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Animal Care/Guinea pig

Guinea Pigs (also called cavies after their scientific name) are rodents belonging to the family Caviidae and the genus Cavia. Despite their common name, the animals are not pigs, nor do they come from Guinea. Male guinea pigs are called boars, females sows and babies are called pups. They are originally native to the Andes, and while they are no longer extant in the wild, they are closely related to several species which are commonly found in the grassy plains and plateaus of this region. The guinea pig plays an important role in the folk culture of indigenous South Americans, especially as a food source, but also in folk medicine and in community religious ceremonies. Since the 1960s, the guinea pig has become increasingly important as a staple food in the Andes, and efforts have been made to increase consumption of the animal outside South America. See the cookbook entry for links to recipes.

In Western societies, the guinea pig has enjoyed widespread popularity as a household pet since its introduction by European traders in the sixteenth century. Because of its docile nature, the relative ease of caretaking, and its responsiveness to handling and feeding, the guinea pig remains a popular pet choice. Organizations devoted to competitive breeding of guinea pigs have been formed worldwide, and a large number of specialized breeds of guinea pig, with varying coat colors and compositions, are cultivated by breeders.

Choosing a Guinea Pig
Taking care in choosing your guinea pig and its possible companions is the first, and possibly the most important, step in keeping guinea pigs. Make sure your guinea pigs are either of the same sex or neutered/spayed.

Health
As prey animals, guinea pigs have evolved to hide any signs of illness, as long as possible in order to avoid becoming the main targets of the dangerous predation. This can make it difficult to recognize an illness or ailment. The best way to check for them is to place the cavy carefully on its back and check the belly. Their feet should be clean-looking and not red or irritated; with no broken or extraordinarily long nails. Check their teeth for length and evenness (see section below). It is also important to check their eyes and nose, to make sure that there is no mucus or crust there. These are signs of an upper respiratory infection, or URI, and can be deadly if left untreated.

Breed
The most common kinds of guinea pig (especially in pet stores) are the short-haired "American" or "Self" breed and the "Abyssinian", which has curly, cow-licked hair. Long-haired guinea pigs (the Sheltie/Silky and Peruvian breeds) are very beautiful pets, but they need daily grooming to be healthy, thus making them not usually suitable for children. The hair near the rear of the Guinea Pig must be cut and cleaned on a regular basis, or it will get caked with feces and the bedding from the cage. Short hair guinea pigs take less effort in the hygienic and cosmetic categories, but still need to be properly cared for. Therefore, the Peruvian guinea pig breed is the most difficult breed to care for due to the long hair. It gets tangled extremely easily, and is not recommended for anyone without extensive time to care for the cavy's hair every day.

How many?
The vast majority of rescues, knowledgeable vets, household breeders and scientists will tell you that guinea pigs should be housed in groups of two or more. Not only is making sure your guinea pigs have companions important for their health and happiness, keeping multiple guinea pigs will improve the fun of having these animals as pets as you watch them interact. In practice, the best option is usually a pair of guinea pigs. Of course, the most important factor in choosing groups is to make sure you will not have any unwanted babies, so make sure your pets are either of the same gender or spayed/neutered. If you are not confident in sexing guinea pigs, buy/adopt whatever guinea pigs you so desire, and then take it to your vet or a cavy-specific rescue to have its gender confirmed before introducing them at all. While groups of boars might get along (provided no females are present and they are carefully introduced), and groups of females are often fine, the easiest combination is one neutered boar (neutering is cheaper and safer than spaying) and one or more females. The personality of individual guinea pigs varies; with some being very amicable to company and others incapable of showing anything but hostility to other cavies.

Behavior
Guinea pigs are active during the day, but are actually crepuscular (most active at dawn and dusk). Guinea pigs are very gentle, and even untamed guinea pigs will not bite unless you are causing them pain or they have been abused in the past.

Guinea pigs have a poor sense of sight, but well-developed senses of hearing and smell. Vocalization is the primary means of communication between members of the species.

 * Wheek - A loud noise that is essentially onomatopoeic, also known as a Whistle. An expression of general excitement, it may occur in response to the presence of its owner or to feeding. It is sometimes used to find other guinea pigs if they are running. If a guinea pig is lost, it may wheek for assistance.
 * Bubbling or Purring - This sound is made when the guinea pig is enjoying itself, such as when being petted or held. They may also make this sound when grooming, crawling around to investigate a new place, or when given food.
 * Rumbling - This sound is normally related to dominance within a group, though it can also come as a response to comfort or contentment. While courting, a male usually purrs deeply, while swaying from side to side and circling the female.
 * Chutting and Whining - These are sounds made in pursuit situations, by the pursuer and pursued, respectively.
 * Chattering - This sound is made by rapidly gnashing the teeth together, and is generally a sign of warning. Guinea pigs tend to raise their heads when making this sound.
 * Squealing or Shrieking - A high-pitched sound of discontent, in response to pain or danger.
 * Chirping - This less-common sound seems to be related to stress.

The Cage or Living Environment
While some older guinea pig resources may say that housing them outdoors is acceptable, this is simply not the case. Wind can blow a hutch over easily; it is also the perfect place for molds to grow. Spiders and insects may bite guinea pigs left outside. There is also no guarantee that temperatures will be acceptable for your guinea pigs to live in. It is also very hard to notice signs of disease in guinea pigs if they are constantly out of sight, and out of mind. Even indoors, sudden drafts or radical shifts in temperature may adversely affect the health of your guinea pig. Outdoors, guinea pigs may still be subject to predators such as raccoons, opossums, birds of prey and cats. Even a guinea pig physically protected from a predator may suffer from the ill effects of stress from the presence of a predator. Guinea pigs in the Andean region of South America are often kept outside on roofs or in milk crates. But these are livestock, not pets. A pet guinea pig is a member of your family and will benefit from the most interaction available. Being inside your home will make it easier and more appealing to care for and play with your guinea pig. Additionally, most secure hutches are designed for rabbits, and as such have mostly wood or wire floors that are unsuitable for guinea pigs. These wire floors are extremely painful for rabbits and cavies alike, and will damage their delicate feet.

Indoor housing can consist of a large cage, with a plastic base (not metal mesh, this can damage the guinea pig's feet; wood will soak up urine permanently) and a large metal top half. As guinea pigs are not climbers, a top is only absolutely necessary if other pets are present in the house. A pet store cage is nowhere near adequate size for a happy guinea pig, and will cost in upwards of $45–50. The minimum size cage for 1-2 guinea pigs is 7.5 square feet. A good cheap option is buying or making a "C&C" cage made of metal mesh cubes (the organizer kind with small plastic connectors, for the outside) and Coroplast (the floor and walls) which is basically plastic cardboard you can buy at any sign store for a very low price. There are instructions at Cavy Cages

Bedding
The housing should be lined with bedding at a minimum of 1 inch deep, ideally deeper in the sleeping areas. You should never use softwoods such as pine or cedar shavings for bedding, as these emit harmful odors called phenols that cause your guinea pig respiratory problems. Hardwoods such as aspen are fine. Other options for bedding are recycled paper products such as Carefresh; these are more expensive, but also stay clean for longer than shavings and are easier on a guinea pig's feet. A cage needs to be cleaned generally every week at the very minimum, but more often as needed.

A newer form of guinea pig bedding is polar or anti-pill fleece. While this may seem strange at first, it is a very hygienic and cost-effective form of bedding. First, an absorbent layer must be in the bottom of the cage, because the function of fleece is to wick the urine away from the guinea pigs' feet. Most fleece users are happy to use 1-2 layers of towels on the bottom of their cage, topped with a single layer of fleece. So, when a guinea pig urinates on fleece bedding, the urine is wicked through the fleece and into the towels, where it is absorbed. Fleece needs to be washed at least once weekly, without fabric softener; it inhibits the fleece's ability to wick urine. It is also a good idea to wash it with an unscented detergent, and some white vinegar to absorb odors. For more information on using fleece as a bedding, please visit

Other essential accessories
Other items needed for your guinea pig's home will be a gravity-fed water bottle (cavies tend to spill and defecate in water bowls), a small bowl for pellets and other food, and "hidey houses". Wild cavy species and feral guinea pigs naturally use dens made by other animals, and all domestic guinea pigs should be provided a safe place to hide in. As they are prey animals, they will feel much more secure in their environments if they have places to hide. This can be a plastic "igloo" or wood house from a pet store, or simply a towel tent. Be aware that some cardboard is put together using glues that can be harmful to your guinea pig, so it is best to avoid these if you can. If you have more than one guinea pig, having both an entrance and an exit to any hiding places can prevent fights between cornered guinea pigs. The more hiding places, the merrier! It is also better for your guinea pigs to keep borders around the cage clear, so that they can run laps.

Toys
Unlike hamsters or rats, guinea pigs don't need fancy toys such as running balls or exercise wheels. Wheels and balls may have a picture of a guinea pig on the box, but you should not buy one for them to play with. A cavy's spine (and other bones) is much more fragile than other pet rodents, its feet are too soft, the balls are not properly ventilated for a larger animal such as a cavy. Mostly they like simple things like cardboard shoe boxes, towel tents, oatmeal tubes, paper bags and other tunnels or places to hide and chew on. Some owners give bird toys, but chewing the plastic is very bad for guinea pigs. Mirrors can be hung from outside the cage, however.

