Power Dressing

By cjohnson | September 16, 2005 11:07 am

Both the title of this post and some of the terminology in the USA Today/AP article entitled Static electricity in man’s jacket leads to burns, are not chosen for their scientific accuracy, but never mind, I’ll not lament about that issue today. The effect seems to have been pretty dramatic…..I heard it on NPR, and then Googled.

***

You know, the above paragraph was going to be the whole post, and then I looked at another article, this one from the Sidney Morning Herald.

There, we see that the voltage has now gone from 30,000 to 40,000 (I guess the editors needed 33.3% more drama), and whereas the USA Today article said

Fire officials took Clewer’s jacket and said it continued to give off voltage.

…the Sidney Morning Herald article said

The firefighters took Mr Clewer’s jacket to the fire station, where it continued to give off a strong electrical current.

Ooooh, the ol’ current-voltage confusion in the media staple. So of course, rather than cycle off for the busstop, I had to check to see what the ABC Online (Australia) article said

The CFA has Mr Clewer’s jacket and says it is continuing to give off voltage.

Hmmm, but I note that they were happy with the less dramatic voltage measurement.

Reuters UK’ artitcle opts for the higher voltage, and reports that

Firefighters took possession of Clewer’s jacket and stored it in the courtyard of the fire station, where it continued to give off a strong electrical current.

So there you have it. Flipping back and forth between current and voltage, depending upon who knows what whim? You see, this is what I’m talking about when I rant on about having somebody in the editorial office know at least a little kindergarten science. It’s no wonder the general public are confused. Sigh. I did end up ranting about this issue after all.

Anyway, Webindia123, in the first line of their article, ticks off the poor guy for wearing polyester, but makes no comment on measurements at the after-party at the firestation.

Finally, the Warrnambool Standard (I get it delivered every day you know) reports that “officers were baffled” (of course), and one of them sought advice from a technician, who said

Mr Clewer’s clothes were at no stage dangerous because they were low in amps which could be deadly.

So watch out for those deadly amps, folks.

-cvj

  • http://www.pyracantha.com Pyracantha

    I hesitate to ask this out of embarrassment at my ignorance, but could you perhaps direct me to a site or other information source which would explain simply to me the difference between “amps,” “voltage,” and “current”? I have missed learning this in my life so far.

  • http://blogs.discovermagazine.com/cosmicvariance/clifford/ Clifford

    Never hesistate to ask, Pyracantha. This is how we all learn, no matter where we think we are on our own trajectories.

    Can’t think of a site right now. Got a few minutes before I have to review some files before an 11:30 meeting, so here goes a very quick bit of info.

    Let’s pretend that our basic charge carriers (the things moving in a circuit’s wires) are electrons – this is often (but not always) the case. Voltage gives you a good measure of the energy associated wth moving an electron through the circuit. It is a sort of energy per charge, and the unit of measurement is the Volt (V). This is nothing to do with current. Current is a measure of how much flow you have have in the circuit. So one way to measure it is to pick a particular point on your wire, and ask how many electrons are going past that point per second. The unit of meaurement for that is the Ampere, or “amp”, (A). Neither of those tell you the whol story about a circuit, but together they can tell you some useful things, like how much energy is being used, supplied, or transferred. So if you know how much energy is involved in going around the circuit for each electron (the Volts) and if you know how many are going around per second (the Amps), you know how much energy is being tranferred (etc) per second. It is the two multiplied together. This is called the “power”, which is measured in Watts (W). Or often, on your electricity company’s statement, it is Kilowatts (kW), 1000 times bigger. So you can see exactly how much energy you used from your statement, as somewhere on there it will have kilowatt-hours (kWh), telling you how many watts over how much time you used…. giving you a total energy. And you pay a certain unit price for each KWh.

    Hope that helps!

    Gotta dash – committee meeting!

    -cvj

  • http://valatan.blogspot.com bittergradstudent

    Here goes a simplified version: Electric charge is a basic quantity of nature. Electric charges come in two types, positive and negattive, which exert forces on each other (think of them as little bar magnets in this regard –likes repel, opposites attract; but realize that they are NOT bar magnets) current is simply the flow of electric charge from one place to another, just like a water current. Amps are a measurement unit for current.

    Electric field is essentially something that pushes electric charges. Just like a gravitational field pushes masses. Consequently, if I take a charge and put it in an electric field and let it go, it will move and pick up energy. How much energy depends on how much charge I put in the field. Going back to the gravitational analogy, if I drop a bowling ball, I will be able to get more energy out of it at the floor (think cracked pavement) than I would from a billiard ball. Similarly, if I have a large charge, I will be able to get more energy out of it than I would a small charge. For this reason, it is advantageous to work with electrical energies in terms of energy per unit charge, rather than the energy p8icked up, as I can put any old charge in an electrical field. Voltage is exactly this, the energy per unit charge that would be picked up by a particle as it travels between two points (ususally the ends of a battery, or the two sockets in an outlet, or something like that).

