41
Physics, Astronomy & Cosmology / bar magnet into ring magnet?
« on: 27/09/2009 18:19:23 »
Huh..
What happened to the previous posts?
What happened to the previous posts?
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42
Physics, Astronomy & Cosmology / bar magnet into ring magnet?
« on: 27/09/2009 18:16:41 »
Thanks again RD. [
]
I remember having some of those on a wooden dowel N to N and S to S so they levitated, fun stuff. I was messing about at the time with an idea for frictionless bearings.
But referring to the bent bar magnet, the first link says "no point is more N-like or S-like. Therefore a toroidal magnet has no poles" and yet we know toroids with poles do exist so I'm still a bit confused.
Its easy to make a ring magnet with poles on the sides but a bent bar magnet seems to retain a magnetic field and yet have no poles. If the poles in this case do migrate to the sides when the ring is formed then its the mechanism that causes this I'm after.
]I remember having some of those on a wooden dowel N to N and S to S so they levitated, fun stuff. I was messing about at the time with an idea for frictionless bearings.
But referring to the bent bar magnet, the first link says "no point is more N-like or S-like. Therefore a toroidal magnet has no poles" and yet we know toroids with poles do exist so I'm still a bit confused.
Its easy to make a ring magnet with poles on the sides but a bent bar magnet seems to retain a magnetic field and yet have no poles. If the poles in this case do migrate to the sides when the ring is formed then its the mechanism that causes this I'm after.
43
Technology / Are electrical plugs watertight?
« on: 27/09/2009 17:23:10 »
Normally watertight plugs are used in conjunction with watertight sockets and would have a dust and water I.P. rating mark. Although sold separate they are normally used in pairs. There's no point in having a watertight plug if the socket is not watertight.
First digit is for dust protection and the second is for water with the highest number giving greater protection.
IP66 = dust tight and sea spray or wave protected
IP68 = dust tight and complete water immersion protected.
If you have accidentally immersed the plug in water then as already said it would be better to cut it off an put on a new one.
First digit is for dust protection and the second is for water with the highest number giving greater protection.
IP66 = dust tight and sea spray or wave protected
IP68 = dust tight and complete water immersion protected.
If you have accidentally immersed the plug in water then as already said it would be better to cut it off an put on a new one.
44
Physics, Astronomy & Cosmology / bar magnet into ring magnet?
« on: 26/09/2009 23:28:31 »
Hi.
If I take a longish bar magnet and bent it into a circle, connecting North to South, what then happens to the poles positions? Do they cancel out and it stops being magnetised or do they change positions? If its the latter then why?
All I've got is a bar magnet and no strength to bend it so I hope spinach is not the answer. [
]
If I take a longish bar magnet and bent it into a circle, connecting North to South, what then happens to the poles positions? Do they cancel out and it stops being magnetised or do they change positions? If its the latter then why?
All I've got is a bar magnet and no strength to bend it so I hope spinach is not the answer. [
] 45
Just Chat! / Is 'being green' being hijacked by policy-makers and advertisers?
« on: 26/09/2009 22:18:37 »
Very interesting..but stupid. [
]
]
46
Geek Speak / Re: Need Help.........pls
« on: 26/09/2009 16:39:46 »
I hope i've understood the question right!
If you wish to reset just the MBR data then you can use the FIXMBR tool on the XP disk. It does not delete the partition but will put drive C: back to its original boot state.
Put the xp cd in the drive and boot up from it, then when given a choice go to the recovery console and enter Fixmbr, the new mbr will then be written to the C: drive. This can also be used to delete any Linux boot entry on the MBR.
If you wish to reset just the MBR data then you can use the FIXMBR tool on the XP disk. It does not delete the partition but will put drive C: back to its original boot state.
Put the xp cd in the drive and boot up from it, then when given a choice go to the recovery console and enter Fixmbr, the new mbr will then be written to the C: drive. This can also be used to delete any Linux boot entry on the MBR.
47
Physics, Astronomy & Cosmology / Re: What is the mass of the cosmic microwave background radiation (CMBR)?
« on: 25/09/2009 20:00:31 »
Quote from the The Physics Factbook, a fair use website. [8D]
http://hypertextbook.com/facts/2004/HeatherFriedberg.shtml
"For your information: there are about 412 cmB photons per cubic cm (with an uncertainty of about 1); the energy density is the equivalent of 0.261 electron Volts per cubic cm (again uncertain by about +/-1 in the last decimal place); the equivalent mass density is 4.66 × 10-31 kilogrammes per cubic metre."
It maybe helpful if you can do the maths, unfortunately I cant. [:I]
http://hypertextbook.com/facts/2004/HeatherFriedberg.shtml
"For your information: there are about 412 cmB photons per cubic cm (with an uncertainty of about 1); the energy density is the equivalent of 0.261 electron Volts per cubic cm (again uncertain by about +/-1 in the last decimal place); the equivalent mass density is 4.66 × 10-31 kilogrammes per cubic metre."
