OT It's all a Bloody con.........

I'm far from sure that will work properly. When an incandescent lamp is turned on, its resistance rises as it heats up, over a period of a fraction of a second. Put two in series, and a slight difference between the initial resistances will cause one to heat up faster than the other. The one that heats faster also sees its resistance rise faster, which in turn means that its rate of heating relative to the other rises further still.

It's easy to see that the end result of this is that one burns out before the other can heat up enough to take its share of the load.

Christmas Tree lights are usually wired in series, but the fact that there's a large number of them reduces this effect.

Sylvia.

Gee, I wonder why NOBODY in this newsgroup had never thought about that before?

Christmas Tree lights are NOT wired in series. If they were, once just ONE bulb blew out, the whole lot wouldn't work. Please think BEFORE you post, in futurer.

Seems to me that I have had to go round a set of Christmas Tree lights to find out which one isn't screwed in properly, thus extinguishing the entire set.

Sylvia.

The older ones with bigger lamps (about 2" long ) were in series but had something in the cap that that conducted when lamp blew and if too many blew the others got brighter until in the end they all blew You were supposed to change them as they went The new tiny lamp strings have a combination of series and parallel.

Addenda. They did not all have the devices in the cap Depend on brand

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As soon as I pressed the send key I knew you'd backpedal with this type of response. Yes Sylvia, SOME older type christmas lights are like you say, and every single light must work or none will work, but since around 1989 they changed the way they made christmas lights and these days it doesn't matter if you have a blown bulb or more - the lights will still operate. But hey, if you want to pick on some obscure set of lights that you bought back some 3 decades or so from a garage sale in Dubbo, then so be it. I most certainly won't lose sleep over it because I know that you were ONLY using the christmas light scenario to try to "prove" that you couldn't put two (2) 120v bulbs in series on a 240v circuit - and you were wrong. Diverting the facts doesn't make the facts any more wrongly.

I was only observing that Christmas tree lights are not a counter-example to my belief that putting two incandescent lights in series is not a good idea.

Saying that Christmas tree lights are wired in series was never going to be able to prove that two incandescent lights can't be wired in series. That much should have been obvious even to you.

Sylvia.

Whilst you are correct, and the life expectancy will be reduced to some degree, in practice it will probably still work out cheaper than buying

240v:120v transformers for every lamp, unless the cost of the globes is much more than current ones. (Remember the current flow is the same for both lamps in series, so they should both stabilise at roughly their expected operating temperatures. Given normal mass production techniques, the filament resistance and temperature characteristics will not vary much for similar globes. Probably NOT a good idea to use dissimilar globes however :-)

However both those ideas are really sub-optimal IMO. And hopefully since most countries are getting on the band wagon, there will now be an impetus to improve alternative lamps, and increased production levels will hopefully reduce their costs even further.

MrT.

Her or YOU?

Yep, very common in the old days. Unfortunately it also means when one globe blows, there is 240V across it's socket, and they were often not well protected. But then standard BC or Edison screw lamps aren't either, but at least are a bit more difficult to reach in most cases.

MrT.

I didn't mean that the life expectancy would be reduced, but that there's at least a good chance that one lamp will blow the first time you turn the pair on.

Yes - if they manage to reach it before one fails. My concern relates to imbalances during the turn on period.

I agree that they would be close for similar globes. But are they close enough to avoid unbalanced heating where the difference in the rate of heating is itself a rising function of temperature difference.

As something of an aside, some may be interested in the explanatory statement for the regulation amendment, which runs to 165 pages.

Sylvia.

For f*ck's sake there are some fools in this NG...and TG'sFM is a prime example...

LED tail lights and brake lights will much react faster than glow-wire lights.

messagenews:496574ce$0$20975$ snipped-for-privacy@news.optusnet.com.au...

OT

Possibly, yes. You are forgetting that ALL incandesent globes are going to be banned from November this year. This includes the brake light globes in your car. So instead of you instantly seeing red brake lights when the car in front hits the brake, you will only see it 20 seconds or so AFTER the brakes are applied. This WILL lead to more tail ender accidents, and as you suggested, it WILL cause many more road deaths. This isn't the trivial issue you first thought is it?

There are PLENTY of Christmas tree lights on the market (at the end of 2008) which consist of one string of incandescent bulbs wired in series. There are also many other types, ranging from LED's to short strings of series-connected bulbs.

messagenews:496574ce$0$20975$ snipped-for-privacy@news.optusnet.com.au...

it's OT

What on earth are you talking about?

20 seconds???

Incandescent tail lights are being replaced by LED's. LED's are MUCH faster than the incandescents they replace, and more reliable. Cars have had center LED brake lights for more than a decade now, haven't you noticed?

Dave.

Works but causes a noticeable flicker unfortunately.

MrT.

There is no effect on 12volt (in fact less than 220volt) bulbs until at least 2015 by which time most if not all automotive lamps will be LED or something better.

John G.

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rry it's OT

right-b...

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No Dave, I haven't noticed. I've had the same car for over 20 years, and ALL the lights are the incandescent - the same as they were when I bought it. I think I would have noticed if someone put in a centre LED light a decade ago. I'm not that stupid that I wouldn't have noticed.

FFS, can't you tell sarcasm when you read it? And besides, you're a top post, so you're in no position to label others as fools. While on the topic of top posting, if you can't control how you post, what OTHER bodily functions can't you control? I hope you don't live near a primary school or day care centre.

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By then cars may be computer controlled so we'll have no need for lights on our cars.