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Copper and sulphur and rainwater can create a galvanic reaction. I will assume (being dumb) that there could have been some sulphur present in the decomposing leaves.
You got zapped by a natural battery.
Were you, by chance, wearing any jewelry on the finger that got zapped? Was your hand also wet?
Hmm...time to call von Daniken!
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Ooh. I know this one. It's definitely possible, especially if the rainwater is acidic. I can't find a link right now, but zinc and copper together can form a weak battery (galvonic cell).
thanks for letting me know this was feasible - they had other reasons for thinking me weird, though. And my slight aversion reaction to puddles after that for a couple of years didn't help.
BTW, I recall that the sensation got stronger as my finger went deeper into the puddle. I had enough sense to stop, although I had to try it a second time - it was too dang weird for me to quite trust my senses. (Of course, these days, there is a problem in a lot of cities with dogs getting fried due to exposed electrical wiring close to the sidewalk. There was an article on it a few weeks ago. It might not seem so weird today.)
It's a pretty safe bet that even 40 years ago, the rainwater in upstate New York was acidic. I don't know if it would be enough to facilitate the reactions you've described, but some of the acidity, I believe, was and is from sulphur in the rainwater.
Not sure what the content was of pennies then - I think the composition was somewhat different than today's pennies, but I could be wrong.
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sndrake, penny composition changed drastically in 1982. From Penny Collector:
quote: Serious collectors will use pennies minted prior to 1982 because after 1982 the mint began to use a percentage of 99.2% zinc with a 0.8% copper - coating. In pre-1982 pennies that percentage was 95% copper, 5% zinc.
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ssywak: that balloon thing sounds like a trick question. Motion is relative: with respect to the vehicle frame, or the ground?
Your #1 story reminds me of a similar real-world geek challenge. Some guys were talking about whether it was current or voltage that killed you. The consensus seemed to be current, since they could cite a definite figure (something like 20mA across the heart can defibrillate you). I heard this walking by and asked them whether they'd rather be struck by lightning (lotsa volts) or touch a car battery (lotsa amps). After some indecision, I walked outside to my car, which has a very big battery BTW, and offered to grab the terminals. (I should have gotten some jumper cables and sparked them together for effect). They were aghast. Should they have been?
In truth, even if I had licked my fingers, series resistance is your friend.
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Ooooh, so many juicy yummy questions! I'll take them in order of least to most effort to answer!
First of all, ssywak's Stump the Chump question #2: Helium baloon inside Dodge Caravan. This one is an old chestnut.
The air inside tries to surge to the back of the van (from the viewpoint of the van), so the helium balloon, which is floating on top of this air, will come to the front. It's similar to how a cork would behave in a bucket of water that you slosh in one direction. The water (relative to the bucket) will slosh away from the direction of motion, so the cork will come forward.
[ April 29, 2004, 10:07 PM: Message edited by: ak ]
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sndrake, your penny in the rainwater thing is still puzzling me. Okay, I can believe there could be some possible galvanic reaction. Yet is it likely that it would be strong enough to shock you like that? That just seems very farfetched to me. I've seen potato batteries and other cute batteries made from common household items, and their voltage is always quite low. Even batteries like watch batteries which are manufactured with considerable ingenuity and optimal materials are still low voltage enough that you can't feel anything when you touch them. A 9V battery (as one might use to power a small radio) would barely be noticable to a wet finger, and gives no more than an interesting feeling (somewhat pleasant) to the tongue.
Yet your puddle shocked you enough, twice, that you decided to GIVE UP A PENNY! I have a hard time believing any accidental galvanic reaction could zap you that hard. No doubt it was an electric shock you felt. However, I'm thinking it must have been powered by a stronger source.
Might there have been any buried power lines in the area? Could there have been water leaking into the underground conduit, finding some break in the insulation somewhere and discharging a fair amount of current through the wet earth?
Whenever there are downed power lines, or if a backhoe has accidentally broken into buried power lines, there can be quite large currents flowing in the earth. In this case, the potential difference between one footstep and the next might be pretty high. You would want to run, not walk, away from such a place. In other words, don't have both feet on the ground at once.
Never buy the house right next to the substation, for that reason.
