Wikipedia:Reference desk/Archives/Science/2011 January 19

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January 19

Volume (sound)

How did it come to be that Volume became associated with loudness?Smallman12q (talk) 00:09, 19 January 2011 (UTC)

According to the OED, the first use of the word "volume" to mean loudness of sound occurs in Byron's Werner, 1822: "I heard‥, Distinct and keener far upon my ear Than the late cannon's volume, this word—‘Werner!’". And it was defined in a musical dictionary as early as 1786 to refer to "the compass of a voice from grave to acute: also to its tone, or power". WikiDao ☯ 00:40, 19 January 2011 (UTC)

We've done this one before. 213.122.48.63 (talk) 01:09, 19 January 2011 (UTC)

Yes, here. Dbfirs 08:35, 19 January 2011 (UTC)

Fire in a Microwave Oven?

Recently, a friend had me watch a video of someone putting a candle in a microwave oven and turning it on. This produced some neat effects, supposedly creating "plasma". (The video was not made by professionals.) My question(s) are: Is this actually plasma? And regardless whether it is or not, what exactly is happening? ^Avic_ennasis @ 07:19, 14 Shevat 5771 / 19 January 2011 (UTC)

I have seen such experiments in reality. a flame is already very slightly ionized. Apparently, the microwaves transfer energy to the plasma, ionizing it further and enlarging it, though I don't know the exact mechanism by which this happens. 157.193.175.207 (talk) 07:47, 19 January 2011 (UTC)

Is there a video online of this anywhere please? 92.24.183.183 (talk) 13:23, 19 January 2011 (UTC)

May not be the same video that Avicennasis saw, but it certainly is a candle in a microwave Darigan (talk) 13:27, 19 January 2011 (UTC)

It's even more impressive when you do it with a grape. 90.193.232.5 (talk) 14:20, 19 January 2011 (UTC)

There are many such videos on YouTube. If you can name it, someone has microwaved it, with comic effect. "Coconut in a microwave" isn't as impressive as you'd think, but I remember when I looked for it, I found it.

There is a wide subset of videos about "ball lightning" in a microwave. I think that this is overly promoted - it is simply that fire is conductive and absorbs more energy, and sometimes the gasses continue to glow a moment after they escape from a hole, etc. that has been built for this purpose. I don't think that the sort of energy or structure present in real ball lightning is actually duplicated --- but if someone disagrees, by all means let us know! Wnt (talk) 17:55, 19 January 2011 (UTC)

Where does the bigger flame come from? My guess is that the heat from the microwave heats up the candle and/or wick, so that more fuel is available to be consumed by the flame. I do not believe that the energy for the bigger flame comes from the microwaving directly, as microwaves do not burn all by themselves. 92.29.123.151 (talk) 23:40, 20 January 2011 (UTC)

It really is a plasma, and is very high energy. Part of the flame of a candle is made of ionized atoms. Ionized atoms are very good conductors. Microwaves will induce large currents in conductors. Thats why they tell you not to put metal objects in a microwave. In the tiny plasma of the flame, suddenly about a kilowatt of power is injected. This greatly heats the plasma, which heats the air around it, and ionizes it, and causes the plasma to grow, which causes it to heat more, which causes it to grow more and in a moment, you have a large ball of plasma at several thousand degrees in your microwave. It will literally destroy the oven if allowed to form for too long. It also stresses the electronics in the oven due to the large currents generated. Once you open the door though, the power maintaining the plasma's temperature disappears and the plasma disappears. Though the melted roof of your microwave oven will remain. 24.127.93.76 (talk) 07:51, 23 January 2011 (UTC)

Need a Formula

i need information the formula 10extera abrasive becuse used oxalic acid —Preceding unsigned comment added by 85.185.25.251 (talk) 07:30, 19 January 2011 (UTC)

I think you need to make your question a little clearer. --ColinFine (talk) 08:48, 19 January 2011 (UTC)

Does Extracting oxalic acid from household cleaner help? Cuddlyable3 (talk) 11:42, 19 January 2011 (UTC)

Why do frozen vegetables taste so bland?

