The electric doorbell is a simple circuit that triggers a sound on the completion of circuit by pressing the button. It is this simplicity that makes doorbell such a marvel. The simple devices in the doorbell put the scientific principle of electromagnetism into action in a useful way. In order to understand the operations of an electric bell, you should first need to understand what is an electromagnet. Well, to put it in simple words, an electromagnet is basically a type of magnet in which the magnetic field is produced with the help of an electric current. When any electrical influences electromagnet it works as a standard magnet (generating magnetic fields). When the power generation to an electromagnet stops, the production of the magnetic field also stops.
So, in an electric bell, an electromagnet forms an important part along with Armature, Spring, Armature rod, Hammer and a Gong.
The image below shows the internal mechanism of an electric bell.
An electric source, for example, a battery can be used to power the electromagnet used in an electric bell. The electric circuit is completed by installing a push switch which you can press to sound an electric bell. The switch also acts as the circuit breaker.
So once the setup is completed, when the switch is pressed, the circuit loop is complete which causes the current to flow through the circuit. The arm which strikes the gong is connected to a spring at one end and an iron ball at the other end. This is called a hammer or a striker. The arm is attached to an iron strip which is attracted to the electromagnet when the circuit is complete and the current flowing through it.
Why does this happen? It’s mainly because the magnetic field created by the electromagnet attracts the iron strip towards it when the circuit is complete. This is the moment when you hear the ringing sound since the hammer keeps hitting the gong. Meanwhile, at its rest position, the hammer is held away from the gong on account of the spring attached to its arm. This is an anchored arm.
Process of the working of an electric bell
Now that you have an understanding of the important parts in an electric bell, the step by step process of the working of the electric bell is described below:
- The switch is pressed and current flows through the circuit.
- The electromagnet is powered and generates a magnetic field that attracts the iron strip towards it.
- The striker strikes the gong (bell).
- When the striking arm strikes the gong, the contact is broken and current stops flowing through the circuit.
- This causes the electromagnet to lose its magnetic field.
- The connected spring arm returns the striker to its original rest position.
- The contact is restored and current flows through the circuit (provided the main switch is still pressed).
- The process is repeated from the beginning.
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