I'm going to go with some sort of leak from power lines in the area being the reason for your hot puddle. Galvanic reaction may be possible in such a situation, and measurable, yet I don't believe it would be powerful enough to keep a boy from nabbing a penny.
[ April 29, 2004, 10:08 PM: Message edited by: ak ]
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Well, you need some solder (usually around 60/40 with minor tweaks in the number depending on what you're soldering and how much flux is involved), a soldering iron (which is just a piece of metal attached to an electric or propane heating element) with a point fine enough to do the soldering job you want, and a steady hand (which may be substituted by robotic machinery with the soldering iron attached to it). You clean off the piece you're soldering (I want to say with acetone, but maybe I've been away from soldering for too long and too involved with chemistry) and the soldering iron, then you "tin" the soldering iron with your solder. Tinning is just coating the tip of the hot soldering iron with solder. Then you put the tip of your soldering iron, the wire/component you want to solder and the end of your solder spool in the place you want to solder. For finer soldering, you probably need a spool with smaller diameter solder. There's kind of an art to it - you don't want to just glob it on there. It might be best to practice a while before doing practical soldering. What kind of fine soldering are you doing?
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The soldering of little components to PCBs is almost always done by factories, if that's what you mean. If you have a project of your own you don't know how to complete by [unsteady] hand, I'm not expert enough to give advice beyond the simple guidelines already above.
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Also, you want to heat the components and let them melt the solder - you don't want the soldering iron to be what melts the solder.
I still remember helping my Dad do a memory add-on for an old Atari 600 XL. He stacked 4 16kbit RAM chips on top of each other, bent one pin of each up, and soldered the chips together pin to pin. He did made 8 stacks like this, ran wires from each bent pin into the motherboard, then seated them all in the sockets. Viola! we had 64K of RAM.
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Dagonee rosin up your bow, and play your viola hard, cause the nitpickers are out in Hatrack, and dyslexia's left you scarred!
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quote:I'll answer the second question first. An adaptor, like one of the little black boxy things affectionally known as "wall warts" converts AC to DC in two main stages. First there is a transformer which converts 120 Volts AC to something lower (perhaps 12 Volts or 6 Volts), but still AC or alternating current. Next there is a rectifying diode network which changes the AC to DC, or a smooth direct current.
I'm only at the level of field technician, but I thought the term adaptor could include changing frequencies (like a European to American adaptor, because some stuff runs better at 60 Hz than 50 Hz) or just changing the voltage (like a stepdown transformer, only without a rectifier). But I'm just being picky because it's obvious that Jon Boy meant something that he would use for his laptop, cell phone charger, etc.
We always learned that a diode is like a check valve, using the water analogy. Maybe you could explain how a diode's made and how it only allows electrons to flow one way.
But here's a question for me. I'm a little embarrassed to ask it because it's so basic. In that picture that Dagonee drew so well of the transformer on Page 1, the voltage in the secondary gets induced by the changing magnetic field caused by the primary coils, right? So if that charge is building up there, and it has a connection to ground, and the current wants to flow through the path of least resistance, why does it go through the load instead of straight to ground?
I'm thinking about it now, and it seems like if the current did go to ground, it would have to pull a train of electrons (assuming electron flow, not hole flow) through the load for current to flow to ground (because the charge building up in the coils has to come from some place). Maybe you can make some sense for me, ak ar anybody else, out of this conceptual quicksand.
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Thanks for the explanation, ak. Geez, but Hatrack moves fast when you're only on a little bit each day.
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Richard, it's actually energy that kills you. This is current times voltage time time. The shock on a doorknob in the wintertime after you walk across a carpeted floor is thousands of volts, I've read. Yet there is so little total charge there to be discharged that the spike lasts only microseconds and the total energy is negligable.
If the room is dark you can see the little sparks, though, which is cool. Cats don't like to be stroked just for the sake of you watching the cool sparks it makes in wintertime, by the way. That annoys them. Then they decide they like watching the neato blood drops on your hands. It's not dark for them, anyway. Their pupils are 10 times the size of ours.