    Now, in reality, these things become easy to confuse, because high voltage power sources will, at first, produce high currents, and high currents often result from a high voltage being present somewhere, though this is not necessarily the case, and electrical equipment is protne to break down under high current situations. Typically, what is dangerous to people is having large currents run close to the electrically sensitve parts of th ehuman body (heart, brain, etc), and what I assumed happened to this man is that his static charge built up a large voltage relative to ordinary objects, so when his jacket touched something, there was a large voltage between the touched thing and the jacket. This caused a large current to flow, which (at a basic level), due to friction between the moving charges and the jacket, produced heat, causing the jacket to ignite.

    Sorry for the long post, and any mistakes above. For more details, any freshman/sophomore level physics textbook (ie. Physics for Scientists and Engineers by Serway) will provide an introduction to these concepts

  • http://blogs.discovermagazine.com/cosmicvariance/sean/ Sean

    As Clifford says, don’t hesitate to ask. Just to pick up briefly on bittergradstudent’s analogy with water pipes, the voltage is like the pressure in the pipes — which characterizes the potential “oomph” in the flow, whether or not the water is actually flowing — while the current is the actual rate of flow. Amps are just units in which the current is measured — a certain amount of charge passing by you in a given time.

    Wikipedia has an entire entry on the hydraulic analogy!

  • citrine

    Also it would help to get the concept of electric potential energy to use a (Newtonian) gravitational analogy. The peak of a tall mountain has a large gravitational potential relative to the bottom. (The amount of potential, is dependent on the location itself.) Once you keep a boulder (object with mass, in this case) at the location of high potential, the object is considered as having a high gravitational potential energy. A boulder that rolls down from the peak will cause a greater impact on the valley down below than the same boulder rolling down from rest, from the peak of a shorter mountain.

  • janet

    Hmm. Much of the above discussion would seem to go beyond kindergarten science (though my memories of kindergarten, I admit, are hazy).

    If I am interpreting the above correctly, though, it might suffice to say that both “Volts” and “current” are terms used to describe how much power something is capable of producing, so it doesn’t make sense to say that an object “gives off” either Volts or current.

  • http://arunsmusings.blogspot.com Arun

    Following Sean’s analogy, where there is a certain amount of relativity in “high” and “low”

    a powerwasher jet would be a high voltage, low current flow,

    water spilling over the top of a New Orleans levee would be low voltage, high current flow;

    water at the turbine in a hydreelectric dam such as at
    http://users.owt.com/chubbard/gcdam/html/hydro.html
    would be high voltage, high current,

    and your kitchen faucet would be a low voltage, low current flow.

  • http://blogs.discovermagazine.com/cosmicvariance/clifford/ Clifford

    janet,

    All the various analogies given by our friends (thanks everyone!) about where the energy comes from and how it is distributed are nice, and useful, but you don’t need them to understand the basic role of the different terms in describing properties of electricity. Look back at what I wrote in comment number 2; I think you get a clear (and not too far from kindergarten) understanding of what current, voltage, and power actually are.

    If you like, do the following:

    *replace energy with money (it does not matter where the money comes from…we just want to understand how it flows)

    *replace electrons with people carrying a certain sum of money 1 volt = 1dollar say

    *the wire is a sidewalk.

    *the current measures the number of people walking past a lampost on the sidewlk every hour. That gives you a measure of the people-traffic.

    *If you know how much money each carries, you know how much money goes by in total every hour.

    Cheers,

    -cvj

  • janet

    Sigh.

    Okay, now I’m going to throw a hissy fit.

    First, I’m still not sure if my summary was correct; I was basing my summary on your post, and wanted to know if I was on the right track. If I’m not getting it, then that’s the kind of summary you need to give in order to explain what is wrong with the way the newspapers were describing the properties of the man’s suit. And if you can’t formulate such a summary, then it’s unfair to diss these stupid editors for not understanding what you consider “kindergarten” science.

    As you have no doubt gathered by now, the word “kindergarten” really pissed me off. It made this post into exactly the sort of thing people (if so inclined) could point to and say “look, scientists are arrogant and look down on non-scientists, and they can’t even explain what they mean in plain language, so why should I listen to them?”

    One reason scientists tend to communicate poorly with lay people when talking about anything related to their field is that they have no idea what is common knowledge — what needs explaining and what doesn’t; what nugget of information someone needs in order to understand the basic point, and what information is useful for someone who wants to delve a little deeper.

    I’m a medical writer by profession, and what I do, mostly, is read medical and scientific information and try to boil it down to something that can be expressed at about an 6th to 8th grade reading level. In order to do a good job of that, I have to be able to go to a doctor and ask questions like “would it be correct to say that blood sugar above 300 mg/dL is an indication the patient is in danger of diabetic ketoacidosis, but that high blood sugar is not the cause of diabetic ketoacidosis?” And it doesn’t help me at all if the doctor then starts explaining more to me about what DKA is — because I already more or less know, and what I now need is confirmation that the conclusion I’ve drawn from it is correct.

