Capacitors vs inductors and current vs voltage. - Page 1
Forum section: electronics / beginners

author: Apokalypz
author_rank: Newbie
timestamp: September 06, 2017, 01:41:48 am
content: I've had a good understanding of what a capacitor does since I was a kid. It charges up to the line voltage (in the he case of a decoupling or filter cap) and when the line voltage dips, it releases some of its voltage... Now I know there is one very important mistake at the end of that sentence, but bare with me.Then I learned what an inductor does a few years ago. It stores current in a magnetic field and releases the current when the current in the circuit drops... Again, I realize the mistake (similar to the mistake I made above).Now, after really thinking about it, it hit me and I discovered where my understanding is flawed. It all revolves around Ohm's law. A capacitor doesn't release it's "voltage", that actually doesn't make sense, it actually releases current to maintain the voltage through the load. Again V=IR. Same thing goes for the inductor, it pushes a higher voltage through the load to maintain the current.I think there's a problem when people try to explain what these passive components do to beginners in EE. It seems like people always use voltage to describe what a capacitor does and always use amperage to describe what an inductor does. Nobody really talks about how the components react with the load to give the complete picture. You just don't think about current when talking about capacitors and voltage when talking about inductors.So I rewrote my own understanding of each component as follows:A capacitor tries to maintain voltage by supplying a variable amount of current to the circuit.An inductor tries to maintain current by pushing a variable voltage through the circuit.So my question is, does my new understanding make more sense? What do you guys think?

author: IanB
author_rank: Super Contributor
timestamp: September 06, 2017, 01:48:04 am
content: Your rewritten sentences are approximately fine.Another way of saying them is this:"A capacitor doesn't like to change its voltage""An inductor doesn't like to change its current"A capacitor "reacts" to attempts to change its voltage by sourcing or sinking current.Similarly an inductor "reacts" to attempts to change its current by increasing or decreasing the voltage across its terminals.This is why such components are said to have reactance in a circuit (rather than resistance).

author: Apokalypz
author_rank: Newbie
timestamp: September 07, 2017, 10:40:21 pm
content: Quote from: IanB on September 06, 2017, 01:48:04 amThis is more or less the explanation given in textbooks and tutorials and is how I came to understand the components when I learned about them. I'm just surprised that all the explanation I've seen limit themselves to this understanding while it doesn't really say how caps maintain voltage or how inductors maintain current.Thanks for the reply.

author: Ratch
author_rank: Regular Contributor
timestamp: September 08, 2017, 03:09:35 am
content: Quote from: Apokalypz on September 06, 2017, 01:41:48 amA cap does not "charge up." It contains the same amount of net charge at 10, 100, or 1000 volts as it does at zero volts. For every coulomb of charge imposed on either plate, the same amount of charge is removed from the opposite plate. This means that the net loss/gain of charge is zero. What you should understand is a cap stores energy in the form of an electrostatic field. Everyone should say a capacitor becomesenergized, not charged. A cap energized to 100 volts contains more energy that a cap energized to 10 volts (E = 1/2 C V^2).QuoteWrong! Neither a cap or coil store either voltage or current. Both store electrical energy (electric fields or magnetic fields). Both the voltage and current involved are consequences of how fast the energy is stored and released, and what type of electrical energy (electric or magnetic) fields are involved.QuoteSame answer as above. Voltage is the energy density of a charge (joules/coulomb). A density (voltage) cannot be stored. It just exists. You would not say velocity can be stored, would you? Neither can density. If a voltage exists across the plates of a cap, you can be sure that energy is being stored in the cap. The voltage represents the electric field energy with respect to the amount of charge difference between the plates (joules/coulomb).QuoteYou have to understand how the speed those electric energy storage components accept and release energy affects the voltage and current.QuoteWrong. The voltage and current are due to the rate of build-up and collapse of the electric and magnetic fields.QuoteYou are wrapping yourself around the axle. You had better reply to this thread with more questions and examples.Ratch

author: IanB
author_rank: Super Contributor
timestamp: September 08, 2017, 03:31:16 am
content: Quote from: Apokalypz on September 07, 2017, 10:40:21 pmI was going to reply earlier today but I didn't have a chance.However, the answer to your question is that a change in the voltage on a capacitor or a change in the current in an inductor involves an change in stored energy, which put another way means thermodynamic work has to be done for the voltage or current to change. The need for work to be done on or by the component is what makes the voltage or current resist change.For a mechanical analogy you can consider a heavy flywheel. It takes an effort to get the flywheel spinning, and once it is spinning takes an effort to slow it down. This is because the spinning flywheel is stores energy. You have to do work to speed it up, and it will do work on the surroundings if you try to slow it down again.