The amount of current you will draw depends on the voltage and the resistance to ground. If you are wearing shoes and not touching metal and stuff, you don't get much of a zap with 120V. It's being barefoot on damp concrete floors that is dangerous. 460V I've never tasted yet (and I hope to keep it that way) but I don't think it's ever nice ever. 24V will hardly bite you unless you try very hard to make a super good connection with your body. Most 24V power supplies won't even supply enough current to hurt you. Instead you'll take the voltage down to nearly zero when you short it out. A car battery can supply a lot of current, yet unless your resistance is quite low, I don't suppose you could draw enough to really zap you. When you grab both leads of an ohmmeter in your two hands, you get megaohms, right? So 12V / 6 Mohms is about 2 microAmps. Itty bitty. Not a problem. (Not that I'd do it on purpose, still.)
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JNSB, an adaptor could be all kinds of things. Even non-electrical things. There are plumbing adaptors and water hose adapters, conduit adaptors, hydraulic adaptors, and so on, as well as myriad electronic devices called adaptors. I was trying to answer what Jon Boy was asking, though, so I guessed which he meant. If I guessed wrong, Jon Boy, then ask again, for sure.
JNSB, do you want to know how the 50-60Hz and 60-50Hz adaptors work? They are combinations of transformers, bridge rectifiers, and oscillators the same as described above. A transformer can't change the frequency, only the voltage and current. So to do that you have to convert the AC to DC with a rectifier bridge, then use an oscillator to generate a square wave of the desired new frequency, then put that through a transformer to get the voltage you need. The transformer will also help smooth out the square wave into a sinusoid. Additional capacitors and resistors will filter it more until it's smooth enough.
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JNSB, don't be embarrassed. Electricity is weird. It takes a lot of thinking about it before it starts to make sense.
Re your transformer house wiring question: The thing the transformer really does is cause there to be a voltage DIFFERENCE across the coil. So if you have one side of that coil connected to ground (potential = 0 Volts) then the other wire must be at your rated voltage, in this case 120 Volts AC. Now that means that there is also 120 Volts across your light bulb filament. It's not absolute potential but a potential difference which makes something work.
(The potential difference across a length of wire is negligable. It's a very good conductor. It has low resistance. You choose a wire size big enough that the wire won't count for much in the total resistance of the circuit.)
Does that make more sense when I explain it that way?
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No ak, if you could just answer the kind of conceptual question I asked at the end of my last post that would be great.[edit: oops you just answered it. So then the coil's inductance provides the impedance necessary to keep the current from flowing to ground?]
Also, to address how electricity can hurt you, there are extra factors to consider. Frequency of the electricity going through you - 60 HZ is fairly close to the frequency of electricity your brain sends to your heart to make it beat (contract) and so it may be more likely to stop your heart than say 45 Hz. As far as how much current can kill you, we were always told 0.001 amps, you feel it, 0.01 amps, you lose muscle control, 0.1 amps, you die. How much jewelry you have on, how wet you are, will affect your resistance and thus how much current passes through you.
posted
I'm trying to think up an electricity poem for Fallow, but I'm stumped.
The only thing that comes to mind is a story we learned at tech. school to help us remember that the voltage leads the current (by 90-degrees of phase shift) through an inductor. Something about ELI the tent-maker. (ELI: where E=voltage, L=induction, I=current)
Yeah, I guess I could make up a poem about ELI the tent-maker, but nobody is going to enjoy it.
Now, back to your regularly scheduled program.
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ELI the ICE maker? In an inductive (L) circuit, voltage (E) leads current (I), and in a capacitive (C) circuit current (I) leads voltage (E).
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Diodes let electricity flow in one direction only, and are a very simple type of semiconductor device. To understand how diodes work you have to understand semiconductors.
Metals conduct electricity easily because they have a lot of free electrons floating about in the outer shells of their atoms. Their atoms form a crystal lattice, with plenty of spare electrons which they easily pass one atom to the next. So current can flow through them with a very low resistance.
Silicon and Germanium have 4 electrons in their outer shells, so they form a nice crystal lattice, too, however there are no free electrons to allow charge to move about. (Moving charge is simply electric current.) Sand (made of silicon crytals) is a pretty good insulator, in fact.
