studiot

Yes there are things in Mathematics that are not in Physics and vice versa. That was partly why I recently started a thread on that very subject, though not many answered. We are not supposed to advertise our own threads so no link I'm afraid, but it was in Mathematics. Engineering is the application of Science and a valid and respectable part of this website. I recently had cause to note there the difference in handling of the word 'Field' in Mathematics and Physics. Elsewhere we had a question posed Why do energy bands form in semiconductors? There are many presentations of this subject online and elsewhere, but they generally seem to state that they do form bands, without explanation. Interestingly the explanation is mathematical, but the also demonstrates a difference between the handling of complex numbers in Mathematics and Physics.

Well put, I keep telling Mike that, and it was a point I made several times in the now closed thread. +1 My emphasis added.

In much of electronics it is bad practice and sometimes dangerous to connect two outputs together, as each device tries to assert its own output. Tristate was invented to cope with this so that two outputs could be connected in opposition without damage by putting one into a don't care (indeterminate is actually a bit of a misnomer) state. Other parts of the circuitry will then determine when the tristate chip output is active or valid, or not. If you like it's the Engineer's answer to how to apply an irresistable force to an immovable object. Edit I see I xposted with John Cuthber. Thank you JC, I note you are using an admittedly incorrect model to cope with the inadequacies of the mathematical modle here. The device is not physically disconnected. If it weere there would be no need for tristate devices. So your model is inadequate in that it cannot distinguish between disconnected and tristate. Edit2 It is ironic that as we chat here I am fixing a Hewlett Packard PC that looks like its ethernet connection has suffered physical damage from the recent electrical storm on Exmoor. Tristate rules OK.

You are wriggling The above is in direct opposition to your other statment in the same post.

So offer me a mathematical model of the output of a 74C126.

Yes indeed, I am not talking about circuit failure or incorrect circuit action. There is a family of logic chips that can be deliberately put into an indeterminate state. This is known as Tri state logic. http://en.wikipedia.org/wiki/Three-state_logic

I suggest physical reality is more complicated than that. That is why I asked about the output of a 74C126 integrated logic chip in my post 264 and received a rude raspberry for it (not from yourself) I chose that chip because there is no calculation or observation that can be performed which can unambigouusly answer the question What is the output state of the chip? The chip is part of a family of chips designed to reflect a sort of Godel's Theorem in electronics where the output can be definitely 1 or definitely 0 or indeterminate.

You don't. Science models nature, not math. Yes you are strictly correct my wording was bad. Maths has axioms and deduced statements. Physical reality has observations. However that does not cover up the fact that a mathematical model must contain mathematical axioms and at least one unprovable mathematical deduction. All these are taken on faith as I said if you are to believe that they also apply to the physical reality. There may be statements in the model that are not reflected in reality. Equally statements in the model may lead us to statements in reality that we have not previously discovered. My position is still the same as set out in my posts 251 and 283 and also by ajb in his post 267.

So how do you model the axioms or the unprovable deduction(s)?

Of course it does or I wouldn't have said it. Though, equally of course, I am happy to explain further. Every system of mathematics has two characteristics, both of which have to be taken on faith. Taken on faith means accepted without question. These characteristics are (1) the axioms and (2) the unprovable deduction(s) required by Godel. (2) is the 'incompleteness' if you like.

Appears? You made the assertion so it is up to you to support it with a logical train of thought, not wishy washy flannel.

If the underlined proposition were so then all of science is based on one or more acts of faith. Godels Theorem tells us that about Mathematics, and applies to anything founded on it. This is of no consequence if the mathematics is an abstract construct, since we can change the founding parameter at will, and arrive at many systems of maths. But Science is meant to enquire into of which physical reality which we would like to think unique.

Darn I thought I had it all bottled up in my hip flask that I keep for April whisky.

Be aware that mathematicians have a much more general definition of the word 'Field' than physicists. For instance in maths the real numbers form a field, but in physics they would be called scalars or zero order tensors.

Negative effective mass. This is not quite the same as ordinary mass.

More help here http://forum.allaboutcircuits.com/threads/clarify-semiconductor-posts.101255/#post-764638

Vexen, one more piece of honest advice. Don't feed the trolls.

Remember that the drain, source and channel are formed from a P type substrate to create an N type region and vice versa. That is the channel and substrate are not the same element of the final MOSFET.

All of the stuff that Enthalpy and others are quoting are interesting but due to external agents, not the mechanism of rocket action. If this question was about how does a rocket work then you need to discount external factors and agents. If the question can be widened to include how to best use that rocket action then rock on.

Please note until today I was unaware of the referred thread as it is not my scene. So I have not contributed to it in any way. First I am going to take your opening post at its face value and say +1 for trying to address the issue. Unlike us from the Old World, New Zealanders are amongst the most isolated and therefore most insulated from traditional predudices. One offered a fair and friendly critique of your discussion. Did you read it? If you did read it can you see the difference between your posts and his and why the difference in the red and green votes? No-one has credence until she had established that she can offer well thought out statements, based on knowledge and rational thought. This may be already established elsewhere if the person identifies themselves as a known expert in that field. Otherwise you should seek to establish your own credentials here by making such statements and comments. The green marks will then flow of their own accord.

All you need is to place an expanding drain pipe stopper in each downpipe before starting and then flush with water at the end.

Hellow Andrew, If you mix water and wallpaper paste powder you can make it as sticky and thick as you like. You will need to tell us more about your project if you are looking for a better answer.

Well first remember that the channel is a length of unobstructed resistive semiconductor material. So current will flow through it if it is connected into a circuit. The channel also forms one plate of a capacitor, the gate of the MOSFET forming the other. So if the gate is connected to a voltage (relative to the source) ie has a charge placed on it then that charge will induce an opposite charge onto the channel. This opposite charge will add to or detract from the current already flowing. But this only occurs if the MOSFET is connected into a suitable circuit. It does not happen if the source and drain are not connected into a circuit, as with any other capacitor. So the simple answer to your question is that the electrons or holes come from the rest of the circuit that the source and drain are connected into. Remember also that the channel can be N type or P type, enhancement or depletion (less common) and that some FETS require a voltage to stop drain source current flowing. Go well in your test.

Dilution with water is the connventional way of dealing with common or garden bleach concentrate. About 250 parts water to 1 part concentrate by volume is about right for your original strength.

Why does it have to be either or? Surely a good chemist (or any other scientist) will employ any and all valid methods appropriately, comparing the results and perhaps even developing new methods as a result?