Question

 Explain why, the core of an electromagnet should be of soft iron and not of steel. 

Answer 1

The core of an electromagnet must be of soft iron because soft iron loses all its magnetism when current in the coil is switched off.
But if steel is used, it does not lose all its magnetism when current is switched off. Contrarily, it becomes a permanent magnet.
Therefore, steel cannot be used for making the core of electromagnets.