    I asked my ex-physicist husband (who says he knows Joanne from his grad school days) whether what I was saying was correct, and he replied: “I think it’s more a matter of conventional usage than right or wrong. If I’ve got a 12V battery I wouldn’t normally say it “gives off” 12 volts, but I could imagine that maybe there’s some community out there that does use that phrase and that they probably use it without confusion.”

    This wasn’t completely helpful, but it was more helpful than your response.

  • http://blogs.discovermagazine.com/cosmicvariance/clifford/ Clifford

    Sorry Janet. I guess I was not helpful then. I don’t know how to make it any simpler, so I have failed. My failing, not yours. Also, I was under the impression that we were all taking the use of the word “kindergarten” in a light-hearted way. Sorry if you got offended.

    I’d still like to claim that the difference between the use of the words “current” and “voltage”, one to do with “rate of flow”, and the other to do with “amount of energy carried” was not totally obscure after what I set out in my reply/clarification….but maybe you’re right…maybe I totally screwed it up. Sorry. I can’t do any better, and will just end up repeating myself.

    And sure, go ahead and call me names, if that helps.

    -cvj

  • serial catowner

    Well, being a layman, I gotta take a stab at putting this in layman’s terms. As I recall, volts times amps equals watts- watts are what you pay for when the bill comes.

    Amperage doesn’t kill you, voltage does. Your 12 volt car battery will even drive your car around (slowly) if you have a standard transmission and crank the starting motor, but it won’t kill you if you accidentally make a circuit. A 20,000 volt charge stored in your tv set will kill you, even if measured in fractions of an amp.

    So why not use small volts and big amps for everything? Because it takes huge wires- see analogies above.

    Any chance the guys jacket will replace coal as a source of electricity?

  • http://blogs.discovermagazine.com/cosmicvariance/clifford/ Clifford

    Janet, I’ll try again, because this is important. I think you’re getting annoyed because I did not directly address your summary. I was not speaking directly to your summary, but was trying to clarify what exactly was needed for getting the difference between current and voltage and power. I did not have time for a longer reply since I was between meetings.

    So I agree with your summary. Neither is a good term on its own. But we might ask which is better if we had to choose one.

    Well, it is very inaccurate to use the term “gives off voltage” because, as I explained in my replies, voltage is just a description of how much energy would be carried by one of the electrons *if* they were to move -in other words, if there was a current. But if they don’t move (if there is no current) then it is not relevant…..

    So although neither is really a good term on its own, I would say that the choice “gives off current” is a bit preferable to “gives off voltage”….because it is speaking to the fact that there is motion of electrons (the static electricity) which is what current is a measure of….. but personally I’d use neither term in that way.

    Cheers,

    -cvj

  • http://blogs.discovermagazine.com/cosmicvariance/clifford/ Clifford

    serial catowner…. I know I seem to be a failure in these explanations….so I should tread carefully, but from my comment number 2, you’ll see that its not Watts that you pay for… you pay for watts per hour (“energy”) (oops: watt-hours, to be careful, as a commenter kindlycorrected my hasty comment) ….. watts are an energy rate (“power”) and so you need to say how long you are using at that rate in order to determine how much energy has been used. All we ever pay for is energy, in one form or another. Its all there in comment number 2. I thought. I may be mistaken.

    Cheers,

    -cvj

  • http://pantheon.yale.edu/~eal48 Eugene

    I think the issue is not that the editors of the media do not know physics; it is that they don’t care enough to actually attempt a layman’s explanation of the issue. Instead, they rely on the public’s fuzzy idea that “electricity can kill you” to convey the sense that the poor man’s clothing is rather deadly.

    A short explanation in any of the articles, like “high voltage may generate enough current, measured in amperes, through a person’s body to damage it” might not tell the whole story, but would at least give a sense that it is “voltage” that drives the electrons around, carrying the energy required to power appliances that we use.

  • http://blogs.discovermagazine.com/cosmicvariance/clifford/ Clifford

    Eugene, I basically agree. Whether they don’t know or don’t care, it amounts to the same thing. This is just a toy example of a larger problem I’ve tried to point up in the earlier posts I linked to in today’s post.

    Cheers,

    -cvj

  • http://pantheon.yale.edu/~eal48 Eugene

    Clifford :

    Well, Jon Stewart was pointing out that there is really no nice “IMBD-type” place for editors to ask basic physics questions, that they can get quick answers to without getting a headache. And the “getting a headache” bit is operative.

    Wikipedia is great as a reference, but we might be asking too much for reporters/editors to actually try to understand it : I know I have a hard time swallowing the volumnous stuff of wikipedia on topics that I don’t know about (say, what is the Gospel of Thomas…), so i can understand how hard it is for non-science people to understand science-stuff.

