At Oxford, a Battery That's Lasted 175 Years -- So Far 211
sarahnaomi writes There sits, in the Clarendon Laboratory at Oxford University, a bell that has been ringing, nonstop, for at least 175 years. It's powered by a single battery that was installed in 1840. Researchers would love to know what the battery is made of, but they are afraid that opening the bell would ruin an experiment to see how long it will last. The bell's clapper oscillates back and forth constantly and quickly, meaning the Oxford Electric Bell, as it's called, has rung roughly 10 billion times, according to the university. It's made of what's called a "dry pile," which is one of the first electric batteries. Dry piles were invented by a guy named Giuseppe Zamboni (no relation to the ice resurfacing company) in the early 1800s. They use alternating discs of silver, zinc, sulfur, and other materials to generate low currents of electricity.
Bullshit (Score:5, Informative)
From The Fucking Article
"You'd think it'd be annoying as hell for a bell to be going off, constantly, for 175 years—but the voltage left in the battery is so low that the human ear can't actually hear the ringing. Instead, the clapper oscillates back and forth between the bell constantly, which you can see happening in this video. At this point, the experiment is more of a curiosity than anything—Croft says that the battery pulls 1 nanoAmp each time it oscillates between the bell’s sides, which is an exceedingly low amount of energy."
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I wonder how long it hasn't been ringing for.
Re:Bullshit (Score:5, Interesting)
From The Fucking Article
"You'd think it'd be annoying as hell for a bell to be going off, constantly, for 175 years—but the voltage left in the battery is so low that the human ear can't actually hear the ringing. Instead, the clapper oscillates back and forth between the bell constantly, which you can see happening in this video. At this point, the experiment is more of a curiosity than anything—Croft says that the battery pulls 1 nanoAmp each time it oscillates between the bell’s sides, which is an exceedingly low amount of energy."
1 nanoamp is so tiny that it may be being recharged from the environment somehow.
Re:Bullshit (Score:4, Interesting)
I expect you are correct. Put the bell in a Faraday cage and see if it stops twitching. The question is, is the signal being switched, electrostatic, magnetic?
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How the hell do you generate 2KV?
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It's an electrostatic bell, so around 1KV should be enough to run such a small one. I imagine the battery has, say, 500 discs at 2V each, all in series.
Re:Bullshit (Score:5, Informative)
9V batteries have more than enough current available to stop someone's heart if put in series. If you have 400-1000V DC worth that's more than enough to kill someone. Be glad that a little knowledge didn't get someone killed.
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I seem to recall that it can take as little as 15mV to stop someone's heart - assuming a good connection and bad luck.
Re:Bullshit (Score:5, Informative)
I do believe that you're thinking of "mA", not "mV". 15 mV is even less than the trigger voltage of an ordinary nerve cell. A few mA, through the right nerves of the heart at the right moment, can _decouple_ the heart's normal pulsing rhythm, causing fibrillation. It's well worth a bit of research into how "defibrillators" work: I'm afraid I'm old enough that I have some acquaintances with implanted pacemakers to control just that sort of problem.
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It's not impossible, but I *really* want to say I heard mV. Of course it's also possible that my source, now lost to the fog of time, were themselves mistaken. Your description certainly sounds about right otherwise.
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You probably could stop someone's heart with 15 mV. But it would have to be applied directly to the heart, and at just the right time.
For external application (i.e. without the open heart surgery) it's going to take rather more than that. You generally need a current of around 100 mA through the heart to stop it. If you're not standing in a puddle of salt water or gripping a water pipe, it's going to take quite a bit more voltage to achieve that.
110 V household current can kill, if you manage to get a go
Re:Bullshit (Score:5, Informative)
Action potentials are a bit funny. They're not actually movements of electrons down a wire like we're used to thinking about, but rather propagating waves of changes in the way cellular pumps move heavy ions through the cell membrane. Action potentials provide essentially no long-distance current, for example.
If you applied 15 mV across the SA node (the heart's built in pacemaker) at just the right time in the cardiac sequence you might be able to interfere enough to stop the organized contraction. There's a lab at my university that's been looking at analyzing chaotic heart contractions in order to use very small, very well-timed pacemaker signals, to correct them.