It's not just the brand, but this is the kind of products I'm wondering about.[1] How are they nutrition-wise? Thanks. Imagine Reason (talk) 12:58, 19 January 2011 (UTC)

I understand the process of freezing damages the cell-structure (water/liquid expanding as it freezes), and then means that when cooked they lose some of their flavour (I know, I've worded that terribly, but have a quick read of the Frozen vegetables article, and I'll have a look for some bette source)... this extract points to the difference in texture between frozen and fresh veg.this source argues that frozen veg are higher in nutritional value than fresh (or, as the case may be, not entirely fresh vegetables). this source also argues that frozen veg are less at risk from contamination, as long as they are not frozen, defrosted and then refrozen - Although, having said that, I am sure that I have seen other sources before that argue that frozen veg in bags that have not been properly sealed are at risk from contamination. Darigan (talk) 13:16, 19 January 2011 (UTC)

It could also be related to the way they are cooked after being frozen -- are you boiling them in water? I've always found that makes veggies taste a lot more bland. -- JSBillings 13:48, 19 January 2011 (UTC)

OR answer here: I have found that frozen vegetables taste better when steamed than when boiled; the "steam in the bag they came in" varieties are particularly close to their fresh cousins. Some vegetables take to freezing better than others. I find frozen carrots and frozen corn-on-the-cob to be pale comparisons to their fresh versions, while green beans (haricots) and garden peas are usually fairly comparable. I'm not much of a fan of many cruciferous vegetables in any form, so I can't comment on frozen vs. fresh broccoli or cauliflower or brussel sprouts. --Jayron32 15:48, 19 January 2011 (UTC)

With peas, it's vastly superior to freeze (or can, though I find canned peas unappetizing) them rather than shipping them "fresh" to a supermarket: the sugar in peas breaks down incredibly rapidly, making it nearly impossible to get good fresh peas, other than by growing them yourself. This is mentioned in Pea#Use, though I'm surprised we don't have anything more on this. I think typically, peas need to be blanched and preserved within a couple of hours of being picked. Buddy431 (talk) 17:15, 19 January 2011 (UTC)

I think your example of corn is illustrative of a few things. Really fresh corn (as in, you put the pot on to boil while you run out to pick the ears) is unbelievably good; it barely even needs a blanching, you just want to warm it up for the butter. Within a day, it's good, but not nearly the same kind of thing. If you IQF freeze it at that point, you'll get a pretty decent product - good enough that it's better than the so-called fresh corn you find in grocery stores that's already 2-3 days old, if not more. Canned corn is pretty abysmal. So you've got a weird sort of graph where really fresh is best, but frozen is better than just about anything else. The trouble with many vegetables, particularly carrots and peas, is that freezing them wrecks the crispness; the flavour might not change much, but the mouth feel is completely different. Matt Deres (talk) 19:00, 19 January 2011 (UTC)

IQF seems to mean individually quick frozen in this context - it stops the corn/peas etc from sticking together. CS Miller (talk) 19:37, 19 January 2011 (UTC)

That's the problem I have with frozen corn: it loses the snappy mouthfeel that makes fresh corn-on-the-cob so tasty. I usually buy my corn at the local farmer's market the day I plan to use it; when it is in season it's usually picked within 24 hours before I buy it. I find all canned vegetables taste more like can than vegetable, so I avoid them pretty much at all cost. --Jayron32 19:23, 19 January 2011 (UTC)

You might find the article on Clarence Birdseye interesting. Vespine (talk) 22:09, 19 January 2011 (UTC)

Wouldn't the vegetables that are used by the frozen vegetables processors be those most manageable for that process? There are lots of varieties of a vegetable. Those destined for freezing are likely to be those that have the handling characteristics that best lend them to mechanical manipulation—from the field to the packaged and frozen product. If any tradeoffs have to be made, taste might get sacrificed in favor of the ease of large scale mechanized agriculture. Even the nonorganic but fresh vegetables on the supermarket shelf might tend to be those varieties of a given vegetable that don't require those qualities that lend themselves so well to the highly mechanized freezing (and harvesting) process but may instead retain some of those qualities that made them desirable in times gone by. Bus stop (talk) 22:23, 19 January 2011 (UTC)

The one exception, I think, is tomatoes, where the canned ones can have better flavor than either fresh or frozen. Freezing destroys them, and even farmer's markets can't usually handle them at the peak of flavor -- canners, however, can process them directly out of the field. Looie496 (talk) 00:12, 20 January 2011 (UTC)