    What I would like to see is a website, with a panel of scientists/educators, that answer questions about stuff like this, where reporters/editors can turn to and get quick responses that don’t give them headache. Not a database, but a “Go-To” place for reporters/editors to email educators and get responses quickly. This can be such a win-win thing for both science, the media and the public. Imagine, “Dr. XXX said that Mr Clewer’s jacket is dangerous because ….”. The media wins because they would then be accurate and have a nice sounding authority to back it up, the public wins because they might even learn some science from this funny story, and the scientists win because they get cited in a newspaper!

    Maybe C-V.com can have a “Ask a Scientist!” section?

    E.

  • http://blogs.discovermagazine.com/cosmicvariance/clifford/ Clifford

    Eugene,

    These databases exist!!!! Editors are too lazy to use them, because nobody is holding them accountable for getting it right. You’re letting them off the hook. Here’s a thing to try. List off the top ten universities you can think of in this country. Now go to their websites. Now see if it takes longer than five….ok ten minutes to figure out where they have a link to their list of “experts” willing to talk about any subject under the sun. What more could you ask? This is one of the reasons why we have universities! Call your local scientist and chat with him or her on the phone for five minutes to decide whether you should use this term, or that term…. or whether this claim is the one to quote, or the other…..

    Not hard. Once their intern has found that site, they need only bookmark it and then they can find it in five seconds. Here is an example, the one at USC.

    Cheers,

    -cvj

    P.S. C-V.com does have an “ask the scientist” section. Several, in fact. They can be found at the bottom of every post that we write. You are reading one of them now.

  • http://pantheon.yale.edu/~eal48 Eugene

    Ops. I am guilty of not knowing stuff like that. Thanks!

  • janet

    Well, now I think it’s my turn to apologize, because I was unclear about a couple of things. First of all, I think I did understand your first explanation. It wasn’t a bad explanation, though it might have been clearer if you’d started by saying something like “Voltage describes the amount of energy that can be carried through a circuit; current is the rate at which energy flows through the circuit,” before getting into details, but that’s a minor point — I realize you were in a hurry. What really bothered me about your explanation is that it didn’t go back to what I see as the original problem, which is “What is the error in these news stories?” That’s what I was trying to address with my one-sentence summary. But I didn’t actually ask whether my summary was correct — I realized this after I posted — so I shouldn’t have expected you to read my mind and answer a question I hadn’t actually asked….

    One other small point about the news stories: all the bits you cite seem to be quotes, or misquotes, of fire officials. That’s where the original error probably came from.

    Anyway, I’m sorry for being unclear and perhaps overly sensitive. This has fast become one of my favorite blogs, and I agree with a lot of what you’ve had to say in this and other posts about bad science reporting — it distresses me too, and it’s more than merely annoying, it’s a serious problem. I’m not a journalist, but I am in some sense a science writer, and I do try to be as accurate as possible, given the constraints of my job, and to make sure that what I write is not only accurate but also relevant. Nevertheless, I’m sure that I make mistakes, because what I’m doing essentially amounts to translating, and because I’m speaking in very general terms, very small things can make a big difference (I once did half a day’s research that resulted in my changing two words). During the five years I’ve been doing this I’ve learned a horrifying amount about what people don’t know, and I’ve become loath to assume that my readers know anything. I recently had a conversation with my editor about whether we could assume that the reader would know what sperm are.

    As for kindergarten, I believe that you didn’t mean to be obnoxious, but that’s the kind of thing you need to be really careful about, because people will take offense.

  • http://capitalistimperialistpig.blogspot.com/ CapitalistImperialistPig

    cvj – “you’ll see that its not Watts that you pay for… you pay for watts per hour (“energy”)

    I love it when people a lot smarter than me make a mistake :) Energy is watts times hours (not watts per hour.)

  • http://capitalistimperialistpig.blogspot.com/ CapitalistImperialistPig

    Somewhat OT, but what makes a graduate student bitter? If you are smart enough to be in grad school, you are smart enough to make a lot more money doing something else, so why not?

  • http://capitalistimperialistpig.blogspot.com/ CapitalistImperialistPig

    Regarding the dangers of static charge: Last winter there was a local case of a guy who slid into his car to warm up while fueling his car. When he slid out, the resulting spark ingnited fuel vapors and a subsequent inferno.

  • http://arunsmusings.blogspot.com Arun

    Perhaps it is a small step from “gives off sparks” to “give off current”, sparks are likely what was observed. Anyway it is interesting that the fire department had an electrometer – surely this is not standard issue?

  • http://www.pyracantha.com Pyracantha

    Gosh what a dialogue I set off…But I suspect that the entire “electric jacket” incident is an URBAN LEGEND rather than an actual occurrence and might be showing up on snopes.com soon.

