Fusing Current refers at which the fuse is designed to melt and disconnect the circuit.  Wiring rules specify the fusing current for different circuits.  It is also known as minimum fusing current.  

Fusing Factor
The Fusing Factor is the ratio of the rated current and the fusing current

Fusing Current = Fusing Factor x Rated Current

The fusing current will always be more than the rated current.  Thus, the fusing factor will always be greater than one.  

‘Polarization’, denoted by ‘P’ is defined as the difference between the induced electric field ‘D’ and imposed electric field ‘E’ within a dielectric medium due to immovable and free charge carriers respectively.

This phenomena occurs if an electric field distortion takes place between negatively charged electrons around positively charged atomic nuclei giving rise to slight difference of charges.

Mathematically, it is stated as-
P = (D-E)/4π

Polarization can also be expressed in terms of electric susceptibility Хe, such as,
P = є0 Хe E

Where, є0 = permittivity of free space, (= 8.85 x 10-12 Farad/metre).

Quantitatively, it is denoted by-

P = p/V
Where, p =amount of dipole moment

  V = volume of polarized material