I'll second that; canning tomatoes also has the practical effect of concentrating the flavor components. I find good canned tomatoes to be more intensely "tomatoey" than even fresh-off-the-vine-minutes-before tomatoes. Which is not to say that fresh tomatoes don't have their place; canned tomatoes make a better sauce than fresh, but I wouldn't ever use them in a salad. --Jayron32 01:27, 20 January 2011 (UTC)

O.R.: Food processing companies such as Green Giant, who have contracts with farmers, pick and process crops (for freezing or canning) at the absolute perfect state of development. If they get a few days behind, they skip the crops which would be post-mature and go on to the next perfect batch. If you buy "fresh" corn or peas, there is no such guarantee that they were picked on the very best day of maturation and presented for your purchase with no delay. The damage due to freezing is likely offset by the benefit of picking at the peak of quality, compared to picking too late, or picking early and shipping of "fresh" vegetables. Of course, you could grow your own produce and guard the crop at night to stave off marauding raccoons, who can detect ripening corn (maize to Brits) from miles away. Edison (talk) 02:19, 22 January 2011 (UTC)

Electrical

Hi I have some basic doubts in electrical I am an electrical student please help me 1)Why we maintain voltage as constant not current?

2)In producing AC there comes both +ve AND -ve voltage in both the ends (slip rings) but in power line only phase has while neutral remain null.

3)Is human body a conductor?

4)If a coil connected to power supply produces magnetic flux will that flux link on that same coil and induce a emf?

5)Fan is an inductive load thus on using it there should be 90° phase out b/w Amps and Volt if so won't it affect Transformer?

6)If a bulb excited by AC what happen when it changed to DC of same rms value of volt and current?Kanniyappan (talk) 14:08, 19 January 2011 (UTC)

Regarding #3, everything is a conductor under sufficient voltage. The human body, being basically a giant bag of salt water (an electrolyte) is actually a pretty decent conductor, even under moderate voltages. Regarding #4, in order to produce an emf through the coil, you must move the coil in relation to the magnet (or visa-versa). Regarding #6, my understanding is that light bulbs (and resistance heaters, and other similar devices) behave roughly the same under AC and DC conditions, as the effects of resistive heating are the same regardless of the direction of the current; in other words the AC or DC nature of the current does not play into Joule's first law. I will let someone who actually knows about this answer the rest (and correct my mistakes). --Jayron32 15:42, 19 January 2011 (UTC)

It is not possible to maintain a constant current except under carefully controlled conditions. "Voltage" is another name for "electro-motive force" (EMF) which you can compare with "pressure" in water pipes. The supply of both electrical and water services aims to maintain a constant "pressure" so that the amount of electricity or water that flows when something is turned on can be reliably predicted. In the case of water, it is usually the tap that controls how much water flows, but, for electricity, it is usually the resistance or reactance of the appliance that determines how much current flows (though dimmer switches work like taps).

AC supply does not have positive and negative. Usually one side of the supply is connected to earth and for this reason is called "neutral", but it doesn't really matter whether this is done or not except for safety reasons. Both "live" and "neutral" wires behave in exactly the same way (except when one is shorted to earth), so there is really no difference between them if they are isolated from "earth". Three phase supply is generated and transmitted with three "lives", each one being 120 degrees out of phase with each of the others. Sometimes there is no "neutral" (delta configuration), and power can be transmitted without any other conductor. More often, each of the phases is generated at a fixed voltage to a common wire "3-phase neutral" which is usually connected to earth. The three main wires for the three phases still carry the main current because the three currents in the three phases will cancel each other out if they are equal, but the common neutral serves to carry any residual current if the phases are not balanced.