An item that is very dangerous and should be avoided is a guinea pig leash. Guinea pigs cannot be trained to walk, and it shouldn't be attempted. While this may seem like a good way to let them run about the yard safely, it is merely dangerous. They have very delicate spines and bones, which are easily damaged by a leash or harness.

An alternative way to get fresh air and fresh grass is an outdoor pen, but it should be used when you will be outside with the guinea pig the entire time. It is good to place their igloo/hut in there with them so if they become startled, they can hide. The igloo/hut will not suffice for sun protection, however, as it will keep in too much heat. You must be careful where you place the pen and must stay with the guinea pig at all times while they are outside in it. Also, it should be noted that if a guinea pig is to be outside, the grass it will be on cannot have had any pesticides or fertilizers on it. These chemicals will kill your guinea pig, and are very dangerous.

Food
A guinea pig's diet should be comprised of three basic groups; grass hay, pellets, and fresh treats. Most importantly, a guinea pig cannot make their Vitamin C (just like people) and will need it either in vitamin supplements (not droplets, these don't work as the C dissolves too rapidly in water) or in plenty of the right fruits and veggies. Of course, every guinea pig needs a water bottle (they tend to poop in water bowls, and it could get very unhealthy).

You should give one adult guinea pig approximately 1/8 cup pellets every day, possibly more for young ones. Pellets should be Timothy hay-based (little green ones), and not a seed mix. They can easily choke on seeds, and seeds are too fatty. Alfalfa-based hay pellets have too much calcium, and should not be fed for guinea pigs over 6 months of age.
 * Pellets

Providing your guinea pig as much Timothy hay or orchard grass as it can eat is very important for its health and happiness. Hay provides important digestive fiber and can prevent a condition in older boars where they lose the ability to defecate properly. Also, guinea pigs have a natural inclination to forage for food almost constantly, not giving them proper hay can cause them stress and result in barbering (chewing their own hair) and other behavioral problems. Alfalfa hay can be fed to guinea pigs younger than 6 months, but should not be fed to older guinea pigs other than the occasional treat. If you do not know the age of your guinea pig, or are unsure, use a different hay that is safe.
 * Hay

If you ever have a question about whether your guinea pig can eat a certain vegetable or fruit, and in which quantities, please visit this link:. It was made by a guinea pig dietary specialist, and is very helpful!
 * Fruits and vegetables

Guinea pigs like to eat lots of green veg, and on the whole this is very good for them, but there are a few things that should be left off your pets menu. Iceberg Lettuce causes bloat and gas, and so should be avoided, no exception. Tomato leaves are also not good for piggies. Carrot in excess can cause liver problems due to the excessive amounts of vitamin A, and in the pregnant cavy can cause birth defects. However, in small amounts to a non pregnant guinea pig, this is fine. Mushrooms and Rhubarb are poisonous. The best fruits and veggies for Vitamin C are Romaine lettuce, Carrot, Kale, Mustard greens, Red bell pepper, Spinach and many others. Oddly, oranges do not have very much vitamin C and can even cause the runs in guinea pigs. They need 10-20 MG of Vitamin C a day if they are healthy. If they are unhealthy, pregnant, or under 3 months, they should get 30-50 MG. For additional vitamin C, you can purchase vitamin C tablets. It is very important that you do not use vitamin C drops, as these can result in dehydration in guinea pigs. Do not give them multivitamins. These can be bad for them and even poisonous.

 * Other things to avoid
 * Mixes or treats with nuts, seeds, dried fruit and dyed pieces.
 * Dairy and meat products (cavies are herbivores)
 * Seeds in husks can be a choking hazard.
 * Cruciferous vegetables (cabbage, collards, bok choy, broccoli) may cause gas in your pet and are best offered sparingly and infrequently.
 * Mineral wheels. Never use Tang (which contains dyes, refined sugars, and very little vitamin C) in drinking water.
 * Commercial treats marketed for cavies (like yogurt drops) which can even be detrimental to their health. Consuming these empty calories (many contain fat, sugars and even excess calcium) can result in decreased consumption of the basic foods they really need. Guinea pigs are very strictly herbivores; therefore, they are lactose intolerant. Yogurt and honey are not good for guinea pigs, and should be avoided.

Problems
Before you bringing home your new guinea pig, you should locate your nearest veterinarian, and go in to the practice to pick up any leaflets or advice sheets on basic first aid for guineas. Staff should be knowledgeable, and will be able to help you with any other queries you might have about your guinea pigs. Make sure to visit a knowledgeable exotic pet veterinarian, as many regular cat and dog veterinarians have limited knowledge of cavies and some may refuse to treat them altogether.

Pain As guinea pigs are naturally prey animals, they instinctively hide pain to prevent appearing as a weak animal within the group. As a result it may be difficult to tell if they are hurting. If you notice changes in behavior, or unusual avoidance of handling, call your veterinarian for advice.

Parasites Guinea pigs can occasionally harbor skin (ecto-) parasites, which may not always be visible to the naked eye. Fortunately these parasites are not zoonotic, meaning your guinea pig cannot give them to you. Treatment with a topical product called Revolution(R) (active ingredient, selamectin) is a very effective method of controlling ectoparasites. Ivermectin is also effective, and is given either as an injection or orally. These medications must be prescribed by your veterinarian. It is not uncommon for pet store bought guinea pigs will harbor lice or mites. For this reason, it is a good idea to have a newly acquired guinea pig examined by a veterinarian before introducing the new cavy to other cavies in your home.

Teeth As guinea pigs are rodents, their teeth grow constantly. The constant availability of roughage (grass hay) is of critical importance in maintaining your guinea pig's dental health. It is also helpful, and fun for your guinea pig, if you include a chew stick (available in most pet shops) or piece of fruit wood for them to gnaw on. Dental examinations are an important part of your guinea pig's health plan. You can easily monitor the incisors (front teeth), but it is difficult to see the premolars and molars (cheek teeth) without an oral speculum. To see the incisors, hold your guinea gently but firmly in one hand, with one finger behind the head to support, lean your pet back. If this doesn't expose the teeth, gently push on the lips to show them. The teeth should appear straight; the top and bottom teeth should overlap only slightly (top over bottom- if they are the other way round, you should consult with your veterinarian). Normal incisors are off-white to yellow in color. Normal mandibular (lower) incisors often appear quite long to the untrained eye. If the incisors curve away from each other or are excessively long, consult your veterinarian. Never attempt to trim or clip your guinea pig's incisors by yourself. This may result in a fractured incisor, which is painful, and may cause further dental problems in the future.

Guinea pigs and other pets Obviously, cats, dogs and ferrets are predators and may kill a small furry creature. However, there are cases of guinea pigs getting along with them, and often as not cats may not know what to think of a guinea pig or even be scared of it. Dogs may be trained to accept guinea pigs as well. Chiefly, never leave a guinea pig alone with any predatory animal, however well-trained. Cohousing of guinea pigs with other rodents such as gerbils, rats and hamsters may increase instances of respiratory and other infections, and such rodents may act aggressively towards the guinea pig. Opinion is divided over the cohousing of guinea pigs and domestic rabbits. Some published sources say that guinea pigs and rabbits complement each other well when sharing a cage. However, as lagomorphs, rabbits have different nutritional requirements, and so the two species cannot be fed the same food. Rabbits may also harbor diseases (such as the respiratory infections Bordetella and Pasteurella), which guinea pigs are susceptible to. Even a dwarf rabbit is much stronger and more aggressive than the guinea pig and may cause intentional or inadvertent injury.

Breeding Pregnant sows have a 25% chance of having a fatal pregnancy complication. It is advisable to not breed guinea pigs, unless you know 100% of what you're doing, you're able to find homes for them, and you know what breeds can cause problems if they cross.

title: Animal Care/Guinea pig


text:
Organic Chemistry/Introduction to reactions/THF

THF stands for Tetrahydrofuran, and is a common ether-type solvent.

Structure
It is a 5 membered ring containing 4 carbons and one oxygen. It is very inert and thus makes a good solvent for many reactions.

Reactions

 * Oxymercuration/demercuration

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/


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User:Omegatron

No longer active
I am most active on en: Wikipedia:user:Omegatron

I started out contributing to the Electronics wikibook and the Robotics book, occasionally. (I have a bachelor's in electrical engineering, and I have built a few robots in my day.) I watched it turn into a complete mess, as a single person turned a book about Electronics into a grand unified book about Life, the Universe, and Everything. (Adding things like Brief History of the Universe, The Solar System, Evolution of the Earth's Atmosphere, Earthquakes and natural disasters, and Global Warming to the Analog Circuits section, which should have been about resistors, capacitors, and op-amps.) There are just too few people on Wikibooks to fight off such disruptions, so it just goes on uncontrolled.

It seems policies are decided the same way. Compare Administrators with Wikipedia:Administrators.

