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Re: Charge Storage in Cap (capacitance 101)
Jim Purcell
manifold,
Here is a question to ponder about capacitance. DisregardingBecause the dielectric constant is different. If they are chemically different they may have produce different capacitance for the same dimensions. Ceramic caps for example are nothing but little discs flashed with metal, hardly any plate surface area compared to tubular, etc. Here's a hint, _very_ pure water is a good dielectric. It is justSo which side are you on as the real storer of the charge, dielectric or plates? Jim |
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Re: Charge Storage in Cap (capacitance 101)
Here is a question to ponder about capacitance. Disregarding
leakage, why do capacitors of the same physical dimensions, i.e., plate spacing and area, with different dielectrics have very different capacities? Here's a hint, _very_ pure water is a good dielectric. It is just not very practicle for use in consumer devices. It should be in that old EE text book somewhere! It could even be in the physics book. I can look it up for more details if anyone is really interested. I think the answer to the static on the comb question is in the details of surface chemistry and triboelectric effects or "rubbing the electrons off the suface". If there is no conducting path to take them back to the other surface then the charge is "stuck" on the insulating comb with no way to move around. Except for maybe the unsuspecting cat/co-worker/sister/mother in law :) Conductors have atoms with an incomplete valance ring - theoutter electron ring of the atom doesn't have as many electrons in thering as the ring capable of having - it isn't full. Since the ring isn'tfull, an electron could move into the ring and then back out. This iswhat current flow is.as many electrons as will fit. It takes more force to get electronsto move from atom to atom. The force required is the dielectricbreakdown voltage. Sometimes whin breakdown occures the resulting currentcauses permanent damage to the dielectric. And sometimes, when the currentflow is stopped, the dielectric will return to its prevous state -yielding the "self healing dielectrics" that someone else mentioned.dielectric. If a voltage potential is applied between the plates, current willflow untill the charge between the plates matches the potential of thethe dielectric. The electrons were simply moved from one plate to theother through the source of the applied voltage.the plates untill a current path( a conductor) is placed between them.so the voltage potential will slowly drop as the dielectric allows asmall current to flow from one plate to the other.it through your hair? The electrons flow from your hair to the surfaceof the comb. If the comb were a perfect insulator, there would be no |
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Some very interesting links for you
James
Hello,
My name is James Roberts and I am primarily associated with the mind-l yahoo group. I have some interesting links for you. The first concerns a public safety study of a mind-altering device comprised of a helmet fitted with electromagnets. It can produce interesting experiences and positive emotional change. The key is the special signals that are recorded on cd. The second concerns an arrangement of high-voltage equipment that produces levitation in magnetic and non-magnetic objects, spontaneous fires, floating lights, etc. Sic Luceat Lux, Xenoticus |
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No metal in MOS?
Doug Hale
The context of no metal had to do with fabrication of the transistor, not interconnecting them.
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MOS means metal oxide semiconductor.. the metal oxide forms the transistor gate. A poly gate transistor has the metal oxide replaced with poly-silicon. We still cal it a MOS transistor - either due to tradition - or because PSS is harder to say(ha ha). (and CPSS instead of CMOS would even be worse) Doug Hale Kevin Vannorsdel wrote: For RAM processes? This is interesting... are you saying you use NO metal interconnects in RAM? Even for power distribution?? |
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Re: Light Activated Alarm
Kenyon Jones
开云体育Jim,
?
I am
very greatful and appreciate you taking the time to formulate this response. Not
being an electronics expert, your detail has helped me to understand what needs
to be done. Incidently, I am an investigator in the transportation industry and
this alarm will be placed inside of packages. If someone attempts to pilfer the
"test" package, the alarm will sound.
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Again,
much thanks to you.
?
Sincerely,
?
Kenyon
Jones
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?
?
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Charge Storage in Cap
Doug Hale
Capacitors are made of two types of material, conductors (plates) and insulators (dielectrics).
