Classification of magnetic magnetic materials

 Classification   of magnetic  materials.     The  magnetic  properties  of  the materials  are  characterised  by their    relative  permeabilities In accordance with  the  value  of relative  permeability  the materials may be  classified  in the following  three ways : 

1. Ferromagnetic  materials.  

The relative  permeability of these  materials are much   greater than unity and dependent on the field  strength  . The principal  ferromagnetic  elements  are iron  cobalt  and nickel  

2 para magnetic  materials.  The relative  permeability  of these  materials  are slightly  greater  than  unity and are slightly  magnetized  Aluminum  platinum and oxygen  belongs  to this category  

 

3 Diamagnetic materials  . The relative  permeabilities  of these materials  are slightly  less than uniy  silver  copper  bismuth  and hydrogen  are all Diamagnetic  materials  

Magnetic materials

  Permeability.  The property  of a material by virtue  of   Relative hich it allows  itself  to be magnetized is called  permeability  the ratio  B/H is called  permeability  of a material  and is the measure  of relative  magnetic  conductivity of materials permeability  varies  on the type of magnetic  material  amount  of saturation  and  temperature  permeability  is denoted  by 

The   magnetic  materials  Must have  high  permeability  so that  large  fluxes may be produced

   

Relative  permeability. The conductivity  power  of a substance  for magnetic  lines  of force  as compared  with air is called  relative  permeability  . The value  of relative   permeability  varies  from material  to material  and  Also  depends  upon  the  degree  to which  the material  is magnetized it may have  a value  as high  as 2500 

          The  permeability        of a                      magnetic material  is given  by

 The  value  for the permeability  of free space  is 4pi×10^-10 H/m  . The permeability  of air is almost  the  same as that  for free  space  

Magnetic materials

Terms  Associated  with  Magnetic  Materials

 

Magnetic  field. The  space  around  a magnet  or a current  carrying  conductor  within  which  its magnetic  effects  can be observed  is called  the magnetic  field  

Field  strength  . The magneto motive  force  per metre  length  of the magnetic  circuit  ( which  is homogeneous  and  of uniform   cross  sectional area) is called  magnetic  field strength  or field  intensity  . It is  represented  by symbol "H" .If the mean length  of the magnetic  circuit is "l" metres then 

Flux  or linear of force. The total magnetic  lines  of flux  passing  through the  material  is called  magnetic  flux   .Its symbol is phi and unit of measurement  is weber  
1 Weber =10^8lines=10^8Maxwell 

Magnetic  circuit  it is a path  of magnetic  flux  forming a closed  circuit  .

Magnetic  force     It is the force  exerted by one magnet on another  either  to attract it or to repel it

Magnetic material

 Materials  which  provide  a path  to the magnetic  flux are the known  as magnetic  material

Magnetic  materials are those materials which  can be mangnetised and which are attracted  to a magnet when magnetised such materials  create  a magnetic  field  around  them  iron cobalt  nikel are highly  magnetic  materials  many alloys  like  cobalt  steel cadmium  etc have useful  magnetic  properties  the number  of magnetic  materials  found  in nature  are very  few .

Magnetic  materials  play and  implement  role in the field  of electrical  engineering  . They  are use for making  magnetic  circuits  in electromagnetic  machine  relays transforms and many  instruments  .they are also use for making  permanent  magnets  in energy  ina transform  and in Electrical  rotating  machines