The degree to which a magnetic field can magnetise a material is expressed in terms of magnetizing force.
Consider a toroidal solenoid with n turns per unit length carrying a current I. The magnetic induction of the field produced will be
B = μnI
The product nI is called magnetizing force, that is
H = nI
B = μH
Therefore, magnetizing force may be defined as the number of ampere turns flowing round unit length of toroidal solenoid to produce magnetic induction B in the solenoid.
Reference: This article is referred from my book “electrical engineering materials” having ISBN: 978-81-272-5069-0.