But an interesting thing happens if you add a small amount of impurities to silicon. If you add just a smidge of Phosphorus or Arsenic, for instance, which have five electrons in their outer shell, they fit nicely into the lattice, but leave these spare electrons which aren't forming any covalent bonds. The extra electrons pass easily from one atom to the next, and electricity can flow, albeit not as well as in a metal. Hence they are called semiconductors. Because there are extra electrons, and electrons carry negative charge, these are called N-type semiconductors.
Another way to make a semiconductor is to add, say, tiny bits of Boron or Gallium to the Silicon. They have only 3 electrons in their outer shell, so they fit into the lattice but leave holes where an extra electron ought to be but isn't. These can easily steal an electron from their neighboring atom, with the result that the hole has shifted over. The holes, because they represent the absence of an electron, act like positive charges, and these semiconductors are called P type semiconductors.
An interesting thing happens when you butt an N-type semiconductor up against a P-type one, and apply a voltage across the two. If the positive lead of your battery (for instance) is hooked to the P type side, and the negative lead is attached to the N type side, the positive charge in the battery will repel the holes and move them toward the junction. The negative charge of the battery will repel the electrons in the N-type side, and move them toward the boundary. There will be plenty of electrons to fill holes at the junction and current will flow.
If you reverse the battery leads, though, the opposite happens. The electrons in the N-type side are attracted toward the positive lead of the battery and away from the junction. The holes in the P-type side are attracted toward the negative battery lead and away from the junction. There are no electrons and holes at the junction to carry charge and the gate just closes. No current flows. This is how a diode is made. It's simply a junction between semiconductor materials of opposite doping.
[ April 30, 2004, 03:06 AM: Message edited by: ak ]
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JNSB, the inductance of the coil is what lets the other coil of the transformer INDUCE a voltage across it. I think that must be where the word comes from.
If you are thinking of the coil as simply a low resistance wire, I can see how you would wonder why it wouldn't just drain its voltage immediately to ground through the coil. But because of the constantly changing magnetic field inside the loops of the coil, there will be a constantly varying potential difference when measuring from one end of the coil to the other. It varies as a sin wave which repeats 60 times a second, positive 120V to negative 120V and back to positive. This is our AC voltage that powers the circuit.
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A good resource for things like this, for all you geekoids, is how stuff works. They have lots of good explanations of cool things there.
I'm still looking for your answer, Slash, on the high power energy weapons. Since it's for good and all. Jacare, I've yet to start on yours but have not forgotten. Posts: 2843 | Registered: A Long Time Ago!
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I like women who know technology. They're in such a tiny minority that each one is precious to geeky males like myself. At the last college I went to, the graduating Computer Science class had three women in it. My CS graduating class has five or six.
Finding a woman to talk technology is sorta like a car guy finding a girl he can talk cars to.
This might be beyond the scope of your knowledge, ak, but I've always wondered how a digital logic gate actually works. All I know from my Digital Circuits class is that they work, not how.
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Well, since we've already had a good explanation of diodes, let's note that very simple, cheap (and impractical ) gates can be made from them directly. For example:
code:
A -->|--|--Z B -->|--| | 5V
Since the diodes will become forward biased if either A or B is connected to the "high" voltage, Z accurately represents boolean A+B.
Unfortunately, to my knowledge you can't make a NOT gate out of diodes, nor can you really string these together. Things you find in the real world are Transistor-Transistor (TTL) or CMOS or other things that make me glad I'm in software.
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It's not terribly different. A TTL NAND looks like a diode AND with the diodes replaced by an NPN junction, for instance. Much as we love AK, Google can draw circuits better than the {code} tag. She can definitely explain them better than I, however.
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quote:Much as we love AK, Google can draw circuits better than the {code} tag.
Richard, I am getting a parsing error on this sentence. I haven't drawn anything at all on here, code tag or not. I linked to one page with circuit pics. And by "google can draw circuits" did you mean doing a search and finding good circuit diagrams? Or is there some cool drawing feature on google of which I'm ignorant? I spent some time searching for anything close to the diagrams I wanted, to no avail. If you have suggestions for a handy blackboard I can sketch circuits on to link, that would be nice. I can draw with ink on paper and scan to jpgs, I suppose, if someone can host those.... but that seems so.... crude. Posts: 2843 | Registered: A Long Time Ago!
