Incandescent Light Bulbs

Introduction

            A light bulb is a device that uses electricity to create a source of light. During the 1800s a lot of different people were trying to invent the first incandescent light bulb. During this time scientist did a lot of research and started to create lights that didn’t last long or were too bright. However, in 1878 Thomas Edison created the first practical incandescent light bulb that would last longer and was suitable for home use and filed a patent for it (History of Light Bulb). This caused more scientists to become interested in light bulbs which led to the improvement of them. Scientists created light bulbs last way longer now than they did before by using different metals to conduct electricity better and by using different techniques to make the light bulbs either brighter or dimmer. Lightbulbs have come a long way as there are different types of lights being used in buildings, phones, streets, etc. This technical description is going to focus on incandescent light bulbs rather than another type of light bulbs.

Fig 1: Incandescent Light Bulb (Dumdroff, 2019)

Structure of an Incandescent Light Bulb

The main structure of a light bulb only contains 8 major parts. These parts are show in Figure 2 below.

Fig 2: Diagram of Incandescent Light Bulb (Harris, 2002)

1. The electrical foot contact is a piece of conductive metal at the bottom of the light bulb which allows electricity to enter the light bulb and has a wire which connects to the filament.
2. The insulation keeps the innards of the bulb in the bulb and only allows electricity to pass through the contacts and wires.
3. The screw thread contact is the ridged part of the light bulb that allows it to be screwed in to different places and contains a wire that is also connected to the filament.
4. The bulb is spherical and made out of glass. It doesn’t allow anything to leave the light bulb or enter it acting as a barrier.
5. The inert gas prevents the filament from evaporating by preserving and protecting it.
6. The tungsten filament is a thin metal (Tungsten) in the center of the light bulb which has electricity flowing through it.
7. The glass mount holds up the filament in place and extends from the base of the bulb to the middle.
8. The support wires keep the filament up and in place on the glass mount.

How does a Light Bulb Work?

            To start off, light is a form of energy that can be released by an atom. It is caused by electrons moving between shells, energy levels, in an atom. When an atom gets excited an electron can absorb the energy and move to a higher-level shell. However, this doesn’t las long as the electron almost immediately returns to its original shell and emits the extra energy as light (How It Works Team, 2012). This occurs in the filament of an incandescent light bulb.

When a power supply is hooked up to the bulb an electrical current flow from one contact to the other through the filament and wires (Harris, 2002). Electricity flows better through conductors that are thick and short as it will involve less work for the electrons to move. That is why the filament is short and not too skinny. When the electricity flows through the filament it causes the filament to heat up and glow either red or white. This produces the light and is the basic concept of how incandescent light bulbs work (Woodford, 2018). Most filaments use Tungsten because it has an extremely high melting point which will prevent it from melting when experiencing high amounts of electricity and heat. However, it could catch fire through the process of combustion which is caused by a reaction of two chemicals, typically oxygen. That is why the bulb is vacuumed and insulated so no gas can seep in. However, this would cause the problem of the tungsten evaporating causing it to disintegrate and collect in the bulb. That is why an inter gas, usually argon, fills the bulb. The inter gas reduces the loss of tungsten because when the tungsten atoms evaporate, they are likely to bounce off the inert gas atoms and land back at the filament where they rejoin the structure (Harris, 2002).

Conclusion

            Incandescent lights were the beginning of light bulbs. However, they are now considered outdated at it has been proven that 95% of the electricity fed into the light bulb is turned into heat (Woodford, 2018). This is shown to be wasteful as it is using a lot of the energy creating something that isn’t its intended use. This problem is the reason why lights are now evolving. People are now turning to LED and CFL lights as they use less electricity to produce light and they also tend to last longer.

References

Drumdorf. “Incandescent Light Bulb | 3D Model.” CGTrader, www.cgtrader.com/3d-

models/furniture/lamp/incandescent-light-bulb.

Harris, Tom. “How Light Bulbs Work.” HowStuffWorks, HowStuffWorks, 19 Feb. 2002,

home.howstuffworks.com/light-bulb2.htm.

“History of the Light Bulb | Lighting Basics.” Bulbs.com, www.bulbs.com/learning/history.aspx.

How It Works Team. “How Do Atoms Emit Light? – How It Works.” How It Works, 26 Oct.

2016, www.howitworksdaily.com/how-do-atoms-emit-light/.

Woodford, Chris. “How Do Incandescent Filament Lamps Work?” Explain That Stuff, 14 Oct.

2018, www.explainthatstuff.com/incandescentlamp.html.