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Insight - How Electric Bulb works

Written By: 

Arpit Jain
An electric bulb is one of the revolutionary inventions ever made in the history of mankind. The working of an electric bulb is quite simple. When electric current flows through the filament made up of tungsten, it heats up emitting visible light.
Electric bulb
Fig. 1: Image of Electric Bulb
The above image shows a commonly used electric bulb. The entire assembly is housed in an envelope of glass. The shape of the glass is responsible for giving directionality to the light.

Internal Structure

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Fig. 2: Close-up View of Internals Parts of Bulb
The above image shows a closer look inside the outermost glass covering. The different parts of the bulb are visible in this image.

Outer Glass & Stem

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Fig. 3: Outer Glass and Stem
The outer glass is attached to the lower casing with the help of a stick material. The environment inside the glass is made inert by filling with a gas like argon. This prevents oxidation of filament at such high temperatures.

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Fig. 4: Assembly of Internal Parts of Bulb

There is another assembly glass assembly inside the outer glass which holds the filament, the support wires, and the contact wires. This glass assembly is also called the stem of the bulb.

Contact Wires & Support Wires

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Fig. 5: Image Indicating the Layout of Wires and Connections with Filament
A closure look shows how the contact wires and support wires are connected with the filament. The purpose of the support wire is to hold the filament. The contact wires provide electrical connection of the filament with the power supply.
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Fig. 6: Closer View of Support Wires
A clear look of the support wires as shown in the image above.


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Fig. 7: Image of Electric Bulb Filament
The filament which is the heart of the electric bulb is shown in the image above. It is made up of tungsten, which has a high melting point and emits light in the visible spectrum when heated. The filament is in the form of a spiral shape wire.
Fig. 8: Wire Connection of Filament to Contact Wire
This image shows how the filament is connected to the contact wire.

Stem Structure & Wires

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Fig. 9: Image Showing Shape of Stem of Bulb
The above image shows the shape of the stem of the bulb. It is glued to the bottom cap using a sticky material.
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Fig. 10: Image Showing wire Layout in Stem
The above image shows the wires (contact wires) coming out of the stem which are connected to the outermost electrical contacts to connect the filament to the power supply.

Electrical Contacts

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Fig. 11: Image Showing Shape and Parts of Outermost Metallic Cap
The outermost metallic cap with two electrical contacts is shown in the image above. The two pipe like structures coming out of the metallic cap are used to hold the electric bulb in the wall holdings.


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