This is topic Everything you've always wanted to know about Electricity or other technology in forum Books, Films, Food and Culture at Hatrack River Forum.


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Posted by ak (Member # 90) on :
 
In the spirit of Jon Boy's cool thread about English, and in homage to it, I thought I would open up the floor for questions about something I know a bit about. I've really enjoyed the inside look he's giving into the things he studies and works with. Is it possible anyone would like to know something about mine?

[ April 28, 2004, 11:09 PM: Message edited by: ak ]
 

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Posted by AvidReader (Member # 6007) on :
 
The bit I never got is: how do the electrons get from the big spinning magnet into the power line? I get the bits before that, I get the bits after that, I don't get that part. Is the electricity around the magnet a field of charged electrons or is it inside the metal?

Now that I'm having to put it into words, I think it's the basics of the big spinning magnet wrapped in copper wire I don't get.
 

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Posted by Suneun (Member # 3247) on :
 
I'm sure I've been told how several times, but how do those elevator buttons work? You know, the metal ones that need touch to turn on.
 

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Posted by ak (Member # 90) on :
 
AvidReader, the electrons are present all throughout the copper that is in the wires of the whole power grid. It's almost as though there is a sea of electrons there. The thing that makes them move about is a sort of "pressure" called voltage. Electricity always wants to flow away from places with higher voltage towards places with lower voltage.

So with a generator what you are doing is temporarily revving up the voltage in the wires at one point (where you're spinning the rotor), and then you're tapping into that and bleeding it back down at a different point (say, in your computer). The electrons themselves actually have to travel in a big circle. There has to be a return path for current to flow. That's why there are two wires, two prongs to your plug.

So what the generator does is sort of shove hard on the electrons at its place, then far away at your house other electrons feel that impulse as a sort of pressure (not actual pressure but analogous to it) and they respond.

The electrons themselves don't jump the gap from the "spinning magnet" (called the rotor (it rotates)), to the wires wrapped around the surrounding metal (called the stator (it stays still)). What they do is create a field which acts to shove the electrons in the stator around. A little like the way a pump can jack up the air pressure in a tank, the rotor jacks up the voltage in the stator, and from there electrons flow down the wires across the transmission lines and out to your house.

I probably ought to say for completeness that the voltage "pressure" in the circuit is actually switching directions 60 times a second (in most of the Western Hemisphere, and other places like Saudi Arabia), or 50 times a second (in most of Europe, Australia and the far east). This is why it's called AC or alternating current. Thomas Edison despised AC and all his electric systems were DC or direct current, like a battery circuit. Westinghouse went for AC, because that made the voltage easier to change up or down using transformers, and in the end Westinghouse won out.

[ April 28, 2004, 11:00 PM: Message edited by: ak ]
 

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Posted by ak (Member # 90) on :
 
Suneun, the elevator buttons work because they constantly measure a quality called capacitance. Capacitance is the ability of something to hold a static charge.

When you touch the button, you suddenly add a lot of capacitance to what the button had by itself. In fact, there is a small charge placed on the button, and though you don't feel it (since it's so minute), a tiny bit of electricity flows from the button over the surface of your body. This tiny surge is what the electronic circuit detects to know that the button has been pressed.
 

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Posted by ak (Member # 90) on :
 
I'll open up the topic to how anything works. This is technology 101. What I don't already know I will find out for you.
 

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Posted by Jon Boy (Member # 4284) on :
 
I don't quite understand alternating current. So if the voltage pressure is switching back and forth, does that mean that the electrons are just moving back and forth and not traveling in a loop through the circuit? How does an adapter change something from alternating to direct?
 

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Posted by ak (Member # 90) on :
 
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.

The transformer is a coolio device which takes advantage of something Faraday noticed, i.e. that when you change the magnetic field inside a coil, it generates voltage. You can try this, in fact. If you shove a bar magnet into the center of a coil of wire, there is a little squirt of voltage in the wire that corresponds to the motion of the magnet. Repeatedly shoving it in and yanking it out will generate a series of pulses of voltage first of one polarity, then the other. (Tries to think of a clever double entendre here and fails.) It works in the other direction too. When you run a current through a coil of wire, any chunk of iron in the center of that coil will be magnetized. This is called an electromagnet. It's like a permanent magnet that you can turn on and off with the flick of a switch.

So the current in a coil is related to the change of the magnetic field inside the coil. This effect is stronger the more loops there are in the coil.

