(i) Magnetic flux density (B): It is the magnetic flux per unit area measured at right angles to the flux path. (Its unit is weber/m2 or tesla).
(ii) Reluctance: It is the opposition offered by magnetic path to flux. It is measured in AT/wb.
(iii) Magnetic Motive Force (MMF): It is defined as the entity (quantity or force) that sets up or creates magnetic flux in a magnetic circuit. It is the product of the number of turns and the current in the coil (MMF = NI). Its unit is Ampere (A) OR ampere-turns
(iv) Permeance: It is the property of magnetic circuit due to which it permits the magnetic flux to set up through it and it is reciprocal of reluctance. Permeance = 1/ Reluctance. Unit: weber/ampere.