Origin of Magnetism
Magnetic properties of solids due to electrons undergoing different motions in atom. Magnetism arises due to the flow of electron around the nucleus & spin of motion, similar to the motion of the planets in our solar system around the sun, and the other is the spin of the electrons around its axis, analogous to the rotation of the Earth about its own axis. The orbital and the spin motion independent on a magnetic moment.
Orbital motion of electron:
Inside an atom, electrons move around a nucleus in specific orbits. Each electron orbit is equivalent to a tiny current loop.It behaves as an elementary magnet having a magnetic dipole.The sum of the orbital magnetic moment of each electron generates the total orbital magnetic moments of an atom.
Magnetic moment is given by= eh/4Ï€me = 9.273*10^-24 A.m2,
e= charge on electron= 1.6*10^-19 C, h= Planks constant= 6.62*10^-34,
Me= mass of electron= 9.1*10^-31 kg
The electron Spin:
Each electron is spinning around itself and this gives rise to a magnetic dipole moment.
Spin magnetic moment= g.e.s/2m= Ï’S
Ï’= Gyromagnetic ratio= -2.003 for electron
S= angular momentum
Ï’= Gyromagnetic ratio= -2.003 for electron
S= angular momentum
Both these motions of electron helps to generate magnetism.
Magnetic induction/Field: (B):
A magnetic flux consists of imaginary lines of flux coming from moving or spinning electrically charged particles. Formule for the spin of both electrons through a wire in an electrical circuit.it's unit is Weber/meter
B = μ0I/2πr
B = magnetic flux magnitude(Tesla,T)
μ0 = permeability of free space 4μ×10^−7T.mA
I = magnitude of the electrical current(A)r = distance(m)
Saturation Induction (Bs): saturation is that the state reached when a rise in applied external magnetic flux H cannot increase the magnetization of the fabric further, therefore the total magnetic flux B more or less levels off.It is denoted by Bs.
Residual Induction( Br): Remanence or remanent magnetization or residual magnetism is that the magnetization left behind during a ferromagnetic material (such as iron) after an external magnetic flux is removed. For movie review SD Movies Point
Note units for the above three induction is weber/meter square.it is denoted by Br.
Magnetic Field strength (H); magnetic flux strength refers to the ratio of the Magnetic driving force which is required to make a particular flux within a particular material per unit length of that material. The unit is A/m.It is denoted by H.
Coercive Field (Hc): A coercive field may be a measure of the power of a ferromagnetic material to face up to an external magnetic flux without becoming demagnetized. The unit is A/m.
Magnetization (M): Magnetization or magnetic polarization may be a vector field that expresses the density of permanent or induced dipole moments during a magnetic material. Magnetization isn't necessarily uniform within a cloth , but may vary between different points. The unit is A/m.
