Which of the following materials would you use as the metallic core of an electromagnet?

The correct answer is "iron nail".

Explanation:

Electromagnet: It is a temporary magnet. It consists of iron core wounded by the coils and then the current is passed through it.

Then, it will act as a magnet as long as the current is passed through it. When the current flows through it then the electromagnet becomes active.

It loses its magnetism when the power is switched off.

Iron inside the coil makes the magnetic field stronger. It becomes magnetized when the current flows through it. It is used in the electromagnet as it loses its magnetism when the current stops flowing through it.

From the given options in the problem, Only the iron nail can be used as the metallic core of an electromagnet.

we can conclude that the melting point of table salt is above room temperature (it's actually 801 deg c). the melting point of mercury must be below room temperature (- 39 deg c).