Just one minor addition to Jayron's answer to #4: If AC is connected to a coil, then the flux does indeed produce an induced EMF in the same coil becuase the current is constantly changing. See autotransformer. Dbfirs 18:24, 19 January 2011 (UTC)

To continue dbfirs points, see earthing systems (most houses use TN or TT, where neutral is tied to ground, see IT for why it is done), three-phase power supply, and single wire earth return for other reasons for earthing neutral. CS Miller (talk) 19:34, 19 January 2011 (UTC)

As far as I know, single-wire earth return is never used in the UK. (I've tried it, unofficially, but probably illegally.) Dbfirs 22:17, 19 January 2011 (UTC)

A/C can have potential on both sides of circuit (although obviously not positive/negative, since it's A/C). Voltage can only be measured as a difference - there is no such thing as an absolute voltage. A/C in households is designed so that the earth is one side of the circuit, and since we stand on the earth, to us the feels like neutral. But it doesn't have to be that way. If you isolate your A/C generator completely from the Earth, then both sides "have" potential (although of course that's meaningless since you need two sides to measure anything). An interesting side effect of this kind of isolation is that you can't get shocked by touching just one wire - you need two to get shocked. Unless of course two different people happen to each touch one wire at the same time and you complete the circuit through both of them via the Earth. You can also make D/C with one side hot and the other neutral - you just need to attach one side to the earth. Ariel. (talk) 22:35, 19 January 2011 (UTC)

Well if you want to be pedantic, AC does have positive and negative on both sides, it just changes 100 or 120 times each second, so I meant that you can't label either conductor positive or negative. Good point that DC can have "live" and "neutral". Is it often supplied this way (other than in motor vehicles)? Dbfirs 23:09, 19 January 2011 (UTC)

Most circuit diagrams have a source and ground, rather that a positive and negative. Computer power supplies are also wired this way - a common ground for everything, and different wires for various voltages/rails/polarities. Ariel. (talk) 00:17, 20 January 2011 (UTC)

Yes, good point, though voltages are quoted positive or negative with respect to the "ground". Is this just because the mains supply is grounded? My laptop just has 19v DC with no ground, but the circuitry probably has an artificial "ground", possibly connected to mains "earth" (I haven't checked). Did early wet and dry battery circuits also have a "ground"? (I was really meaning long-range supply of DC, but this is relatively rare.) Dbfirs 13:05, 21 January 2011 (UTC)

Real mains fans have some corrective circuitry to bring the current much closer in phase to the voltage. See power factor. Dbfirs 18:37, 19 January 2011 (UTC)

1. Mains supplies provide a constant voltage so that any number of appliances can be connected and disconnected without affecting one another. Each receives the standard voltage and only the total current varies. A constant current mains supply is impractical because the current to an appliance would change every time another appliance was connected, and dangerously high voltage will be delivered if no appliance is connected.
2. A basic two-wire or "single-phase" AC supply usually has one wire called neutral connected to earth which we may call 0V. The voltage on the other wire alternates between +ve and -ve voltages.
3. The human body is a conductor. See the article Electric shock.
4. An emf is induced in a wire in a changing magnetic field. A coil is an example of an inductive load. When a coil is connected to a DC power supply, the current in the coil grows slowly because it produces an increasing magnetic field that induces an emf that opposes the supply voltage. For the same reason, when a coil is connected to an AC supply the current is slow to follow the voltage changes. The time delay can be expressed in degrees where a full alternating cycle is 360. If the coil has no resistance, the current lags the AC voltage by 90.
5. A fan motor is an inductive load. When the fan shaft rotates the motor is also a generator of emf that opposes the supply voltage.
6. The filament of a lamp bulb glows because of the heating effect of current flowing through its resistance. The heating power is proportional to the voltage squared (so both positive and negative voltages give heating). An AC supply with rms (root mean square) voltage equal to the voltage of a DC supply has the same heating power as the DC supply. So there will be no change in the lamp brightness if one switches between the two supplies. Actually the brightness flickers at double the frequency of the AC cycles but you cannot see this because mains supply frequency is too high. Cuddlyable3 (talk) 22:59, 19 January 2011 (UTC)

• On question 6: Similar light bulbs connected to DC or to AC of the same RMS voltage will produce similar light and heat, and consume similar power initially. However a bulb connected to DC may show a light streak, like an inverse shadow, behind the leg of the filament connected to the positive supply. This "shadow" led to discovery of Thermionic emission, the basis for Vacuum tubes and electronics. I suppose an AC powered bulb might display a less distinct shadow in line with each filament leg, since each in turn has each polarity. If the frequency of the AC is low enough, many people can see objectionable flicker. I have seen this in bulbs of street cars powered by 25 cycle electricity. This slight flicker at twice the mains frequency can also produce a slight strobe effect when viewing a vibrating or rotating object. If there is a magnet or magnetic field near the bulb, the filament may vibrate quite a bit when powered by AC, depending on the construction and how the filament is supported. If powered by DC, it could move in one direction and stay there as long as the field and current continue. This was very clearly visible with early carbon filament lamps: See [2]. Edison (talk) 22:04, 21 January 2011 (UTC)

