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

-cvj

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?

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

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.

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.

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,

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?

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

-cvj

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

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.

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

Cosmological associations and brane features.

Historical correlation of this developement might help?

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

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.

-cvj

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

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.