It maybe helpful if you can do the maths, unfortunately I cant. [:I]
48
Physiology & Medicine / Are we made to die?
« on: 24/09/2009 16:58:02 »
Hi Dimi.
Have a read about calorific restriction, something that I practice. I wont go into the mechanism of it here but its stated that it can increase life expectancy by many years.
http://en.wikipedia.org/wiki/Calorie_restriction
Have a read about calorific restriction, something that I practice. I wont go into the mechanism of it here but its stated that it can increase life expectancy by many years.
http://en.wikipedia.org/wiki/Calorie_restriction
49
Just Chat! / What is the symbol for Unobtainium?
« on: 21/09/2009 17:55:52 »
Have you not seen the film The Core?
Its a joke material that the outer shell of the vehicle was made with and just as Laura stated it don't exist.
Its a joke material that the outer shell of the vehicle was made with and just as Laura stated it don't exist.
50
Geek Speak / How can we download whole play list from Youtube ?
« on: 21/09/2009 17:40:00 »
If you use the Firefox browser then you can "grab" the video but you have to play each video first. Once played it then gets stored in the browsers "cache" which can then be copied. Don't close firefox until its finished playing and the file has been copied or the file may be corrupt.
Path:
documents and settings/yourname/local settings/application data/mozilla/firefox/profiles/cache
If you view the cache folder while playing the video you will see what file is being updated. The file will have a number with no . extension so when the video has stopped copy and rename the file and add .flv extension.
I have successfully copied physics vids that way and then transferred them to mpg format.
There are other software programs that can do this but I cant seem to get any of them to work right so this is now the way I do it.
Path:
documents and settings/yourname/local settings/application data/mozilla/firefox/profiles/cache
If you view the cache folder while playing the video you will see what file is being updated. The file will have a number with no . extension so when the video has stopped copy and rename the file and add .flv extension.
I have successfully copied physics vids that way and then transferred them to mpg format.
There are other software programs that can do this but I cant seem to get any of them to work right so this is now the way I do it.
51
Physics, Astronomy & Cosmology / Why I Don't Like String Theory
« on: 21/09/2009 17:13:42 »
I must admit I also don't like the idea of string theory for the same reason. Its an abstract concept created by mathematicians that needs extra dimensions to make it work and is far from simple. I think quote number 3 is about right.
Many things can be predicted in quantum physics but that does not mean that they will all necessarily be correct, just that they are possiblities. String theory predicts magnetic monopoles, QM predicts Gravitons and singularities but again they are just other examples of possibilities that MAY exist.
Correction. I forgot about the old simpler concept of strings (ropes or threads) that dates back to c1885 and was primarily written as an exercise in Karma.
Many things can be predicted in quantum physics but that does not mean that they will all necessarily be correct, just that they are possiblities. String theory predicts magnetic monopoles, QM predicts Gravitons and singularities but again they are just other examples of possibilities that MAY exist.
Correction. I forgot about the old simpler concept of strings (ropes or threads) that dates back to c1885 and was primarily written as an exercise in Karma.
52
Just Chat! / What is the symbol for Unobtainium?
« on: 20/09/2009 19:43:16 »
I think that's a core question in physics.. []
]
53
Technology / Re: How do you select the appropriate power supply for an application?
« on: 20/09/2009 19:36:46 »
For a simple and stable circuit just use a bridge rectifier with a large ripple capacitor and add a 3 pin +5v voltage regulator such as the LM805 range.
You don't state what the output of the transformer is but the LM805 can operate up to 30-35v input with minimum being 7.5v.
You don't state what the output of the transformer is but the LM805 can operate up to 30-35v input with minimum being 7.5v.
54
That CAN'T be true! / Snake with a Foot
« on: 17/09/2009 17:05:17 »
Poor snakey. [
]
As an owner and breeder of snakes I agree with JnA, the bulge gives it away.
Another one that was not so lucky;
http://news.bbc.co.uk/1/hi/world/americas/4313978.stm [:0]
]As an owner and breeder of snakes I agree with JnA, the bulge gives it away.
Another one that was not so lucky;
http://news.bbc.co.uk/1/hi/world/americas/4313978.stm [:0]
55
Physiology & Medicine / Are cramps caused by lack of salt?
« on: 13/09/2009 21:31:59 »
Earlier this year I started suffering from leg cramps at night and was prescribed quinine sulphate for the condition.