You would absolutely have to do it internally though ("applied directly to the heart"). The human body is basically a bag of salt water, which conducts quite well (about 300 Ohm from head to toe IIRC) surrounded by skin, which is a pretty good insulator. So if you want to electrocute someone, stab the electrodes in first.
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I would not be surprised if a frequency component were also necessary, but clearly there will be some V/A threshold you have to cross before you do damage.
Though really, a sufficiently sustained blast of DC would probably do the job as well - how long can the heart remain clenched before it won't start beating again? If nothing else eventually you'll die of oxygen deprivation, heart and all.
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It's the frequency of an alternating current supply that causes fibrillation, not the current or the voltage.
The current or the voltage is what causes the electricity to flow through the heart in the first place, it doesn't always happen even when someone touches something with both hands.
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I can stop your heart with 2microvolts if it's attached to a 9mm slug.
To keep the oscillator going, a nanoamp is one measure, but voltage pushes that current through the coil to make it move. Voltage, difference in potential, is unlikely to come from ambient sources, so the there's still a little bit of a kick left in the battery, not the surrounding area.
Re:Bullshit (Score:4, Funny)
9V batteries have more than enough current available to stop someone's heart if put in series.
You can stop someone's heart with a standard 1.5V dry cell, you just need to apply it directly to the heart. Stick a bayonet in through the ribs and into the heart, hook a battery to it, and just like magic the heart will stop.
Re: Bullshit (Score:2, Insightful)
Even without the power a bayonet will do that to you
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Make a deep cut in each thumb. Touch the bleeding thumbs to the terminals of a 9 volt battery. Report the results to us. If you haven't yet fibrillated, snap two batteries together in series and touch the contacts again. Keep adding a battery and reporting back.
Re:Bullshit (Score:5, Informative)
Actually, you can kill yourself with a single 9 V battery -- or the 12 V battery of your car. One man did:
http://darwinawards.com/darwin... [darwinawards.com]
The computation goes as follows. The issue, as several people have pointed out, is that it is current across the heart that causes defibrillation (basically interrupting the heart's natural rhythm so that it pulses chaotically), not a matter of cooking the person (which will also work, BTW, but isn't the most common cause of electrical shock deaths). It isn't even the case that more current is always worse -- there appears to be a range of currents that are more toxic than others. A brief explanation of this is here:
https://www.physics.ohio-state... [ohio-state.edu]
The maximally toxic range of currents across the thorax is empirically 0.1 to 0.2 amps. Below that it isn't enough to defibrillate, above that the heart muscle clamps all the way which means that when the current is removed it is actually more likely that it can with help or will on its own restore a normal rhythm.
The internal resistance of the human body once you introduce probes through the comparatively insulating skin is around 100 ohms. A 9V battery across ~100 ohms makes a thoracic current of roughly 0.1 amp, right at the start of the maximally fatal range. The Darwin above was given because an idiot didn't believe this and stuck probes through his skin to "prove" that it wasn't so.
Personally I've experienced shocks from 12 V car batteries when screwing around with them on rainy nights with salt water on my hands. That's another good way of reducing skin resistance. I didn't take the hit across the torso, but it was every bit as painful as a 110V shock through dry skin -- more so, actually -- and caused my muscles to contract like lightning.
None of this is actually news -- it has been known as long as there has been electricity, because people have been killing themselves accidentally with electricity just that long. My scout leader 50 years ago worked for GE (as an inventor, actually -- one of the people who invented the photodiode controlled light). He taught me that long ago to ground one finger and then brush another finger of the same hand against any possible hot wire so that you find out with a jolt across your hand, not through your torso. Hand to foot, hand to hand, not so good. People used to kill themselves all the time touching hot electrical switches while standing in wet feet on bathroom floors before ground fault circuits were invented and mandated by code.
None of which has much to do with TFA, but it is good to know if you work at all with electricity. Physicists need to know it just to be able to teach it to their students so THEY don't kill themselves accidentally one day. It isn't the voltage that kills you, it's the current, and it doesn't take much current to do the job (or much voltage to create a fatal current).
Re:Bullshit (Score:4, Interesting)
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Re:Bullshit (Score:5, Insightful)
> 1 nanoamp is so tiny that it may be being recharged from the environment somehow.