  • Tom Renbarger

    Re: giving off voltage, I must admit it’s a usage that makes my teeth itch. Borrowing from one of the analogies given earlier, you may as well say that something gives off elevation above sea level.

    Maybe if “give off” is meant to be synonymous with “discharge” you could argue for the legitimacy of the usage, but I’d prefer discharge myself.

  • http://blogs.discovermagazine.com/cosmicvariance/clifford/ Clifford

    Janet: I’m relieved that I did not make as much of a pig’s ear of explaining as your second comment seemed to imply. All’s well that ends well. Keep in touch with us here at CV.

    One small, tiny, miniscule, infinitessimal, little point-ette though: Your husband is wrong. Tell him from me. It is important to get the terminology right, and not let it slide. The terms exist for a reason and help to guide our thoughts, you see. One allows the harmless misuse of “current” here, and “voltage” there, and then pretty soon when you need to figure something pretty simple out using these misapplied terms, you end up going (as most people do) “I don’t understand electricity!! It’s all so complicated”. And it most certainly is not. Same applies to several other things with simple little bits of science language, none of which are individually challenging concepts (really not far from kindergarten -oops), but it can add up to important conceptual missteps.

    -cvj

  • http://blogs.discovermagazine.com/cosmicvariance/clifford/ Clifford

    Pyracantha:- I live for the dialogue. Thanks. I hope that the answer I gave was of use.

    -cvj

  • http://dftuz.unizar.es/~rivero/ Alejandro Rivero

    you know how much energy is being tranferred (etc) per second. It is the two multiplied together. This is called the “power”, which is measured in Watts (W)

    And, we should add, it is the main source of Wrong Physics in amateur experimental sites, due to the phase between the product of Amps and Volts when we speak about alternating current.

  • http://eskesthai.blogspot.com/2005/09/cft-and-tomato-soup-can.html Plato

    I know I shouldn’t do this, but hint to a further time when the fermion idealization held to brane can be expressed in a clear and consistant way?:)

    Cosmological associations and brane features.

    Historical correlation of this developement might help?

    Faraday, Maxwell and Einstein leading into “abstract” mathematics??

  • http://blogs.discovermagazine.com/cosmicvariance/clifford/ Clifford

    Plato: relevance to the thread? -cvj

  • http://valatan.blogspot.com bittergradstudent

    CapitalistImperialistPig: grad school is hardly anyone’s vision of a final destination in life, and after having to spend hours and hours of time TAing awful labs or classes, filled with students on a desperate mission to avoid thinking, and in the meanwhile, feeling under quite a bit of pressure to do research and perhaps even publish, while taking classes and attempting to have a private life is quite enough to make one bitter. Not to mention that all of this is happeneing in an atmosphere of nonstop NSF cuts that prevent us from getting research assistantships, and threaten our future employment opportunites (when I started, dear leader’s war on science was not yet apparent) Though the name really is mostly tounge-in-cheek.

    As for maximizing earning potential, grad school for anything but a law or med degree probably isn’t very rational. I don’t know any scientists that are in it for the Benjamins, that’s for sure

  • janet

    Clifford,

    I paraphrased your comment about terminlogy for my husband, but I think the two of you will have to discuss that, if he decides to come over here and comment — I keep sending him posts to entice him (I think the one on the SLAC Summer Institute wine list was my best shot so far, but maybe one of your gardening posts would do the trick).

    We ended up having a discussion about this post at dinner last night with two friends, including another physicist. My husband, who is very good with words, couldn’t think of a good way to explain what voltage measures in non-technical terms, without using analogies. He and our friend could think of plenty of analogies — water pressure in a pipe was one of the first to come up, and there was some loose talk about bowling balls dropped on one’s head from a second-story window vs. a feather being dropped from the moon — but in the latter case you would have to do it in a vaccuum, which presumably would mean that the feather, or even the bowling ball, would be the least of your problems.

    He was also wondering how “current” comes into the pictures when the subject is static electricity.

  • http://blogs.discovermagazine.com/cosmicvariance/clifford/ Clifford

    Hi janet,

    Recall that in earlier posts I expressed the hope that people would talk about science in their dinner conversation alongside everything else? I’m so glad to have helped that happen for at least one conversation! Thanks for letting me know.

    Your questions at dinner. Let’s stop with the analogies, and talk about the thing itself. Moons and feathers confuse the issue when talking about what voltage is. It is all about work and energy, as I’ve said previously. But I did not say (since it was not neccessary) whose work and whose energy. Now I will. Your electrons are acted on by electric fields. This is (mostly) always how electrons are moved around in the world as objects in their own right: They are moved or held in place by electric fields. Such an electric field is what drives the electron along the path through the circuit. We say that the electric field “does work” on the electron to move it, and therebye gives it some energy. (In the same way that you do work on your coffee cup to move it….. and by doing work you are converting energy from one form to another….giving the cup energy of motion, “kinetic energy” for example) I am not going to explain why electrons are acted on by electric fields, because nobody knows. (People will write in and say other stuff, but bottom line is that nobody knows why….we are very good at describing it as a fundamental fact from which several other things follow, but the “why” is a different matter.) Let us just use this as a starting point.

