studiot

Two responders here have chosen to limit the atmosphere quite arbitrarily. Fred did not do that in his OP. We have also had a recent thread about the 'limit' of the atmosphere and these arbitrary limits were discussed, but the physics answer was that the atmosphere never actually stops in our models. Yes there are good reasons for these limits but that was not the question. I still challenge that. Consider a shaft in the ground 2 metres square in section, 5 metres deep and open to the atmosphere. However the the atmosphere in the shaft comprises over 20% carbon dioxide. How long will it take for the atmosphere to equalise with the lower % in the normal atmosphere above? In case you are wondering this was the standard video shown in 1990 by HSE when I did my confined space training. Three men died of suffocation in that shaft over the course of more than a day.

Does it? Then why does it list the composition of the atmosphere at 1000km altitude?

Is that so. Then perhaps you can explain away these figures. http://wordpress.mrreid.org/2014/08/01/the-composition-of-earths-atmosphere-with-elevation/

Neither. In the abscence of a body force a gas expands to fill its material container. The atmosphere has no material container, except at the surface of the Earth. So it is contrained to Earth by the body force of gravity. Now gravity acts differentially on 'heavier' (more massive) particles. We can see this effect in the settling of suspended particles in a liquid. The heavier particles settle first at the bottom and we and up with the lightest on top. The average molecuklar weight of atmospheric particles (molecules) is 30 but carbon dioxide the mw is 44 so you can see it is a 'heavier' particle. The the gaseous makeup of the atmosphere is stratified, like the settling sediment in water with the greatest concentration of carbon dioxide at the Earth;s surface and the percentage of lighter gases increasing with altitude. The stratification is not banded it is gradual. That deals with vertical distribution. Horizontal distribution is fairly even since the mixing times for a gasesous atmosphere is measured in days. By contrast the ocean mixing times can be measured in years to centuries. In the atmosphere, just as in the ocean, where you get a continued concentrated input there will be local variations and a balance will be set up between input and dispersal.

Welcome, bay, and thank you for your contribution. Don't you think you are unecessarily and arbitrarily limiting the definition of nothing to the abscence of concrete nopuns? What about all the abstract nouns like love, hate, tiredness, celerity, and so on?

No. In fact if you had asked the question does an electric generator need magnets at all the answer would still be no. A simple example is piezoelectric generators. There was even a proposal and some experiments to recover energy from vehicles braking by the use of 'hit plates', using this method.

Now that we have the beginning's of a circuit, I can comment on Stranges post#17 and your over-casual dismissal of it. In a perfect world Strange's comment would be correct. You have gained nothing in power efficienty terms over a straightforward DC supply at the same voltage. However in the real world your configuration has reduced power efficiency significantly since all real world supplies have an internal impedence. The internal impedence of the 'off' supply would appear as a load in parallel to the load resistor for the 'on' supply. In other words the on supply would try to drive current back through the off supply. In addition to ineficiency, this is likely to lead to the early demise of one or both supplies. I forget which but it is rule 0 or rule zero that you do not connect two outputs together without very special measures.

Connecting them both to what? That is why I keep asking for a full circuit digram.

I don't quite get what you actually 'know about' after repeating my post 3 times, But I respectfully suggest your second sentence indicates you need to know more about electrical power theory and practice before making judgements.

If you are not sure why do you think it is very stupid, or even a little bit stupid.? We can discuss it if you wish, I am not trying to hide details. Why are you avoiding my question about distribution details? Whatever the waveshape,AC or DC it is the RMS current that is important to determine the power. Since we buy and use electricity in terms of power not current a given supply requires a specific RMS current and therefore the wires have to be the same.

Please don't anyone try these experiments. Old time service engineers were taught to keep one hand in their pocket when probing around electronic circuits in case they accidentally touched a live (at DC) terminal. I can tell you that even the bite from the 90volt battery they used to use in valve portable radios hurts and has been known to kill. Directdude, electricity is dangerous. But properly treated it is also useful to essential so let us concentrate on your 3 wire distribution system. You need to provide proper details to discuss, it is up to you, not me, to work it out for you. I note that 3 wires is one more wire than 2, which represents a greater than 50% cost increase since it would also require stronger support structures. I can't comment more without knowing what the proposed voltages at all stages are. Please also note that most consumers receive their current AC supply over 2 wires. In the US this is transformed to what is correctly known as split phase, although too many call it two phasse, which it is not. There were once DC supplies in both the US and Europe, which were abandoned for very sound technical reasons. There have been experiments in the US with superconducting primary distribution extra high voltage lines at DC. But at the consumer end, the size, weight, cost and efficiency of machinery and some circuitry is least at DC and rises with increasing frequency at AC. Why do you think most vehicles now have alternators rather than dynamos?