At that rate it doesn't need any recharging. A continuous 1 nanoamp draw (it doesn't make sense to say it draws 1 nanoamp per oscillation because amperage is a rate not a quantity) would discharge a small 1 Amp-Hour battery over one billon hours, or 114,000 years. The fact that it hasn't discharged through interal leakage is pretty impressive though.
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Yanno, the Germans, Norse and Saxons could all make the same complaints about English.
Re:Bullshit (Score:5, Informative)
(175 years) * (2 kV) * (1 nA) = 11045 Joules ]
Which in terms most people can relate to is about 3 Watt-hours, or about the same as a singe AA battery. Not very impressive.
Re:Bullshit (Score:5, Insightful)
Well, put a AA in a box and come back in 175 years, and try it out. Then we'll see how impressive that is.
Re:Bullshit (Score:5, Funny)
Then we'll see how impressive that is.
Not nearly as much as his coming back...
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A regular AA can't do this. But it wouldn't be particularly hard to design a battery that could provide such a tiny current for a long time. It's just that there's very little practical applications for such very low currents.
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Well, put a AA in a box and come back in 175 years, and try it out. Then we'll see how impressive that is.
Oh-ho, smart guy, see how may of those you'd sell!
It is impressive though. Torpedoes need a high-power battery that can be stored for many years and still be at 100% when needed. They used to cheat, though, and use a wet cell with the chemicals stored separately - mix everything together when it's time to load, and you're ready to go. No leakage unless there's actual leakage. I wonder what they do today - a dry cell with no leakage would be safer and easier.
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Dry cells wouldn't be able to provide much instantaneous current.
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Why would they need that much instant current? The battery doesn't power the torpedo through the water, it just runs the guidance system.
Population is provided by "Otto fuel II" which is a hot expanding gas that provides an average of 7 minutes of run time, but at 55+ kts it is enough.
Oo-er, matron! (Score:3)
It's caused by something expanding, but it's not a gas. At least mine isn't.
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http://en.wikipedia.org/wiki/O... [wikipedia.org]
The explanation exceeds that which is interesting to all but the REALLY curious...
There you go... :)
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I'm not an expert on torpedoes, but parent claimed that Torpedoes need a high-power battery. Given that torpedoes only operate for a short time, I drew the conclusion that they must provide a high current.
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The Mk-48 ADCAP torpedo does require prep time, they aren't generally kept in a "ready to fire" situation all the time.
I would imagine one simple solution would be a capacitor, since the battery has to be good in storage for long periods of time, but when actually needed, only has to work for between 10 minutes an hour. So the torpedo has some spin up time while the battery charges the capacitor, however it is also possible to get its initial charge from the launching vessel (while in the tube), they are w
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It is possible that if they drain the tubes and pull them out, the batteries have to be replaced.
If that's true, then we are talking about big currents (multiple Amps). A capacitor would not have enough capacity for a reasonable size. Batteries are much better.
Re:Bullshit (Score:5, Insightful)
That assumes the bell had been drawing the same current that entire time. The bell used to ring, meaning it was drawing much more current then.
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Probably not a whole lot more. Batteries have a reasonably constant voltage during most of their discharge cycle.
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Batteries have a reasonably constant voltage during most of their discharge cycle.
Different types differ, and you don't know what type of battery this one is.
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>Croft says that the battery pulls 1 nanoAmp each time it oscillates between the bell’s sides, which is an exceedingly low amount of energy
That isn't a unit of energy. It tells you nothing about the energy consumed.
Re:Bullshit (Score:5, Funny)
Yeah, we americans would never keep under performing, outdated electrical appliances around for the historic factor: http://en.wikipedia.org/wiki/L... [wikipedia.org]
And we have no attachment whatsoever to historical figures: http://en.wikipedia.org/wiki/M... [wikipedia.org]
Re:Bullshit (Score:5, Interesting)
1 nanosecond..., honestly, that's typically British. In the US that battery would have been trashed already. The Brits are way too much attached to these long lasting historical figures. And royalty is another example.
Well, there is a light bulb in Livermore, CA that's been burning for 114 years. [centennialbulb.org] That hasn't been continuous as there have been some power outages and it's been moved a few times but the Livermore fire department seems pretty attached to it.
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I was commenting more on the "In the US that battery would have been trashed already." comment than anything else.