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quote:The soldering of little components to PCBs is almost always done by factories
If you mean that the soldering is always done automatically by machine I will have to raise a slight quibble. In the commercial electronics world, where production runs routinely run in the hundreds of thousands, this is true. However, in the government/military electronics world, where production runs quite frequently run in the tens or fewer, rather a lot of PCB components (even teensy little SMT components) are soldered by hand.
I know you said this was for stuff you skipped in a class, but I think you may find it more useful (and a bit easier, at least in terms of a layman's [non-mathematical] explanation) to understand how CMOS gates work, since most digital logic these days is built using CMOS instead of TTL. Anne Kate?
------------------
quote:By the way, what flavor of electrical engineer are you?
I've often wondered this myself. And also who else around here is an EE.
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quote:If my monitor will not longer display the color red, is there any hope of fixing it?
Most likely this is because one of the pins in the connector is bent or broken. Shouldn't be impossible to fix.
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I have a pretty good intuitive idea of digital circuits and what most of the components are used for. But I'm clueless about most things analog. What are the nuts and bolts of analog circuits, and what do they do intuitively?
And, what is an op-amp? How is it used? How does it work?
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Oh, wow, people! This is so cool! I'm gratified and amazed that people have taken such an interest in this.
What flavor EE am I? <tastes forearm> Hmmmm, definitely chocolate ... with spicy undertones of ... <closes eyes and runs tongue over palate> cinnamon .... cloves .... and ... is that ozone?
<Sorry for the above. I guess I'm feeling the competition from Dr. Spears' site.>
<ahem> Actually, I do industrial control systems for a number of different industries: pulp and paper, water and waste water, textiles, petroleum, industrial diamond manufacturers, makers of compressed air tanks, food processing, everything you can imagine.
Lately I've been doing combined heat and power generation systems, where an engine-generator set makes electricity, and the cooling water for the engine is used to power an absorption chiller (which uses hot water as its power source) to make cold water for air conditioning. The hot water also is used to heat domestic hot water for laundry, dishwashing, etc. and to provide building heat. It's a very cool setup. I want one for my house. (They actually are used for hotels, office buildings, hospitals, etc. though I'd think one would be good for a neighborhood.)
[ April 30, 2004, 04:39 PM: Message edited by: ak ]
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Dagonee, rest assured I'm working diligently on the plasma gun thing. Thank you for your continued patience.
The next question to be addressed, and the reason I'm wearing my symbolic screenname <bows> is Wheat Puppet's query about logic gates. My name, (though the dash should be centered and the equals and dash both should be touching the D), is the symbol used in digital logic diagrams for an AND gate. I was dubbed And Gate by my fellow EE students, after I told a Lab TA to call me that once. He was fresh from China and struggling with English pronunciation. He mangled all attempts at my name badly, but when he taught us about AND gates, was able to say that in a way which was quite clear and sounded very much more like my name than his earlier attempts. The other gEEks thought that was funny, and so it stuck. I would sometimes sign notes with that symbol.
An AND gate is an electronic component which behaves in such a way that the output will be high (there will be voltage present on the output wire (the dash)) if and only if there is voltage on both input signals (the legs of the equals sign).
<digression> When you say something is "on" or "high" or "set" or "1", in digital electronics, you mean there is a voltage present. "off", "low", "reset", or 0" mean there is no voltage present. It's "digital" because things are designed so that they're always either on or off, which means that the element will be at a potential of perhaps 3 Volts DC (on) or zero Volts DC (off) with respect to ground. Newer devices typically use lower voltage as their "on" state, to reduce the heat generated. In all cases the voltages aren't always exact, but anything close to 3V (in our example) will be considered on. If it's below 1.5V, for instance, it counts as off. </digression>
It's called an AND gate, because the output is on only if input A AND input B are on.
I'm going to break this up into several posts to build the suspense, as is working so well on Dan Raven's thread (Can't wait for the next installment, Dan!) and so they don't look too daunting.
posted
I had a whole post asking questions about semiconductors typed up, and then I finished reading the thread and saw ak had already posted an explanation. I still had some questions after that so I started typing a new post. In figuring out the wording of my questions, I think I figured out the answers, but I just want to make sure.