Rephrased: relaxing voices

Sorry to the board, it wasn't supposed to be a medical question. I will attempt to rephrase the question. Why do some voices, e.g., Bob Ross's, cause people to relax? I've read on other forums that people will watch his show to help them fall asleep. Thank you very much! Reflectionsinglass (talk) 18:54, 19 January 2011 (UTC)

To answer a question with a question, why is some music relaxing and other music exciting? Why do some people find traffic noises soothing, and others find it irritating? Ariel. (talk) 22:37, 19 January 2011 (UTC)

Ice expanding, minimum density

It is my understanding that when water is cooled (at standard pressure), it reaches a maximum density at 4°C (due to hydrogen bonds, and then starts to expand as it is cooled further. As it transitions to Ice Ih it expands by about 9%, and then continues to expand as it cools further. At what temperature does ice reach its minimum density? I did a quick websearch and found [3] which indicates that it is at 70K. Is the minimum density really this cold? — Preceding unsigned comment added by Csmiller (talk • contribs) 20:10, 19 January 2011 (UTC)

Under Ice#Characteristics it says: "The density of ice is 0.9167 g/cm³ at 0°C [...] Density of ice increases slightly with decreasing temperature and has a value of 0.9340 g/cm³ at −180 °C (93 K).", quite the opposite of your statement. But it doesn't say what ice does on further cooling or where minima/maxima of density are. Another image on commons ([4]) also implies that density rises when ice is cooled. Oh, just read through your link again, and as I understand it, ice increases its density when heated up starting from 0K to 70K, then it apparently decreases again--178.26.171.11 (talk) 21:03, 19 January 2011 (UTC)EDIT: The minimum density should be at 0°C then (unless there's a way of "superheating" ice above that without melting it at standard pressure.--178.26.171.11 (talk) 21:05, 19 January 2011 (UTC)

A very similar question was asked a couple weeks ago.[5] Red Act (talk) 23:23, 19 January 2011 (UTC)

Allergen

I'm trying to pin down whether an item would be a high risk to cause an allergic reaction. The ingredients listed on the website for it are: Water, denatured alcohol (<5%), sodium iminodisuccinate (<1%), zinc diricinoleate (<1%), cocamidopropyl betaine (<1%), menthol (<1%), microorganisms (<1%), citric acid (<1%), polydimethylsiloxane emulsion (<1%). The microorganisms in this product are non-genetically modified, naturally sourced, non-pathogenic (i.e. do not cause disease) dormant bacteria, and are the primary “active ingredients” in this formulation. They work by eating up all of the accumulated dander, dead dust mites, and dust mite fecal matter that has accumulated in your mattress/ pillows/ furniture/ car upholstery over time, eventually converting those allergens into carbon dioxide and water.
Obviously, people can be allergic to just about anything, but do any of these items seem like likely candidates? Their use of "naturally sourced" bacteria kind of raised my eyebrow, for one thing. I've heard of cleansers touting their "enzymatic action!" before, but not bacterial. Anything else on there look weird? Matt Deres (talk) 20:37, 19 January 2011 (UTC)

Wow. That's like an ingredient list that includes "...chemicals. All our chemicals are safe, trust us..." To give a parallel example with a more defined set of natural microorganisms, consider the regulation of raw-milk cheeses by the U.S. and Australia. Wnt (talk) 20:52, 19 January 2011 (UTC)

You also may take interest in the zinc diricinoleate (the basic component there is ricinoleic acid, with two conjugated to zinc. See [6] [7] [8] for some leads. (It is widely used, but I'd like to know who puts castor oil in chocolate? Remind me to avoid that brand...) Wnt (talk) 21:03, 19 January 2011 (UTC)

Castor oil in chocolate?! Sounds like something the Whizzo Chocolate Company would trot out. Matt Deres (talk) 23:12, 19 January 2011 (UTC)