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Anyway, my main point is that the battery voltage will decay exponentially.
No. A battery voltage absolutely don't follow the law of a capacitor voltage. On a battery, the voltage drop no so much as long as the chemical process is still producing charges. Depending on the chemistry of the battery, some components might change over time, over temperature, over chemical contamination, or current flow, and this result on a drop of voltage from the nominal one. Anodes stability in for example a critical component in many battery chemistry.
Take time to read datasheet of some batteries a
Oops (Score:5, Funny)
Actually the janitor changes it once a week when he cleans the room.
Re:Oops (Score:5, Interesting)
Actually the janitor changes it once a week when he cleans the room.
Hehe.. maybe he is. The municipal power company in Reykjavik, Iceland built a Focault pendulum [raunvis.hi.is] in their HQ as a showpiece. Local urban legend has it that after it was first installed the thing would stop swinging at seemingly random intervals which caused the artist and the physicist who designed it a lot of head scratching. No amount of calculations, physics theory and modelling could explain these mysterious disruptions in the predicted workings of the pendulum so finally they set up a camera to observe the thing. The footage showed the pendulum swinging away for hours and hours until suddenly a member of the cleaning staff walked into the frame, stopped, looked at the pendulum, reached out, stopped it with his hand and then walked out of the frame. Mystery solved... dunno if the story is true but it made me laugh.
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There are similar stories in IT about a mysterious inexplicable server outage occuring at the same time each day, after office hours, that continued even after reformatting it to eliminate any software issue. When an administrator tried staying after closing time to watch it, he found a cleaner unplugging the mysterious humming box to plug the floor buffer in.
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And _this_ is why I use things like these, wehre possible, in machine rooms and office spaces.
http://www.homedepot.com/b/Ele... [homedepot.com]
It protects the power plugs from being jarred and dislodged by someone poking around the back of an ill-managed server cabinet, and it can be labeled to indicate which machines or rack it currently powers. It can even be marked with the relevant fuse from the wiring closet.
Re:Oops (Score:5, Interesting)
I hate to tell you this, but most people who've worked support in manufacturing and office environments have similar stories. I spent close to two months getting paged by Northern Telecom in Bramalea, ON for a manufacturing system failure on the shop floor at 2-3 AM most days per week. It was only by deciding to hang out for an entire night watching the area that I found out it was being caused by a cleaning lady unplugging the network bridge to plug in her radio while cleaning the area.
So seeing as I have one of those stories myself, I find them a lot easier to believe than most of you kids do.
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*sympathy* You can't even call her up to the union like we did the cleaning lady... *LOL*
Not a lot of power. (Score:3, Interesting)
At the current estimated power draw, thats only (1 nanoampere) * 175 years = 0.00153401723 ampere hours. It's a long time: impressive durability, but not really amazing capacity. Laptop batteries are often ~1000 times that. I don't know the voltage here, so I can't do energy comparisons, just total amp hours.
Interstellar missions... (Score:2)
At the current estimated power draw, thats only (1 nanoampere) * 175 years = 0.00153401723 ampere hours. It's a long time: impressive durability, but not really amazing capacity. Laptop batteries are often ~1000 times that. I don't know the voltage here, so I can't do energy comparisons, just total amp hours.
Deep space exploration could benefit from that kind of durability. It's lasted longer than most governments...
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Re:Interstellar missions... (Score:5, Informative)
Deep space tends to be very cold
This is misleading at best.
Space in itself is a near vacuum, which (a) has no temperature of its own, and (b) is a wonderful insulator. Which is why a thermos uses vacuum for insulation.
Objects in space can become very cold over long time spans, as heat slowly radiates away without being replenished at the same rate. But space itself doesn't cool them down.
Voyager 1, which is the operative craft that's been in service the longest and receives the least amount of heat from the sun is, after most of the heaters have been turned off to conserve energy, running at around -80C temperatures. That's a veritable furnace compared to other older objects in space that have radiated away more heat over much longer time.
Also, you say "chemical batteries". Well, yes, it is, but this is a dry battery. The composition doesn't change with colder temperatures, unlike wet batteries where liquids freeze. Dry batteries don't have that problem, which is why it is interesting.
