How do you know that a person is waiting at your gate? The incoming person presses the switch installed at our gates, and we hear a known ring. This ring alerts us that someone is at our door. This device is an Electric Bell. Placed inside our homes or offices, the incoming guest presses the switch to ring the bell, and the sound generated by the ringing informs the occupants of the home that a person is waiting at the door.

Electric bells in all our houses are actuated using an electric switch. This switch is set up at the main gate, and its wired connection is made with the ringer(signalling device), which is generally installed within the house. Let us have a detailed understanding of electric bells in this article. Continue reading to know more about Electric Bell!

What is an Electric Bell?

An electromechanical device that works with the help of an electromagnet is called an electric bell. In a classic bell, on applying an electric current, the to and fro movement of a small hammer on a gong would produce the sound of a bell. Thus, an electric bell is an electric device generally used for signalling the presence of a guest or visitor.

These days the electric bells even play songs or tunes when rung. Since the \(19^{th}\) century, these mechanical-electric bells have been widely used in schools, burglar alarms, railway crossings, telephones and industries. An invention of its kind, the electric bell, is widely used as electronic sounder worldwide. An electric bell consists of an electromagnet attached to a strip of iron that makes the hammer hit the gong, thereby producing the ringing sound.

Principle of Working of an Electric Bell

The working of an electric bell is based on the principle of electromagnetism or the magnetic effect of the current. According to the phenomena of electromagnetism, magnetic fields are associated with moving electric charges. Whenever an electric current flows through a conductor, the magnetic field is generated. The direction of this magnetic field can be determined using the right-hand-thumb rule. Electromagnets are constructed using this principle. Electromagnets are widely used in electrical devices like televisions, radios, speakers and even an electric bell.

Construction of an Electric Bell

An electric bell consists of a gong, an electromagnet, a soft iron rod and a contact screw. Electromagnet plays a very crucial role in the construction of an electric bell. Let us learn a little detail about electromagnets.
Electromagnet: An electromagnet is an artificial magnet in which the flow of current produces an electric field. An electromagnet consists of a wire wound in a coil. When an electric current passes through the wire, it generates a magnetic field around it, and the wire behaves like an electromagnet. The magnetic field around an electromagnet lasts as long as there is current flowing through the wire. The strength of the magnetic field of an electromagnet can be increased by increasing the number of turns in the coil, increasing current through the coil and wounding this coil around a magnetic material like soft iron. An electromagnet behaves essentially like a normal magnet as long as there is electric power across its ends. When the electric power is switched off, the magnetic field around the electromagnet disappears.

Electromagnets are used in cranes to pick cars in a scrapyard, in waste disposal systems to separate iron from all the garbage. These are used in appliances like electric motors, generators, transformers and buzzers. These are a part of loudspeakers, headphones, MRI machines and particle accelerators. At our homes, we use electromagnets in electric fans, induction cookers, magnetic locks and electric doorbells.

What are the Parts of an Electric Bell?

1. An electric bell comprises a \(U-\)shaped electromagnet in front of a soft iron strip or armature supported by a spring.
2. This spring is then connected to an adjustable screw.
3. The iron strip is then attached to an iron hammer which is allowed to move to and fro depending on the movement of the iron strip.
4. The armature carries a strip of flexible steel at its back. In a normal position, this armature remains in contact with the screw.
5. Lastly, a metallic gong is placed close to the hammer so that the hammer will be able to strike it when required.
6.  Terminal \(T_2\) is connected at one end of the electromagnet’s coil, and its other end is connected with the spring.
7. The spring is connected to the terminal \(T_1\) through the adjustable screw.
8. A battery is connected between the two terminals.

How does the Electric Bell Work?

Below we have provided detailed information on the working of the electric bell:

1. When the switch is pressed into the ON state, the current flows through the electromagnet into the contact points.
2. As the current passes through it, the \(U-\)shaped electromagnet gets magnetized, and it attracts the armature towards it.
3. Now, the hammer attached to the iron strip strikes the gong and produces a ringing sound, alerting everyone.
4. As the hammer moves, the attached screw and spring contact gets broken, and the circuit now becomes open.
5. Thus, the current stops flowing through the circuit, and the electromagnet gets demagnetized.
6. The position of armature gets restored due to the action of the spring. Again, it comes in contact with the screw if the current is still flowing through the circuit.
7. Thus, the process is repeated from the start, and the bell will continue to ring.

Energy conversion in an electric bell: In an electric bell, the electric energy produces sound. Firstly the electric energy of the current gets converted into mechanical energy of the armature. The armature hits the gong, and the mechanical energy of the armature gets transformed into sound energy.

Applications of an Electric Bell

The applications of the electric bell are as follows:

1. The most common application of an electric bell is in our homes, buildings or offices.
2. Electric bells are also installed as a part of a burglar alarm system to let us know if a thief tries to break in.
3. They are used in industries as a part of fire alarms to sound caution in a fire breakout.

Summary

An electromechanical device that works with the help of an electromagnet is called an electric bell. The working of an electric bell is based on the principle of electromagnetism or the magnetic effect of the current. According to the phenomena of electromagnetism, magnetic fields are associated with moving electric charges. An electric bell consists of a gong, an electromagnet, a soft iron rod and a contact screw. When the switch is pushed on, the circuit is completed, and the current starts flowing through the \(U-\)shaped electromagnet creating magnetic flux in the core. This in turn attracts the iron armature, moving the armature towards the electromagnet. The hammer strikes the gong and rings the bell.

As the armature moves towards the electromagnet, the contact with the adjustment screw breaks which in turn breaks the closed circuit, and stops the current. When there is no current, there’s no electromagnetism, and the armature returns to its original position. This making and breaking of the circuit of the electromagnet continue as long as the button remains pressed.

FAQs on Electric Bell

Q.1. What are the parts of an electric bell?
Ans: An electric bell consists of a metal gong, electromagnet, adjustable screw and a hammer, iron strip and an armature.

Q.2. Describe the working of an electric bell.
Ans: When the current flows through the electromagnet, it gets magnetized, and it attracts the iron strip, and as a result, the hammer attached to the strip strikes the gong producing the sound. The pull from the electromagnet breaks the circuit, and the strip will move to a normal position due to spring action. The process gets repeated as long as the current continues to flow through the circuit.

Q.3. State the principle of an electric bell.
Ans: An electric bell works on the principle of electromagnetism.

Q.4. What is an electromagnet?
Ans: An electromagnet is an artificial magnet in which the flow of current produces an electric field. An electromagnet consists of a wire wound in a coil. When an electric current passes through the wire, it generates a magnetic field around it.

Q.5. Which magnet is used in an electric bell?
Ans: An electromagnet is used in an electric bell. It is not a permanent magnet, and it loses its magnetic properties as soon as the current through it is stopped.

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