To be clear, p-type and n-type semiconductors are both electrically neutral, because they have the same numbers of protons of electrons. The shortage and excess of electrons in the two types refer to how the electrons fit into the structure of the material. Right?
Here's a quote from a book on electricity and electronics:
quote:When most of the charge carriers are electrons, the semiconductor is called N-type, because electrons are negatively charged. When most of the charge carriers are holes, the semiconducting material is known as P-type because holes have a positive electric charge. But P-type material does pass some electrons, and N-type materal carries some holes. In a semiconductor, the more abundant type of charge carrier is called the majority carrier. The less abundant kind is known as the minority carrier.
So a hole is a space in the lattice where an electron should be but isn't, and an excess electron is an electron that is not part of the lattice structure and so is free to move around (I picture it as an ice skater on top of the ice, free to move because it is not part of the ice itself). And both can exist within the same material. Is this accurate?
quote: If the positive lead of your battery (for instance) is hooked to the P type side, and the negative lead is attached to the N type side, the positive charge in the battery will repel the holes and move them toward the junction. The negative charge of the battery will repel the electrons in the N-type side, and move them toward the boundary. There will be plenty of electrons to fill holes at the junction and current will flow.
If the free electrons fill the holes in the lattice, why does current flow?
A preemptive thanks. Posts: 2149 | Registered: Aug 2000
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WoW! what a great thread! great link there too ak. I wish my calc based physics II teacher had been a quarter as smart or the communicator or had a tenth the patience as ak. Might have actually learned something other than what I got from studying my brains out for the first four weeks. Kinda sad in a way that I still managed a "B" in the lecture( along with an audit of lab ). Still gotta take the class again... electromagnetism is really really good and cool and interesting but dang is it hard to grasp! Didn't really even understand well about a third of what was on this thread. So abstract.
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Suntranafs - also see the second page of the Nuclear Power thread for more on electromagnetism.
quote:If the free electrons fill the holes in the lattice, why does current flow?
If you're asking why current flows through the semiconductor when you have the leads attached correctly, I can explain it using a bit of "hole flow". I think.
Holes are empty places where an electron wants to be because balances out a charge in that molecule. When there's a junction between the N-type and P-type materials, electrons rearrange themselves in the P-type material to be closer to the positive lead (which is away from the junction and away from the negatively charged N-type material). Thus, holes appear to "move" toward the N type material.
As electrons from the N-type material fill in those holes in the P-Type material, the supply of electrons in the N-type material are constantly being replenished by the negative lead. This keeps a kind of "pressure" at the junction, pushing all the electrons through the holes. The electrons in the holes still sense the whole mess of holes at the positive lead, and keep on trucking through to them because they're at a higher potential (or thinking about how positive attracts negative, the larger positive of that huge mass of holes attracts the electrons, so they just pass through the P-type material).
Also, there's that mass of electrons in the N-type material just waiting to get to all the holes as well. They repel the electrons in the P-side (like repels like), giving those electrons in the holes even greater incentive to keep passing through.
Lower potential goes to higher potential. Hmmm, I think I see part of what you're driving at. Maybe you're asking why the electrons don't just fill in the holes and stay there until the P-type material becomes neutral because all the holes are filled up.
Atoms want various things, two of which are a filled outer shell orbital and a balnced charge. Well, the type of atoms the P-material is "doped" with are atoms that have only one electron in an orbital that is far from the nucleus(its outer shell orbital - the rest of the orbitals are filled). This electron is easily taken out of orbit (because the next orbital down is filled - loss of just one electron leaves the atom with a filled outer shell orbital), and finds it hard to stay attached to that atom. The atom wants the electron, and is positively charged without it. But it's very easy for it to give one up. So the holes remain, well, "holey."
The N-type material has atoms that need an electron to complete its outer shell, but become negatively charged when an electron does. Because the electron is so far from the positively charged nucleus, the overall negative charge of the atom is displaced over a wider volume and is not as important as completing the outer shell.
Here's a site. Somebody correct me if I'm wrong or I said something weird. ak will eventually come along...
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) gates can be made from them directly. For example:![[Kiss]](graemlins/kiss.gif)
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). Still gotta take the class again... electromagnetism is really really good and cool and interesting but dang is it hard to grasp! Didn't really even understand well about a third of what was on this thread. So abstract.