author: Ratch
author_rank: Regular Contributor
timestamp: September 08, 2017, 03:41:39 am
content: So what does "electrify" mean? Just about anything you want it to mean as long as it pertains to something involving electromagnetic science. To say that a capacitor becomes energized describes precisely what is happening. It is storing energy. Why talk technical trash TTT) like NASA does when they describe their astros as "walking in space". When they work outside their capsule, do the look like they are walking? If their tether should break, would they walk away? It is all right to use colloquial expressions for informal banter. But when precise meanings and technical descriptions must be conveyed, then precise language should be used.Ratch

author: IanB
author_rank: Super Contributor
timestamp: September 08, 2017, 03:59:33 am
content: Quote from: Ratch on September 08, 2017, 03:41:39 amPrecise anduseful. To say a capacitor stores no charge when it is charged up is a precisely pointless statement. It has no value and serves no purpose.

author: Brumby
author_rank: Unknown
timestamp: September 08, 2017, 04:08:34 am
content: Quote from: Ratch on September 08, 2017, 03:41:39 amThe language is precise.When someone says a capacitor is "charged" - everybody who is familiar with the concept knowsexactlywhat is meant. It is unambiguous. It is precise.It is only those who do not understand it who will trip over any potential confusion in the use of the words "charge" and "charged". This is where education is required.It is unfortunate that we feel the need to find an alternate word to the one that is in common usage across an industry, just to address the issue of two words spelled very similarly.

author: Ratch
author_rank: Regular Contributor
timestamp: September 08, 2017, 04:10:21 am
content: Quote from: IanB on September 08, 2017, 03:59:33 amSo why do folks say a cap is charged when it is not? Unless you mean charged with energy. Then you might as well say energized. Actually, what I said was a cap stores a charge on one plate and depletes the same charge on the opposite plate for a net change of zero.Ratch

author: Brumby
author_rank: Unknown
timestamp: September 08, 2017, 04:16:33 am
content: Quote from: Ratch on September 08, 2017, 04:10:21 amThis:Quote from: Brumby on September 08, 2017, 04:08:34 amYou are focussing on:Quote from: Brumby on September 08, 2017, 04:08:34 am

author: Ratch
author_rank: Regular Contributor
timestamp: September 08, 2017, 04:23:42 am
content: Quote from: Brumby on September 08, 2017, 04:08:34 amThe language is syntactically correct, but the meaning is wrong. Its correct meaning is well understood by a clique of insiders who have practiced electrical science, and used the wrong phraseology so long that they do not give it any thought.Another bogus phrase is "current flow" which literally means "charge flow flow". Charge doesn't flow twice. Folks should just say "current exists", or current is present, or just current if it is grammatically correct.Ratch

author: Brumby
author_rank: Unknown
timestamp: September 08, 2017, 04:27:32 am
content: Be the pedant all you want - but the terms are well understood, despite any real or perceived tautological aberrations.

author: Brumby
author_rank: Unknown
timestamp: September 08, 2017, 04:30:51 am
content: To show how silly this type of debate can be ....If we take your assertion at face value, then you can never say the current is 0A. You can't talk about the flow of charge if there is no charge flowing. The term "current" becomes undefined at that point.

author: Ratch
author_rank: Regular Contributor
timestamp: September 08, 2017, 04:31:06 am
content: Quote from: Brumby on September 08, 2017, 04:27:32 amI believe talking technical trash (TTT) confuses newcomers and makes it harder to learn the basics.Ratch

author: Brumby
author_rank: Unknown
timestamp: September 08, 2017, 04:33:50 am
content: Quote from: Ratch on September 08, 2017, 04:31:06 am... and you think this sort of thing is helpful?I can see your point - but I don't believe it's the best way to go.

