The following table presents important Magnetic Units, Symbols, and Their Formulas as a reference, or source of information. These formulas play a key role while dealing with magnetic circuits such as Transformers, Inductors.
| Flux (lines) | ϕ |
Weber (Wb)=number of lines 108 Weber (Wb)=number of lines 108
|
| Flux density(magnetic flux per unit cross-sectional area at right angles to the flux lines) | B | B=ϕA=Tesla (T)B=ϕA=Tesla (T) |
| Magneto motive Force(that which forces magnetic lines of force through the magnetic circuit) | MMF | Ampere-Turn orA−T=NIA−T=NI |
| Magnetic field intensity(magneto motive force per unit length) | H | NIlength=A−TlengthNIlength=A−Tlength |
| Permeability (Ability of a material to pass, conduct, or concentrate magnetic flux; analogous to conductance in electrical circuits), i.e., the ease of establishing magnetic flux through the material. | μ | Webers per ampere-turn per meter
μ=lRAμ=lℜA where length (l) is length in meters reluctance (ℜ) is ampere-turns per weber area (A) is cross-sectional area in square meters Note: Free space, or vacuum permeability (μo) is considered to be: 4π×10-7 |
| Relative Permeability(Not constant because it varies with the degree of magnetization) | μr | Relative permeability of a material is a ratio. Thus,
μr=flux density with core material flux density with vacuum coreμr=flux density with core materialflux density with vaccum core
Where flux density in the core material is: B=μoμrHB=μoμrH teslas, and absolute permeability of core materials is: μ=BH=μoμrμ=BH=μoμr |
| Reluctance(Opposition to the establishment of magnetic flux) | ℜ | Ampere turns per Weber
R=MMFϕ=A−TWb |