There's no clear distinction between where Wikipedia's goals end and Wikibooks' begin. I'm just going to focus on Wikipedia from now on.

"Next section" functionality
I think Wikibooks could really use "next"/"previous" functionality for sections. Wikipedia has soundly rejected such functionality several times, but Wikibooks is inherently a progression through topics. Here is a sandbox for myself to try some things:

User:omegatron/navtesting

and some bookmarks to related ideas:

 * meta:Help:Variable
 * meta:Help:Template
 * en:Template:Pope
 * Manual of Style

Spell checker
See en:User:Omegatron

title: User:Omegatron


text:
User talk:80.136.125.19

Auch die ausführlichen Artikel fett, würde ich sagen.

title: User talk:80.136.125.19


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User talk:217.1.206.56

Welche Wörter sollen denn kursiv sein und welche nicht?

 * Alle Alternativausdrücke, nicht jedoch Füllwörter wie "gefunden bei" usw., außerdem auch Namen von Zeitungen und Zeitschriften sowie von Büchern kursiv.

 * Bei vielen Begriffen sind die Alternativen aber nicht kursiv.

 * Stimmt, das soll aber nicht so bleiben.

 * Oder wie war das gemeint?

 * Jetzt klar?

title: User talk:217.1.206.56


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Field Guide/Wildflowers

 * /Western US and Canada/
 * /Eastern US and Canada/
 * /Western Europe and the British Isles/
 * /Eastern Europe/
 * /Alpine Region/
 * /Scandinavia/
 * /Australia and New Zealand/
 * /Mexico and Central America/
 * /Caribbean/
 * /Northern South America/
 * /Amazon Rainforest/
 * /Southern South America/
 * /Andean Region/
 * /India/
 * /Japan/
 * /Indonesia and Malaysia/
 * /Middle East/
 * /North Africa/
 * /Southern Africa/
 * /West Africa/
 * /Horn of Africa/
 * /Siberia/
 * /Central Asia/
 * /Caucasus/

title: Field Guide/Wildflowers


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Electronics/Aim

The aim of this textbook is to explain the design and function of electronic circuits and components. The text covers electronic circuit components, DC analysis, and AC analysis.

It should be useful to beginner hobbyists as well as beginner engineering students, teaching both theory and practical applications.

It should be thought of as a companion project to the Wikipedia articles about electronics. While Wikipedia covers many details about the technology used in electronics components and related fields, the Electronics Wikibook covers a lot of the "how-to" aspects that aren't covered in an encyclopedia. The book will focus on how to use the components to build useful circuits.

title: Electronics/Aim


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Talk:Field Guide/Wildflowers

The regions as I've defined them here are totally off the top of my ignorant head. Change at will. There's no reason there can't be broad guides and specific ones. If nothing else, a list of species present in Virginia would be useful for someone trying to identify Virginian wildflowers, and if the field guide entry for each species is on a different page, I don't see a problem with having that extra level of redundancy. There are surely specialized regions that should maybe be distinct in some way -- the Chesapeake Bay and the Everglades come to mind. TUF-KAT 22:48, 19 Mar 2004 (UTC)

Here's a blank template:

A few comments; judging by a look through what's been done so far, it doesn't look very well thought out: en.wikipedia.org/wiki/User:MPF 28 November 2004
 * 1) Use of common names can be very confusing; 'Twinflower' to many or most refers to Linnaea borealis, not (as given at Field Guide:Wildflowers - Western US and Canada) Dyschoriste oblongifolia. I've amended the template above to Scientific name.
 * 2) What is a 'wildflower'? Does it include: Woody plants (e.g. trees)? Plants other than Angiosperms (e.g. ferns, conifers)? Non-native naturalised plants? The title and coverage needs a lot more thinking.
 * 3) Scientific (metric) measurements should be the standard.
 * 4) The dark purple box color makes the type hard to read. A paler color would be better; I'd recommend following wikipedia's choice of light green (#90ee90) for plants.
 * Color changed

title: Talk:Field Guide/Wildflowers


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User:Vuara/Viet vowel cluster

1	a	ba 	(three) 	tác	tách	tam	tan	tang	tạp	tát 2	ă	tăm	(toothpick) 	tắc			tăn	tăng	tắp	tắt 3	â	cân 	(to weigh) 	bậc	bậch	tâm		tấng	tấp	tất 4	e	đem 	(to take) 	téc	téch	tem	lén	téng	tẹp	tét 5	ê	đêm 	(night) 	đếc	đếch		tên	têng	tếp	tết 6	i	vali 	(luggage) 	tíc	tích	tim	tin	ting	típ	tịt 7	o	cho 	(to give) 	óc	óch	nhóm	nhọn	ong	họp	tọt 8	ô 	tô 	(big bowl) 	tốc	rốch	tôm	tôn	tông	nộp	tốt 9	ơ	sơn	(to paint) 	tác	tách	tam	tan	tang	tạp	tát 10	u	thu 	(autumn) 	túc	ụch	túm	run	rung	rụp	lụt 11	ư	sư	(monk) 	tức	ứch	tưm	lừn	lưng	chựp	mứt 12	y	ly 	(glass) 13	ai	ai	(who) 	ai 14	ao	ao	(pond) 	ao 15	au	đau	(to be painful) 	au 16	âu	Âu	(Europe) 	âu 17	ây	ấy	(that) 	ây 18	eo	beo	(panther) 	eo 19	êu	kêu	(to order food) 	êu 20	ia	ỉa	(to have BM) 	ia 21	iê	biết	(know) 	iê	biến	biếc	thiêng 22	iêu	hiêu	(understand) 	iêu 23	iu	iu	(to be soggy) 	iu 24	oa	òa	(to burst into tears)	loạn	loạt 25	oặ	hoặc	(or) 	oặ 26	oai	oai	(to look stately) 	oai 27	oay	xoay	(turn on axis) 	oay 28	oe	oe	(to cry like baby)	oe 29	ôi	tôi	(I) 	ôi 30	ơi	với	(with) 	ơi 31	ua	cua	(crab) 	ua 32	uă	quăn	(to be curled) 	quắt 33	uâ	quất	(to dry up) 	quân 34	uai	quai	(handle) 	uai 35	uay	quay	(to spin) 	uay 36	uây	khuây	(to be at ease)	uây 37	ue	què	(to be crippled) 	quen	quét 38	uê	uế	(to be dirty) 	uê 39	ueo	queo	(to be dried up)	ueo 40	ui	ngửi	(sniff) 	ui 41	uô	thuốc	(medicine) 	uô	buốt 42	ươ	ướt	(wet) 	được	lươn 43	uôi	đuôi	(tail) 	uôi 44	ươi	ươi	(gorilla) 	ươi 45	ươu	bướu	(goiter) 	ươu 46	ưu	ưu	(to be excellent) 	ưu 47	uy	huýt	(to whistle) 	uy 48	uya	khuya	(late at night) 	uya 49	uyê	tuyết	(snow) 	tuyên 50	uyu	khuỷu	(elbow) 	uyu 51	yê	yên	(saddle) 	yê 52	yêu	yêu	(to love) 	yêu

title: User:Vuara/Viet vowel cluster


text:
Electronics/Definitions

Get ideas from here:

http://en.wikipedia.org/wiki/List_of_electronics_topics

(BUT WE ONLY WANT THINGS THAT MATTER TO A TWO YEAR LEVEL. No "quadrature amplitude modulation" or anything like that.)

SI Units and derived units

Definitions in Alphabetical Order:

Another order could be definitions by subject such as DC, AC, radio, integrated circuit, etc.

 * AC : Alternating current. Consists of a periodic oscillation between two different voltages.  Usually said to look like a sine wave, but is not always.

 * AM : Amplitude modulation. In radio communications, a signal controls the amplitude of a carrier wave that is at a much higher, constant frequency.  The carrier wave is filtered out and a loudspeaker plays based on the amplitude of the signal.

 * Ampere (A) : The SI unit for current I. (Commonly spoken as "amps", "milliamps", etc.)  The ampere is officially defined as that constant current which, if maintained in two straight parallel conductors of infinite length, of negligible circular cross-section, and placed one meter apart in vacuum, would produce between these conductors a force equal to 2×10-7 newton per meter of length.  There is another definition which is based on the deposition rate of silver (in electrolysis?), which is much easier to measure.  The other electronics units  are derived units based on the ampere definition.

 * Amplify : To increase the strength of the signal. Often an "amplifier" is used to pass a signal with both an increase or a decrease in gain.

 * Anode : An electron collector. Means up the path from a negative to a positive voltage.  An anode has a more positive voltage relative to a cathode.

 * Attenuate : Decrease the strength of a signal.

 * Band-Pass Filter : An analog filter that absorbs low and high frequencies (f) but allows a band of frequencies in the middle to pass through.

 * BJT : Bi-polar junction transistor. A transistor in which the resistance of the channel is controlled by a current at the gate.  Can be thought of as a current-controlled resistor.  FET is the other major type of transistor.

 * Capacitor : An electronics component that stores energy in the form of electric charge (static electricity). It resists a sudden change in voltage.