author: Ratch
author_rank: Regular Contributor
timestamp: September 08, 2017, 04:40:12 am
content: Quote from: Brumby on September 08, 2017, 04:30:51 amI don't understand what you are saying. Why can't we say no current exists, or no current is present? Amps are the rate of charge flow. Why can't zero amps mean a rate of zero for charge flow? Why can't a vehicle have a zero velocity or zero rate of movement when stopped? Inquiring minds would like to know.Ratch

author: Brumby
author_rank: Unknown
timestamp: September 08, 2017, 04:41:18 am
content: Quote from: Ratch on September 08, 2017, 04:23:42 amThe only thing bogus is your understanding of the English language."current(noun)flow(verb)""charge flow(noun)flow(verb)"The use of the word "flow" is different - and therefore, legitimate.To argue that it is repetitive and inappropriate shows a lack of understanding of grammatical structure and a focus on the arrangement of individual letters.

author: Ratch
author_rank: Regular Contributor
timestamp: September 08, 2017, 04:44:42 am
content: Quote from: Brumby on September 08, 2017, 04:33:50 amI am in agreement with a lot of folks who believe that it is best to learn it correct from the beginning and not use sloppy definitions or concepts.Ratch

author: Brumby
author_rank: Unknown
timestamp: September 08, 2017, 04:45:51 am
content: Quote from: Ratch on September 08, 2017, 04:40:12 amWe can - but that example doesn't have the same grammatical error that your assertion about "current flow" does.

author: Brumby
author_rank: Unknown
timestamp: September 08, 2017, 04:47:06 am
content: Quote from: Ratch on September 08, 2017, 04:44:42 amSo - Do you promote the teaching of electron flow rather than conventional current flow? (Oh, darn ... there's that phrase again!)

author: Brumby
author_rank: Unknown
timestamp: September 08, 2017, 04:49:10 am
content: This is getting tedious and it's ground that's been covered, trampled and stomped on before ... a number of times.One more response here - and then I'm done with this thread.

author: Ratch
author_rank: Regular Contributor
timestamp: September 08, 2017, 04:53:48 am
content: Quote from: Brumby on September 08, 2017, 04:41:18 amNo, "current" in electrical science means charge flow or rate of charge movement. If you want to use rate as a noun, then it implies charge movement, and the second word "flow" is redundant and ridiculous. Find any sentence using current flow and see how much better it sounds using my suggestion.

author: Ratch
author_rank: Regular Contributor
timestamp: September 08, 2017, 04:56:38 am
content: Quote from: Brumby on September 08, 2017, 04:45:51 amI don't think you proved my assertion about current flow is wrong. See my answer to your statement.Ratch

author: Ratch
author_rank: Regular Contributor
timestamp: September 08, 2017, 05:07:43 am
content: Quote from: Brumby on September 08, 2017, 04:47:06 amYes, you should have left off the word flow in the last sentence.I always use the mathematical convention that positive charges flow from the positive terminal and return to the negative terminal of a voltage source. That is the way semiconductors are marked and ammeter polarities are shown. That does not always agree with the real physical direction of the charges, but it is easy to reverse direction if the real physical direction of negative charges need to be known. Assigning a physical direction at the beginning of an analysis by the polarity of the charge carriers is a recipe for confusion.Ratch

author: IanB
author_rank: Super Contributor
timestamp: September 08, 2017, 05:16:54 am
content: Thank you for derailing yet another thread and filling it with off-topic posts.

author: Ratch
author_rank: Regular Contributor
timestamp: September 08, 2017, 05:21:58 am
content: Quote from: IanB on September 08, 2017, 05:16:54 amNonsense. I only answered questions and statements presented to me. Nothing is stopping the OP or anyone else from asking questions more pertinent to the original post. Your assertion is bogus.Ratch

author: Brumby
author_rank: Unknown
timestamp: September 08, 2017, 05:27:34 am
content: Quote from: Ratch on September 08, 2017, 04:53:48 amYou have just proved my point about grammatical constructs. You don't understand how language is put together.Look up the definition of the word "current". In that definition, you will find the usage for it in the electrical realm is as a NOUN. It doesn't matter what words make up thedefinitionof that quantity - those words are only used to provide information about what the quantity represents. Once that is done, IT HAS ITS OWN EXISTENCE - as a NOUN. Nouns can have verbs associated with them. This is grammar 101.This is never going to be resolved to your satisfaction - so I am going to bow out, as promised.Doesn't mean I think you are right, though.

