| Prof. Elisabeth von Uhl |
| Light Bulb |
| Technical Description |
| Shafit Kazi
4-15-2022 ENGL 21007 E2 (Spring ’22) |
Table of Content
- Definition – 2
- Fig 1: An incandescent lightbulb 2
- Overview – 2
- Fig 2: Ohm’s Diagram 3
- Components – 3
- The Globe
- Fig 3: The Glass shell / Globe 4
- The Filament
- Fig 4: The Filament 4
- Fig 5: Tungsten 5
- Wires and a Stem
- Fig 6: Wire and stem 5
- Invisible Gases
- Fig 7: An example of gas (illustration) 6
- The Base
- Fig 8: Base of a light bulb 6
- Conclusion 7
- Reference 7
- The Globe
Definition
The electric light bulb has been called the most important invention since artificial fire. The invention of the light bulb changed the world in many ways, including facilitating the creation of large power grids, changing society’s social and economic structure, and bringing other appliances into the home. Interior lighting altered the structure of society, allowing activities to extend into the night. The light bulb helped establish social order after sundown, extended the workday well into the night, and let us navigate and travel safely in the dark. Without the light bulb, there would be no nightlife. No city that never sleeps.
Fig 1: An incandescent lightbulb
Overview
How do light bulbs work? By any standard, the invention of the light bulb was a real light bulb moment. And it didn’t come a moment too soon. Because although we’d known how to produce electricity through chemical reaction since 1800 and how to generate it mechanically since 1831, thanks to Michael Faraday. There weren’t many uses for the new force other than impressing other Victorian scientists by using it to make sparks and flashes. Of course, the early electrical pioneers were bright enough to realize you could use an electrical current to make a wire glow — and if you made a thin enough piece of wire with a high enough melting point, then it would glow white-hot.
The light works by an electric current traveling from cathodes on the ends of the bulb to the gases, which radiate energy. The tubes have a phosphorus coating, which takes the energy and converts it to light. The fluorescent bulbs last longer but contain gases, so they need to be disposed of.
In pretty much the simplest possible terms, the atoms in the metal release some light photons when their electrons become excited by the electrical current. The problem with using these glowing wires as a light source became apparent after a couple of minutes of use. The oxygen in the air would quickly oxidize the metal and disintegrate. The light bulb was the solution: a see-through sleeve to protect the hot wire.
Fig 2: Ohm’s Diagram
Like many good ideas, it had many fathers. Georg Ohm first published his mathematical equation for the correct use of electricity in circuits in 1827. Ohm’s law calculates the correct voltage of electricity given the current and resistance of any electrical circuit. Ohm’s law was devised 27 years after Humphry Davy invented the first light bulb and 52 years before the American and British inventors invented the first household light bulb. The light bulb as we know it was invented simultaneously on both sides of the Atlantic in 1870 by Joseph Swan, who was British, and by Thomas Edison, who was American. And the basic idea has barely changed since. The light bulb is made from fragile glass and contains a wire filament made from a metal chosen to have a very high melting point – usually tungsten, twisted around in a coil pattern. Early light bulbs included a partial vacuum, the space around the filament was emptied of most of the air, reducing the potential for an oxidizing reaction to occur. More modern bulbs switched over to an inert gas, which doesn’t react with the white-hot element for the same effect. The result is a bulb that could provide up to 1000 hours of light at the flick of a switch, and sometimes considerably more. One manufactured in 1883, just five years after the light bulb was invented, is still in daily use in the UK, 130 years later. America claims another light bulb that’s been switched on continuously for 109 years.
Components
The Globe
The outer glass shell of the light bulb is called the globe. The glass ensures maximum light efficiency and provides strong support for the other parts of the bulb. The light bulb has a shape like a plant bulb; the light rays from the filament are much more effective with this shape.
Fig 3: The Glass shell / Globe
The Filament
Fig 4: The Filament
The filament inside of the light bulb is shaped like a coil. It is manufactured through a process known as drawing, in which tungsten is mixed with the material. The filament inside the light bulb is shaped as a coil to allow the required length of the tungsten within its small environment to produce an abundant amount of light. Tungsten is a natural solid metal and a chemical element brittle in its raw state, but its purer form is decisive. It must be, as the filament heats up to a blistering 2,550 degrees Celsius (4,600 degrees Fahrenheit).
Fig 5: Tungsten
Wires and a Stem
Within the inner center of the light bulb, there is a centralized stem made from glass, which supports the filament in its place. The connecting wires ensure the steady flow of electricity through the light bulb components. Like how the human heart works when blood travels to and from the heart, a wire takes the electricity from the light bulb’s base and another wire that completes the electrical circuit back to the ground.
Fig 6: Wire and stem
Invisible Gases
Fig 7: An example of gas (illustration)
Unseen within the light bulb are inert gases usually formed of argon and nitrogen. These low-pressure gases prevent the filament inside the bulb from burning out; it also relieves some of the stress on the glass globe from normal atmospheric pressure, lessening the chance of glass breakage.
The Base
The base of the light bulb has three main functions. First, it securely supports the light bulb within an electrical source unit, like a lamp or a light fixture. The second job of the base is to transfer the electricity from the primary electrical source to the inside of the light bulb itself. The last function is to secure the globe and all components inside the bulb, creating a reliable and convenient light source.
Fig 8: Base of a light bulb
Conclusion
But for all its ubiquity, the light bulb isn’t what you’d call an advanced piece of kit. Even its name is a bit of a misnomer — we should probably call it the heat bulb, as over 90 percent of the energy is converted into heat. Visible light is a fantastic by-product. The old-fashioned light bulbs get hot enough if you’re making an incubation cage for some chickens or trying to heat a student apartment when your landlord has turned the gas off, But not ideal(call 311 ). This is why the humble light bulb has become a threatened species. More modern compact fluorescent energy-saving light bulbs are four times more efficient for producing the same amount of light, and the new generation of LED-based lights is still more frugal. The production and sale of the old incandescent light bulb are now regulated in many countries, with believers in the old ways having to buy in stocks of bulbs for the future, like in the war. And it’s not just in homes, schools, and offices that the light bulb is running out of time. Mercedes recently launched a new car that doesn’t have a single bulb; every bit of illumination (including the headlights) is done by LEDs. That was their big light bulb moment. Except it was LED. LED moment sounds a bit feeble. What will cartoonists do if they can’t draw a glowing light bulb over a loony toon’s head to indicate a good idea? The LED moment doesn’t have quite the same ring to it. The future of this marvelous invention is something we all should keep an eye for.
Reference