 * Cathode : An electron emitter. A cathode has a more negative voltage relative to some other place.

 * Choke : Another name for an inductor, specifically referring to those used in power regulation.

 * CMOS : Complementary metal oxide semiconductor. Complementary means that it has N-channel and P-channel transistors.  Metal oxide is the type of gate.  CMOS is a type of Integrated Circuit (IC) that is voltage based, since it is made of FETs.  Digital circuits tend to use very little current, because the paths for current flow are effectively open or closed circuits except during the transition between states.

 * Coil : A helix of wire (the same shape as a spring or Slinky). Its height, width, thickness, and material can all vary.  Used as an inductor.  The loops of wire can overlap.

 * Condenser : Another name for capacitor.

 * Conductance : The inverse of resistance. Measured in siemens (obsolete name mhos), which are the inverse of ohms.  1 S = 1/Ω = 1 A/V = 1 A2/W

 * Coulomb (C) : The SI unit for electric charge Q. Defined in terms of the ampere.  1 coulomb is the amount of electric charge carried by a current of 1 ampere flowing for 1 second.  It is also about 6.24×1018 times the charge on an electron.  1 C = 1 A·s

 * Current : The drift of electrons in an electric field. This is perceived as a flow.  It is measured in amperes.

 * Cycles per second (cps) : An obsolete name for hertz, the standard SI unit. As the name implies, a measurement of frequency in full cycles of a wave per second.   The unit cps (or kilocycles, megacycles, etc.) is more often seen in older documents.

 * dB : Decibel. Used to measure logarithmic ratios like signal to noise ratio (SNR), total harmonic distortion (THD), volume relative to a nominal level.  Similar to percent (%) in that it has no units.   dB SPL is used to measure sound levels relative to 20 micro-pascals (µPa).  dBu is used to measure voltage relative to 0.775 V.

 * DC : Direct current. A constant voltage and a constant current flow in one direction.

 * Diode : A one way valve for current. Semiconductor diodes typically have a voltage drop of 0.6 V (silicon) or 0.2V (germanium) when conducting in the forward direction.

 * EMF (E) : Electro-Motive Force. A force for moving electrons.  See Voltage.

 * Ethernet: is a family of frame-based computer networking technologies for local area networks (LAN). It defines a number of wiring and signaling standards for the Physical Layer of the standard networking model as well as a common addressing format and a variety of Medium Access Control procedures at the lower part of the Data Link Layer.

 * Farad (F) : The SI unit for capacitance (C). A capacitor is one farad if it has a coulomb (1 C) of charge on it with a voltage separation of a volt (1 V). 1 F = 1 C/V

 * FET : Field Effect Transistor. Can be thought of as an Electric Field Transistor.  A transistor in which the voltage at the gate controls the resistance of the channel.  (i.e. a FET has voltage-controlled resistance.)  BJT is the other major type of transistor.

 * FM : Frequency modulation. Changing the frequency of a carrier signal to represent the amplitude of the original signal.

 * Forward Biased : The voltage polarity through a part which causes it to conduct current.

 * Frequency (f) : The number of revolutions (cycles) per unit time. Usually expressed in either radians per second or cycles per second (Hz).

 * Gain : A multiplier of voltage or current.

 * Ground : Ground is defined as the point in the circuit which is at zero voltage. Voltage is relative, and is the same throughout a conductor, so any point in the circuit can be defined as ground, and all other voltages are referenced to it.  Usually it is defined as the most negative point in the circuit, for convenience.  Sometimes it is defined in the middle of two bi-polar rails, for "balanced" circuits. In many cases this circuit point is connected to the Earth (Ground) by some buried conductor.

 * Henry (H) : The SI unit for inductance. 1 H = 1 Wb/A

 * Hertz (Hz) : The SI unit for frequency. One Hz is one cycle per second.    1 Hz = 1/s

 * High-Pass Filter : An analog filter that absorbs low frequencies (f) but allows high frequencies to pass.

 * Horsepower (hp) : The amount of force F a horse can exert. I don't think it is related to horses anymore. 1 hp = 746 W

 * IC : Integrated circuit. A circuit constructed on one chip of semiconductor, rather than as discrete components.

 * Impedance : A more generalized form of resistance. The impedance of a device varies with the frequency of the electricity applied.  A perfect resistor will have a constant impedance for all frequencies.  Capacitors and inductors have varying impedances at different frequencies.  Measured in ohms.

 * Inductor : An inductor is a device that stores energy in a magnetic field. It opposes a sudden change in the flow of current.  A solenoid is usually shaped like a spring or a Slinky.

 * Joule (J) : The work required to exert a force of a newton (1 N) for a meter (1 m). 1 J = 1 N·m

 * LASCR : Light activated silicon controlled rectifier. A light activated SCR.

 * LDR : Light dependent resistor. As light intensity increases, its resistance decreases.

 * Length (l) : Distance is measured in meters (m).

 * Low-Pass Filter : An analog filter that absorbs high frequencies (f) but allows low frequencies to pass.

 * Magnetron : A special form of vacuum tube, typically used as the microwave emitter in a microwave oven, or in Radar systems.

 * Meter (m) : The SI unit for distance. The distance light travels in 1/299,792,458 second.

 * MOSFET : Metal-oxide-semiconductor field effect transistor. An FET that uses a thin layer of oxide (usually silicon) to insulate the gate terminal from the underlying channel

 * Ohm (Ω) : A measure of resistance or impedance. 1 Ω = 1 V/A = 1 W/A2

 * Op-amp : Short for operational amplifier. An op-amp amplifies the voltage between its two inputs.

 * Oxidation : A reaction where something loses electrons. Given that oxygen will strip electrons from most elements, this has historically meant a reaction involving oxygen.  A cathode (electron emitter) is constantly oxidized as it looses electrons.

 * PCB : Printed circuit board. This is a piece of plastic or fiberglass with copper attached.  The copper is typically chemically etched away to leave "traces" for the electricity to be conducted through.  Other electrical components are soldered to the traces.

 * Period : The time between cycles of a periodic wave.

 * PM1 : Phase modulation. Sending information by modifying relative phases.

 * PM2 : Pulse modulation. Sending information in binary pulses.

 * Power : Voltage times current. The amount of work being done by a circuit.

 * Rectify : Convert AC current to DC current.

 * Redox : A reaction where oxidation and reduction take place. A cathode (electron emitter) is oxidized (loses electron).  The electron travels and is absorbed by an anode (electron acceptor) that is reduced (gains electron).

 * Reduction : A reaction where something gains electrons. In gaining electrons its charge value is reduced.  An anode (electron acceptor) is constantly reduced as it gains electrons.

 * Resistance : Properties of a circuit that impede the flow of electrons. Resistance converts electrical energy into photons that are given off as waste heat.  Resistance is measured in ohms.

 * Reversed Biased : The inverted voltage polarity on a part.

 * Root-Mean Squared (RMS) : The effective DC value for an AC value.

 * SCR : Silicon-controlled rectifier.

 * Second (s) : The SI unit for time.

 * SI : The standard system of units.

 * SMT : Surface mount technology. This is a circuit built on a PCB with the components soldered directly to pads on the surface, without going through the board.  The components and boards are usually much more compact than through-hole boards.

 * Speed of light : Varies depending on the medium it is traveling through. Maximum speed c of 299,792,458 m/s is only in a perfect vacuum.  Light has been slowed down to less than 17 m/s (~40 mph) in special mediums.

 * Speed of wave propagation (v) : Speed that an electromagnetic wave travels through air, cables, or wires. A typical speed for a typical coax cable is (2/3)·c.

 * Thermistor : Temperature based resistor. As temperature increases resistance decreases.

 * Thyristor : A type of electronic switch. It has two states which are triggered by another voltage or current.  SCRs and switching transistors are examples of thyristors.

 * Tesla (T) : Unit of magnetic flux density. 1 T = 1 Wb/m2

 * Through-hole : This means the circuit is built on a PCB with holes drilled in it for the component leads to go through. The leads are soldered on the other side of the board.

 * Time (t) : The symbol for time in seconds (s).

 * Transformer : Used to raise or lower the AC voltage between two circuits. This is based on the ratio of turns between the two coupled inductors.  Transformers operate by way of induction between two inductors.

 * Triode : A three-element vacuum tube.

 * TTL : Transistor-Transistor Logic

 * Volt-amperes (VA) :

 * Voltage AC (VAC) : AC Voltage

 * Voltage-amperes reactive (VAR) : Reactive voltage.

 * Variac : A type of transformer with a movable tap to provide a variable output voltage. Also "Powerstat".

 * Volt (V) : A potential due to an electric field. One volt is defined as the potential difference across a resistor that is passing one ampere and dissipating one watt. 1 V = 1 W/A

Volt

 * (changed to demonstrate subsection headings)
 * A potential due to an electric field. One volt is defined as the potential difference across a resistor that is passing one ampere and dissipating one watt. 1 V = 1 W/A

 * Voltage (V) : An electric field between two charges. Similar to gravity this acts as an electric potential.  Measured in volts.

