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

P-N junction diode

A P-N junction diode is a basic diode. It is the combination of P-type and N-type semiconductor. symbol : P-N junction and potential barrier : A P-N junction is the basic building block of many semiconductor devices like diodes and transistors. P -n  junctions are formed by joining  n -type and  p -type semiconductor materials. Since the  n -type region has a high electron concentration and the  p -type a high hole concentration this difference in concentration creates density mismatch across junction which results to creation of potential barrier. The value of potential barrier v b  is 0.3 for germanium and 0.7 for silicon. Working : Forward bias: Application of positive charge at p-side pushes holes towards potential barrier and similarly negative charge at N-side pushes electrons towards barrier if input voltage is grater than potential barrier then electrons diffuse from the  n -type side to the p-type side. Similarly, holes flow by diffusion from the p-type side to the n-type side...
4 comments
Read more

inductor

An inductor is a passive electronic component that stores energy in the form of a magnetic field. In its simplest form, an inductor consists of a wire loop or coil. The inductance is directly proportional to the number of turns in the coil. Inductance also depends on the radius of the coil and on the type of material around which the coil is wound.   The standard unit of inductance is the Henry abbreviated H. This is a large unit. More common units are the micro Henry, abbreviated µH (1 µH =10 -6 H) and the milli Henry, abbreviated mH (1 mH =10 -3 H). Occasionally, the nano Henry (nH) is used (1 nH = 10 -9 H).             inductors in series & parallel : applications : Inductors are used extensively in analog circuits and signal processing. Applications range from the use of large inductors in power supplies, which in conjunction with filter capacitors remove  fluctuations from the direct current output.          
1 comment
Read more

relay

A relay is an electrically operated switch. These are remote control electrical switches that are controlled by another switch. A relay is used to isolate one electrical circuit from another. It allows a low current control circuit to make or break an electrically isolated high current circuit path. The basic relay consists of a coil and a set of contacts. The most common relay coil is a length of magnet wire wrapped around a metal core. When voltage is applied to the coil, current passes through the wire and creates a magnetic field. This magnetic field pulls the contacts together and holds them there until the current flow in the coil has stopped. The diagram below shows the parts of a simple relay. Operation: When a current flows through the coil, the resulting magnetic field attracts an armature that is mechanically linked to a moving contact. The movement either makes or breaks a connection with a fixed contact. When the current is switched off, the armature is usually returned by...
1 comment
Read more