Electric bell. It is a mechanical device that works on the principle of an electro magnet. This produces sound on repeated passing of electric current
Principle. A soft iron piece placed inside a copper coil carrying current behaves like a magnet.
Construction.
It consists of the following main components:
1. Electromagnet. It consists of a laminated metal wire which is wrapped around an iron bar. This bar becomes an electriomagnet when an electric current passes through wire.
2. Hammer. It is an iron blade/ leaf with a small metal ball at one end called a hammer. It is placed near the electromagnet. There is a contact screw near the iron leaf.
3. Gong. It is made of a cup shaped metal. When the hammer is attracted it hits the bell and a sound is heard.
Working.
When we turn on the switch, Battery the contact screw comes in contact with the iron leaf due to which an electric current flows in the electric coil and it becomes an electromagnet. This electromagnet attracts the iron leaf, causing the hammer to strike the bell and make a sound but during this operation the contact of the hammer is broken by the screw which breaks the electrical circuit. Due to this the coil now has the same properties as an electromagnet and cannot attract an iron leaf. Now the iron leaf returns to its original position and touches the contact screw again. It again generates an electromagnet and the hammer strikes the bell again. This action is repeated quickly and the bell rings again and again.