Here's the cool part. You can run this trick in both directions at once. If you wrap one wire around a chunk of iron (called the core) say, 100 times, and another wire around the same core 200 times, then you can run electricity (AC) in the first wire, which changes the magnetization of the core back and forth 60 times a second, and hence generates a voltage in the second wire at double the original voltage! (This is neglecting small losses from inefficiency.) This little device is called a transformer, and it can be used to convert the voltage of AC either up or down. The only thing that determines the voltage change is simply the number of turns of the coils in the input (called the primary) and the output (called the secondary) wires.

That's why we use AC, in fact, because transformers make it very easy to change the voltage to whatever we want, at will.

[ April 29, 2004, 01:49 AM: Message edited by: ak ]
 

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Posted by ak (Member # 90) on :
 
The second part of the "wall wart" adaptor is the rectifier, which changes the AC to DC. Next I want to explain how this works.

Diodes are electrical devices that allow current to flow in one direction only. A rectifier bridge is a circuit in which four diodes are connected together in a such a way that whichever way the voltage flipflops on the AC input, it always has the same polarity on the DC output.

I really need to show you a picture. Look there about a third of the way down where it says transformer + rectifier + smoothing. The diamond shaped diagram in the middle is how a rectifier is shown schematically. The little triangles are sort of like arrows pointing in the only direction the electricity can flow. The straight lines at the head of the arrows symbolize the fact that when electricity tries to flow back the other way, it hits a "dam" of sorts, and can't go that way.

When AC (which is a wavy line (sine wave) positive and negative) is hooked up to the left and right corners of the diamond, the diode network makes sure the output connected to the top and bottom corners of the diamond is always positive in the same direction. It's still very bumpy, though, because all it's done is take the part of the sine wave that's underneath and make it positive instead.

So the last stage is a smoothing function, which is usually done by a capacitor. A capacitor stores charge temporarily and squirts it back out. Most of these wall warts will still show a little 60 Hertz ripple in their DC output voltage. As long as it's not too much, it's usually no problem. You wouldn't want to use that in any audio circuits, for instance, or it would give you a rather loud B flat hum.

60 Hertz (cycles a second or Hz), is the note B flat (slightly sharp). If you are a musician and you have relative pitch but not perfect pitch. If you ever want to fake perfect pitch, just stop and listen to the world around you. There will be some refrigerator or pump or flourescent lighting or something in the area which is humming quietly that pervasive B flat.

Rainbow Bright, for those of you who remember her, had this belt that made a strong 60 Hz hum when she energized it. Obviously her technology for colorizing the world and generating rainbows you could travel on used 60 Hz power. Murky and Lurky probably just used DC or something.

[ April 29, 2004, 12:58 AM: Message edited by: ak ]
 

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Posted by ak (Member # 90) on :
 
Jon Boy, yes, the individual electrons are just travelling back and forth. However, there must be a continuous loop of metal or other conductor all the way around the circuit for it to work. Think of waves in the sea. Lots of power is traveling from a storm far out at sea to the shore, but hardly any actual water is moving that whole distance. Mostly each bit of water is shoving the water next door, and on and on, until the water near the shore shoves itself up onto the beach.

The energy you use actually comes from the voltage drop across your lightbulb or strip heater or whatever device you have plugged in.

Another way you can think of it is like a small waterfall where you get energy from the water dropping over a dam. Picture a very strange dam built in the middle of a lake which is sloshing back and forth so that the water level on each side keeps reversing. Whichever side is higher, you can still get energy from letting water drop across from the high side to the low side.
 

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Posted by fallow (Member # 6268) on :
 
Ak,

Sorry to impose on this tech thread. I was wondering if you might have any poetry to go along with this topic, or not. I would dearly like to read some.

fallow
 

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Posted by ak (Member # 90) on :
 
I should write some. It always saddens me that no poets seem to feel the beauty of these things, of their deep resonances. I know of none.

But one song, if you like: Transformer, by the Smashing Pumpkins. Enjoy!
 

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Posted by fallow (Member # 6268) on :
 
ak,

please don't make me beg. please?

gimme a bottom-drawer poem, please?

fallow
 

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Posted by ak (Member # 90) on :
 
I don't have any electricity poetry, sorry.

But I do have this one that's quite old. Maybe I should do an astronomy thread someday.

Skygazer

Stars like clotted dust across the sky,
You fit the Barlow, focus, squint your eye,
While gleaming planets swim into your view,
I watch the night, the telescope, and you.