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Space may be a wonderful insulator, but the flip side to that is that there's nothing to reflect back your own heat. Radiative cooling can happen very quickly. This is why a desert can go from 100F to near freezing in a matter of hours when the Earth rotates and the desert is radiating heat out into space.
There's a reason why a vacuum flask (aka thermos) is silvered--it reflects radiation. A vacuum flask is silvered on the _inside_ (including the vacuum-facing walls) as well as the outside, otherwise any co
Re:Interstellar missions... (Score:4, Insightful)
This is why a desert can go from 100F to near freezing in a matter of hours when the Earth rotates and the desert is radiating heat out into space.
Deserts are not vacuums. Deserts cool down at night mainly through air convection. High altitude air on the planet's night side is less buoyant, and is replaced by warmer air from lower altitudes, and this process repeats all the way down to the surface. Katabatic winds are often a result, which the California "sundowner" winds is a good example of.
Needless to say, that isn't much of a concern for the microclimates of spacecraft.
Re:Interstellar missions... (Score:5, Insightful)
I don't think that's true. On a cloudy but windy night in the desert it doesn't get nearly as cold as on a clear windless night all other things being equal. In fact when I searched for "Desert nighttime cooling" here is the first thing that came up. [asterism.org] It basically says under clear low humidity conditions at night radiative cooling is by far the the largest reason for cooling.
Re:Interstellar missions... (Score:4, Funny)
Deserts cool down at night mainly through air convection
So where are those supplies of near-freezing air around desert areas ?
Re:Interstellar missions... (Score:4)
That is true as far as it goes, but in a sufficiently large, flat desert you don't have much winds, and dry air has much lower specific heat, so it can't conduct heat away from surfaces nearly as fast as moist air. Nevertheless desert nights are usually much colder than you would expect.
What's special about deserts in this regard is that same dry air also means the atmosphere is much more transparent to infrared than, so that far more of the thermal energy radiated towards the sky by the soil escapes from the Earth entirely, rather than being reflected back to the surface. It's basically the exact opposite of the "cloud blanket" effect where dense clouds that blow in near dusk can keep it from cooling off much overnight because the greatly elevated water levels in the clouds reflect much more of the radiated heat. (obviously the effect is much less pronounced in coastal deserts where the air is heavy with moisture even if it rarely rains.)
We actually had a post here several weeks back of a new surface designed to harness the effect for cooling anywhere at any time of day: it was highly reflective over the high-energy solar spectrum, and tuned to radiate thermal energy at a specific frequency at which the atmosphere was almost perfectly transparent. More primitive technology such as coolth cells work like an inverse solar heater - heat is radiated away from a thermal reservoir overnight, and the cold water used to chill the air during the day.
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With the absence of significant surface
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Why are you so opposed to the idea of radiant cooling? Radiation is one of the "big four" methods of heat loss - that's the entire idea behind mylar emergency blankets (well, okay, used well they they also slow convection and evaporation - but any large trash bag will do that even more effectively) . And in a desert the sky is far more transparent.
You do realize that, Hollywood stereotypes aside, desert != sand, right? Most of them are even fairly green, though not nearly as vibrantly so as elsewhere. T
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The previous posters are correct - the clear, low humidity air over deserts is more transparent to infrared light and radiative loss is the major reason for fast cooling at night. I've spent the night out in the Sahara. When the air cools off and you dig into the sand you realize that not only is the sand a decent insulator, just below the surface it's also much warmer than the air.
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> (a) has no temperature of its own, and (b) is a wonderful insulator.
Oh, my. I'm afraid that both these assumptions are overstated. The background temperature of the universe is only a few degrees Kelvin, but the "vacuum" in near Earth orbit is considerably warmer and more dense than the universe at large. It's also a very good insulator as you state, but when exposed to sun light it has to cope with roughly 2 Watts/square inch of solar radiation. Even left to itself, in the shadow of some astronomical
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No contradictions there. An insulator is a barrier to conductive and convective heat transfer, but as long as it's transparent to photons, radiative heat doesn't even notice it. Spacecraft instruments that need low temperatures have steered radiators that are kept pointed at dark space.
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Voyager 1, which is the operative craft that's been in service the longest and receives the least amount of heat from the sun is, after most of the heaters have been turned off to conserve energy, running at around -80C temperatures.