    So your circuit is a place where motion of electrons can follow a well-defined path. To drive the motion, an electric field has to be created. There are various ways of doing that, and we need not concern ourselves with the details of how. It is enough to know that your AAA battery sets up a such a driving electric field. Connect a light bulb using wire from one end of the battery to another and you have a circuit. What happens is that the field drives the electron around the circuit in one direction. It leaves the battery at one end and goes around the circuit (passing through the light bulb on its way) and returns to the other end of the battery, completing the loop that the system was designed to do. The light bulb actually glows. This means that energy was transferred to the lightbulb from the battery, which was our intent. This is what voltage is a measure of. Exactly how? Each electron, in going from one terminal of the battery from another along the circuit, loses a specific parcel of energy in going once around the loop. The volt is simply a measure of this parcel of energy, and convention has it that we divide this number by the amount of electric charge the electron has to get the unit that we call the Volt. Where did that energy that it lost go? Into lighting the lightbulb, (and heating it a bit too).

    This is the principle by which all the appliances in your house are using electricity. It is just a clever way of storing energy (batteries), moving energy from one place to another (transmission lines etc) and then using it to do work (forming a circuit in which your microwave oven, etc, takes the place of the light bulb). When you plug something in, or flick a switch, you’re just creating one of these circuits/paths/loops around which electrons will be driven (by the electric fields in your battery or generated by burning coal at the power station, or by the solar cells on your roof), giving up their energy as they go through the device you wish to operate.

    Summary (as in comment 2): The volt is a measure of how much energy each electron gives up in going around the circuit.

    Notice I’ve said nothing about current. This has nothing to do with volts…. it is a measure of the number of elecrons going around the circuit during a given interval of time. That is measured in Amperes (amps). Knowing both the volts and the amps together can then tell you how much power is involved, and if you know for how long your system is working at that power, you know how much energy you used in total. See comment 2.

    He was also wondering how “current” comes into the pictures when the subject is static electricity.

    It does not matter what “type” of electricity is being discussed. The meaning of volts and amps is still the same. All we’ve changed is the way in which our basic electric field -which will drive our circuit- has been prepared. In the case of static electricity, the materials in the jacket are such that it is easy to create an excess of, or a deficit of, electrons on some surface (by rubbing them off, for example). Once you have a large number of electrons present or missing (which it is depends upon the material), guess what you have? An electric field that can drive electrons in a circuit if one is formed. The electrons are all trying to get away from all the other electrons and return everything to a situation where there are no excesses or deficits. The distribution of electrons themselves sets up an electric field which will move them to this better situation (if the opportunity arises) If they could get to the “ground” (roughly, the earth itself…a super large body that is so huge it can take the excess, or provide extra to fix a deficit), this would do the trick. The “30,000 volts” referred to in the story is a measure of how much energy (in the sense described before) an electron would lose if the field drove it around the circuit. But if there is no circuit, it won’t happen. (This is why “give off voltage” is just so silly.) With static buildup like that, nobody usually connects wires to make a circuit and drive a lightbulb. What acutally happens is that the electrons find a way of getting to “ground”. Either someone or something (which conducts electrons – allows them to flow through them) forms a path through which this happens, or if the charge separation is really extreme, it will cause the air itself to act as a conductor and these guys will just jump….this is the spark that you see with static electricity. Or lightning. When that happens, you have a flow of electrons – a current is a measure of that flow.

    So summary (as in comment 2): current is a measure of the rate of flow of electrons in the circuit.

    Ok. So I probably totally answered the wrong questions and now you’re going to beat the BeJesus out of me for being an incompetent explainer of basic concepts, and a hypocrite for pointing out examples of the media’s failing to even bother to try. Ok, go for it…. :-) I hope it was useful for somebody, anyway.

    Best,

    -cvj

  • http://blogs.discovermagazine.com/cosmicvariance/clifford/ Clifford

    One last thing. About the use of the term “kindergarten”. Of course, it was in jest, so please don’t get annoyed, anyone…but there is a serious point there. I claim that it should not be too much to expect to live in a society where the HUGE difference between voltage (to do with energy) and current (to do with flow) is taught to small children as a matter of basic education, as laid out in the first half of my explanation in comment 2. It is not that hard, and is no harder than several other concepts we teach in kindergarten or just beyond! This is not the same as teaching them about electric fields, properties of electrons, asking them to handle Maxwell’s equations for electromagnetism…or even getting them to write an equation expressing Ohm’s Law. I’m asking for just a plain understanding of “energy” vs “flow”. I claim that this is not too much to ask. We should at least be striving in that direction. That is my basic point: It is actually near-kindergarten material, or should be. Then people will be less likely to grow up with a fear (stemming from misinformation and confusion) about that most basic tool we employ all around us: electricity.

