how does a light bulb work?

Answer 1

This depends upon the type of light bulb that you are talking about.

There are several good (even if lengthy and cut and paste) answers above on how an incandescent bulb works. These are the ones with a classic "bulb" shape and the tungsten element which has a high resistance and heats up to release photons (the light).

There are several other kinds of light bulbs including fluorescent, neon and others. Arc lamps such as Xenon and Mercury also work on a different principle.

Instead of writing pages to cover all of these, please look at the sites below if you have an interest in how these other bulbs work.

Answer 2

The tungsten filament in a modern light bulb is supported by several molybdenum wires. The ends of the support wires are embedded in a glass button at the top of the glass support rod. The copper and nickel lead-in wires, which carry the current to the filament, are supported by a glass support stem. One lead-in wire is soldered to the metal contact at the base of the bulb, while the other is electrically connected to the side socket contact. The contacts are separated by an insulating plate.
An electrical current can pass in either direction through the filament. During manufacture, the bulb is evacuated through the exhaust tube and filled with nitrogen/argon gas. The bulb is partially re-evacuated and the lower end of the tube heat-sealed. The lead-in wires are soldered to their contacts and the glass bulb cemented to the threaded metal base.
Light is generated in a light bulb when an electric current passes through a filament, which heats the filament white hot.
Current can pass in either direction through the filament. The current flows through the filament through the lead-in and support wires.

Answer 3

The filament of a light bulb is made of tungsten, a very hard metal that conducts electricity very poorly. It imposes so much resistance to the flow of electricity, it glows white hot when electricity is run through it and thus emits light.

Neon tubes force electricity to pass through the neon gas inside the tube, and you see the millions of electric "hops" from electron to electron as the current finds its way through the gaseous matrix to the other end of the tube.

The first electric light bulbs are pictured on stone hieroglyphs of ancient Egypt. There is no evidence of ash or other indicators of burning substances to light the way in the various labyrinths uncovered by archeology in ancient Egypt.

Answer 4

Electricity, passing through the filament gets it hot. As it heats, electrons in the shells of the filament atoms are raised to higher energy levels. As they fall back to their rest energy, a photon of light is emitted. Think of this process like the surface of boiling water, with little droplets of water spraying off the top. Except in this case, the droplets (photons) pass out of the bulb and ultimately strike the retina in your eye.

A vacuum in the bulb keeps the filament from oxidizing, which would cause it to burn out very quickly. So why does the filament burn out at all? The metal filament gets hot enough to actually evaporate atoms off of the surface. This is a slow process, but eventually, after many hours of running, the filament gets thinner and thinner and finally breaks.

Time for a new bulb at that point!

Light photons exit the surface of the filament in all directions. Sometimes this is desirable, as in a bulb for a lamp, but sometimes its not, as in a flashlight. In that case, a reflector is used to reflect the light going in the wrong direction (backwards) back out the front. In this way, the flashlight looks brighter than it would without a reflector since most of the light is directed forward.

Hope this helps...

Answer 5

A light bulb works because nobody else wants the job.

Answer 6

U Flip The Switch On The Wall

Answer 7

the electrons go though the wires in the bulb and move so fast that light is produced.

Answer 8

Rough Answer:
Electricity passes into the lightbulb, then through the heating element which heats enough to produce a visible white light.

Answer 9

High Performance Tactical Flashlight - http://FlashLight.uzaev.com/?ThlB

Answer 10

Before the invention of the light bulb, illuminating the world after the sun went down was a messy, arduous, hazardous task. It took a bunch of candles or torches to fully light up a good-sized room, and oil lamps, while fairly effective, tended to leave a residue of soot on anything in their general vicinity.



When the science of electricity really got going in the mid 1800s, inventors everywhere were clamoring to devise a practical, affordable electrical home lighting device. Englishman Sir Joseph Swan and American Thomas Edison both got it right around the same time (in 1878 and 1879, respectively), and within 25 years, millions of people around the world had installed electrical lighting in their homes. The easy-to-use technology was such an improvement over the old ways that the world never looked back.

The amazing thing about this historical turn of events is that the light bulb itself could hardly be simpler. The modern light bulb, which hasn't changed drastically since Edison's model, is made up of only a handful of parts. In this article, we'll see how these parts come together to produce bright light for hours on end.

Light Basics
Light is a form of energy that can be released by an atom. It is made up of many small particle-like packets that have energy and momentum but no mass. These particles, called light photons, are the most basic units of light. (For more information, see How Light Works.)

Atoms release light photons when their electrons become excited. If you've read How Atoms Work, then you know that electrons are the negatively charged particles that move around an atom's nucleus (which has a net positive charge). An atom's electrons have different levels of energy, depending on several factors, including their speed and distance from the nucleus. Electrons of different energy levels occupy different orbitals. Generally speaking, electrons with greater energy move in orbitals farther away from the nucleus. When an atom gains or loses energy, the change is expressed by the movement of electrons. When something passes energy on to an atom, an electron may be temporarily boosted to a higher orbital (farther away from the nucleus). The electron only holds this position for a tiny fraction of a second; almost immediately, it is drawn back toward the nucleus, to its original orbital. As it returns to its original orbital, the electron releases the extra energy in the form of a photon, in some cases a light photon.