author: Ratch
author_rank: Regular Contributor
timestamp: September 08, 2017, 05:30:09 am
content: Quote from: blueskull on September 08, 2017, 05:22:44 amWould you be so kind as to explain why the above non-technical statement is showing up in this thread. Please be specific and use examples if necessary.Ratch

author: Ratch
author_rank: Regular Contributor
timestamp: September 08, 2017, 05:46:27 am
content: Quote from: Brumby on September 08, 2017, 05:27:34 am

author: rs20
author_rank: Super Contributor
timestamp: September 08, 2017, 05:54:30 am
content: Hmm, it's been a pleasant couple of months since I had come across a Ratch post.Quote from: Ratch on September 08, 2017, 03:09:35 amYou did not contribute usefully to this thread. The OP's new understanding is much improved compared to his/her old understanding, but rather than recognizing that you had your utterly worthless kneejerk reaction to the use of the single word "charging". I wish you luck at teaching everyone on the planet to "re-energize" their phone batteries because they're "not recharging them" because "they retain a net neutral charge". What's your next crusade, reversing the flow of conventional current to match the flow of electrons?

author: Cliff Matthews
author_rank: Unknown
timestamp: September 08, 2017, 10:55:52 am
content: I read this far to find hapless pedantic's again..

author: Ratch
author_rank: Regular Contributor
timestamp: September 08, 2017, 01:21:16 pm
content: Quote from: rs20 on September 08, 2017, 05:54:30 amEvidently, you did not read post #24 of this thread where I do discuss current direction and charge polarity. How can you tell what the OP's understanding is? Nowhere do I see a definitive statement from you challenging the veracity of what I said. Therefore, I assume you are disparaging the messenger, but not the message. The planet is a big place, so I cannot hope to point out to everyone the false meaning of their phraseology.Ratch

author: Ratch
author_rank: Regular Contributor
timestamp: September 08, 2017, 01:22:35 pm
content: Quote from: Cliff Matthews on September 08, 2017, 10:55:52 amNo one is forcing you to read or reply.Ratch

author: Zero999
author_rank: Super Contributor
timestamp: September 09, 2017, 08:38:47 pm
content: Quote from: Ratch on September 08, 2017, 04:10:21 amWhen people say a capacitor is charged, they really mean that charge has been transferred, from one plate to the other, not in or out of both plates! Why do mathematical formulae, give the charge on a capacitor in Coulombs, a unit of charge? It is an abbreviation and is used in plenty of EE papers. No one is going to re-write them because you don't think it's specific enough.Quote from: Apokalypz on September 07, 2017, 10:40:21 pmYes, that's pretty much correct.The mechanical analogy is a good one. A flywheel is like an inductor and a spring is similar to a capacitor. The same could be said with a circular canal, filled with water vs dam, with a lot of water behind it.

author: Ratch
author_rank: Regular Contributor
timestamp: September 10, 2017, 01:19:54 am
content: Quote from: Hero999 on September 09, 2017, 08:38:47 pmNo way. The dielectric of a good cap is impermeable to charge carriers, so the charge on one plate cannot pass to the other plate through the dielectric. Neither can thesamecharges get from one plate get to the other plate through the voltage source, because there are so many other charge carriers ahead of them. In and out is the only way to describe what is happening, and although the amount of charge movement is equal on both plates, it is not transference. Why do you have such a hard time calling a storing of energy, "energizing"? Charging is meaningless in this operation.QuoteBecause a coulomb (not capitalized) is a unit of charge in the MKS system. The formulas pertain to the charge difference between the plates, not a charge in or on a cap.QuoteCoulomb is not an abbreviation, it is a fully spelled out word.QuoteI don't expect anything already published to be edited. Specificity is not what I am talking about,. Accuracy is.Ratch

author: IanB
author_rank: Super Contributor
timestamp: September 10, 2017, 01:41:29 am
content: Every part of regular circuit analysis satisfies Kirchhoff's current law, which says that there is no local accumulation of charge in a circuit: all flows of charge around any control element are balanced, in = out. Capacitors are no different, so it escapes me why you keep trying to make such a fuss about something that bothers nobody else in the world, ever.If you discharge a capacitor then current flows in the circuit, and by your own statement current is the flow of charge. If charge flows, then there must have been a movement or displacement of charge. This is what is meant by the charge stored in a capacitor, something appreciated by everyone in the world except you. If it is you against the world, why do you keep trying? You cannot win your argument, ever. It is a futile waste of energy on your part.

