Question

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

Answer 1

Hint: Recall the construction of an electromagnet. Recall the basic requirements for an element or a compound material to be an electromagnet. Check the magnetic properties of the soft iron and steel like which of the materials get magnetized and demagnetized quickly when the current flowing around them is turned off.

Complete answer:
An electromagnet is an artificial magnet in which an iron core is wrapped with wire to form a coil.When an electric current flows through the coil, the magnetic field is induced in the soft iron core and it behaves as a magnet.

Also this soft iron behaves as a temporary magnet. This means when the current is flowing through the coil of the electromagnet, the soft iron gets quickly magnetized and behaves as a magnet. But when the current flowing through the coil is switched off, the soft iron quickly loses its magnetism, get demagnetized and remains no more a magnet.This property of the soft iron to get easily and quickly magnetized as well as demagnetized whenever needed is more desirable for an electromagnet.

On the contrary, the steel used in the electromagnet instead of the iron core, also gets magnetized and behaves as a magnet when an electric current flows through the coil of the electromagnet. But when the current flowing through the coil is terminated, the steel does not get demagnetized quickly. Rather, it still continues behaving as a magnet though the current is stopped. This shows that it becomes a permanent magnet.This property of steel to get magnetized and behave as a permanent magnet even after current is switched off is not desirable for an electromagnet.

Hence, the soft iron is used in the electromagnet and not the steel.

Note: One may think that the steel can also be used as an electromagnet as it shows magnetic properties and behaves as a magnet when current passes around it. But the important property of an electromagnet is it loses magnetism when the current is stopped which is not fulfilled by steel.