wattage

[Big_Spark]

BAS...I was simply commenting that you failed to even think it was simply a typo on my part I missed..

As for the rest of your post..I simply cannot be bothered to get into a discussion when you are reading into things that don't exist.....

For a start where did I say the wattage of the lamp would be the same regardless...???????????????????????????????????????????????

 

[ban-all-sheds]

BAS...I was simply commenting that you failed to even think it was simply a typo on my part I missed..

OK - if you'll accept them at this stage I offer my apologies for not thinking that it could be a typo and that your attention to detail was insufficient.

As for the rest of your post..I simply cannot be bothered to get into a discussion when you are reading into things that don't exist.....

For a start where did I say the wattage of the lamp would be the same regardless...???????????????????????????????????????????????

Where did I say you had?

What I said was that your calculations with the example of the 60W lamp used the same resistance for the filament at two very different temperatures.

Which is fundamentally flawed, ignores the laws of physics, and relates directly to my opening question about how you thought you could "simply" calculate the wattage of a lamp based on the resistance of its filament at room temperature.

 

[Big_Spark]

OK - if you'll accept them at this stage I offer my apologies for not thinking that it could be a typo and that your attention to detail was insufficient.

Always...none of us are perfect and we all drop clangers..

As for the rest of your post..I simply cannot be bothered to get into a discussion when you are reading into things that don't exist.....

For a start where did I say the wattage of the lamp would be the same regardless...???????????????????????????????????????????????

Where did I say you had?

In your LONG post a couple ago...perhaps not what you meant..but it is how it read...

 

[ban-all-sheds]

Not much I can do if you read comments about resistance and think they're about wattage....

 

[Big_Spark]

as many, if not the majority of materials do,

Name me a metal that does not have a positive temperature coefficient of resistance.

I said MATERIALS not Metals..

however as I said, the resistance of the coiled coil is FIXED..it's resistance at a given temperature is the same at all times,

I see why you read my post (This bit) how you did, I have reread it and realised that whilst I knew what I meant..it was about as clear as mud to others..

What I was saying was that at any given temperature the resistance remains fixed. ie: at 10C it will always be 2 Ohms, at 30C it will always be 100 Ohms and at 1500C it will always be 1000 Ohms (Examples only). This is true, unless there is a change to the overall mechanical or molecular structure of the coil, whether it is the first time it is energised or the 10,000th time it is energised..

Perhaps now you will understand what I meant...apologies for the original muddy bit!!

 

[plugwash]

actually i'd imagine the resistance would increase slightly over the bulbs lifespan as the metal boils off until finally it gets hot enough at one spot that the coil fails completely.

 

[Big_Spark]

actually i'd imagine the resistance would increase slightly over the bulbs lifespan as the metal boils off until finally it gets hot enough at one spot that the coil fails completely.

Plug...that is why I said

This is true, unless there is a change to the overall mechanical or molecular structure of the coil, whether it is the first time it is energised or the 10,000th time it is energised..

Obviously there will be changes to the mechanical and molecular structure of the filament over time, but for the purposes of the discussion at hand they are not too relevent..well not as relevent as clearing up what I said and actually meant...

 

[Stoday]

All great fun.

No amount of excuses can persuade anyone who reads Big_Spark's first two posts that he completely forgot that the filiament's resistance increases significantly when it gets hot.

There's only one guy I've ever come across who continues to dig and dig when he's in the deepest of holes - FWL Engineer.

Waddya know? A little research shows Big_Spark to be the one and only FWL!

 

[Big_Spark]

Stoday, I didn't forget, I ignored it completely..as the information I had from the manufacturers stated the resistance at room temperature, and when calculated gave the stated wattage of the lamps.

It was as the discussion went on that I dug deeper and discovered that the manner they have written it is misleading as they state room temperature, but in fact the resistance figure quoted MUST be the working temeprature resistance. I can only assume this has been done purely for simplicities sake to save explaining about temperature coefficients...I fell into the trap and didn't spot it..only after I looked into it again as the thread progressed I realised what the situation was.

As for the FWL...well I ended my association wil Franklin-Wood, so the name was hardly appropriate, the DIYNot Admin kindly changed my login name..but everyone here knows that...

So no need for you to make assenine comments.

 

[ban-all-sheds]

Stoday, I didn't forget, I ignored it completely

You certainly did in your example calculation..

only after I looked into it again as the thread progressed I realised what the situation was.

But as I've observed, here and elsewhere, we first had to go through the all-too-familiar cycle of you waffling and insulting people before you finally accept that you might have been wrong and look again at what you were claiming.

Why??

 

[Big_Spark]

FFS Ban..I did not waffle or insult anyone. I said he was talking ****e..OK perhaps that was harsh but hardly any different to the snide comments I get from you and several others here..

Why do you not simply accept what i have said in my last post and leave it at that...

You accepted in your earlier post I made a typo with the example..YES I should have checked the post and spotted, I was lazy or hasty (take your pick) and din't spot it...Now you fu cki ng bang on about it again..

To be honest half the time I dig my heals in is not because a typo or an error is pointed out..but the fecking snidy two faced way it is done by certain people..and I tend to let my temper get the better of me...

I have my failings..temper being one of them anf this blinds me occasionally..especially when Tired....but why BAS, do you simply follow me about and often attack me..when others here posts total tosh and yet you say feck all...I think the word HYPOCRITE is in order on occasion...