author: Ratch
author_rank: Regular Contributor
timestamp: September 10, 2017, 02:22:04 am
content: Quote from: IanB on September 10, 2017, 01:41:29 amMany folks think caps and batteries store net charge. They don't. I agree that caps follow K's current law. Who said I did not?QuoteYes, current is present in a closed cap circuit when a cap is de-energized by supplying a conduction path. However, no net current was stored in the cap. The plates of the cap are simply rebalancing the net charge which is zero.QuoteI know I cannot change the whole world. And you have no way of knowing if I am the only one who believes a capacitor cannot hold a net charge. I am winning this argument at this point in time because I have given a clear explanation of what I believe and no has proven my assertion wrong thus far.Ratch

author: IanB
author_rank: Super Contributor
timestamp: September 10, 2017, 02:29:27 am
content: Quote from: Ratch on September 10, 2017, 02:22:04 amBecause no-one cares. If there is something that bothers you and bothers nobody else, then it is up to you to learn how not to be bothered by it. Neither I, nor anyone else has any trouble with the language of capacitors. We don't have to prove your assertions wrong. We are not troubled by the notion of capacitors storing charge. For us everything is perfectly fine.

author: Ratch
author_rank: Regular Contributor
timestamp: September 10, 2017, 02:43:29 am
content: Quote from: IanB on September 10, 2017, 02:29:27 amAnd, most folks are happy to think that NASA astros "walk" in space. I think it is funny and others are perfectly fine and happy.However, one particular participant got confused by your way of looking at caps. Seehttp://www.electro-tech-online.com/threads/conservation-of-charge.151864/Ratch

author: IanB
author_rank: Super Contributor
timestamp: September 10, 2017, 02:53:42 am
content: Quote from: Ratch on September 10, 2017, 02:43:29 amMany people get confused by many things.There are equations that describe the behavior of capacitors. If you apply the equations correctly, you reach correct conclusions. If you don't apply the equations, and instead try to argue from verbal descriptions, then you may get the wrong answer.

author: Ratch
author_rank: Regular Contributor
timestamp: September 10, 2017, 03:07:03 am
content: Quote from: IanB on September 10, 2017, 02:53:42 am

author: Simon
author_rank: Unknown
timestamp: September 10, 2017, 08:21:07 am
content: Quote from: Ratch on September 10, 2017, 03:07:03 amWhat are you trying to achieve ? Your behaviour is the same that got another member recently banned. Splitting hairs over every word does not help anyone and disrupts the forum, and eventually will get you banned as it derails every thread!

author: Ratch
author_rank: Regular Contributor
timestamp: September 10, 2017, 03:46:50 pm
content: Simon,I am simply correcting mistakes in terminology. Everything I said is true, even if you and others don't believe it. I also give reasons and examples for what I aver. If no one is required to read or reply to what I say, how can I disrupt the forum? If this forum does not acknowledge different viewpoints, what good is it? I am doing this forum a favor by imparting some true knowledge, even if there are those who don't appreciate it because it goes against what they believe. Let them prove me wrong. Disparaging the messenger does not change the message.Ratch

author: tooki
author_rank: Super Contributor
timestamp: September 10, 2017, 04:05:27 pm
content: Quote from: Ratch on September 10, 2017, 03:46:50 pm"Correcting" to a private definition at odds with the commonly-understood terminology is not correcting, nor is it educational, it's simply pompous intellectual dick-waving that distracts from the topic at hand. And it's that distraction that makes it disruptive. You aren't doing anyone any favors, as the plethora of objectors to your stupid comments show.