Apparently this is being done by Hershey's, Nestle, and Mars, Incorporated, as part of a campaign to sell cocoa butter to the cosmetics industry and replace it with cheap substitutes in chocolate.^[9] Which is just one small reason why American chocolate doesn't taste like chocolate. And people wonder why this country keeps running record trade deficits... Wnt (talk) 04:18, 20 January 2011 (UTC)

This site: http://www.cosmeticsdatabase.com/ is pretty good for that kind of thing. You can either look up individual ingredients, or register an account and enter all the ingredients of a product and it will give you a grade. (Not just allergies, any kind of potential risk.) Ariel. (talk) 22:52, 19 January 2011 (UTC)

That site looks helpful - thanks; I'll give it a look when I get some time to play around. I don't know if it matters, but the substance in question isn't a cosmetic, it's for spraying on beds and other furniture to reduce dust mite allergens and odour. Matt Deres (talk) 23:12, 19 January 2011 (UTC)

Water and brick question

My daughter has a science project in 5th grade this week. I was watching the discovery channel last night and the segament was about taking a 5gal. water jug,filling it a 1/4 with wate, connecting a hose to it,then connecting the end to a hot water bottle.Then take 5 blocks and put them on top of the water bottle.Once that is complete,turn the 5gal. jug upside down about 4ft. high ,then the water should fill the bottle and knock off the bricks. What is the topic of this project? — Preceding unsigned comment added by Jeffryan777 (talk • contribs) 22:01, 19 January 2011 (UTC)

Can't you ask your daugher? (I added a header) SmartSE (talk) 22:37, 19 January 2011 (UTC)

The topic appears to be pressure, in that the head of water in the hose is sufficient to lift the bricks. --Tagishsimon (talk) 22:41, 19 January 2011 (UTC)

This is a demonstration of hydraulics using communicating vessels, the field is fluid mechanics.Vespine (talk) 22:46, 19 January 2011 (UTC)

You could also discuss conservation of energy. Lifting the 5 gallon jug takes work (in the literal and technical sense of the word). That work is transferred, via the hydraulic pressure, to lift the blocks. One useful property of hydraulic machines is that they can multiply force - so it can be possible to lift some pretty heavy cinder-blocks (which requires a large force), by exerting a smaller force over a large distance to lift the water (hence, to pressurize the fluid). (The force is increased, but the energy is conserved). Nimur (talk) 23:33, 19 January 2011 (UTC)

And because of this force multiplying, hydraulic systems similar to the one described can act like many types of levers, pulleys and other simple machines. SemanticMantis (talk) 00:02, 20 January 2011 (UTC)

t (radiation and testosterone)

does radiation lower testosterone — Preceding unsigned comment added by Tommy35750 (talk • contribs) 22:06, 19 January 2011 (UTC)

"Radiation therapy may lower testosterone to the low-normal range in some men" source - so yes. (That could be worked out a lot quicker by googling "radiation lower testosterone") SmartSE (talk) 22:35, 19 January 2011 (UTC)

Radiation could increase free testosterone but our article on Testicular Cancer does not mention this. Could someone please expand this, as I'm not sure of certain details.--Aspro (talk) 22:38, 19 January 2011 (UTC)

It depends on what type of radiation, how it was applied, where it was applied, and so on. A lot of research has been performed to study the effects of localized radiation applied to the testes or to the prostate as part of a cancer treatment. Here are some relevant papers on that topic that were found using this Google Scholar search: Effect of Graded Doses of Ionizing Radiation on the Human Testis, Serum testosterone levels after external beam radiation for clinically localized prostate cancer, and so on. If you are trying to evaluate medical options, you should consult a physician. Significant other research has studied the effects of environmental radiation (like if you work in a room or laboratory near radioisotopes, or near a uranium mine, or if you have a radon gas problem in your home); for example, Environmental endocrine disruption: an effects assessment and analysis. We can point you to better resources, and provide better answers if you can specify your question a little more clearly. "Radiation" is a very broad term for a lot of different kinds of energetic effects from a lot of different places: nuclear radioisotopes; strong electromagnetic sources (like mobile phones); and even ultraviolet radiation from overexposure to the Sun or tanning booths. Nimur (talk) 23:45, 19 January 2011 (UTC)