BAS...those that live in glass houses should not throw stones...I suggest you rightly point out any typo's or mistakes I make, but perhaps you might like to also go after the liars, trolls and other ****eheads that frequent this BB these days..inlcuding those who post under several names as they are gutless dweebs.

 

[Stoday]

As for the FWL...well I ended my association wil Franklin-Wood, so the name was hardly appropriate, the DIYNot Admin kindly changed my login name..but everyone here knows that...

Well, sorry, but I didn't know. That may be because I've looked in on the forum less frequently of late. It got a bit quite during your absence, but now you're back it's sure to liven up a bit.

 

[ban-all-sheds]

FFS Ban..I did not waffle

Well, that guff about manufacturers quoting filament resistances at room temperature and having allowed for the thermal coefficient of resistance came across as waffle. Maybe one man's poorly explained idea is another man's waffle.

or insult anyone. I said he was talking s***te..OK perhaps that was harsh but hardly any different to the snide comments I get from you and several others here..

Except it wasn't **** was it? It was correct, and yet you simply refused to look at what he said, called it **** and tried to contradict it with an "example" that was utterly wrong. I'd say it was pretty insulting towards Cork for you to dismiss like that something he'd written that was correct without taking the trouble to read it or think about it.

And you also said to me

As for the rest you post..**** fella

That looks like an insult to me.

Why do you not simply accept what i have said in my last post and leave it at that...

You accepted in your earlier post I made a typo with the example..YES I should have checked the post and spotted, I was lazy or hasty (take your pick) and din't spot it...Now you fu cki ng bang on about it again..

I didn't mention the typo at all - I merely agreed with you that you had ignored the fact that tungsten has a significant thermal coefficient of resistance.

To be honest half the time I dig my heals in is not because a typo or an error is pointed out..but the f*****g snidy two faced way it is done by certain people..and I tend to let my temper get the better of me...

I have my failings..temper being one of them anf this blinds me occasionally..especially when Tired....but why BAS, do you simply follow me about and often attack me

I don't "follow you around" - don't flatter yourself.

Nor do I "often attack you". If you find that I often say that you are wrong then it's because you are often wrong. And if it gets heated it's because of your sheer intransigence - something that a lot of other people have noted as well - remember the "full load current" debate?

..when others here posts total tosh and yet you say f**k all...I think the word HYPOCRITE is in order on occasion...

I invite you to read the recent exchanges I've had with bazdaa, sijaysee, dave9 and seahawk2nigel.....

BAS...those that live in glass houses should not throw stones...I suggest you rightly point out any typo's or mistakes I make, but perhaps you might like to also go after the liars, trolls and other ****heads that frequent this BB these days..

... and joe-90....

 

[Big_Spark]

Well I have just performed a litttle experiment..and I was rather surprised by the result...

I have a fitting in my hall that take three RO40 SES Reflector lamps....so they have lovely tungsten filament coils in them..

Anyway, I zeroed my meter and then measured the resistance at the terminals of the lamp..

The resistance cold was 106.1 Ohms..

I them put the lamp min the fitting for 5 minutes, took it out and immediately measured the resistance of the hot coil...it was only 160.7 Ohms..it hovered for a split second and then started to fall at a steady 0.2 Ohms per second as the coil cooled. Now I estimate it took me about 4 seconds to unscrew the lamp and measure it..so allowing for this cooling it implies the at temperature resistance of the lamp is around 162 Ohms..

Now I appreciate this is not very scientific, but it does give us an idea.

So we have a

Cold resistance of 106.1 Ohms
Hot Resistance of 162 Ohms

Measured Voltage of supply 237.6 V

Frequency of supply averaging 49.85 hertz

From Ohms law we know that to find the Power used by something we need to find out the current drawn..

So at Hot... I= V/R = 237.6 / 162 = 1.466 A

P = VI = 237.6 x 1.466 = 348.32 Watts of energy....

This had me baffled...so I then did the test 5 times each on two different lamps...the results were the same everytime...although there was about 0.7 Ohms between the two lamps...

I just tested a 100W Tungsten Filament Lamp...

Cold resistance...31.2 Ohms

Hot Resistance 64.9 Ohms

So doing the same equations for this..

I= V/R = 237.6 / 64.9 = 3.66A

P = VI = 237.6 x 3.66 = 869.61 Watts of energy?

This seems very wrong to me as I do not think filament lamps use this much energy..but could there rated wattage actually be simply the VISIBLE light wattage rather than the actual power used...I certainly have no information or even experience either way...

Next test will be clamp meter on the core to directly measure load...just have to rig up a test bed now to do it...

What is interesting here is that the ratio bewteen the power used by calculation and the rated wattage of the lamp is almost identical at 8.7/1...for me that is a little too coincidental and implies there is something real there...

This blooming thread has me going now..one of those everyday things we never think about and yet seems to fly in the face of what we thought we know...Thanks for all the contributors...I love this sort of mystery I can get my teeth into...

 

[moderator]

Its "Christmas", obviously you two have a disagrrement, but moaning about who said what does not help any one on this forum.

You two are some of the most influential posters with regard to electrics, if you do not make up, or agree to dissagrre i will remove the post (besides you two swear too much)