 * VCC : Common-collector voltage source (+). This is an alternate label for the power supply in electronic diagrams for BJT-based circuits such as common-collector amplifiers. (There is also VEE, VDD, VSS do we want one for each?) That might work if they were grouped together.
 * http://encyclobeamia.solarbotics.net/articles/vxx.html
 * http://www.control.com/1026184337/index_html

 * Watt (W) : A measure of power (P). A watt is a joule (1 J) of work done in a second (1 s). 1 W = 1 J/s

 * Wavelength (λ) : The distance between two peaks of a wave.

 * Weber (Wb) : Unit of magnetic flux. 1 Wb = 1 V·s

to be merged
superfluous stuff from "overview of electronics", which should be merged in with these definitions:

Charge: Particles can have three possible types of charge: positive, negative, or neutral (no charge). Electrons are negatively charged, protons are positively charged, and neutrons are (surprise!) neutral. Opposite charges tend to attract, while particles with the same charge (both positive or negative) tend to repel.

Electricity: the flow of electrons.

Electronics: is the study of gadgets that use electricity, typically creating or handling signals, not just switching power.

??? are devices which take in input, perform some function, and return some output, through the use of electricity.

Circuit: The path electrons take as they are pushed by some power source, flow through various electrical components in a gadget, and return to the power source.

Electric Field: field created by the presence of charge. The field represents the force that would be felt by a positive charge.

Voltage: Accelerates charge.

Voltage is a gravity-like potential due to the separation of a negative and a positive charge. Voltage accelerates negatively charged electrons from the negative to the positive charge, and accelerates positive charged protons and ions the other way. Pushing accelerates the charges in what is known as current.

Resistance: When moving electrons (current) collide with atoms, energy is given off as heat. Resistance is the measure of a material's tendency to cause this type of energy loss. Resistance acts to limit the flow of current due to a given voltage. As the resistance becomes infinite the current stops flowing and becomes an open circuit. When there is no resistance the circuit shorts and the current becomes infinite. (Current 'prefers' the path with the lowest possible resistance.)
 * Air has higher resistance than wire.

Resistor: A device whose primary use is to provide resistance.

Short Circuit: there is no resistance between two points. Current flows without a change in voltage.

Open Circuit: there is infinite resistance between two points. Current is unable to flow, but there is still a voltage between the two points.

Voltage Source creates a voltage, which creates a current.

Current Source, which creates a current and a voltage for the current.

Voltage Drop When the current goes through resistance it loses some of the push of the voltage.

When the current comes to an intersection it has multiple paths it can take and flows according to its resistance.

Permittivity: (ε) A measure of how much energy a material absorbs in response to an electric field. Materials (εr) absorb more energy than the vacuum (ε0). The permittivity of a material is known as its dielectric constant.

Cell: Two materials with a voltage difference between them.

Capacitor: Two metal plates with a gap between them. Voltage causes charge to drain from one plate and accumulate on the other plate. This charge separation creates a voltage in the capacitor that opposes the other voltage and stops the flow of current. When a dielectric is placed between the plates it weakens the electric field between the plates and allows more charge to accumulate.

Capacitance: Any two pieces of conducting material separated by some distance have capacitance. Simply, a measure of the tendency of some configuration of metal to act as a capacitor.

Inductor: A coil of wire. Current starts to flow through the wire and creates a magnetic field. This magnetic field creates an opposing magnetic field which stops the current through the wire. Over time the inductor stops opposing current and turns into a wire.

Transformer Two connected inductors, which operate through mutual inductance. Current flows through the first inductor and creates a magnetic field that is fed to the second inductor. In response the second inductor creates an opposing magnetic field and current. Having a permanent magnet between the two inductors intensifies their magnetic fields.

Vacuum tube: An arrangement of two or more electrodes in a vacuum. Typically placed in a glass bulb to keep air from leaking in.

Triode: The first electrical amplification device. A triode is a type of vacuum tube with three connections:
 * The cathode emits electrons.
 * The anode accepts electrons.
 * The 'grid, placed in the middle, which controls the flow of electrons from the cathode to the anode.

Diode: A 2 wire device that allows current to flow easily in only one direction.

Transistor: A 3 wire device, with one wire (the "base" or "gate") that controls the flow of electrons between the other 2 wires. Replaced vacuum tubes.

Light waves: (Electromagnetic waves)

title: Electronics/Definitions


text:
Trigonometry/The Unit Circle

The Unit Circle is a circle with its center at the origin (0,0) and a radius of one unit.

Angles are always measured from the positive x-axis (also called the "right horizon"). Angles measured counterclockwise have positive values; angles measured clockwise have negative values.

Defining sine and cosine in terms of the unit circle
In the unit circle shown here, a unit-length radius has been drawn from the origin to a point (x, y) on the circle.

A line perpendicular to the x-axis, drawn through the point (x, y), intersects the x-axis at the point with the abscissa x. Similarly, a line perpendicular to the y-axis intersects the y-axis at the point with the ordinate y. The angle between the x-axis and the radius is $$\alpha$$.

So, we can say that the sine of an angle is the ordinate of the point on the unit circle at that angle, and the cosine of an angle is the abscissa of the point on the unit circle at that angle.

We define the basic trigonometric functions of any angle $$\alpha$$ as follows:

$$ \begin{matrix} \mathrm{sine:} & \sin(\alpha) & = & y \\ \mathrm{cosine:} & \cos(\alpha) & = & x \\ \end{matrix} $$

$$\tan(\theta)$$ can be algebraically defined.

$$\tan(\theta)=\frac{\sin(\theta)}{\cos(\theta)}\qquad\cos(\theta)\ne0$$

$$\tan(\alpha)=\frac{y}{x}\qquad x\ne0$$

These three trigonometric functions can be used whether the angle is measured in degrees or radians as long as it specified which, when calculating trigonometric functions from angles or vice versa.

Alternative definitions

 * A previous chapter used Soh-Cah-Toa to define the trigonometric functions. The advantage of the unit circle is that θ can be extended outside the first quadrant $$\left[0,\frac{\pi}{2}\right]$$, which allows us to define these functions on the interval $$(-\infty,\infty)$$.
 * If trigonometry is applied to vectors, it is more convenient, if the radius of the circle is not equal to unity. For example, if vector A has magnitude $$A=\left|\mathbf{A}\right\vert$$:

$$ \begin{matrix} x=r\cos(\alpha)&\to & \mathbf{A}_x=\mathbf{A}\cos(\alpha) \\ y=r\sin(\alpha)&\to & \mathbf{A}_y=\mathbf{A}\sin(\alpha) \\ r=\sqrt{x^2+y^2}&\to & \mathbf{A}=\sqrt{\left(\mathbf{A}_x\right)^{2}+\left(\mathbf{A}_y\right)^{2}}\\ \end{matrix} $$

It is important to know why the above equations are true. Knowing $$\cos(\alpha)=\frac{x}{r}$$, $$r\cdot\cos(\alpha)=r\cdot\frac{x}{r}=x$$. The same could be said for the definition for $$y$$. Finally, the final line is the Pythagorean identity.

Video links
More about this topic can be found at the 'Khan Academy:'

 * The unit circle definition of trigonometric function
 * Unit circle definition of trig functions

Some values for sine and cosine
A unit circle with certain exact values marked on it is below:

Unit circles form the basis of most analog clocks and animations on computers since the cos and sin correspond to the x and y positions of the end of the line segments representing the hands of the clock.

The unit circle on the left has the degree, the radian, and the coordinate value on the unit circle. For a coordinate value $$(x,y)$$, if walking around the circle $$\frac{\pi}{3}$$ radians anti-clockwise from the horizontal axis, the coordinate value at which the person walked around the circle is $$\left(\frac{1}{2},\frac{\sqrt{3}}{2}\right)$$.

Remember that on a unit circle, the angle $$\theta$$ anti-clockwise from the horizontal axis gives $$\cos(\theta)=x$$ and $$\sin(\theta)=y$$. The same is true for radians. As such, for $$(x,y)$$ corresponding to $$(\cos(\theta),\sin(\theta))$$ on the unit circle, $$\frac{\pi}{3}$$ radians when substituted in the cosine or sine function is the coordinate value on the unit circle. That is:
 * $$\left(\cos\left(\frac{\pi}{3}\right),\sin\left(\frac{\pi}{3}\right)\right)\to\left(\frac{1}{2},\frac{\sqrt{3}}{2}\right)$$, OR, equivalently,
 * $$\left(\cos\left(60^{\circ}\right),\sin\left(60^{\circ}\right)\right)\to\left(\frac{1}{2},\frac{\sqrt{3}}{2}\right)$$

The unit circle is very useful to your mathematical studies of trigonometry because it tells you the EXACT value of certain angles. Later, you will learn how to find other ratios of angles and radians without needing to rely on the special values of the unit circle – 30, 45, 60, and 90.

It is worth your time memorizing some of the values of sine and cosine on the unit circle (cosine is equal to $$x$$ while sine is equal to $$y$$). You should at least become familiar with the values for $$0^\circ, 30^\circ 45^\circ, 90^\circ$$ and know where $$\frac{\pi}{2},\pi,\frac{3\pi}{2},2\pi$$ are on the unit circle.