Yes, but it has a nuclear power cell onboard. Given sufficent plutonium, it's pretty easy to keep warm.
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Dry batteries don't work well in the cold because chemical reactions slow down the colder it gets. Wet batteries don't *survive* the cold because things freeze. I say this both as someone whose camera batteries often needed to be hand warmed, and as someone who's had to change a car battery at -40 because it discharged, froze and cracked it's case.
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Actually photons don't have a temperature as such. Sometimes you'll hear people talking about "300K light" - but it's not that the photons themselves have a temperature, but that they have an energy distribution approximating that of a black body radiator at 300K. Photons can impart energy when absorbed, which may rapidly thermalize, or they can carry away thermal energy, but they themselves don't obey the normal temperature laws. Heat only flows form higher temperature to lower temperature; however, a 3
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Photons also have a temperature in the sense that it's the maximum temp you can raise a blackbody to (or maintain it at) no matter how many photons at that frequency you use (the blackbody curve is for an ideal gas, so the idea doesn't extend well to ionizing radiation).
what exactly the physical mechanism is by which kinetic energy causes photons to be emitted
At the level I understand it: knock two molecules together, and sometimes you get a electron elevated to a higher energy state instead of an elastic collision. The difference between that energy state and the ground state is the energy of t
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Ah, of course - where a car frame might crumple on impact to dissipate energy, an atom's electron cloud can only bump one or more electrons to a higher energy state. Makes sense, thanks.
I have my doubts about the "maximum temperature" thing though - The black body peak at 310K (body temperature) is ~9350nm. If I blast you with a billion gigawatt 9350nm laser, it seems very unlikely that you would somehow become a perfect mirror to avoid heating up further. Perhaps there's n additional qualifier? Maybe t
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Exactly. That paragraph was responding specifically to the claim:
>Photons also have a temperature in the sense that it's the maximum temp you can raise a blackbody to (or maintain it at) no matter how many photons at that frequency you use
Which appears nonsensical, as demonstrated by my ridiculous scenario. If the statement is true in some context, then there are almost certainly major additional assumptions that have gone unstated. That the radiant source is itself a blackbody seems like a likely cand
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Technically, heat is only the energy moving as a result of a temperature difference. The average (translational) kinetic energy is proportional to the temperature. The kinetic energy of molecular motions is the internal energy.
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Corrosion is how it works (Score:2)
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>Researchers would love to know what the battery is made of, but they are afraid that opening the bell would ruin an experiment to see how long it will last.
Sort of suggests that nobody knows the chemistry involved, does it not?
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Nobody knows the details for sure, but similar dry piles have been examined, so we have a good idea of the sort of stuff to expect.
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I don't know the actual voltage but dry piles of that type generally generate thousands of volts. It's probably a good thing the current is so weak! Effectively, it's a source of static electricity.
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0.0015 ampere hours = 1.5mAh. A smallish phone battery such as the one found in an iPhone 6 is 1800mAh, with previous generations being about 1500mAh, so it's about 1000x less than that. A high end phone is typically around 3000mAh.
Laptops tend to be in the 5,000mAh range and upwards.
The Karpen Pile (Score:5, Informative)
http://en.wikipedia.org/wiki/N... [wikipedia.org]
The Karpen Pile, currently on display at the Dimitrie Leonida National Technical Museum in Bucharest, Romania, still gives out 1V after 60 years.
This one has a glass enclosure so it can be studied.
Hold your horses (Score:2, Informative)
Let's put this in perspective. The only "amazing" thing here is simply that the chemicals used in the battery are very stable. The amount of energy we're talking about is very, very low.
FTA, it takes around 1 nanoampere to ring the bell once. It rings around around 2 Hz. Thus it takes 2 nanoampere a second, which works out to 7200 nanoampere-hours.
So let's see how long a AA battery could run that bell. The better AAs produce 3 amp-hour of power. That is 3000000000 nanoamperes. 3000000000 / 7200 gives
Re:Hold your horses (Score:5, Insightful)
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Here's modern reproduction. Even when the battery is new, there's not much of a sound.
https://www.youtube.com/watch?... [youtube.com]
Re:Hold your horses (Score:5, Interesting)
Actually I have to correct myself. I assumed it was low voltage, like a single cell battery, and thus around 1-2 volts. That's not the case - the voltage is around 2,000 volts:
http://www.sharingtechnology.n... [sharingtechnology.net]
That means my calculations were off by a factor of 1333. So if you divide the times I stated for AA and D batteries by 1,333 and you'll get a more accurate figure. So even a deep cell 12 V battery, which is around 120 watt-hours, could only run the bell for 9.5 years. Guess that makes it more impressive than I thought.