The question of whether the charge is stored in the dielectric or the plates can be understood by knowing a little of the material science of conductors and insulators. Conductors have atoms with an incomplete valance ring - the outter electron ring of the atom doesn't have as many electrons in the ring as the ring capable of having - it isn't full. Since the ring isn't full, an electron could move into the ring and then back out. This is what current flow is. Insulators have complete valance rings - there outer ring has as many electrons as will fit. It takes more force to get electrons to move from atom to atom. The force required is the dielectric breakdown voltage. Sometimes whin breakdown occures the resulting current causes permanent damage to the dielectric. And sometimes, when the current flow is stopped, the dielectric will return to its prevous state - yielding the "self healing dielectrics" that someone else mentioned. A capacitor is formed when two plates are seperated by a dielectric. If a voltage potential is applied between the plates, current will flow untill the charge between the plates matches the potential of the applied source. The current DID NOT into or through flow through the dielectric. The electrons were simply moved from one plate to the other through the source of the applied voltage. If the voltage source is now removed, the charges will remain on the plates untill a current path( a conductor) is placed between them. Dielectrics have "leakage" because they are not a perfect insulator so the voltage potential will slowly drop as the dielectric allows a small current to flow from one plate to the other. PERFECT capacitors would have dielectrics that have an infinate breakdown voltage and zero leakage and conductors that have no resistance to limit current flow. Charges are stored on plates because dielectrics don't conduct. OK, now what about collecting static charges on a comb as you run it through your hair? The electrons flow from your hair to the surface of the comb. If the comb were a perfect insulator, there would be no current flow to the surface of the comb. Doug Hale |
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Re: Fuses--for kevin;-)
Kevin Vannorsdel
For RAM processes? This is interesting... are you saying you use NO metal
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interconnects in RAM? Even for power distribution?? Very curious. KV. ________________________________________________ Kevin Vannorsdel IBM Arm Electronics Development 408-256-6492 Tie 276-6492 kv@... KF6YCI Please respond to Electronics_101@... To: <Electronics_101@...> cc: Subject: Re: [Electronics_101] Re: Fuses--for kevin;-) hey , just to add...now we use polysilicon instead of the metal...:-) Regards :-), --himanshu sharma ----- Original Message -----
From: Kevin Vannorsdel To: Electronics_101@... Sent: Monday, October 29, 2001 9:54 PM Subject: Re: [Electronics_101] Re: Fuses vs. resistors I'm new to this group so missed the CMOS topic (which I would have enjoyed)... CMOS transistors use metal as interconnects - mainly aluminum. The latest silicon processes are beginning to use Copper as interconnects. This is fairly widely publicized so you may all know this. The CMOS transistor itself is made of standard P and N type silicon (with various doping levels) along with Poly-Silicon for the gate and a bunch of silicon dioxide for the gate dielectric. Metal is still a very important issue in IC design. See my previous comments on electromigration... KV. ________________________________________________ Kevin Vannorsdel IBM Arm Electronics Development 408-256-6492 Tie 276-6492 kv@... KF6YCI Please respond to Electronics_101@... To: Electronics_101@... cc: Subject: Re: [Electronics_101] Re: Fuses vs. resistors heros, or that the length of a wire has nothing to do with resistenceSince these quotes are all mixed up and shortened I don't know who said what and for certain what he said. Here's my parting shot on the fuze, resistor, etc. topic. I was wrong when I originally said that a fuze has no resistance, and of course the resistance is required for it to fuze, i.e. blow, when it's rated current passes through it. That something has resistance doesn't make it a resistor. If it did we'd have to call everything that is not an insulator a resistors, transformers, wires, fuzes, etc. A resistor is not simply a device that has resistance but one in which resistance is utilized as part of the circuit design, to achieve a voltage drop when connected in series, to bypass current in a device when in parallel, i.e. shunt like the old D'Arsonval (SP?) analog meters when used to measure current. Someone earlier said that CMOS devices actually no longer use Metal, I don't know whether that is so, but we don't stop calling them CMOS, which may be why I didn't know that metal is no longer used in their manufacture. Anyway, that's my swan song on the issue. Jim To unsubscribe from this group, send an email to: Electronics_101-unsubscribe@... Your use of Yahoo! Groups is subject to To unsubscribe from this group, send an email to: Electronics_101-unsubscribe@... Your use of Yahoo! Groups is subject to the Yahoo! Terms of Service. Yahoo! Groups Sponsor ADVERTISEMENT [IMAGE] [IMAGE] To unsubscribe from this group, send an email to: Electronics_101-unsubscribe@... Your use of Yahoo! Groups is subject to the Yahoo! Terms of Service. |
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Re: all my freinds
Lise Quinn
开云体育I think you glorify it too much. A hacker's goal is
most often to get around a security or licensing issue. You can romanticize a
thief all you want but they will still serve real time for their crimes. And
they don't look so cool?behind bars. Our own government is considering
equating web-defacing and Denial of service attacks to acts of terrorism.
