Types of Magnetic Materials Flashcards
What is a paramagnetic material?
A material containing atoms that have a net magnetic moment that is of the order of the Bohr magneton.
What happens to a paramagnetic material when placed in a magnetic field?
The magnetic field exerts a torque on each magnetic moment.
What effect does the torque have on the magnetic moments in a paramagnetic material?
The torque tends to align the magnetic moments with the field.
What is the relative permeability of a material?
A dimensionless factor which describes the size of the magnetic field at any point relative to the size it would be in a vacuum.
How are the equations that relate magnetic fields to their sources adapted to the situation in which the current-carrying conductor is embedded in a paramagnetic material?
By replacing mu0 with K*mu0. This product is denoted as ‘mu’ and is called the permeability of the material.
What is the amount by which the relative permeability differs from unit called?
The magnetic susceptibility denoted by ‘chi’.
Is ‘Chi’ a positive or negative value for a paramagnetic material and is it temperature dependent?
‘Chi’ is positive and is temperature dependent. Magnetisation given by M = CB/T.
What is a diamagnetic material?
A material in which an external magnetic field induces an internal magnetic field in the opposite direction.
Is ‘Chi’ a positive or negative value for a diamagnetic material and is it temperature dependent?
‘Chi’ is negative and very nearly temperature independent.
What is a ferromagnetic material?
A material in which the strong interactions between atomic magnetic moments cause them to line up parallel to each other.
What are the regions of parallel moments in a ferromagnetic material called?
Magnetic domains.
What happens to the domains in a ferromagnetic material when an external magnetic field is applied?
They tend to orient themselves parallel to the field. The domains that are magnetised in the field direction grow and those magnetised against the field direction shrink.
What is the relative permeability, K in a ferromagnetic material compared to unity.
It is much larger, around 1000 to 100,000.
What is saturation magnetism?
Nearly all the magnetic moments in the ferromagnetic material are aligned parallel to the external field.
What is magnetic hysteresis?
The lag in the response of magnetic induction to changes of magnetic intensity.
