Magnetic Substance

Magnetic Substance

On the basis of magnetic behavior, Magnetic substances can be:
1. Diamagnetic substance
2. Paramagnetic Substance
3. Ferromagnetic substance


1. Diamagnetic substance
Diamagnetic substances are such substances which when placed in a magnetic field, acquire feeble magnetism opposite to the direction of magnetic field.
Examples : Bismuth, Zinc, Copper, Silver, Gold, Diamond, Water, Mercury.


2. Paramagnetic Substance:
Paramagnetic substances are such substances which when placed in a magnetic field acquire a feeble magnetism in the direction of the field.
Examples : Aluminum, Platinum, Manganese, Sodium, Oxygen etc.


3. Ferromagnetic substance :
Ferromagnetic substances are those substance, which when placed in a magnetic field, are strongly magnetized in the direction

Domain

Atoms of ferromagnetic substance have a permanent dipole moment i.e. they behave like a very small magnet. The atoms form a large no. of effective regions called domain in which 1018 to 1021 atoms have their dipole moment aligned in the same direction. The magnetism in ferromagnetic substance, when placed a magnetic field, is developed due to these domain by:
1. the displacements of boundaries of the domains
2. The rotation of the domains

Curie Temperature

As temperature increases, the magnetic property of ferromagnetic substance decreases and above a certain temperature the substance changed into paramagnetic substance. This temperature is called Curie temperature.

» Permanent magnets are made of steel, cobalt steel, ticonal, alcomax and alnico.
» Electromagnets, cores of transformers, telephone diaphragms, armatures of ynamos and motors are made of soft and stalloy.

Terrestrial Magnetism

Our earth behaves as a powerful magnet whose south pole is near the geographical north pole and whose north pole is near the geographical south pole. The magnetic field of earth at a place is described in the terms of following three elements :

1. Declination : The acute angle between magnetic meridian and geographical meridian at a place is called the angle of declination at that place.

2. Dip or Inclination : Dip is the angle which the resultant earth's magnetic filed at a place makes with the horizontal. At poles and equator, dip is 90⁰ and 0⁰ respectively.

3. Horizontal component of earth's magnetic field : At a place it is defined as the component of earth's magnetic field along the horizontal in the magnetic meridian.
Its valve is different at different places, (approximately 0.4 gauss or 0.4 x 10^-4 tesla).

Magnetic Maps

Magnetic maps are the geographical maps on which the values of three magnetic elements of earth are represented. On the magnetic maps, following lines are important:

Isogonic lines : The lines joining the places of same declination isogonic lines.
Agonic line: The line joining the places of zero declination is called agonic line.
Isoclinic lines: The lines joining the places of same dip are called isoclinic line.
Aclinic line : The line joining the places of zero dip is called aclinic magnetic equator.
Isodynamic lines : The lines joining the places of same value of Horizontal component of earth s magnetic field are called isodynamic lines.