Exploding starsurf winds, galactic seas
Across the aeons spins in mysteries
Of long ago, of here, the never now,
The deeping cold, the whistling void, and thou.
 

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Posted by Richard Berg (Member # 133) on :
 
I'll use this thread to make a techie's confession: no matter how much I stare at the diagrams on howstuffworks, I can't picture an engine in my head. Especially if it's DOHC, all those valves somehow reciprocating in time... I blame all those 3D paradox posters, of which I've been able to "see" precisely zero.
 

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Posted by fallow (Member # 6268) on :
 
ak,

yer a wonder to me.

thanks. I ever do appreciate.

fallow
 

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Posted by ak (Member # 90) on :
 
Richard, you should maybe rebuild one, or go take a long look at one being rebuilt. There are really 4 dimensions you have to see something like that in (3 spatial plus time), and it's very hard to depict with diagrams.

Another thing you can do is look at simpler versions and understand them completely first. The first widely available internal combustion engines were single cylinder and sold to run farm equipment with belts. A retired engineer I know collects them, refurbishes them, and shows them. He's fanatical about it. There are other like minded people who share his passion, and they have get togethers to which they all bring their toys and have demonstrations. They're the most incredible infernal contraptions you can imagine. They make a ludicrous noise like something in a mad scientist's laboratory. Absolutely delightful!
 

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Posted by Derrell (Member # 6062) on :
 
ak, while I don't have a question at the moment, I would like to thank you for starting this thread. I've always been fascinated by technology and how it works.

Oh, wait, I just thought of a question. How does a camera flash work? Does it have a capacitor in it? I'm referring to a stand a lone flash unit as opposed to the ones that are built into point and shoot cameras.

I have a 35mm camera and a detachable flash unit. I'd love to know how it works. Thanks.
 

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Posted by ak (Member # 90) on :
 
A flash unit for a camera is like a very bright neon light (only using xenon gas instead of neon). The light from them comes from the ionization of the gas inside. The electrons in the gas jump into higher orbits in the presence of a strong electric field, then emit photons when they fall back into their normal orbits. Since neon lights need high voltage, and because a camera flash must be powered from a battery which supplies low voltage, a number of other electronic components are needed to make up the total flash package.

First of all, there is an oscillator which changes the DC to AC. This is basically a switch that turns on and off very rapidly. The high pitched whine that you may hear while the system is charging comes from this switch.

Secondly, there is a transformer to change the AC electricity from low voltage to high voltage. It does this by way of turns of wire around an iron core, similar to the description for the "wall wart" adaptor, above, but this time with a whole lot more turns of wire on the output coil (or secondary) than on the input (primary). That way we can take, for instance, 1.5 Volts in (a typical battery voltage) and get out the 500 Volts or more that are needed for the very bright light.

Next, there has to be a capacitor to store the charge that's building up, because a small battery can provide energy rather slowly, and we need an awful lot of energy in a short time to make our flash very bright. Capacitors are essentially metal foil sheets which are close together but not allowed to touch. The two sheets of foil are sandwiched together with a third sheet between them (the dielectric), which keeps them from touching and discharging. The whole sandwich is typically rolled up into a little cylinder. When you apply a voltage across a capacitor, it can store energy, similar to a battery, but with much shorter charge and discharge times, since no chemical reaction is taking place as it is in a battery.

Then finally, of course there is a trigger switch, which is wired in with the camera's shutter, so that the flash will correspond exactly with the time the shutter is opened.

When you press the button to ready the flash, the oscillator turns DC from the battery to AC, which then goes through the transformer to be jacked up to a higher voltage and stored in the capacitor. Once the capacitor is sufficiently charged, the indicator light will light. Then when the camera shutter is opened, the trigger fires and lets all this stored energy light up the xenon in the little tube.

[ April 29, 2004, 01:37 PM: Message edited by: ak ]
 

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Posted by Dagonee (Member # 5818) on :
 

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The electrons themselves actually have to travel in a big circle. There has to be a return path for current to flow. That's why there are two wires, two prongs to your plug….

I probably ought to say for completeness that the voltage "pressure" in the circuit is actually switching directions 60 times a second

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      Transformer -----black wire----light bulb
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          ----white wire-------Service entrance ground
  
 

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This is fascinating, by the way.

