Question

A permanent magnet is made of steel and loses its magnetism easily. Explain it.

Answer 1

Hint: A permanent magnet is a magnet that doesn’t lose its magnetic strength. We must know that steel is an alloy of iron and carbon. Naturally steel is not magnetic in nature but it can be modified into one. If a material needs to be turned into a permanent magnet, it should have proper atomic orientation.

Complete solution: First of all, we need to understand why steel is used for making permanent magnets. When a nonmagnetic piece of steel is applied to a magnetic field, the atoms align and create a permanent magnet.

That means, steel is a ferromagnetic material and when a ferromagnetic material is imposed with a magnetic field in a particular direction, the magnetic moments will not come back to its original position when the applied field is withdrawn. The amount of how much the material is magnetized is known as remanence.

This magnetization could be reversed by applying an opposite field, this required field for demagnetization is known as coercivity. If we are applying an alternating field to the material, and plot the magnetization in a graph, it will trace a loop called hysteresis loop.
So, this hysteresis loop is related to the existence of magnetic domains in the material. Steel is a material with high coercivity. That means more fields are needed to demagnetize it. So it could be used for making a permanent magnet.

Now, it could lose its magnetism easily. This is due to the energy given to the material such as heat or demagnetizing the field. If we give these oriented magnetic moments an external opposing energy, they will be reversed again. This property of ferromagnetic materials can be called magnetic memory. The materials which retain much of their magnetization can be used as permanent magnets.
The hysteresis loop of steel is found to be,

Note: Steel is one of the materials having high coercivity, That means more energy will be needed to demagnetize steel. So it is an ideal material for making permanent magnets. The case of electromagnets is just the opposite where those materials must have low coercivity and high permeability. We must know that steel is not magnetic in nature but it can be transformed.