author: Simon
author_rank: Unknown
timestamp: September 10, 2017, 04:14:20 pm
content: The simple answer is that if you are going to disrupt every thread by splitting hairs over terminology when everyone is clearly able to understand the concepts being discussed without confusion you will just be disrupting the forum and derailing threads and that gets you banned! and you would not be the first to be banned for this sort of behaviour. you have managed 200 posts without being brought to my attention so whatever you were doing before maybe you should go back to it. We have plenty of knowledgeable peoples on here and are very glad of their help (I am personally anyway) but they are also humble people that put their oar in when required and when it is positively helpful and they actually share information and insight instead of being walking dictionaries, being a smart ass is not helpful. I have nothing further to say on the matter, it's up to you how you conduct yourself and I can't stop people from responding to your provocations. If and when the time comes that we deem you causing more hassle than due you will be banned without further warning! It's a process that takes under a minute and far outweighs the headache that disruptive members can cause. We are a very laid back forum and try to allow for "individuality" but will NOT let that individuality ruin the experience for others, we don't have hard and fast rules but then neither does any social interaction, we expect people to use common sense.

author: Ratch
author_rank: Regular Contributor
timestamp: September 10, 2017, 07:51:52 pm
content: Quote from: tooki on September 10, 2017, 04:05:27 pmPointing out the mistakes in a definition, whether public or private, is acorrection no matter how much you think otherwise. If pausing and evaluating what you believe is a disruption, so be it. You have not said that my comments were false, only that you and others did not like them. I cannot help that. The facts are what they are.Ratch

author: Ratch
author_rank: Regular Contributor
timestamp: September 10, 2017, 08:02:32 pm
content: Quote from: Simon on September 10, 2017, 04:14:20 pmWhat you call splitting hairs, I believe is a major misbelief. I gave an example of that with a link to another thread within reply #40 of this thread. The OP of that thread was definitely confused because he believed what many on this thread proclaim.I think this forum is very uptight, not laid back as you claim. However, let's make a deal. You keep this thread open until everyone has a chance to take a whack at me. I promise to answer to only this thread, and after it is finished, I will never post on this forum again. If fact, I will probably never even read this forum again, so you can ban me or not. It is only fair that everyone should get a chance to express their opinion. OK?Ratch

author: IanB
author_rank: Super Contributor
timestamp: September 10, 2017, 08:58:24 pm
content: Quote from: Ratch on September 10, 2017, 07:51:52 pmNo-one disagrees with the statement that there is no change in the net charge on a capacitor. Everyone understands that charge removed from one plate is balanced by the charge added to the other plate.What everyone is trying to tell you is that insisting that capacitors do not get "charged" is pointless, unfruitful, and serves no useful purpose. Nobody is arguing with your facts, but everybody is arguing that it is pointless and a waste of time to make a big deal out of it.Consider your example of charging two capacitors and putting them in series. Each capacitor individually has a net charge of zero. Therefore when putting them in series the combined capacitor has a net charge of zero plus zero, equals zero. The answer you get is completely accurate, and yet completely useless. No useful understanding is gained from this.

author: Ratch
author_rank: Regular Contributor
timestamp: September 10, 2017, 09:09:32 pm
content: Quote from: IanB on September 10, 2017, 08:58:24 pmYes, the charge balance evens out. There is a dichotomy in your reasoning. How can an accurate answer be completely useless? The OP of that thread certainly gained some understanding. He even said he liked my explanation.Ratch

author: Zero999
author_rank: Super Contributor
timestamp: September 10, 2017, 09:11:22 pm
content: Quote from: Ratch on September 10, 2017, 01:19:54 amThat was never implied. You made that up.QuoteThe electromotive force applied to the capacitor, moves charges through the conductors, causing an imbalance in charge, between the plates of the capacitor. The fact that they're not exactly the same charge carriers is immaterial.QuoteBecause it's meaningless, non-standard terminology. "An electric fence is energised" and "One should be careful when working on energised mains circuits" are examples of how the word energised is normally used in electrical engineering. The only time I think I've seen energised used in the context of capacitors is in a safety manual, on the lines of "Take care when working with circuits, containing capacitors charged to hazardous voltages. The circuit can remain energised for a considerable length of time, after the mains power has been isolated."QuoteAnd that's what people mean by charging a capacitor. They're referring the difference between charge on the plates. The same principle applies to when one mentions battery voltage. Why do you have such a hard time understanding these very basic concepts?Everyone knows about the conservation of charge and that batteries and capacitors never ever gain or loose any net charge. All you're doing is creating confusion and derailing the thread.