From John Donne 'Undertaking'

This statement needs amplification. Further I cannot agree with you about safety. One characteristic of DC is that a victim who has grasped a live conductor cannot let go. This is not true at AC.

I thought this question was going to be more difficult than it turned out. To understand the voltage distribution use the simplest model for a transistor. This is a pair of 'back to back' diodes as shown in my sketch (correct for an NPN 2n3904 transistor). This means that the pair block in both directions between collector and emitter when nothing is connected to the base. So any current flowing will be the collector - emitter leakage with abse open circuit Iceo Now look first at the BE diode. It is forward biased, that is it allows current to flow in the direction from the +9 volts to 0 volts. An ideal diode has zero forward resistance so both terminals will be at the same voltage. The actual diode will be very close to this so the emitter is set at zero so the base will be slightly more positve as observed. Now look at the CB diode This is reverse biased so blocks current. The collector is set at +9 volts. This is the cathode of the upper diode If this were an isolated diode you could tie the anode of this diode to any voltage and it would be blocked. In this case the anode is also the base of the transistor which is set to near zero by the forward biased lower diode. As regards to the electric field part of the question. The electric field and potential in a resistor change (perhaps linearly) along the resistor from one end to the other. Components acting like this are said to be acting in resistive mode. The field and potential change abruptly across a reverse biased diode whose action is blocking. This is like a capacitor and components acting like this are said to act capacitively or in capacitive mode. It may be of interest to know that this ability of a reverse biased diode to act capacitively is exploited in so called varicaps or voltage dependent capacitors.

OK dude, I now understand your system and I agree it could physically work. One immediate disadvantage I can see is that it requires three wires to distribute it, rather than the traditional two. A second disadvantage would be the increased complexity of the wiring of appliances to operate on such a supply. Please explain the distribution of such a system ie where it would be generated, at what voltage and how it would arrive at the consumer? Would the system be distributed from the power station as DC or would it be AC and converted somewhere down the line? Finally I think this proposition is a fine candidate for proper use of the speculations forum. It is, after all, a speculation, though based one real physics rather than guesswork which is why I say proper use.

Mathematics is not always about the real world at all. When spreadsheets first came in they were welcomed because they allowed quick and easy access to the "What if " game. What if the price of oil doubles / halves ? What if the electronegativity of copper was 1.6 or 2.1 instead of 1.9? What could I spend a lottery win of £100,000 on? None of this actually happens but mathematics allows us to speculate.

Thank you both for your interest. I am trying to promote old fashioned virtues as known by any competent secretary. When sending people important pieces of paper (fiveworlds I have to store these documents as part of the accounts for at least 7 years HMRC rules and UK business law). It is sad to think that you youngsters think that standard good practice that has developed over a couple of centuries is of little consequence and somehow the recipient's ( ie my) fault.

5,000 invoices would require 5,000 plastic pockets. And the pockets are bigger so require abnormal sized ring binders. Cost?

Is it because modern day programmers have never heard of a hole punch or is it due to something more sinister? I refer to the modern practice of failing to provide a proper binding margin on documents designed for computer printout. Organisations large and small, government and private seem more and more prone to this failing. Here is an example. Only the left hand column heading is detroyed in this case, but I have plenty of invoices where consignment information is lost.

I answered the question, as presented on this forum. Having just read your blog I see we are at cross purposes so I suggest you prepare a version of your blog, condensed to about 25% in length and leading to a specific question and then post it here. I also suggest keeping the question to a single example. If you wish to use the balloon as your example at a height of 32km there will have been significant expansion work either against the thinning atmosphere or against the much stiffer balloon skin. Accepting a constant atmospheric pressure and density for a height rise of 32 km is not realistic.

That's how refrigerators work.

Perhaps you have a different definition of hysteresis from mine? Would you like to elaborate?

Hysteresis only occurs in cyclic processes. We are not told if the process concerned is cyclic.

This question cannot be answered. Each system is closed which is defined as meaning that mass may not enter or leave either system but energy may. Since we are not told the complete energy balance for either system, the exchange energy between the two systems may or may not be the only energies exchanged between the two systems and the surroundings.

Hello Mountain Guardian, and welcome. When did the Navy start guarding mountains? When discussing waves it is important to distinguish between pre-existing waves due to ordinary air/sea interaction which act as you say and the wave drag as Klaynos described, which will still occur in a flat calm sea. The interaction between a hull at the surface and the surface causes waves to spread out from bow and stern, sapping energy from the boat's progress. These are caused by the moving boat and not a characteristic of the sea state.