    -cvj

  • Tom Renbarger

    Another way to think of the point Clifford makes in comment 34 — consider if a newspaper made a mistake along the lines of confusing your/you’re or it’s/its. There would (rightly) be howls of outrage at the silliness of such an error by professional journalists. But an error between voltage/current passes (nearly :-) ) without comment, even though in relation to the subject, the distinction is about as basic as the difference between possessive pronouns and contractions.

  • http://capitalistimperialistpig.blogspot.com/ CapitalistImperialistPig

    Bitter grad student – OK, but grad school was truly fun for me, studying physics, the camraderie, even the problem sets.

    On the other hand, writing up my dissertation in those pre TeX days really sucked.

  • http://eskesthai.blogspot.com/2005/09/cft-and-tomato-soup-can.html Plato

    1.Sean:which characterizes the potential “oomph” in the flow

    2.citrineThe peak of a tall mountain has a large gravitational potential relative to the bottom.

    3.Arun powerwasher jet would be a high voltage, low current flow,

    water spilling over the top of a New Orleans levee would be low voltage, high current flow;

    water at the turbine in a hydreelectric dam such as at
    http://users.owt.com/chubbard/gcdam/html/hydro.html
    would be high voltage, high current,

    and your kitchen faucet would be a low voltage, low current flow.

    Sorry I couldn’t repsond sooner to answer Clifford. I am answering quickly here as I have to go, yet I want to be clear here. I’ll come back tomorrow.

    In terms of the “field” Inverse Square law. The “electrical potential” in gravitational collapse, as a cosmological process.

    Photon, informaton “released” and held to event?

    “Measure” in terms of distance from that event “in time” till now?

  • janet

    Tom, you’re kidding about that “it’s/its” comment, right? I see errors of that sort, and much more serious grammar and usage errors, in newspapers all the time. I don’t even react any more, unless it’s something really egregious, such as this true SF Chronicle headline — headline! — from a few years ago: “20 Years Later, Insult Still Wrangles.” My sister and I spent a few minutes laughing and scolding over that one, but neither of us wrote to the paper, and I doubt anybody else did, either. Sometimes when I find myself in a group of writers and editors, we spend hours griping about our pet peeves, but aside from doing our best in the trenches, there’s little to do. Not much can be accomplished just by complaining. I’m one of the few people I know who didn’t think much of “Eat Shoots and Leaves,” especially since the author is far from sinless herself.

    I rarely correct people’s grammar any more, for a few reasons.

    1. A lot of errors are not the result of ignorance, or even sloppiness, but just the inevitable imperfection of human behavior. I’ve noticed a few grammatical errors in posts on this blog, for example, but I can tell from the general quality of the writing here that they are the kinds of errors any good writer makes from time to time, and that even good editors occasionally let slip through (I have found typos in the New Yorker, which is famed for the excellence of its editing). I will not swear that there are no grammatical errors or spelling errors in this comment.

    2. People are taught all sorts of bad grammar in elementary school, so that they insist that it’s incorrect to start a sentence with “but” or “and,” or end a sentence with a preposition — neither of which is a hard-and-fast rule — and absolutely will not budge, even if you show them a passage in a good grammar reference that supports your argument (the Chicago Manual of Style has a particularly withering critique of these “rules”). Yet these same people create howlingingly funny dangling modifiers and repeatedly confuse subjective and objective pronouns. It is virtually impossible to convince people that they’re, especially if they’re just doing what their 3rd grade teacher taught them. I spend a lot of time talking to doctors who are reviewing manuscripts I’ve written, and they’re always trying to “correct” my grammar. Since I need to be polite, I can’t argue with them — it is very aggravating.

    3. Usage conventions vary: it would be wrong for me to spell “program” with an extra “me” tacked onto the end, or use “s” instead of “c” or “z” in words like “practice” and “patronize,” or spell “favor” with a “u,” but perfectly correct for Clifford to do so, since he uses British spelling; it would therefore be rude and ignorant of me to “correct” him or vice versa. Punctuation conventions also vary in British and American usage.

    4. Usage changes. I still remember the first time I heard the word “proactive.” It was the fall of 1985, and I remember my immediate “that’s not a word” reaction. But alas, ugly and redundant as it is, “proactive” has entered the language, and these days I barely flinch when I hear it. And that’s pretty much the way it has to be: language changes, meanings change, ideas about what is and is not “good style” change, and what is or is not “good style” depends on what you’re writing and who the audience is. I happen to be a fan of long, intricate, architecturally complex 19th-century sentences, but when I’m writing a technical document I try to keep my sentences as straight-forward as possible, because the point is not beauty, but clarity (which can be beautiful in itself).

