Here is your answer!
The construction of an electric bell:
The construction of an electric bell consists of a gong, an
electromagnet, a soft iron rod and a contact screw.
The working of an electric bell:
When the current passes through the electromagnet, it
becomes magnetized which helps to attract the armature and after this the
hammer raids and attract the armeture. At that time, electromagnet didn’t behave
as a magnet because of the breaking contact with the screw. So, again armeture comes
down to make the contact with the screw. This cycle keeps on repeating.