Why is argon better than a vacuum?

In summary, Argon gas is used in lightbulbs because it is non-reactive and prevents the filament from evaporating and coating the inside of the bulb. It is also cheaper than creating a perfect vacuum inside the bulb. Additionally, the pressurized gas helps to withstand pressure differentials and prevent the bulb from shattering. However, there are other factors to consider such as heat transfer and diffusion.
  • #1
eurekameh
210
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Argon gas is used in a lightbulb because it's not reactive, whereas air is. But why is it better than a vacuum?
 
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  • #2
My guesses:
1) If there is pressure inside the bulb, you don't need the glass to be as strong.
2) The gas will conduct heat away from the filament, cooling it down. (I'm not sure this is a good thing though.)
 
  • #3
Prolongs the life of the filament.
 
  • #4
eurekameh said:
Argon gas is used in a lightbulb because it's not reactive, whereas air is. But why is it better than a vacuum?

A near perfect vacuum would be required. Argon is non-reactive and replaces the air.
Basically, it's a manufacturing cost/benefit ratio type of thing.
Argon infusion is cheaper than vacuum.
 
  • #5
Doesn't the partial pressure also discourage the bulb coating and filament materials from slowly evaporating, as they would tend to do in a vacuum?
 
  • #6
vacuum will also cause the shell to shatter under the atmosphere
 
  • #7
Curl said:
vacuum will also cause the shell to shatter under the atmosphere

Why would you say that? Bulbs are actually very good at withstanding pressure differentials. In fact, up until about 1913, light bulbs were manufactured with a vacuum (or at least as close as they could come).

Today, most bulbs are pressurized at about 0.7 atmospheres at room temperature to accommodate for expansion as the bulb heats.
 
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  • #8
Ding ding, DaveC426913 wins. The primary need for an internal gas is not structural but to prevent the filament from evaporating and coating the inside of the bulb with a thin layer of opaque metal. With some partial pressure (ideally from an inert gas so as not to react with the filament), any metal atom that evaporates from the filament will get bounced right back instead of traveling, line-of-sight, to the glass. http://books.google.com/books?id=a6...resnum=1&ved=0CDcQ6AEwAA#v=onepage&q&f=false"
 
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  • #9
Algr said:
2) The gas will conduct heat away from the filament, cooling it down. (I'm not sure this is a good thing though.)

Not trying to be pedantic, just learning physics, and this is a bit of a derail, but wouldn't this heat transfer be primarily convection and not conduction?
 
  • #10
KingNothing said:
Why would you say that? Bulbs are actually very good at withstanding pressure differentials. In fact, up until about 1913, light bulbs were manufactured with a vacuum (or at least as close as they could come).

Today, most bulbs are pressurized at about 0.7 atmospheres at room temperature to accommodate for expansion as the bulb heats.

Really? Try blowing glass with a perfect symmetry. Then ding it against the table and see what happens if there is a vacuum inside.
Also, let the filament heat the glass up and then hang it from a wall and see what creep is.
There is also diffusion which means a vacuum won't stay long. In 1910 the bulbs were made thick, it was pretty much a jar with a wire in it. Now they're trying to save money and are 400 microns thick in some cases.

The no.1 reason is what Dave said, but I wasn't going to repeat it and was just offering another reason why Argon is good.
 

1. What is the difference between argon and a vacuum?

Argon is a chemical element with atomic number 18 and symbol Ar. It is an inert gas that is commonly used in various industrial and scientific applications. A vacuum, on the other hand, is an area devoid of any matter, including gas molecules. In simple terms, argon is a gas while vacuum is the absence of any gas.

2. Why is argon considered better than a vacuum?

Argon is considered better than a vacuum in certain situations because it has several advantages over a vacuum. For example, argon can be easily controlled and manipulated, making it useful for various processes such as welding, lighting, and insulation. It also provides a more stable and controlled environment compared to a vacuum, which can vary in pressure and temperature.

3. How does argon compare to a vacuum in terms of insulation?

Argon is a better insulator than a vacuum because it has a higher thermal conductivity. This means that it is better at trapping heat and preventing it from escaping, making it useful for insulation in windows, refrigerators, and other applications. In contrast, a vacuum does not have any gas molecules to trap heat, so it is not as effective as an insulator.

4. Can argon be used in place of a vacuum in all situations?

No, argon cannot be used as a substitute for a vacuum in all situations. While it has many advantages, a vacuum still has certain applications where it is preferred. For example, in electronic devices, a vacuum is often used to prevent oxidation and contamination, which cannot be achieved with argon.

5. Is argon more expensive than a vacuum?

Yes, argon is more expensive than a vacuum. This is because argon is a gas that needs to be produced and stored, while a vacuum is simply the absence of any gas. The cost of producing and storing argon contributes to its higher price compared to a vacuum.

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