I don't know if it worked as I had to stop taking it after 3 days as it left a very bitter taste in my mouth that was hard to get rid of. This effected the taste of all food and drink and also made me feel a bit nauseous. I was later surprise to learn that quinine has been banned in the USA for this use because of its side effects. [
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I don't use salt or add any extra to my diet and the doctor never suggested it was due to lack of salt as blood tests showed no deficiencies. Glad to say the cramps stopped after 2-3 weeks without any extra intervention.
I don't know if it worked as I had to stop taking it after 3 days as it left a very bitter taste in my mouth that was hard to get rid of. This effected the taste of all food and drink and also made me feel a bit nauseous. I was later surprise to learn that quinine has been banned in the USA for this use because of its side effects. [
]I don't use salt or add any extra to my diet and the doctor never suggested it was due to lack of salt as blood tests showed no deficiencies. Glad to say the cramps stopped after 2-3 weeks without any extra intervention.
56
Physics, Astronomy & Cosmology / Why do bicycles have such big wheels?
« on: 06/09/2009 22:24:00 »
Sir Clive Sinclair developed a portable folding bike with small wheels called the A-Bike and was described by some as a bit "wobbly" because of the size of the wheels.
I remember a science lesson at school when we had several sized bicycle wheels each mounted on a small axle that we could hold in outstretched arms. We sat on a desk type chair (one on wheels) and held the bicycle wheel out in front of us. Someone then spun the wheel and then we were asked to tilt the wheel from the vertical and also simulate it turning like a bikes front wheel.
The outcome was the chair, with you in it, spun round a bit. The different sized wheels produced different sized effects with the larger wheels producing greater effects. Unfortunately that was years ago and I cant remember exactly what that lesson was about but I think it was something to do with the gyroscope effect. [:I]
I remember a science lesson at school when we had several sized bicycle wheels each mounted on a small axle that we could hold in outstretched arms. We sat on a desk type chair (one on wheels) and held the bicycle wheel out in front of us. Someone then spun the wheel and then we were asked to tilt the wheel from the vertical and also simulate it turning like a bikes front wheel.
The outcome was the chair, with you in it, spun round a bit. The different sized wheels produced different sized effects with the larger wheels producing greater effects. Unfortunately that was years ago and I cant remember exactly what that lesson was about but I think it was something to do with the gyroscope effect. [:I]
57
Technology / Why Does A Tall Power Thing Hum ?
« on: 05/09/2009 19:37:20 »
"I've ignored the 3 phase thing which could cause all three conductors to do a nice little dance with each other, I guess"
You often see (and hear) that dance on the 3 phase cables in lift shafts.
You often see (and hear) that dance on the 3 phase cables in lift shafts.
58
Physics, Astronomy & Cosmology / Infinite Density Within A Black Hole !..Why does It Not Destroy Itself ?
« on: 05/09/2009 05:24:20 »
Hawking radiation has been predicted but never observed so its not actually a fact to be relied on. Its a good theoretical argument, been changed a bit and still subject to change.
Maybe they will find it but so far its not proven to exist when it should. []
Maybe they will find it but so far its not proven to exist when it should. [
]
59
Physics, Astronomy & Cosmology / Infinite Density Within A Black Hole !..Why does It Not Destroy Itself ?
« on: 02/09/2009 23:55:21 »
That thinking leads to an event horizon first and then a singularity. What some have suggested so far is that the singularity does not exist so the idea of any event horizon cant either. If that is the case then a black hole does not have to contain that much mass.
What I suggested has nothing to do with exit portals for this universe only that matter could be funnelled through the vortex and deposited elsewhere. As a vortex goes its usually only one way, a bit like a "Dyson" cleaner.
So to answer neilep, I don't think there is infinite density to a black hole and that's why it don't destroy itself. []
What I suggested has nothing to do with exit portals for this universe only that matter could be funnelled through the vortex and deposited elsewhere. As a vortex goes its usually only one way, a bit like a "Dyson" cleaner.
So to answer neilep, I don't think there is infinite density to a black hole and that's why it don't destroy itself. [
]60
Physics, Astronomy & Cosmology / Infinite Density Within A Black Hole !..Why does It Not Destroy Itself ?
« on: 02/09/2009 20:03:03 »
I agree with others. Its just a mathematical fudge created by mathematicians who love to try and complicate even the simplest of things.
I don't believe that a black hole contains a singularity or any mass whatsoever. I see it as just a hole in space that contains nothing, no hypothetical particles such as gravitons, no photons, no Hawking radiation and no mass in the centre. A one way vortex membrane that sucks (bad word) matter in and deposits it elsewhere on the other side of the hole.
I don't believe that a black hole contains a singularity or any mass whatsoever. I see it as just a hole in space that contains nothing, no hypothetical particles such as gravitons, no photons, no Hawking radiation and no mass in the centre. A one way vortex membrane that sucks (bad word) matter in and deposits it elsewhere on the other side of the hole.