1) Initial Permeability, µi
This is the limit value of B/H where H is indefinitely close to
 zero at the initial magnetization curve of a ferromagnetic substance. 	 	 
µi =  1	 lim	    B	 	
  µ0    (H--->0)    H                                                                                                   
Where	  µ0	 Permeability in Vacuum (4πx10-7H/m) 
            H	 Magnetic Field Strength (A/m)
            B	 Magnetic Flux Density (T)		 	 
                                        
2) Effective Permeability, µe
Effective Permeability of a core forming a closed circuit where 
 leakage flux is negligibly small. 	 	 	 	 	 	 	 	 
µe =	   Le	 	 	 	 	 	 
   µ0AeN2	 	 	                                                                                                                     
Where    L	 Self Inductance of Coil with Core (H)	 	 
      N	 Number of Turns in Coil	
      Le	 Effective Magnetic Path Length of Core (m) 	 	 	 	 	 	 
      Ae	 Effective cross sectional area of Core (m2)

3) Saturation Flux Density, Bs (T)	 	 	 	 	 	 	 	 	 	 	 	 
Saturation flux density is the maximum attainable flux density when a 
very high magnetic field is applied to a soft magnetic material 
as shown in the figure below.

4) Residual Magnetic Flux Density, Br (T)
This is the amount of residual magnetic flux density retained by the 
 core after the magnetic field is weakened and finally removed,
as shown in the figure above.

5) Coercivity, Hc (A/m)
This is the strength of the magnetic field whereby the residual flux 
 density becomes zero under the intensification in the opposite 
direction of the magnetic field, as shown in the figure above.

6) Loss Factor, tanδ
The loss factor can be split up into three parts as tanδ= tanδh+
 tanδe+ tanδr
Where          tanδh	 	Hysteresis loss
    tanδe	 	Eddy-current loss	
    tanδr	 	Residual loss 	 	
                             
7) Relative Loss Factor, tanδ/µ
This is the amount of loss per unit permeability and is defined as
 below.
tanδ/µi (for magnetic material)
tanδ/µe (where gaps are added to the magnetic circuit)

8) Hysteresis Material Constant, ηB (10-6/mT)	
Hysteresis material constant characterizes the change of the
 hysteresis loss of the material when  the flux density is increased.
ηB =	Δtanδ	
  µeΔB 	 	
Where         tanδ	 	Loss factor	 	 
    µe	 	Effective Permeability	 
    B	 	Magnetic Flux Density (mT)

9) Temperature Coefficient, αµ (K-1)	
This is the fractional difference of permeability per oK in a 
 temperature range from T1 to T2 (T2 >T1)
αµ  = 	(µ2-µ1)/µ1(T2－T1)	 	 	 	 
Where	µ1	 	Permeability at temperature T1
  µ2	 	permeability at temperature T2
                              
10) Relative Temperature Coefficient, αµr (K-1)
This is the temperature coefficient per unit permeability
αµr=	(µ2-µ1)/µ12(T2－T1)		 	 	 
             
The temperature coefficient of an actual core is obtained from below
αµ = 	aµpx µe	 	 	 
                       
11) Curie Temperature, Tc (℃) 	 	 	 	 	 
The Curie temperature Tc is defined as the temperature at which the
magnetic core changes from the ferromagnetic to the paramagnetic state.

12) Resistivity, ρ (Ωm)	 	 	 	 	 	 	 	 	 	 
This is the electrical resistance per unit length and cross-sectional
 area of a magnetic core.	 	 	 	 	 
                                            
13) Density, d (kg/ms3) 	 	 	 	 	 	 	 	 	 	 	 
This is the weight per unit volume of a magnetic core.	 	 	 	 	 	 	 	 	 	 
d = W/V	 	 	 	 	 

Where：	W	 Weight of magnetic core (kg)	 	 	 	 	 	 	 	 	 	 
          V	 Volume of magnetic core (m3)	 	 	 	 	 	 	 	 	 	 
                                                     
14) Power Loss density, Pc (kw/m3) 	 		 	 	 	 	 	 	 	 	 	 	 	 	 	 
Power loss denotes the loss under a magnetization condition featuring
 a high frequency and a large amplitude. Operating magnetic flux
density is generally expressed for a sinusoidal wave as below.
Bm = E/(4.44f NAe)	 	 	 	

Where           Bm  Peak value of magnetic flux density (T)	 	 	 	 	 	 	 	 	 	 
     EV  oltage effective value applied to test coil (V)	 	 	 	 	 	 	 	 	 
     f   Frequency (Hz)	 	 	 	 	 	 	 	 	 	 	 	 	 	 
     N   Number of coil turns	 	 	 	 	 	 	 	 	 	 	 	 	 
     Ae  Effective cross-sectional area of core (m2)	 	 	 	 	 	 	 	 	 

15) Inductance Factor, AL (nH/N2)  	 	 	 	 	 	 	 	 	 	 	 
AL= L/N2	 	 

Where	  AL	 	Self-inductance of coil with core (H)	 	 	 	 	 	 	 	 	 
    N	 	Number of coil turns	 	 	 	 	 	 	 	 	 	 	 	 
                                                                                
The inductance factor is generally united by 10-9H/N2 (nH/N2)