Filaments are made from tungsten.
This silver-white metal is both strong and durable, as well as malleable and elastic. On one hand, when combined with other metals, tungsten can be fabricated into tough, high-speed cutting tools (i.e., table-saw blades), or sturdy drill bit tips. On the other hand, it can be molded into light bulb filaments that look quite fragile, yet are so durable they can withstand extreme heat and modest jarring without fracturing.
Geography
Tungsten cannot be found as a free metal. It only occurs in the Earth's crust as a compound metal, such as calcium tungstate or lead tungstate. Worse, it is present in small amounts, about 1.5 grams for every ton (1,016,000 grams) of rocks. Fortunately, it is recyclable. In fact 30 percent of the supply for tungsten comes from recycled material, which helps keep the cost down.
Identification
Tungsten (atomic number 74; atomic weight 183.84; elemental symbol "W") is a silvery-white metal that resists oxidation and reactions to acids and alkalis. It has a high melting point (3,410 degrees Centigrade), and at temperatures greater than 1,650 degrees Centigrade, tungsten offers the greatest tensile strength---or elasticity---of any element. This means that tungsten is not only sturdy, it can stand up to the heat that a light bulb puts out.
Significance
Both halogen and incandescent light bulbs use heat---up to 3,000 degrees Centigrade (5,720 degrees Fahrenheit)---to produce light. Roughly 90 percent of the energy given off by these bulbs is heat. As a result, tungsten's high melting point is ideal for high-temperature materials, like electronic elements and lamp filaments.
Features
Some pieces of equipment and appliances require the use of metals that are thermally compatible---glass-to-metal seals, for instance. In the case of light bulbs, the glass has a boiling point that is very close to tungsten. Furthermore, heat expansion rates for both tungsten and glass are the same, which contributes greatly to their glass-metal seals.
Potential Problems
Because they are so durable and heat resistant, tungsten filaments will not break easily or burn out quickly, increasing the cost effectiveness of light bulb production. A few things, however, can shorten a bulb's lifespan, such as vibration (e.g., from garage door openers), voltage fluctuations along power lines, or appliances that put out more voltage than the light bulb can handle. Try changing to a light bulb with stronger filaments or higher voltage ratings. If problems persist, have an electrician check power coming into and running through the building.
Tags: light bulb, degrees Centigrade, high melting, high melting point, light bulbs, melting point