If you have some trouble memorizing the values, here are some helpful hints and patterns. Try to find some more other than what is listed.
 * The coordinate value $$(x,y)$$ on the unit circle has the $$\text{numerator}$$ decrease from $$\sqrt{3}$$ in the $$x$$-value coordinate at $$\frac{\pi}{6}$$ to $$\sqrt{1}=1$$ at $$\frac{\pi}{3}$$. The denominator is always $$2$$. Here, see what we mean. Ignore the y-value for now:
 * $$\left(\frac{\sqrt{3}}{2},\sin\left(\frac{\pi}{6}\right)\right)$$, $$\left(\frac{\sqrt{2}}{2},\sin\left(\frac{\pi}{4}\right)\right)$$, $$\left(\frac{1}{2},\sin\left(\frac{\pi}{3}\right)\right)$$.
 * Like the $$x$$-value coordinate, the $$y$$-value coordinate has a pattern in the numerator. As the angle increases, between $$30^\circ$$ and $$60^\circ$$ (inclusive), the $$\text{numerator}$$ increases from $$\sqrt{1}=1$$ in the $$y$$-value coordinate at $$\frac{\pi}{6}$$ to $$\sqrt{3}$$ at $$\frac{\pi}{3}$$. From the above bullet, putting it together, you get the following pattern:
 * $$\left(\frac{\sqrt{3}}{2},\frac{1}{2}\right)$$, $$\left(\frac{\sqrt{2}}{2},\frac{\sqrt{2}}{2}\right)$$, $$\left(\frac{1}{2},\frac{\sqrt{3}}{2}\right)$$.
 * Certain radian values are simply reflections of the other. Take a look at the ones with the same denominator and see if you can correspond any patterns to what you see.

If you are to ever be tested on this, make a quick sketch of the first quadrant of the circle, and remember the pattern that underlies the unit circle.

 * What angle (a) in degrees and (b) in radians do the hour and minute hands of a clock move through in:
 * One hour
 * One minute
 * How far apart in degrees are the hour and minute hand at five minutes past five? (you should take into account that the hour hand is not exactly at the five, but has moved a little further)

title: Trigonometry/The Unit Circle


text:
Trigonometry/Geometric Definitions of Trig Functions

Geometrically defining tangent
In the previous section, we algebraically defined tangent as $$\displaystyle\tan\theta=\frac{\sin\theta}{\cos\theta}$$, and this is the definition that we will use most in the future. It can, however, be helpful to understand the tangent function from a geometric perspective.

A line is drawn at a tangent to the unit circle: (i.e. $$x = 1$$). Another line is drawn from the point on the radius of the circle where the given angle falls, through the origin(O), to a point (Q) on the drawn tangent. The ordinate (QP) of this point is called the tangent of the angle.

The slope of the line OQ = $$\frac {KC}{OC}$$ and as we mentioned before

KC = sin(θ) , OC = cos(θ)

Hence, the Slope of the line OQ = $$\frac {\sin(\theta)}{\cos(\theta)}$$

and also the slope of OQ = $$\frac {QP}{OP}$$ = $$\frac {QP}{1}$$ = $$\frac {\tan(\theta)}{1}$$ = tan(θ)

Hence, we can deduce that tan(θ) = $$\frac {KC}{OC}$$ = $$\frac {\sin(\theta)}{\cos(\theta)}$$ = QP = the ordinate of the point Q = the slope of OQ

Domain and range of circular functions
Any size angle, positive or negative, can be the input to sine or cosine — the result will be as if the largest multiple of 2π (or 360°) were subtracted from or added to the angle. The output of the two functions is limited by the absolute value of the radius of the unit circle, $$|1|$$.

$$ \begin{matrix} & \mathrm{domain}&\mathrm{range} \\ \mathrm{sine} & \mathbb{R} & [-1,1] \\ \mathrm{cosine} & \mathbb{R} & [-1,1] \\ \end{matrix} $$

R represents the set of all real numbers.

No such restrictions apply to the tangent, however, as can be seen in the diagram in the preceding section. The only restriction on the domain of tangent is that odd integer multiples of $$\frac{\pi}{2}$$ are undefined, as a line parallel to the tangent will never intersect it.

$$ \begin{matrix} & \mathrm{domain}&\mathrm{range} \\ \mathrm{tangent} & \mathbb{R} \setminus \left \{ \cdots,-\frac{\pi}{2},\frac{\pi}{2},\frac{3\pi}{2},\frac{5\pi}{2},\cdots \right \} & \mathbb{R} \\ \end{matrix} $$

for a deep understanding of trigonometric functions explore this Applet

Applying the trigonometric functions to a right-angled triangle
If you redefine the variables as follows to correspond to the sides of a right triangle:

• x = a (adjacent) • y = o (opposite) • a = h (hypotenuse)

Next Page: Right Angle Trigonometry

Previous Page: The unit circle

Home: Trigonometry

Matemática elementar/Trigonometria/Razões trigonométricas na circunferência


text:
Trigonometry/Thales Theorem

= Construction of Right Triangles = Right triangles are easily constructed. Recall that a diameter is a straight line which starts at one point on the circle and goes through the center to the other side. Using this property of a circle:

 * 1) Construct a diameter of a circle. Call the points where the diameter touches the circle a and c.
 * 2) Choose a distinct point b on the circle (any point that is neither a nor c).
 * 3) Construct line segments connecting points a, b and c.

Provided the above three directions are followed, the resulting triangle Δabc will be a right triangle. This result is known as Thales' theorem.

This right triangle can be further divided into two isosceles triangles by adding a line segment from b to the center of the circle.

To simplify the following discussion, we specify that the circle has diameter 1 and is oriented such that the diameter drawn above runs left to right. We shall denote the angle of the triangle at the right θ and that at the left φ. The sides of the right triangle will be labeled, starting on the right, a, b, c, so that a is the rightmost side, c the leftmost, and b the diameter. We know from earlier that side b is opposite the right angle and is called the hypotenuse. Side a is opposite angle φ, while side c is opposite angle θ. We reiterate that the diameter, now called b, shall be assumed to have length 1 except where otherwise noted.

By constructing a right angle to the diameter at one of the points where it crosses the circle and then using the method outlined earlier for producing binary fractions of the right angle, we can construct one of the angles, say θ, as an angle of known measure between 0 and π / 2. The measure of the other angle φ is then π - π/2 - θ = π/2 - θ, the complement of angle θ. Likewise, we can bisect the diameter of the circle to produce lengths which are binary fractions of the length of the diameter. Using a compass, a binary fractional length of the diameter can be used to construct side a (or c) having a known size (with regard to the diameter b) from which side c can be constructed.

= Using Right Triangles to find Unknown Sides =

Finding unknown sides from two other sides
From the Pythagorean Theorem, we know that:

 * $$a^2 + b^2 = c^2. \,$$

Recall that c (the diameter/hypotenuse in the above example) has been defined as having a length of one, therefore:

 * $$b^2 = 1 - a^2. \,$$

permits us to calculate the length of b squared. It may happen that b squared is a fraction such as 1/4 for which a rational square root can be found, in this case as 1/2, alternatively, we could use Newton's Method to find an approximate value for b.

Finding unknown sides from one side and one (non-right) angle
As any triangle could be compared to our basic triangle (formed from a circle with a diameter of one), a table enumerating the relationships between angles and side lengths would be very useful to understanding the properties of any triangle. However, such a table would be unwieldy in practice and it is often not necessary to know the exact value.

Of course, given an angle $$\theta$$, we could construct a right angled triangle using ruler and compass that had $$\theta\,$$ as one of its angles, we could then measure the length of the side that corresponds to a to evaluate the $$\cos$$ function. Such measurements would necessarily be inexact; it would be a problem in physics to see how accurately such measurements can be made; using trigonometry we can make precise predictions with which the results of these physical measurements can be compared.

The most common way of communicating the idea that relationships exist without providing exact details takes the form of a 'function'. A function is like a machine that takes some simple input and produces some simple output. Usually a function defines some kind of rule ([| Function]) and provides us a handy notation useful in trigonometry. That way, we know that we're using a certain relationship without needing to know the exact numerical values. Basic trigonometric functions are simply stand-ins for the relationship between angles and sides of a triangle.

One such function, which allows us to know the relationship between any value of $$\theta\,$$ and the corresponding value of $$a\,$$ is called the cosine or $$\cos\,$$. This universal relationship is represented as: $$\frac{a}{c} = \cos\theta$$ which would save us the work of constructing angles and lengths and making difficult deductions from them.

This means that if you know the cosine of an angle, you also know the relationship between the lengths of the sides. The actual size of the triangle can be bigger or smaller, but the mathematical relationship represented by the cosine does not change so long as the size of the angle remains constant.

