*Magnetic circuit *can be defined as *path or route which can be easily followed through magnetic flux. *There are important termswhich have the main connection with magnetic circuits that can be listed below:

**Permeability (µ)**. Permeability is having the main relation withany material which can be easily measured in terms of ease where the atoms arrangedeasily. Henry/meter*(H/m) is the unit *for permeability is taken in S.I form

Relative permeability is denoted by (µr) which is havingterm of numeric value that canexpress such kind of degree where the material proves to be better conductor of magnetic flux that can have the main comparison with free space.

Consider

µ_{r}= air along with materials of non magnetic in nature which is equal to 1

µ_{r},= is taken for diamagnetic materialswhich are slightly low than one

µ_{r},= is taken for paramagnetic materials which are slightly more than one

µ_{r}, = is taken for ferromagnetic materials which are coming in hundreds or thousands

(µ_{r} =ferromagnetic materials which canchange with strength of magnetic field

**Magneto motive force (m.m.f.).** The Magneto motive force *helps in the driven of flux by passing through *a *circuit of magnetic *which easily have the main correspondence with electromotive force (e.m.f.) in the field of circuit. M.m.f. is such a condition where it is equal to the work completion in joules which is also helps in holding a unit ofpole in magnetic formwhich is passing throughmagnetic circuit once.

M.m.f. is have the measurement in ampere-turns (AT),which easily taken out by *multiplying of number *of turns*in magnetic circuit along with the current in those amperes which are denoted by (I) *in turns.

Mathematical form

*AT=NI*

**Reluctance**. It is electric circuit current which have the main limitation by resistance; whereas asmagnetic circuit flux is in limited form by reluctance which is denoted by(symbol S) of magnetic circuit. Therefore *reluctance *is taken as measurement*of opposition which is provided by magnetic circuit in order to set up of flux.*

Reluctance of a magnetic circuit is stated as* *

l is magnetic circuitlength,

Cross-sectional area of the magnetic circuit is denoted by A

= relative and absolute permeability, and

Reluctance of circuit that is in magnetic field is having the ratio **in terms of** **m.m.f. along with flux.**

We can say that themagnetic circuit reluctance is the quantity of ampere-turns which have the main requirement in eachmagnetic flux circuitweber.* Reluctance unit is denoted by AT/Wb. *where AT/Wb = l/henry *“reciprocal henry” is reluctance unit.*

**Permeance. **Permeance is reluctance reciprocal

It have the measurement on henryin Wb/AT

**Reluctivity**. Special type of reluctance which have the main correspondence with resistivity to a resistance which is specific in nature.

**Relation between flux density (B) and magnetic field strength (H):**

µ is (permeability) which is the ratio of flux having density to the strength of magnetic field.