author: IanB
author_rank: Super Contributor
timestamp: September 10, 2017, 09:14:27 pm
content: Quote from: Ratch on September 10, 2017, 09:09:32 pmA helicopter was flying around above Seattle when an electrical malfunction disabled all of the aircraft's electronic navigation and communications equipment. Due to the clouds and haze, the pilot could not determine the helicopter's position and course to fly to the airport. The pilot saw a tall building, flew toward it, circled, drew a handwritten sign, and held it in the helicopter's window. The pilot's sign said "WHERE AM I?" in large letters. People in the tall building quickly responded to the aircraft, drew a large sign and held it in a building window. Their sign read: "YOU ARE IN A HELICOPTER." The pilot smiled, waved, looked at her map, determined the course to steer to SEATAC airport, and landed safely. After they were on the ground, the co-pilot asked the pilot how the "YOU ARE IN A HELICOPTER" sign helped determine their position. The pilot responded "I knew that had to be the Microsoft building because, like their technical support, online help and product documentation, the response they gave me was technically correct, but completely useless."

author: Ratch
author_rank: Regular Contributor
timestamp: September 11, 2017, 02:02:56 am
content: Quote from: Hero999 on September 10, 2017, 09:11:22 pmYou said transfer, did you not? One was to transfer the charge is through the dielectric if it were possible. Actually the charges do get moved in and out to/from the plates.QuoteQuoteThen let's not call it a charge transfer. That implies the same charges are moved to a different place. Perhaps a better description is a charge redistribution.QuoteQuoteEnergized means becoming infused with energy. That is true for the safety examples you gave and a capacitor.QuoteQuoteDescribing something that really happens does not create confusion or derail a thread. You and I know that a cap works by rearranging its its charge so that a difference occurs on its plates., But I have found that a lot of folks who don't know better think that a cap or battery "swallows" the charge, and stores it for later release. Come on, you know that they do. The OP in my link did. Referring to a capacitor as energized is unambiguous, definite, precise, and descriptive.Ratch

author: Ratch
author_rank: Regular Contributor
timestamp: September 11, 2017, 02:11:41 am
content: Quote from: IanB on September 10, 2017, 09:14:27 pmInteresting funny story. The pilot should have asked where he was over the ground. But it doesn't apply to cap energization, because like I said in the last post, referring to a capacitor as energized is unambiguous, definite, precise, and descriptive.Ratch

author: Ratch
author_rank: Regular Contributor
timestamp: September 11, 2017, 02:24:53 am
content: To the Ineffable All,I will be absent for the next two days while on vacation. If no replies are addressed to me on this thread when I return, it will be the last time you will hear from me.Ratch

