Saturday, December 5, 2015

FAQ-3 Random Question About Incandescent Light Bulb

Do you know there is an incandescent light bulb that is on for about 114 years? Sounds weird right! Because most of the similar lamps that we use usually dies within couple hundred to thousand hours of service, but this light bulb at California, USA is actually here for about this time. Anyway good evening everyone this post will be about as you have already guessed Incandescent lamp.

Incandescent light probably is the oldest type of electrical light bulb and it is here for a pretty long time now, although they are kinda at the end of their prime but they are still used in many different places where heat is needed as this light bulbs are very inefficient, they puts out huge amount of heat and also in places where cheap lighting solution is needed. Anyway maybe will post some more on to this topic later, for now let's look at the questions.



Q1. Why does incandescent light bulb damages mostly during they turn on?

Well it is a very interesting question, you will see that this type of lights usually burns out while you switch them on, yes they do get damaged during service but what I have seen and pretty sure many other people have seen, they tend to get damaged while the turn on process. To understand why we have to know how this light bulbs actually work. Incandescent lamps are probably the simplest thing to understand, the only thing they have is a filament in either vacuum or inert gas filled glass structure. This metal filament (mostly tungsten) is coiled and is attached to two metal connector which provides the electrical connection. Whenever you put it in a power source the voltage across this filament pushes current through it, and pushing current through a wire with resistance makes it hot and starts glowing, hence we get the light. Now why it is covered in the glass? Mostly because if it was open it would have oxidized pretty easily and burn out the filament in seconds so the glass chamber and it is vacuum. Although vacuum can get rid of the oxidization problem but while the light is on, the metal filament starts to evaporate, hence lowering the strength of the filament and eventually leading to failure. To prevent this inert gas is introduced at 0.7 atmospheric pressure which redeposit the evaporated metal on to the filament again and increasing life span of the lamp. Yet none of this is 100% accurate so lamps do get damaged over time, the filament gets weak.

So back to the original question, you see when the lamp is first turned on the metal filament is cold and we know cold metal have less resistance than hot metal, so during the first turn on the lamp allows a high amount of current through it but as soon as the filament heats up the resistance starts to increase thus decreasing the current through it. Consider this, a incandescent lamp is on and it is taking in a certain amount of current and with time the filament is getting weaker, but okay for the amount of current it is carrying during the comparatively high resistance hot filament state but you have turned it off after say a 20 hour service and the filament is weaker than before, so when you turn on next time the amount of current can be such that it blows the filament, so this is what usually happens and we see that incandescent lamps got damaged mostly while being turned on.


Q2. What is the life span of a normal incandescent lamp?

About 1000 hours, but there is more to this question, actually incandescent lamps have much greater life-span but manufacturers intentionally lowers that to 1000 hours to make more sale. This is a very interesting story,will put a link below.


Q3. What is the efficiency of this type of lamps?

About 10% at best, if you need light. If you need heat, well then the efficiency is much higher.


Q4. What type of load is a incandescent lamp is?

Like I said earlier it can be treated as a resistor so it is a purely resistor based element which means it has a power factor of 1 and it can be used on AC or DC without any problem.

So anyway I don't actually have any more frequently asked question about this topic but if you have any please do let me know and this incandescent lamp was an enormous innovation to be honest, you know what people say about them? "The most profound invention since man-made fire", they served us pretty well and still serving us, they are clean, cheap and easy to work with but due to their lack of efficiency many countries are banning them or replacing them but no matter what people will never forget these lamps for sure.


Resources:


The incandescent lamp that is on for about 114 years! 

So I was talking about manufacturers limiting the life-span to 1000 hours, here take a look at this article.

Want to know more about incandescent lamp? Read this!

Interested in reading some more? Here, visit the index page of my blog!

Picture is taken from internet.

Have a great day! 

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