Dagonee
 

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Posted by ak (Member # 90) on :
 
Wow, kat! Great question. You want the underlying reason these things work as they do? You cut to the heart of the matter, don't you?

I think this is what you are asking. You may be asking a much easier question which is where is the energy put into the system that we take out when we use electricity in our houses. The answer to that is simple, it's at the generator. Some engine is running, or turbine turning, converting something we get for free, like wind or waterfalls or the chemical energy inside a lump of coal into electrical impulses.

But I think the real question you are asking is the deep one. Why do electrical charges behave the way they do? What is charge? Why are there such things as electrical fields? This is really the same question you can ask for gravity or any other feature of the universe. Why is there gravity? Why do the laws of physics work the way they do? And the answer to that one is extremely cool and interesting.

Richard Feynman, one of my greatest heroes, addressed that question in a book he wrote called The Character of Physical Law. The laws of physics are just equations. Matter is knots in the fields, and fields are numbers in space. We can describe perfectly HOW the laws of physics work, but there is no WHY that we can discern in our instruments. There is no underlying nuts and bolts mechanical explanation of everything.

For gravity the equation (classically) is F = GmM/R^2. The force between two masses is directly proportional to the product of their masses and inversely proportional to the square of the distance between them. In electrostatics there is a similar equation with charges instead of masses (and the added twist that there can be both positive and negative charges).

Feynman would say to his classes "In the middle ages they thought the planets traveled around in circles due to angels flying along behind them pushing with their wings. Now we have a different theory. Now the angels push inward."
 

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Posted by ak (Member # 90) on :
 
Dagonee, yes, you've got it, (in simplified form)!
 

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Posted by JohnKeats (Member # 1261) on :
 
...This is putting me in the mood for that old laser game we all played some time ago.
 

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Posted by Dagonee (Member # 5818) on :
 
OK. That also helps explain why grounding the green whire at the same point as the white wire is so bad.

I get it now.

Dagonee
 

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Posted by saxon75 (Member # 4589) on :
 

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transformers make it very easy to change the voltage to whatever we want

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Feynman would say to his classes "In the middle ages they thought the planets traveled around in circles due to angels flying along behind them pushing with their wings. Now we have a different theory. Now the angels push inward."

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Yes!! Yes, that's exactly the question I was asking.

And thank you for that gorgeous answer.

[ April 29, 2004, 02:51 PM: Message edited by: katharina ]
 

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Posted by ak (Member # 90) on :
 
saxon75, yeah, I was hoping someone would ask me that question about transformers; how come you can jack the voltage up as high as you like for free.

No they are not perpetual motion machines. Every time it doubles the voltage, it halves the current. Transformers are definitely magic, but not quite so magical as that.
 

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Posted by Ralphie (Member # 1565) on :
 
If only I was smart enough for this thread, think of the things I'd be learning!

Instead, I'm reading it, eating cheetos, and drooling cheese powder on my shirt. But I remembered to wear a bib this time, so I'm already learning.
 

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Posted by ak (Member # 90) on :
 
Ralphie, people who have wired up things, or played with electricity all their lives, will be asking questions at a different level than someone who hasn't.

I'd love to get questions from people who haven't, too. Think of a question. I'll do my best.

I am curious for my part how people who aren't technological geeks see the world, too. When you use the myriad devices and systems you use every day, how are you thinking about them? How are they modeled in your mind? What is electricity like, to you? Maybe it's just not something you think about much at all. Sort of like me with social dynamics or taxes? Or maybe you know more or less what behavior to expect from different devices and leave it at that?

[ April 29, 2004, 03:07 PM: Message edited by: ak ]
 

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Posted by saxon75 (Member # 4589) on :
 
I keep trying to come up with a good "stump the expert" question (which I know is insufferably rude, not to mention a bit unfair since ak and I are in the same line of work [granted, she has more experience than I do]), but the only one I really care about is why my stupid card keeps making the stupid system crash on what seems to be a totally nondeterministic time frame.

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Or maybe you know more or less what behavior to expect from different devices and leave it at that?

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quote:

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design engineer, field technician, computer hobbyist, Trekker, average netizen, theater major, Amish

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That's brilliant.

I'm somewhere between Trekker and computer hobbyist. I'm secretly fascinated by technical stuff, but fear it's beyond my ability to comprehend. And, honestly, I think it comes down to math, which I've never excelled at simply because I'd forget to carry an integer, or misplace a decimal point, or something else equally as stupid. I like mess about with technical things in my hand, but if I have to figure out WHY something does something, and if it includes math, I go back to drooling cheeze-dust on my kitchy Rainbow Brite shirt.
 