Or my calculations are still way off.
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Your figures look about right. It is a good bit of capacity but with really poor discharge characteristics. But it's no mystery. Being a dry pile, practically the whole thing is reactants.
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You can't have "nanoamperes per second". Every time the bell swings back and forth you have a small charge that's transferred. Together, the small charges add up to a current, which is estimated at about 1 nA. Using the 2000 Volt estimate, the total energy after 175 years (1534017 hours) is 1534017 hr * 2000 V * 1 nA = 3 Watt hour, which is about equal to a single AA battery.
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That's still not correct. It consumes 1 nA per ring, and it rings at 2 Hz. Thus it comes 2 nA per second, or 7200 nA per hour. According to your math you're assuming it only consumes 1 nA per hour, so that's off by a factor of 7,200.
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Or my calculations are still way off.
Or the battery in your calculator is failing.
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Correct me if I'm wrong but without knowing the voltage isn't comparing amperage hours to one another useless?
5v * 1Ah = 5watt hours
12v * 1Ah = 12watt hours
Amp-hour isn't actually a unit of energy potential.
One AA battery has about 2.6ah * 1.5v = 3.9 watt/hr
One D Battery has about 18ah * 1.5v = 27 watt/hr
175 years = 1533000 hours * 7200 nanoampere seconds per hour = 11.06 ah. Which if it's .1 volt would be 1 watt/hr of capacity. Or if it was 10v it would be 100 watt hour. Makes a pretty big difference.
Re: (Score:2)
"nanoamperes a second" is a completely nonsense measure. An ampere is already a time rate of transfer of charge. One ampere equals one coulomb per second.
Re:Hold your horses (Score:5, Informative)
FTA, it takes around 1 nanoampere to ring the bell once. It rings around around 2 Hz. Thus it takes 2 nanoampere a second, which works out to 7200 nanoampere-hours.
Ouch! Your bad maths is making my head hurt. Amp is a measure of current, not energy or charge.
A nA is one nano-couloumb per second. WTF does "nanoampere a second" even mean? Current acceleration?
One nano-Amp for an hour is precisely one nano-Amp hour, duh!
Better known as 3.6 microcoulombs. At 2kV, it is 7.2 milli-joules of energy.
For that idiocy you get a +5? Mods need to stay in school.
The better AAs produce 3 amp-hour of power. That is 3000000000 nanoamperes.
FFS! First you equate amp-hours with power, and then you equate it with amps. Where did the time unit go? :-) /.?
Your 3AHr battery at one nano-Amp will last 3 x 10 to the 9 hours, or 342,000 years. (neglecting internal leakage
Of course you will need a few of them in series to equal the 2kV of the Oxford Bell.
What has happened to
(disclaimer: After that rant, I'm almost certain to have made an error myself.)
Re: (Score:2)
Yeah, this was a pretty intelligent discussion for /. until that one came over the transom.
Re: (Score:2)
FTA, it takes around 1 nanoampere to ring the bell once. It rings around around 2 Hz. Thus it takes 2 nanoampere a second, which works out to 7200 nanoampere-hours.
What idiots modded this as "Informative"?
He seems to think that a nanoampere is a unit of energy. Then suddenly he converts " 2 nanoampere a second" to "nanoampere-hours" which in terms of dimensional analysis [wikipedia.org] means he has somehow acquired a T (ie time) squared component from somewhere !
Re: let the experiment run (Score:5, Funny)
I'm sure Chuck Berry would agree that is an awfully long time to be playing with your ding-a-ling!
Re: (Score:2)
Re: (Score:2)
Researchers would love to know what the battery is made of [...] It's made of what's called a "dry pile," [...] They use alternating discs of silver, zinc, sulfur, and other materials to generate low currents of electricity.
Well.. that answers that question.
Yeah, just gotta get me some of them other materials and I can build one of my own! Maybe Amazon sells them.