    By now you may have concluded that I’m hopelessly relativist and wishy-washy, but that would be incorrect. Rules of grammar and style exist for a good reason: to make written communication possible, and ideally pleasurable. Without some agreement on how a written English sentence is put together, writing and reading become confusing, difficult, and ultimately impossible. The challenge is to write well and read intelligently while keeping in mind that language is open-ended and constantly changing. The thing that bothers me about how writing is taught is not that people aren’t learning the rules right, but that people aren’t learning why the rules matter, and why they should care about them — which brings me to a point similar to the one that Clifford has been trying to make about the way that science should be taught.

  • janet

    Clifford,

    Nope, I’m not going to beat the beJesus out of you — that was actually very clear, and made a lot more sense than the analogies that people have been using to explain things. The analogies are a useful shortcut, though, if you don’t want to get into the specific details. Anyway, thanks. Notice, though, that it took you several paragraphs. If a reporter brought it in as part of a funny news story about a guy’s suit, the average editor would red-pencil the whole thing. The reporter would have to either avoid technical terms altogether (which would mean paraphrasing the fire officials who were using the terms incorrectly), or find a two-sentence way of explaining the terms. Things would be very different if a reporter were working on a story about some new kind of battery, and that was the point of the story, and the reporter had a couple of days to work on it.

    About a year ago I was writing something about tests that a person might undergo as part of a diagnostic process (I can’t remember what it was), and one of the possible tests was an MRI. I just had a few lines, but I wanted to make it as accurate as possible, and besides, I’d never understood how MRIs work, and I was curious. So I did some research and even though I ended up understanding MRI technology a bit better (I still find it somewhat mystifying), it didn’t help me at all with what I had to write, because of the space constraints I had — all I could really say was that an MRI is a 3-D imaging test that uses a strong magnet. The main topic of the document was not MRI, and I just couldn’t spend much space on it; you might say that it would still be a good thing for the reader to learn more about MRI, but I would have to reply that saying much more about it would be a distraction from the main topic I’m trying to inform them about. Journalists write under similar space and topic constraints, and a lot more time pressure.

    I basically agree with you about science education, but I tried to imagine how to introduce these topics to the very bright 5-year-old son of a friend of mine, and I decided that at that level of cognitive development I would have to work through demonstration and analogy — which doesn’t negate what you’ve said about education, just underscores the importance of knowing your audience.

    One last observation: even before all of this, if someone had asked me I would probably have said that “give off Voltage” didn’t make sense, but I couldn’t have explained why, except to say (maybe) that voltage is a property of the object itself. It’s possible to know how words are used without understanding the concepts underlying them.

    Now, I am going to use various electrical devices to bake a pie and do some laundry.

  • http://blogs.discovermagazine.com/cosmicvariance/clifford/ Clifford

    Janet. Nope. You just introduced a major red herring. Nowhere in my discussion did I ask that the editors or journalist stop and explain electricity in their article! That’s ridiculous! I just asked that they consider using the terms and concepts properly, that’s all. That does not take paragraphs to get right. To use the grammar analogy (carefully), we do not ask editors or writers to write a small essay explaining the rules of grammar in every article, we just ask them to use good practice and use those rules properly when writing sentences. Simple really.

    Finally, I think you are not giving your five year old friends the credit they deserve. They can understand the difference between “flow” and “energy”, and hence “current” and “voltage”. I betcha!

    Cheers,

    -cvj

  • Aaron

    “So watch out for those deadly amps, folks.”

    Oh no!!! My next physics exam is going to be full of amps. Should I scribble them out and replace them with coulombs per second? Or should I just wear heavy rubber gloves?

  • http://blogs.discovermagazine.com/cosmicvariance/clifford/ Clifford

    …and boots. Don’t forget the boots.

    -cvj

  • NoJoy

    In the post, Clifford mentions polyester, so I well be telling a (possibly apocryphal) story to which he was already alluding. When I was in college, a story ran in the Weekly World News about a man who was electrocuted while removing his polyester clothing from the dryer. The story reported a 40,000-volt shock. Reaction on campus was split. When SEs (science and engineering students) heard the story, they replied, “Yeah, but how many amps?” When academs (liberal arts students) heard the story, they replied, “That’s what you get for wearing polyester.”

    And Clifford, is your last comment a general safety warning, or a reference to the similar “heavy boots” story?

  • janet

    I wasn’t going to post again to this thread, on the principle of not beating a dead horse, but since people are still adding to it I do want to make it clear that I’m not trying to be an apologist either for sloppy reporting or the dumbing down of science education. Quite the opposite. My question wasn’t whether kindergarteners can understand concepts such as “energy” and “flow,” but rather, how to teach these concepts. If not by demonstration or analogy, how? Children aren’t stupid, and in the right circumstances they have a capacity to learn, imagine, and invent that puts the average adult to shame, but their ability to abstract is still developing. The smartest kids often misunderstand abstract concepts in amazingly creative ways. That’s all.

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