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Posted by ak (Member # 90) on :
 
saxon75, stump the chump is a GREAT game! I LOVE the hard ones. I particularly love the ones that are hard because you've never ever thought of it that way before.

Anything I don't know I will look up. Or I will consult the tea leaves, halibut bones, and the pig entrails. I will scan the heavens for a sign. I will use dice and other arcane instruments of my craft.

Your card is making your system crash in a non-repeatable way because ... <pauses while eyes roll back in head> ... the card is flaky. Try another one, if easily available. Otherwise reread the entire documentation on the card, check that all installation instructions were followed, dip switches are set correctly, and so on, test your power supply and check all your inputs, and the reason will eventually become clear. If none of that works, reorient the cabinet with respect to the surface of the earth using your foot or other source of kinetic energy.
 

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Posted by saxon75 (Member # 4589) on :
 

quote:

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the card is flaky.

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Unfortunately it is my job to understand why it is flaky.

quote:

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Try another one, if easily available.

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quote:

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Otherwise reread the entire documentation on the card,

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If none of that works, reorient the cabinet with respect to the surface of the earth using your foot or other source of kinetic energy.

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Oh, how happy that would make me... I think I'll just go take my lunch break now instead, though.
 

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Posted by ak (Member # 90) on :
 
Ralphie, I'm also one who makes stupid math mistakes. I have to double and triple check all my calculations because of that. Unlike on tests, at work you have plenty of time for that.

Minus signs, decimal places, arithmetic. I screw up those all the time. I can't add 2 and 5 reliably without my trusty HP calculator with Reverse Polish notation (I call it my prosthetic brain).

Understanding how things work is what counts in my job. Math mistakes are easy to take care of by double- and triple-checking.
 

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Posted by ssywak (Member # 807) on :
 
Stump the Chump #1:

(Real world example)

quote:

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One day, years ago, when I was at the beach with Peg & the kids, we met a group of friends (not our friends; they were their own friends, though) struggling to start their car. When they saw me "chirp" my car alarm, they must have figured I knew about car alarms (not really, but let us continue) and came over to us.

Apparently, they also had one of those self-installed car alarms, with a siren and with a starter cut-off. But their "key fob" thingie was dead. They had unlocked and opened the car anyway, and had clipped the wire to the siren to keep from going insane. But the starter cut-off was working as designed, and they could not start their car (I do still hope it was their car...).

Being the geek that you all know me to be, and having either a pen-knife or Leatherman pliers with me, I was able to unscrew the back of their key fob remote. As I had assumed, the battery was dead--the contacts were visibly corroded. I removed the battery and noticed that it was about the same diameter and one-third the length of a AAA battery--and, it was a 12 volt battery!

Now, as you know (if you don't, then you really shouldn't be answering questions like this), cars have a 12 volt battery also. But the battery in a car is about the size of your head, typically larger. This key fob battery was smaller than your pinky.

Apologies, of course, to people who may have been born without pinkies, or who may have lost their pinkies later in life. Or their heads.

But, to continue. I also had a set of jumper cables in the back of my car.

Here's your question: Can you really jump start a 1 inch square by 1/4 inch thick key fob with a battery big enough to jump start a 2000 pound automobile? Or did it just blow the hell up in my hands? Explain your answer.

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(You know you spend too much time on the Internet when you Google yourself just to find something you posted 5 months ago, so you don't have to retype it now)
 

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Posted by ak (Member # 90) on :
 
Ohhh! It's a prototype!

And the designers are gone!

Hahahahahahah!

That's REALLY fun! In that case test everything you can test, whether it would seem relevant or not. Check all your assumptions about everything. Try different screwy things just to see how it behaves. First play around with it trying to get it to work, then play around with it trying to get it to not work. Pay attention to dreams and fortune cookies that you get during this phase of discovery. Sooner or later, some datum that you shake loose in this way will give you the aha that you need. There's no telling how long it will take, though. Good luck!
 

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Posted by Jacare Sorridente (Member # 1906) on :
 
If I make a stripline using dielectric materials with different dielectric constant of say, 4.2 and 2.6 above and below the signal line, will the transmission be Transverse electric and magnetic (TEM), quasi-TEM, or something else? Will there be any effect on group delay?
 

