Krystal is exploring the properties of iron. she takes a large iron nail and finds that the nail does not attract other metal objects. next, she uses a battery and copper wire to transform the nail into an electromagnet. when she connects the circuit, the nail becomes magnetic and can pick up small metal objects like paper clips. this is shown in the illustration below.
what best describes what has happened to the iron in the nail that causes it to become magnetic?

Explanation:

Iron has tiny magnetic domains inside it. Each domain acts like a tiny magnet with its own magnetic field. These domains are randomly distributed thus resulting in zero magnetic field and iron doesn't behave like a magnet.

When a copper wire is wound around the nail and current is passed through the coil, magnetic field is generated. This magnetic field penetrates through the nail. Due to this the magnetic domains of the nail align in the same direction thus having a net magnetic field. The nail behaves like a magnet till the time current flows through the coil.

electromagnetic shielding is the practice of reducing the electromagnetic field in a space by blocking the field with barriers made of conductive or magnetic materials. shielding is typically applied to enclosures to isolate electrical devices from their surroundings, and to cables to isolate wires from the environment through which the cable runs. electromagnetic shielding that blocks radio frequency electromagnetic radiation is also known as rf shielding.

the shielding can reduce the coupling of radio waves, electromagnetic fields and electrostatic fields. a conductive enclosure used to block electrostatic fields is also known as a faraday cage. the amount of reduction depends very much upon the material used, its thickness, the size of the shielded volume and the frequency of the fields of interest and the size, shape and orientation of apertures in a shield to an incident electromagnetic

from wikipedia