Edison effect for Incandescent Bulb?

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In summary, the conversation discusses the process of thermionic emission in incandescent light and whether it still occurs in modern bulbs without anode collectors. It also raises questions about the amount of electron gas in the vacuum space within the bulb. Research has been done on this topic in relation to vacuum tubes, but not specifically for incandescent lamps.
  • #1
wang0073
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Hi,

I would like to ask a question on incandescent light.

attachment.php?attachmentid=65536&stc=1&d=1389528471.jpg


From the Thermionic emission (Edison effect), heated tungsten filament emits electrons that could be collected by an anode (like a foil connected to positive voltage).

The wiki also mentions that in order to facilitate thermionic emission, tungsten is often treated with mixture of barium, strontium and calcium.

Does this emission happen in a normal incandescent lamp? In the bulb which Edison discovered the effect, there is a plate(foil) inserted into the bulb from the base, this is absent in normal bulbs. Does the tungsten filament still emit electron in this case? If it does, where would the emitted electron go? Without an anode collector, will they be suspended in the vacuum (assume a vacuum bulb) space inside the bulb?

This further brings up a question to the energy balance (conservation) question in a vacuum bulb:

attachment.php?attachmentid=65534&stc=1&d=1389527590.jpg


This is the fundamental equation for all tungsten filament temperature calculation when the inside of the bulb is vacuum, and appears in Irving Langmuir’s 1936 http://prola.aps.org/abstract/PR/v50/i1/p68_1 and numerous others.
Do we need to consider the thermionic effects for an ordinary incandescent bulb? How should we modify the equation above?



Wang
 

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  • #2
If the filament is hot enough, emission has to happen. However, as the emitted electrons have nowhere to go except back into the filament, and the filament becomes positive due to the emission, they will tend to go back to the filament. There is going to be some equilibrium amount of electron gas in the bulb but most likely not very significant to bother about.
 
  • #3
Definite figure?

Dear voko,

I agree very much with your answers and believe that an equilibrium will eventually (and very soon) be reached wtih very small amount of electron gas actually suspended in the vacuum space within the bulb.

There is another Physical Review http://prola.aps.org/abstract/PR/v29/i2/p337_1 (Vannevar Bush, MIT, 1927) which also dealt with thermionic emisson on tungsten filament.

Do you know where can I get some definite quantitative figure/data on the amount of electron emitted and henceafter remain in the vacuum bulb space?


Wang
 
  • #4
I would actually be surprised if somebody researched electron emission in an incandescent lamp. On the other hand, the theory required for that is part of the theory required to analyze and design vacuum tubes, and a lot has been written on that. Hopefully that should give some ideas on what to look for.
 
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  • #5
,

Thank you for your questions regarding the Edison effect and its relation to incandescent bulbs. I am happy to provide some insight on this topic.

Firstly, it is important to note that the Edison effect is a phenomenon that occurs in all incandescent bulbs, not just the one that Edison discovered. This effect is a result of the thermionic emission of electrons from a heated tungsten filament. This means that in a normal incandescent bulb, the filament is heated and releases electrons that can be collected by an anode, which is typically connected to a positive voltage source.

In order to facilitate this thermionic emission, the tungsten filament is often treated with a mixture of barium, strontium, and calcium. This treatment helps to lower the work function of the tungsten, making it easier for electrons to be released from the filament.

Now, to address your question about the absence of a plate or foil in normal incandescent bulbs. While this may be true for some bulbs, it is not necessary for the Edison effect to occur. The emitted electrons would still be collected by the positively charged anode, which is typically located at the base of the bulb. Without an anode, the electrons may remain suspended in the vacuum space inside the bulb, but they would eventually dissipate.

Regarding the energy balance in a vacuum bulb, the thermionic effect does play a role in the temperature calculation of the tungsten filament. However, it is not the only factor to consider. Other factors such as convection and radiation also play a role in the energy balance of the bulb. As a result, the equation you mentioned may need to be modified to account for these additional factors.

In conclusion, the Edison effect is a crucial aspect of incandescent bulbs and plays a role in their operation. While it may not be the only factor to consider in the energy balance, it is an important phenomenon to understand in order to fully grasp the functioning of incandescent bulbs. I hope this helps to answer your questions.
 

1. What is the Edison effect for Incandescent Bulb?

The Edison effect is the phenomenon where a current can flow between two electrodes in a vacuum tube without any external electric field. This effect is crucial for the functioning of incandescent bulbs, as it allows for the production of light through the heating of a filament.

2. Who discovered the Edison effect for Incandescent Bulb?

The Edison effect was discovered by Thomas Edison in 1883. He observed that when a current was passed between two electrodes in a vacuum, the current flow would increase as the temperature of the filament increased.

3. How does the Edison effect work in Incandescent Bulbs?

The Edison effect works in incandescent bulbs by heating a thin filament made of a material with a high melting point, such as tungsten. This causes the electrons in the filament to gain energy and become excited, creating a flow of electrons from the hot filament to the cooler electrode, thus producing light.

4. What are the applications of the Edison effect in Incandescent Bulbs?

The Edison effect has many applications in incandescent bulbs, as it allows for the production of light through the heating of a filament. This technology is widely used in residential and commercial lighting, as well as in automotive headlights and flashlights.

5. Is the Edison effect still relevant in modern lighting technology?

While the Edison effect is still relevant in incandescent bulbs, it is not commonly used in modern lighting technology. Most modern lighting solutions, such as LED and fluorescent bulbs, use different mechanisms for producing light, making them more energy-efficient and longer-lasting compared to incandescent bulbs.

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