One student has to make an electromagnet using a coil of copper wire. He needs a ferromagnetic material to make its core. This core material should have

High permeability, low retentivity

The correct answer is Option (4) → High permeability, low retentivity

For an electromagnet, the core should magnetize easily and lose its magnetism quickly when current is switched off.

Hence, it must have:

• High permeability → to get strong magnetization

• Low retentivity → to lose magnetism easily

Correct Option: High permeability, low retentivity