Permeability of Magnetic Circuit
The flow of flux created by the magnet not solely depends on the magnetic flux strength but conjointly on one vital property of the magnetic material is named permeability. It’s associated with the medium within which the magnet is placed. The force exerted by one magnetic pole on different depends on the medium within which magnets are placed.
For any magnetic material, there are two types of permeability. They are
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Absolute permeability
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Relative permeability
Absolute permeability (µ)
The magnetic field strength (H) decides the flux density (B) to be created by the magnet around it in an exceedingly given medium- The magnitude relation of magnetic flux density B. In a specific medium (from vacuum or air), the magnetic flux strength H producing that density is named the absolute permeability of that medium.
It is denoted by µ and mathematically may be expressed as
µ = B / H
B = µ x H
The permeability is measured in units of Henries per meter, denoted as H/m.
Permeability of Free house or Vacuum (µo)
Suppose the magnet is placed in exceedingly free space, vacuum, or air. In that case, the magnitude relation of density B and magnetic field strength H is named permeability of free space, Vacuum, or air.
It is denoted as µ0 and measured in H/m. It denotes the convenience of the magnetic flux permeating the free house, vacuum, or air.
It is by experimentation found that this µo, i.e., magnitude relation of B and H in vacuum remains constant all over within the vacuum, and its value is 4πx10-7 H/m.
µ0=B/H in vacuum
µ0= 4 π x 10-7 H/m
The ratio of B to H is constant solely for free space, vacuum, or air that is µo = 4π x 10-7 H/m.
Relative permeability (µr)
Generally, the permeability of various magnetic materials is outlined relative to the permeableness of free space (µ0). The relative permeability is outlined because of the magnitude relation of density created in an exceedingly medium (other than free space) to the density created in free space, underneath the influence of the same magnetic field strength and underneath identical conditions.
Thus if the magnetic flux strength is H that is producing density B within the medium, whereas density B0 in free space, then the relative permeableness is outlined as,
µr=B/B0 Where “H” is the same
It is dimensionless and has no units.
For free space, vacuum or air is µr=1
According to the definition of absolute permeability, we are able to write for given H,
µ = B/H in medium ——>1
µ0 = B0/H in free space ——->2
By dividing 1 & 2, we get
µr=B/B0
∵ µr= µ / µ0
∴ µ= µr x µ0
The relative permeability of metals like Iron, Steel varies from 100 to 100,000 times.