The wavelength of the emitted light (which determines its color) depends on how much energy is released, which depends on the particular position of the electron. Consequently, different sorts of atoms will release different sorts of light photons. In other words, the color of the light is determined by what kind of atom is excited.

This is the basic mechanism at work in nearly all light sources. The main difference between these sources is the process of exciting the atoms.

Light bulbs have a very simple structure. At the base, they have two metal contacts, which connect to the ends of an electrical circuit. The metal contacts are attached to two stiff wires, which are attached to a thin metal filament. The filament sits in the middle of the bulb, held up by a glass mount. The wires and the filament are housed in a glass bulb, which is filled with an inert gas, such as argon.





When the bulb is hooked up to a power supply, an electric current flows from one contact to the other, through the wires and the filament. Electric current in a solid conductor is the mass movement of free electrons (electrons that are not tightly bound to an atom) from a negatively charged area to a positively charged area.

As the electrons zip along through the filament, they are constantly bumping into the atoms that make up the filament. The energy of each impact vibrates an atom -- in other words, the current heats the atoms up. A thinner conductor heats up more easily than a thicker conductor because it is more resistant to the movement of electrons.

Bound electrons in the vibrating atoms may be boosted temporarily to a higher energy level. When they fall back to their normal levels, the electrons release the extra energy in the form of photons. Metal atoms release mostly infrared light photons, which are invisible to the human eye. But if they are heated to a high enough level -- around 4,000 degrees Fahrenheit (2,200 degrees C) in the case of a light bulb -- they will emit a good deal of visible light.

The filament in a light bulb is made of a long, incredibly thin length of tungsten metal. In a typical 60-watt bulb, the tungsten filament is about 6.5 feet (2 meters) long but only one-hundredth of an inch thick. The tungsten is arranged in a double coil in order to fit it all in a small space. That is, the filament is wound up to make one coil, and then this coil is wound to make a larger coil. In a 60-watt bulb, the coil is less than an inch long.

Tungsten is used in nearly all incandescent light bulbs because it is an ideal filament material. In the next section, we'll find out why this is, and we'll examine the role of the glass bulb and inert gas.

The Right Materials
As we saw in the last section, a metal must be heated to extreme temperatures before it will emit a useful amount of visible light. Most metals will actually melt before reaching such extreme temperatures -- the vibration will break apart the rigid structural bonds between the atoms so that the material becomes a liquid. Light bulbs are manufactured with tungsten filaments because tungsten has an abnormally high melting temperature.

Bright, Brighter, Brightest
Light bulbs are ranked by their power -- the amount of light they put out in a certain period of time (measured in watts). Higher-watt bulbs have a bigger filament, so they produce more light.
A three-way bulb has two filaments of different wattage -- typically a 50-watt filament and a 100-watt filament. The filaments are wired to separate circuits, which can be closed initially using a special three-way socket.

The switch in the three-way socket lets you choose from three different light levels. On the lowest level, the switch closes only the circuit for the 50-watt filament. For the medium light level, the switch closes the circuit for the 100-watt filament. For the brightest level, the switch closes the circuits for both filaments, so the bulb operates at 150 watts.


But tungsten will catch on fire at such high temperatures, if the conditions are right. Combustion is caused by a reaction between two chemicals, which is set off when one of the chemicals has reached its ignition temperature. On Earth, combustion is usually a reaction between oxygen in the atmosphere and some heated material, but other combinations of chemicals will combust as well.

The filament in a light bulb is housed in a sealed, oxygen-free chamber to prevent combustion. In the first light bulbs, all the air was sucked out of the bulb to create a near vacuum -- an area with no matter in it. Since there wasn't any gaseous matter present (or hardly any), the material could not combust.

The problem with this approach was the evaporation of the tungsten atoms. At such extreme temperatures, the occasional tungsten atom vibrates enough to detach from the atoms around it and flies into the air. In a vacuum bulb, free tungsten atoms shoot out in a straight line and collect on the inside of the glass. As more and more atoms evaporate, the filament starts to disintegrate, and the glass starts to get darker. This reduces the life of the bulb considerably.

In a modern light bulb, inert gases, typically argon, greatly reduce this loss of tungsten. When a tungsten atom evaporates, chances are it will collide with an argon atom and bounce right back toward the filament, where it will rejoin the solid structure. Since inert gases normally don't react with other elements, there is no chance of the elements combining in a combustion reaction.

Cheap, effective and easy-to-use, the light bulb has proved a monstrous success. It is still the most popular method of bringing light indoors and extending the day after sundown. But by all indications, it will eventually give way to more advanced technologies, because it isn't very efficient.

Incandescent light bulbs give off most of their energy in the form of heat-carrying infrared light photons -- only about 10 percent of the light produced is in the visible spectrum. This wastes a lot of electricity. Cool light sources, such as fluorescent lamps and LEDs, don't waste a lot of energy generating heat -- they give off mostly visible light. For this reason, they are slowly edging out the old reliable light bulb.