When the atomic dipoles are aligned partially or fully, there is a net magnetic moment in the direction of the field in any small volume of the material. The actual magnetic field inside material placed in magnetic field is the sum of the applied magnetic field and the magnetic field due to magnetization. this field is called magnetic intensity (H) given by H = B/μo - M where M is the magnetisation of the material and B is the total magnetic field and μo is the permittivity of vacuum.

A solenoid has a core material with relative permeability 251 and its windings carry a current of 2A. The number of turns of the solenoid is 1000 per metre. What is the magnetization of the material? 

5 X 10⁵ Am^-1

Magnetic intensity = H = nI and μ_r = χ +1, M =  χH