Skip to main content

conduction, polarization & magnetization

Materials contain charged particles that under the application of external fields respond giving rise to three basic phenomena known as conduction, polarization, and magnetization.


Conduction:

  • Conduction is the phenomenon whereby the free electrons inside the material move under the influence of the externally applied electric field with an average velocity proportional in magnitude to the applied electric field.

  • the conduction current density, is measured in amperes per square meter (A/m2).


JC= σE

  • σ is the conductivity of the material units are Siemens per meter (S/m).

  • J is the current density.


 Polarization:

          Polarization is the phenomenon of creation and net alignment of electric dipoles, formed by the displacements of the centroids of the electron clouds of the nuclei of the atoms within the material, along the direction of an applied electric field.




  • relationship between D and E, which is given by D = εΕ .



  • considering polarization in to account electric flux density is given as D = ε0Ε + P.


ε0 = 8.85* 10-12  (permittivity of free space)

P is the polarization vector or dipole moment per unit volume.

polarization

 Magnetization:

Magnetization is the phenomenon of net alignment of the axes of the magnetic dipoles, formed by the electron orbital and spin motion around the nuclei of the atoms in

the material, along the direction of the applied magnetic field.

  • The relation between the B and H is given as H=B/μ

  • μ is permittivity of material measured in newton per ampere square or Henry per meter.


                                     B= μ0 H + μ0 M

where μ0 = 4π * 10-7, M magnetization vector or magnetic dipole moment

magnetic

 

 

 

 
Labels:

Comments

Post a Comment

Popular posts from this blog

BJT (bipolar junction transistor)

A bipolar junction transistor is a three terminal semiconductor current controlled device with two P-N junctions. The three terminals are emitter(E), base(B) and collector(C). the emitter junction is heavily doped, base is less doped and made very thin and collector terminal is moderately doped. Collector has grater size than emitter and base terminal is thinner than both. (The thinner the base, the stronger the E-C electric field, and the larger the impact of a small current injected into the base. Explained clearly in active mode operation below) emitter terminal is moderate in size. A BJT has two types of transistors: NPN transistor PNP transistor NPN transistor : In an NPN transistor a p-type material is sandwiched between two n-type materials. [gallery ids="979,978" type="rectangular"] PNP transistor : In a PNP transistor a n-type material is sandwiched between two p-type materials. [gallery ids="989,990" type="rectangular"] Oper...
2 comments
Read more

voltage

Voltage, is is the difference in potential between two points  in an electric field. also called electromotive force. voltage is the   pressure from an electrical circuit’s power source that pushes charged electrons (current).           grater the voltage grater the flow of electric current. Voltage is symbolized by   V or E . The standard unit is the volt. One volt will drive one columb  (6.24 x 10 18 ) charge.such as electronics through a resistance of one ohm. Voltage can be direct or alternating. A direct voltage maintains the same polarity. In an alternating voltage, the polarity reverses direction periodically. The number of complete cycles per second is the frequency which is measured in hertz.
3 comments
Read more

Diode

Frederick Guthrie invented the diode in 1873, but did not put it into practical use. Thomas Edison independently developed it in 1880, then used it in his 1883 patent of the incandescent light bulb. John Ambrose Fleming received the first patent on the diode itself in 1904. A Diode is a two terminal active component that conducts primarily in one direction. Diodes are one of the simplest, but most useful of all semiconductor devices. Many types of diode are used for a wide range of applications. Rectifier diodes are a vital component in power supplies where they are used to convert AC mains (line) voltage to DC. Zener diodes are used for voltage stabilization, preventing unwanted variations in DC supplies within a circuit. Signal diodes are used to obtain the audio and video signals from transmitted radio frequency signals (demodulation) and can also be used to shape and modify AC signal waveforms (clipping, limiting and DC restoration). Diodes are also built into many digital integra...
1 comment
Read more