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Just because one did no harm after compromising a
system doesn't mean that it is not wrong or 'bad' to do so, I think the argument
that such people give opportunities to create better security is very weak, and
if it were to float at all then it would be true in all cases. Just because you
don't have a steel door and an enhanced security system for your house doesn't
mean that it's alright for anyone to come into your front door and have a party
in your house. To use the security argument, they were just showing you that you
should have better locks on your doors.
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Lise
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Recomendations on books
Doug Hale
I just ate lunch next to a Radio Shack and decided to stop in and look at their begining electronics books. After spending a few minutes thumbing through them, I would recomend them. There are three that I looked at;
Begining Electronics Begining Digital Electronics Begining Comunications Electronics These should be availible at retail outlets as well as the online Radio Shack Web site. Doug |
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Re: all my freinds
Himanshu Sharma
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Re: Digest Number 134
Jim Purcell
"Mr.",
My understanding of the capacitor is that the actual electronIs that a derived understanding or does it come from a direct statement made by someone who knows.? The closer you can get themThe dielectric doesn't conduct, that's why it's also called an insulator. The reason for greater capacitance when the dielectric is thinner is that there is less distance through which the charge has to act. A conductor just cannot be charged. It's electrons are free and will not be permanently removed or added to it's atoms. Because insulators not not easily give up or accept electrons, once they do they stay that way. At least until a path is provided for things to neutralize or even to become charged with the opposite polarity. force they exert on each other. Both parts are involved, but theNope. The part the plates play is their size, large plates involve more dielectric surface area to the potential difference that charged it. As does larger plate area. Jim |
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Re: all my freinds
Jim Purcell
Himanshu,
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what i say is that hackers are not bad and niether they are evil.. |
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Re: books needed from india
Himanshu Sharma
开云体育hey ,
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You can start your electronics journey with
....
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Arts of Electronics----Horowithz(Cambridge
pub.)
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Rest depends on your interests..!!
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Regards :-),
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--himanshu sharma
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Re: Digest Number 134
Mr.
--- In Electronics_101@y..., Jim Purcell <jpurcell@w...> wrote:.
amount of capacitance depends in part on the kind of dielectric. A conductorwill not store a charge, only provide a path for it. Insulators respond tothe potential Jim, My understanding of the capacitor is that the actual electron are stored on the plate, or conductor. The closer you can get them together (meaning a thinner and less conductive dielectric), the more force they exert on each other. Both parts are involved, but the charge is on the plates. Rex |
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Re: Light Activated Alarm
Kenyon Jones
开云体育Jim,
?
Thank
you for your response. It seems that the photo transistor is conducting enough
to send minimal current through the relay but not enough to activate the switch,
so to speak. My problem is that I need the circuit to be such that the alarm
continues, even if light is removed from the photo transistor. Could you tell me
more about "putting the alarm device in series with the collector and VCC.
Again, I appreciate your help.
?
Sincerely,
?
Kenyon
Jones
?
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Re: Digest Number 134
d nixon
Jim,
Dammit, now I HAVE to look this up. Thanks. -Mike From: Jim Purcell <jpurcell@...> _________________________________________________________________ Get your FREE download of MSN Explorer at |
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Re: PIC resources
Mounir Shita
开云体育Hi
Michael,
?
I have
some years experience with PIC.Actually 5-6 years to be exact. I've built quite
a few projects. My biggest was my senior project at college 3-4 years ago when I
built a speech recognition system with a PIC16 and a PIC17. Worked okay, only
got 70% recognition rate. Also built tons of small projects. Right now I'm
playing with a robot I'm gonna squeeze a PIC18F to do some simple
navigation.
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Mounir
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Re: Capator tester
d nixon
I have seen several capacitor testers in books by Delton T. Horn (TAB books). Check your local library.
-Mike From: "Michael Carey" <mpc@...> _________________________________________________________________ Get your FREE download of MSN Explorer at |
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Re: Fw: communication concepts ??
d nixon
Outer space is not a total vacuum, but it's pretty dang close. As far as rockets go...
There doesn't have to be anything for the rocket to push against. Remember..."For every action there is an equal an opposite reaction." So as long as the rocket pushes *something* out the back it will move forward. Rockets are different that propellered airplanes. Props must have something to push, rockets generate thrust through chemical reactions. -Mike From: "angtengchat" <angtengchat@...> _________________________________________________________________ Get your FREE download of MSN Explorer at |
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Re: books needed from india
Here is a good link for an on line elecronic text book of
electronics. It is in the bookmarks section of this site. --- In Electronics_101@y..., rahuljayawant@y... wrote: hi i am a new member of this group.i am doing electronics andby which i can improve my fundamentals of electronics and |
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