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Posted by ak (Member # 90) on :
 
Stump the chump question 1 answer. The voltage is all that matters. If the thing is in good shape apart from a dead battery, and if you are careful not to short anything out when you apply the 12V from the car battery to the device, then it should work just fine. The current will be limited by the resistance in the device.

However, it's possible the battery is dead because something shorted out inside the key fob and drained it, too. Or it's possible the dead battery had corroded and spilled acid all over the key fob and now it's ruined. But assuming neither of these is true, then it could certainly work.

[ April 29, 2004, 03:57 PM: Message edited by: ak ]
 

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Posted by Slash the Berzerker (Member # 556) on :
 
Dear Electronics Goddess:

How might I go about designing and building high power energy weapons (Charged particle projectors, plasma based weapons, high intensity lasers, and so on) in the comfort of my own home?

I promise to use them only for good, never for evil.
 

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Posted by ssywak (Member # 807) on :
 
ak,

Correct. I will tell you, though. When you've got those jumper cables in your hands, you definitely think twice about applying them to that tiny little key fob. And the guys who owned the car looked at me as if I were crazy to try such a thing.

Puzzler #2:

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You take a regular helium-filled balloon, and you put it in the (otherwise empty) passenger area of your Dodge Caravan. You're stopped at a traffic light, your windows are closed, and your climate control fan is off. The light turns green, and you gently press on the accelerator pedal. Since it is a Dodge Caravan, it hesitates about 20-30 seconds before it decides that it should really engage the transmission, and then it takes off like a bat out of hell.

Which way does the balloon move, and why?

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[ April 29, 2004, 04:07 PM: Message edited by: ssywak ]
 

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Posted by sndrake (Member # 4941) on :
 
This just might be the thread where I get an answer to something that's been bugging me since I was five years old (that's a lot of time).

Our driveway had a depression which served as a collector for water and debris carried along with the water. One summer day, I was walking past the puddle that had been sitting there in the sun, and noticed a penny sitting in the puddle, on top of a bunch of (probably) decomposing leaves.

I reached for it. When my finger hit the water, a weird sensation spread up my finger, like my finger was vibrating - very unpleasant. The sensation stopped at the knuckle joint. After a couple tried (I catch on slowly), I left the penny alone.

Years later, I realized what the sensation was when I accidentally hit an electrified cattle fence with a soda can - twice (like I said, I catch on slowly). The sensation was the same, except the one from the cattle fence was much stronger, with the sensation terminating at the elbow joint.

Questions: Is this feasible or am I really as whacked out as the few adults I told this to when I was a kid thought I was?

If it's feasible, what's the mechanism involved here?

You can solve a mystery that has been bugging me for over four decades!
 

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Posted by Derrell (Member # 6062) on :
 
Thanks ak, you are truly cool.
 

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Posted by ssywak (Member # 807) on :
 
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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Posted by Dagonee (Member # 5818) on :
 
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).

Dagonee
 

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Posted by sndrake (Member # 4941) on :
 
ssywak and Dag,

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.

This is very very cool!

Thank you!

[ April 29, 2004, 04:53 PM: Message edited by: sndrake ]
 

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Posted by rivka (Member # 4859) on :
 
sndrake, penny composition changed drastically in 1982. From Penny Collector:

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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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Posted by Richard Berg (Member # 133) on :
 
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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Posted by ak (Member # 90) on :
 
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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Posted by ak (Member # 90) on :
 
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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Posted by Toretha (Member # 2233) on :
 
how does one go about getting very very very precise soldering done?
 

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Posted by JonnyNotSoBravo (Member # 5715) on :
 
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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Posted by Richard Berg (Member # 133) on :
 
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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Posted by Dagonee (Member # 5818) on :
 
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.

Now that's geekdom!

Dagonee
 

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Posted by Toretha (Member # 2233) on :
 
jewelry.
 

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Posted by rivka (Member # 4859) on :
 
*tunes Dagonee's viola*
 

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Posted by Dagonee (Member # 5818) on :
 
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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Posted by rivka (Member # 4859) on :
 

 

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Posted by Dagonee (Member # 5818) on :
 
That's funny enough that I'm not even going to fix my spelling in the post above.

Dagonee
 

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Posted by JonnyNotSoBravo (Member # 5715) on :
 

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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Posted by Jon Boy (Member # 4284) on :
 
Thanks for the explanation, ak. Geez, but Hatrack moves fast when you're only on a little bit each day.
 