author: Assafl
author_rank: Frequent Contributor
timestamp: September 11, 2017, 07:59:18 am
content: Quote from: Apokalypz on September 06, 2017, 01:41:48 amWhat a weird argument this question stirred up.Your understanding is correct. That is more or less how they function within a circuit.But may I suggest a more "physical" understanding (after all - electronics is just a highly simplified application of physical phenomena).All electronic components do (in a physical context) is to convert energy from one form to another.- The most basic example is resistors which convert energy to heat (tiny colorful heaters).- Capacitors and Inductors convert the kinetic energy of electron flow to potential energy.- Capacitors build an electric field;- Inductors a magnetic one.Potential energy (according to Wikipedia) is: "In physics, Potential Energy is the energy possessed by an object because of its position relative to other objects, stresses within itself, its electric charge, or other factors."So the capacitor and inductor, once the electrical and magnetic fields have been created, now POSSES energy within them.(BTW - a side note: This is not different from a huge boulder poised precipitously on an overhang - all the kids in the car terrified it will roll down (it has Potential energy). Or a mountain bike shock which has an air spring with massive caution labels warning to release the air before servicing (again - potential energy). Or the energy waiting in your mains socket - posed and ready to operate a device - or to shock a careless person.).Once we are aware that these are all manifestations of conversion of kinetic (electron flow) to potential energy, it will help to understand why storing electric (stored by a capacitor) - and magnetic fields (stored by an induction) are so useful to us.This is where the fundamental beauty of electrodynamics branch of physics comes in: Maxwell's equations (Faraday and Ampere's laws) describe how changing one causes a change in the other.So modifying a magnetic field (Faraday's law) induces a electric field. In other words, as an inductor's field is being demolished (i.e. current source decays over time), the inductor will create an electric field. For us EEs, it means we can measure it as a voltage using a Volt meter.Similarly, modifying an electric field cause a magnetic field to be created. Or, as the electric field breaks down (e.g. some reckless dude shorts the capacitor), a magnetic dipole field will form. For us EE it means that a current flows somewhere (magnetic fields cannot exist without electrons moving or spinning somewhere) and we can measure it using an Ampere meter.Understanding the relation between the energies is useful. Consider an LC circuit. It is a tuned circuit. It works by back and forth building and destroying electric and magnetic fields in its capacitor and coil. And resistance will squander that energy and make it a less "quality" oscillator.A microwave oven's magnetron is a super complex example of exactly the same principles occurring over and over multiple times:It uses heater filament to excite electrons which (given enough excess energy) are released into a vacuum and are then accelerated (given kinetic energy) by an electric field (the Anode voltage is what provides the field).But the magnetron tube is suspended between two extremely powerful magnets. So the electrons spin (Lorentz's law). They spin and hit precisely located copper vanes, hitting the copper atoms, and releasing more electrons. The distance between the vanes is such that a 2.45Ghz signal is formed. That is to say that an alternating electric field between the vanes and magnetic field (electrons hurtling between the vanes) occurs (just like an LC circuit).Remember that within the copper all this signal is an oscillation of extra electrons. So they route these extra electrons from one of the vanes to an antenna. An antenna is just a tuned device that converts this flow of electrons to Electromagnetic wave energy - alternating electric and magnetic waves.In the last conversion of the process, these waves excite the resonance of water molecules. These oscillate, and by friction, convert the energy to heat.Obviously, this heat energy - is partly the target (to warm food) but can then supply extra energy to cause cooking (e.g. hasten chemical reactions, denature proteins, etc.). Also, using this knowledge we can deduce all kinds of stuff. E.g. since it is water that is being heater - it will max out at 100C/212F.For example, experience shows that it is very difficult to brown foods in a microwave. So as an example Maillard and Caramelization (responsible for food browning) cannot occur (since they both need temperatures to exceed 120-160C).Hmm. Popcorn needs 180C - so how does that work (Hint - 100C is for boiling at sea level)?Understanding the physics makes the world of devices substantially simpler. They are all the same - just different configurations....

author: Zero999
author_rank: Super Contributor
timestamp: September 11, 2017, 09:01:03 am
content: Quote from: Assafl on September 11, 2017, 07:59:18 amMicrowave ovens do no excite the resonance of water molecules, which occurs at a much higher frequency, than 2.45GHz. Dielectric heating and eddy losses are the primary forms of heating in microwave ovens. Most polar molecules will heat in a microwave oven: sugars, starches and some fats too.Popcorn will heat in a microwave, but not that much. Microwave popcorn comes in a container with a microwave absorbing surface on the bottom, tuned to 2.45GHz. When bombarded with microwaves, it heats up and cooks the popcorn on top of it, in a similar way to it being heated in a pan.

author: Assafl
author_rank: Frequent Contributor
timestamp: September 11, 2017, 10:50:10 am
content: Quote from: Hero999 on September 11, 2017, 09:01:03 amThank you for correcting me. I will have to research the eddy current aspect of heating using microwave (like an induction cooktop - how cool is that!).Agree about the popcorn bag. There is some water in popcorn (that is what makes it pop). Interesting popcorn article:http://rsif.royalsocietypublishing.org/content/12/104/20141247Oddly enough, if one were to keep the popcorn bag one could use it to brown foods.... BTW - if sugars heat it should be possible to caramelize sugars in a Microwave. For some reason it is hard to do well.