Question

Why is soft iron used as the core of the electromagnet in an electric bell?

Answer 1

Hint: Soft iron acts as a magnetic core for the electromagnet in case of an electric bell. When current passes through it, it magnetizes and produces a strong magnetic field and also increases its strength. This core creates a stronger and denser magnetic field of lines and works as a temporary magnet when current passes through it.

Complete answer:
A coil of wire wound around a soft iron core plays the role of electromagnet in case of electric bell.
When the current passes through it, it gets instantly magnetized to generate a strong and dense magnetic field which means it directs the field of lines through it giving a strong magnetic field.
Also, when the current is stopped as circuit breaks, it gets instantly demagnetized which in turn stops the sound of the bell.
Adding a piece of ferromagnetic or ferrimagnetic material in the centre of the coil can increase the magnetic field by hundreds or thousands of times; this is called a magnetic core. The field of the wire penetrates the core material, magnetizing it, so that the strong magnetic field of the core adds to the field created by the wire.
In general, a material such as soft iron which has high permeability and high coercivity is being used in the electric bell.

Note:
These materials may increase the strength of the magnetic field but they become a reason for some losses too.
In alternating current devices they cause energy losses, called core losses, due to hysteresis and eddy currents in applications such as transformers and inductors.
To reduce the eddy current in such circuits we even used laminated iron core for electromagnets.