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Posted by ak (Member # 90) on :
 
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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Posted by ak (Member # 90) on :
 
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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Posted by ak (Member # 90) on :
 
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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Posted by JonnyNotSoBravo (Member # 5715) on :
 
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.

[ April 30, 2004, 01:24 AM: Message edited by: JonnyNotSoBravo ]
 

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Posted by skillery (Member # 6209) on :
 
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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Posted by JonnyNotSoBravo (Member # 5715) on :
 
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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Posted by ak (Member # 90) on :
 
How a diode works:

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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Posted by ak (Member # 90) on :
 
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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Posted by ak (Member # 90) on :
 
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.
 

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Posted by WheatPuppet (Member # 5142) on :
 
Wow.

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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Posted by JonnyNotSoBravo (Member # 5715) on :
 
I think you're prolly talking about SCRs... which fits right in with ak's talk about how diodes are made...

technically, you might call a diode a type of logic gate...
 

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Posted by Richard Berg (Member # 133) on :
 
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

---

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.
 

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Posted by Jacare Sorridente (Member # 1906) on :
 

quote:

---

Jacare, I've yet to start on yours but have not forgotten.

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quote:

---

The soldering of little components to PCBs is almost always done by factories

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quote:

---

I was more aiming at TTL-based IC

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quote:

---

By the way, what flavor of electrical engineer are you?

---

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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Posted by Mike (Member # 55) on :
 
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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Posted by celia60 (Member # 2039) on :
 
saxy, you forgot to use the [shameless plug][/shameless plug] tags.
 

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Posted by saxon75 (Member # 4589) on :
 
I posted. That should be indication enough.
 

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Posted by ak (Member # 90) on :
 
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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Posted by Dagonee (Member # 5818) on :
 
You know, some of us waiting very patiently to learn how to build our plasma guns.

*taps foot*

Dagonee
 

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Posted by =D- (Member # 5886) on :
 
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.

[ April 30, 2004, 10:07 PM: Message edited by: =D- ]
 

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Posted by fallow (Member # 6268) on :
 
maDAMN Tesla!

ak



*quivers*

fallow
 

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Posted by Dagonee (Member # 5818) on :
 
AK, that's fine, we'll wait. Just so long as it's posted publicly. I don't think any of us want Slash to be the only one with a plasma gun.

Dagonee
 

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Posted by JonnyNotSoBravo (Member # 5715) on :
 
*bump* I'm still waiting for ak's next installment...
 

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Posted by Miro (Member # 1178) on :
 
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.

---

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.
 

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Posted by suntranafs (Member # 3318) on :
 
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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Posted by JonnyNotSoBravo (Member # 5715) on :
 
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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Posted by HollowEarth (Member # 2586) on :
 
I've always like that its called annihilation when a hole meets an electron.
 

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Posted by Samuel Bush (Member # 460) on :
 
Howdy, ak. Great thread.

I once met a guy who had a wooden box with a metal handle on top and a metal crank on the side. I asked him what it was and he said to go ahead and turn the crank. So I did and got a big surprise. And the harder I cranked the more my arm muscles convulsed.

It was way cool!

(And the box had sign on it. "Warning. Do Not Crank Handle" which I thought was a nice touch.)

So when the guy stopped laughing, he told me there was a magneto inside. So my question is:

Can a magneto like that generate enough 'lectricity to kill a person? (Assuming that person doesn't have a pacemaker or weak heart.)

Oh yes, and another question I have is: where can I get a working magneto really cheap? Ever since then I've wanted to make one of those boxes. And I have some sons who are one up on me on the practical joke tally sheet. (hey, it's a guy thing)
 

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Posted by ak (Member # 90) on :
 
Oh, I have been quite remiss in my duties as resident mad scientist! I must beg all of your forgiveness and try to remediate this deficit very soon. My only excuse is that I have been very busy with my researches in the laboratory, and am on the cusp of a great new discovery involving feline mediated neurological torture mechanisms. Details to follow.
 

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Posted by suntranafs (Member # 3318) on :
 
bumpity bump just for kicks
 

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Posted by WheatPuppet (Member # 5142) on :
 

quote:

---

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).

---

quote:

---

I wanted to know how a logic gate is built

---

code:

---

     S       G        D
     |  _____|______  |
     |  |   ins    |  |
----------------------------
  |  P  |          |  P  | 
  |-----|          |-----|
             N

----------------------------

---