Cosine example
Some explicit values for the cos function are known. For $$\theta\, = 0$$, sides $$a\,$$ and $$c\,$$ coincide: $$a = c = \frac{a}{c} = 1$$, so $$\cos\left(0\right) = 1$$. For $$\theta = \frac{\pi}{2}$$, sides $$b\,$$ and $$c\,$$ coincide and are of length 1, and side $$a\,$$ is of zero length, consequently $$a\, = 0$$, $$c\, = 1$$. $$\frac{a}{c} = 0$$ and $$\cos\frac{\pi}{2} = 0$$.

The simplest right angle triangle we can draw is the isosceles right angled triangle, it has a pair of angles of size $$\frac{\pi}{4}$$ radians, and if its hypotenuse is considered to be of length one, then the sides $$a\,$$ and $$b$$ are of length $$\sqrt{\frac{1}{2}}$$ as can be verified by the theorem of Pythagoras. If the side $$a\,$$ is chosen to be the same length as the radius of the circle containing the right angled triangle, then the right hand isosceles triangle obtained by splitting the right angled triangle from the circumference of the circle to its center is an equilateral triangle, so $$\theta$$ must be $$\frac{\pi}{3}$$, and $$\phi$$ must be $$\frac{\pi}{6}$$ and $$b\,^2$$ must be $$1 - \frac{1}{2}\cdot\frac{1}{2} = \frac{3}{4}$$.

= Properties of the cosine and sine functions=

Period
A full revolution is an angle of 2π radians, so increasing an angle by this amount gets you exactly back to your starting point. Therefore, a perfect circle is maintained, along with the relationships formed by triangles within, by adding 2π to any angle θ. This is called the period, --the size of the angle or the time period over which the relationships begin to repeat (correlating the two is complex, and allows us to talk about wave theory).

Using functions, we can represent this fact in terms of the cosine function by stating that : $$\cos\theta = \cos\left(\theta + 2\pi n \right),\,$$

Knowing the period of the sine and cosine functions (and by derivation, that of other functions) is useful because it means that we can substitute one angle for another when we know that the period is the same. This helps in calculations, such as when there is the need to add or subtract angles.

Half Angle and Double Angle Formulas
We can derive a formula for cos(θ/2) in terms of cos(θ) which allows us to find the value of the cos function for many more angles. To derive the formula, draw an isosceles triangle, draw a circle through its corners, connect the center of the circle with radii to each corner of the isoceles triangle, extend the radius through the apex of the isoceles triangle into a diameter of the circle and connect the point where the diameter crosses the other side of the circle with lines to the other corners of the isoceles triangle.

Therefore:

$$\cos (\theta /2) = \sqrt{\frac {1 + \cos \theta}{2}}$$

which gives a method of calculating the cos of half an angle in terms of the cos of the original angle. For this reason * is called the "Cosine Half Angle Formula".

The half angle formula can be applied to split the newly discovered angle which in turn can be split again ad infinitum. Of course, each new split involves finding the square root of a term with a square root, so this cannot be recommended as an effective procedure for computing values of the cos function.

Equation * can be inverted to find cos(θ) in terms of cos(θ)/2:

$$\begin{matrix}&\cos (\theta /2) =  \sqrt{\frac{1 + \cos (\theta)}{2}}\\ \Rightarrow &  \cos^2(\theta/2)  =  \frac{1 + \cos(\theta)}{2} \\ \Rightarrow &  \cos^2(\theta/2) - \frac{1}{2}  =  \frac{\cos (\theta)}{2}  \\ \Rightarrow & 2\cos^2(\theta/2) - 1   =  \cos(\theta) \\ \end{matrix} $$

substituting $$\delta\ = \frac{\theta}{2}$$ gives:

$$2\cos^2(\delta) - 1    = \cos(2\delta) \,$$

that is a formula for the cos of double an angle in terms of the cos of the original angle, and is called the "cosine double angle sum formula".

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Home: Trigonometry

Matemática elementar/Trigonometria/Trigonometria do Triângulo Retângulo

title: Trigonometry/Thales Theorem


text:
File:Otto Engineering Thermodynamics.png

Otto cycle

prologues := 2; beginfig(1); numeric u; u := .4cm; drawarrow (0, 0) -- (10u, 0); label.bot("V", (10u, 0)); drawarrow (0, 0) -- (0, 10u); label.lft("p", (0, 10u)); vardef arrowhead expr p = save A,u,a,b; pair A,u; path a,b; A := point length(p)/2 of p;   u := unitvector(direction length(p)/2 of p); a := A{-u}..(A - ahlength*u rotated 30); b := A{-u}..(A - ahlength*u rotated -30); (a & reverse(a) & b & reverse(b))--cycle enddef; pair p, q, r, s; p := (2u, 8u); q := (7u, 3u); s := p shifted -(0, 3u); r := q shifted -(0, u); dotlabel.lft("1", s); drawarrow s .. p; dotlabel.lft("2", p); drawarrow p .. controls (((p + q)/2) shifted -(.7u, .7u)) .. q; dotlabel.rt("3", q); drawarrow r .. controls (((s + r)/2) shifted -(.5u, .5u)) .. s; dotlabel.bot("4", r); drawarrow q .. r; currentpicture := currentpicture scaled 2; currentpicture := currentpicture shifted -llcorner currentpicture; endfig; end;


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File:Si bandgap.png

Silicon Bandgap diagram

title: File:Si bandgap.png


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File:GaAs bandgap.png

GaAs Bandgap

title: File:GaAs bandgap.png


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File:Carrier density.png

Carrier density for doped semiconductor

title: File:Carrier density.png


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Cookbook:Zupa Ogórkowa (Polish Cucumber Soup)

 * Polish cuisine | Soup

Zupa ogórkowa is a traditional Polish soup made out of sour, salted cucumbers.

Ingredients

 * 4 chicken wings
 * 1 small leek (or 1 small onion)
 * 2 carrots
 * ½ celery root (optional)
 * 1 parsnip root
 * 3 medium potatoes
 * 3 big sour-salted (pickled) cucumbers
 * 1 tablespoon butter
 * 1 teaspoon flour
 * 2 bay leaves
 * 3 pimentos
 * Salt
 * Pepper
 * 1–2 tablespoons of cream or half and half (optional; yoghurt is also acceptable but not traditional)

Procedure

 * 1) Put the chicken wings, salt, pepper, bay leaves and pimentos into a saucepan or stock pot with 1.5 L (1½ quarts) cold water. After bringing it to a boil, let it simmer for 25 minutes on low heat.
 * 2) Add the peeled carrots, celery root, parsnip root, and leek, and boil it for 10 more minutes. During that time peel the potatoes and dice them into quarter inch (cubes 0.25 x 0.25 inches).
 * 3) Take out the leek, and add the potatoes to the pot. Boil them for 10–12 minutes and make sure the potatoes are cooked through.
 * 4) Grate the sour-salted (pickled) cucumbers and put them into a sauté pan with the melted butter. Sauté for 2 minutes, and add the flour and constantly stir it over low heat.
 * 5) Add ½–⅓ cups of water to the sauté pan and continue stirring.
 * 6) When the potatoes are cooked, add the prepared sour cucumber preparation to the stock pot and mix them well. Boil for 3–5 minutes and season the soup to taste. If you like, mix some soup with cream or sour cream in a small cup and add it to the pan, or a smaller amount to each individual serving.
 * 7) Bon appétit! Smacznego!

Notes, tips, and variations

 * It is very important to add the potatoes first, and then the sour cucumbers. If you add them in reverse order, the potatoes will not be cooked through.


text:
Cookbook talk:Wiejska (Polish Pork and Veal Sausage)

This module used text origionally published in the Wikipedia article Kielbasa. The page history of the article at the time the text was transfered is included below:

* (cur) (last). . 06:57, 13 Mar 2004. . Halibutt * (cur) (last). . 02:34, 13 Mar 2004. . Sfdan (Settlers in the United States) * (cur) (last). . m 21:50, 16 Feb 2004. . Cogibyte (Spelling) * (cur) (last). . m 17:55, 2 Jan 2004. . Halibutt * (cur) (last). . 09:30, 17 Dec 2003. . 194.129.50.189   * (cur) (last). . 09:18, 4 Dec 2003. . 217.44.152.179   * (cur) (last). . 04:15, 18 Nov 2003. . Gentgeen (wikified, format) * (cur) (last). . m 21:32, 20 Oct 2003. . Jerzy (Copy edit) * (cur) (last). . m 00:51, 9 Oct 2003. . Robbot (Robot-assisted disambiguation Baden) * (cur) (last). . m 23:31, 6 Oct 2003. . 217.85.202.66 (Andre Engels: Robot-assisted disambiguation America) * (cur) (last). . 23:36, 9 Sep 2003. . 24.229.11.78 (Got rid of the ref. to Polish sauage. Added marjoram to recipe. Added note about ice.) * (cur) (last). . m 08:34, 4 Sep 2003. . Sannse (Disambiguating German) * (cur) (last). . 07:19, 29 Aug 2003. . Wirehead (Minor polish deli factoid) * (cur) (last). . 19:57, 28 Aug 2003. . 67.4.153.240 (This user uses far too many capital letters. (Everyone who writes about recipes does that, apparently. Maybe we need to gang up on them and fix the problem.)) * (cur) (last). . 19:23, 28 Aug 2003. . Thoth * (cur) (last). . 19:21, 28 Aug 2003. . Thoth * (cur) (last). . 19:17, 28 Aug 2003. . Thoth * (cur) (last). . 19:15, 28 Aug 2003. . Thoth

This module was the featured recipe on the main Cookbook page from May, 16, 2004 - May 23, 2004. Gentgeen 12:33, 23 May 2004 (UTC)

Naming
Wiejska is in Polish a singular, feminine adjective. When trying to specify the name of this meal you should use also kiełbasa word to avoid confusion. We may say that wiejska describes something but we don't know what until we point on kiełbasa!

