Question

A. Ferromagnetic materials will lose their magnetism if heated above a point known as Curie temperature.
B. You would have to re-magnetize the magnet again, either in a solenoid or with another permanent magnet, in order to restore the magnetism.
C. If you are heating a magnet up a little bit, it will lose some of its magnetism, but on returning to room temperature full magnetism can be restored.
Which among the following is/are true?
A. Only A
B. Both A and B
C. Only C
D. All A, B and C

Answer 1

Recall the basic concepts of the ferromagnetism and ferromagnetic materials. Also recall the concept of Curie temperature and what happens when a material is heated above the Curie temperature. Also check about the different ways to restore the magnetism of a magnet.

Complete step by step answer:
The materials which are strongly attracted towards the magnet and show magnetic properties for some time even if the external applied magnetic field is removed are known as the ferromagnetic materials.
The ferromagnetic materials lose their magnetism if they are heated above a certain temperature. This temperature is called Curie temperature.
Below the Curie temperature, the spins of the atoms of the ferromagnetic material are aligned and parallel. Above the Curie temperature, the spins of the atoms remain no longer aligned and become random. Hence, the ferromagnetic materials lose their magnetism above the Curie temperature.

Hence, the statement A is correct.

The magnets may lose their magnetism if heated for a very high temperature. To restore the magnetism of the magnet or to re-magnetize it again, mainly two procedures are used.
One can cool the magnet and expose it again to another permanent magnet or the magnetic field to regain its magnetism.
The other method of re-magnetizing is to wrap your magnet with a copper wire which forms a solenoid around the magnet. Then attach the two ends of the copper wire to a power supply. The current flowing through the wire induces the magnetic field and helps the magnet to regain its magnetism.

Hence, the statement B is correct.

Some of the materials lose their magnetism if heated a little bit up, but they can regain their magnetism when cooled down without applying any external magnetic field.
Hence, the statement C is correct.
So, the statements A, B and C are correct.

Hence, the correct option is D.

Note:
One should keep in mind that not all the materials show the same behavior when heated. Some materials can show different behavior depending on the spin construction in their atoms. Also, one should keep in mind that there is not always a need to expose the material to magnetic fields to regain its magnetism.