-iron oxides and are also called ferrites.

To find the magnetic moment due to a single particle, it is advisable to consider the equivalent current due to it

If r is the radius of the circle,
then L=2πr or, r=L/2π
Area=A=πr²=πL²/4π²​= L²​/4π
Magnetic Moment=IA= IL²/4π

The units of magnetic pole strength is (A-m) and magnetic dipole moment of a bar magnet is (JT-¹)