So, the proper, full name of this meal is kiełbasa wiejska — this also should be reflected in the names of articles considering this matter and in a way that meal is referred to.

193.0.96.15 12:15, 21 April 2006 (UTC) Konrad


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Cookbook:Wiejska (Polish Pork and Veal Sausage)

| Cuisine of Poland | Sausage | Meat Recipes

Wiejska is the most popular form of Kielbasa, or Polish sausage, in the United States.

Ingredients

 * 1½ lb lean boneless pork
 * ½ lb boneless veal (optional)
 * 1 tsp salt
 * 1 tsp pepper
 * 1 tsp marjoram
 * 2–3 cloves garlic, crushed
 * 1 tbsp mustard seed
 * ¼ cup crushed ice
 * Sausage casing

Procedure

 * 1) Cut the meat into small chunks, then grind it with the seasonings and ice, and mix this well.
 * 2) Stuff the meat mixture into the casing. When making sausage by hand, tie a knot about 3 inches (76 mm) from one end of a cleaned sausage casing and fix the open end over the spout of a wide-based funnel, easing most of the casing up onto the spout. Then spoon the mixture into the funnel and push it through into the casing with your fingers.
 * 3) Knot the end and roll the sausage gently on a firm surface to distribute the filling evenly.
 * 4) Smoke in an outdoor smoker following the manufacturer's directions; alternatively, place the sausage in a casserole, cover it with water, and bake about 1.5 to 2 hours at 350°F until water is absorbed.

Notes, tips, and variations

 * The purpose of the ice is to keep the fat in the pork solid, which is very important in the final texture of the sausage.
 * If you do not add the veal, then add 1 lb additional pork.

Warning

 * While this sausage is typically prepared in a cured form, the above recipe is for fresh sausage. As such it must be fully cooked before eating in order to prevent food poisoning. Alternatively, this sausage can be prepared as a cured product.


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Cookbook:Rosół (Polish Meat Soup)

| Cuisine of Poland | Soup

Rosół is a traditional Polish meat broth. The most popular variety is Rosół z kury, or clear chicken (hen) soup. It is commonly served with fine noodles, often home made, like Jewish lokshen. It is important to differentiate the type of meat used for the preparation of this particular dish. Young chicken meat will result in a different flavour than that obtained from an older cooking hen. Additionally, the type of meat will result in a different fat content. Finally, other meats, or a mix of beef and/or veal may be used.

Ingredients

 * 1 chicken
 * 1 onion
 * 1 small leek
 * 2 carrots, peeled and sliced lengthwise
 * ½ celery root
 * 2–3 sprigs green celery
 * 1–2 parsley roots
 * 1 bunch of parsley
 * Salt
 * Pepper
 * ⅛ sweet cabbage
 * Garlic, to taste
 * Bay leaf, to taste
 * Juniper seeds
 * Dried wild mushrooms
 * Allspice, to taste

Procedure

 * 1) Quarter the chicken and place in a stock pot with ~1.5 cold water. Do not add salt at this time, as this may harden some meats. Bring to a boil on high heat, then simmer for 30–45 minutes. At this time, remove (skim) the surface flotsam (a mix of protein and some fat).
 * 2) Add peeled garlic clove, carrots, celery root, parsley root similarly prepared, and other vegetables previously washed.
 * 3) Sauté onion halves in minimal oil to caramelize the flesh. Add to the soup. Omitting this step will result in a clearer, less-yellow product.
 * 4) Simmer on low heat for approx 2 hours or more. Rosół should not boil, as this will result in a cloudy consistency.
 * 5) Season to taste with salt, pepper, bay leaf, allspice, juniper seeds, dried wild mushrooms, etc.
 * 6) Continue simmering. You may skim fat off the surface, if so desired (traditionally it should be as fat as possible)
 * 7) Remove cabbage, parsley, celery root and any "undesired" vegetables. Carrots are usually left in and served with the broth.
 * 8) Serve hot with noodles and fresh parsley. Individuals may season with maggi, soy sauce, freshly ground black pepper and/or chilli flakes.

Notes, tips, and variations

 * Instead of chicken you may use ½ kg (1 lb) of veal or beef.
 * In the traditional Polish way, the chicken is not quartered or cut whatsoever.
 * To avoid having to remove surface flotsam use the blanching technique: bring large amount of water (unsalted) to a boil. Remember to leave enough space for the chicken. When in vigorous boil put the chicken in. Let it boil for about a minute. Take the chicken out and put under cold, running water until cold. Now you can add chicken to your rosół, and not worry about the flotsam. It will also make rosół clearer, which is one of the indicators of a good rosół dish.
 * Adding vegetable stock or a stock cube is a personal choice. Some argue that it is unnecessary, as the vegetable and meat give enough flavour to the broth.

title: Cookbook:Rosół (Polish Meat Soup)


text:
Engineering Thermodynamics/Applications

One Component Systems
All materials can exist in three phases: solid, liquid, and gas. All one component systems share certain characteristics, so that a study of a typical one component system will be quite useful.

For this analysis, we consider heat transferred to the substance at constant pressure. The above chart shows temperature vs. specific volume (1/density) curves for at three different constant pressures. The three line-curves labeled p1, p2, and pc above are isobars, showing conditions at constant pressure. When the liquid and vapor coexist, it is called a saturated state. There is no change in temperature or pressure when liquid and vapor are in equilibrium, so that the temperature is called saturation temperature and the pressure is called saturation pressure. Saturated states are represented by the horizontal lines in the chart. In the temperature range where both liquid and vapor of a pure substance can coexist in equilibrium, for every value of saturated temperature, there is only one corresponding value of saturation pressure. If the temperature of the liquid is lower than the saturation temperature, it is called subcooled liquid. If the temperature of the vapor or gas is greater than the saturation temperature it is called superheated vapor.

The amount of liquid and vapor in a saturated mixture is specified by its quality x, which is the fraction of vapor in the mixture. Thus, the horizontal line representing the vaporization of the fluid has a quality of x=0 at the left endpoint where it is 100% liquid and a quality of x=1 at the right endpoint where it is 100% vapor. The blue curve in the preceding diagram shows saturation temperatures for saturated liquid i. e. where x=0. The green curve in the diagram shows saturation temperatures for saturated vapor i. e. where x=1. These curves are not isobars.

$$ x = \frac{m_g}{m_f + m_g} $$

$$ v_x = \left(   1 - x  \right)v_f + xv_g $$

$$ v_{fg} = v_g - v_f $$

If you also consider the solid state, then we get the phase diagram for the material. The point where the solid, liquid, and the vapor state exist in equilibrium is called the triple point. Note that as the saturation temperatures increase, the liquid and vapor specific volumes approach each other until the blue and green curves come together and meet at point C on the pc isobar. At that point C, called the critical point, the liquid and vapor states merge together and all their thermodynamic properties become the same. The critical point has a certain temperature Tc, and pressure pc, which depend on the substance in question. At temperatures above the critical point, the substance is considered a super-heated gas.

This diagram is based on the diagram for water. Other pure (one-component) substances have corresponding temperature vs. specific volume diagrams which are fairly similarly shaped, but the temperatures, pressures, and specific volumes will vary.

The thermodynamic properties of materials are given in charts. One commonly used chart is the Mollier Chart, which is the plot of enthalpy versus entropy. The pressure enthalpy chart is frequently used in refrigeration applications. Charts such as these are useful because many processes are isenthalpic, so obtaining values would be as simple as drawing a straight line on the chart and reading off the data.

Steam tables give the values of specific volume, enthalpy, entropy, and internal energy for different temperatures for water. They are of great use to an engineer, with applications in steam turbines, steam engines, and air conditioning, among others.

Gas tables give the same equations for common gases like air. Although most gases roughly obey the ideal gas equation, gas tables note the actual values which are more accurate in many cases. They are not as important as steam tables, but in many cases it is much easier to lookup from a table rather than compute answers.

Gibbs Phase Rule
Gibbs phase rule states that for a heterogeneous system in equilibrium with C components in P phases, the degree of freedom F = C - P + 2. Thus, for a one component system with two phases, there is only one degree of freedom. F=1-2+2 F =1 That is, if you are given either the pressure or temperature of wet steam, you can obtain all the properties, while for superheated steam, which has just one phase, you will need both the pressure and the temperature.

Psychrometry
Psychrometry is the study of air and water vapor mixtures for air conditioning. For this application, air is taken to be a mixture of nitrogen and oxygen with the other gases being small enough so that they can be approximated by more of nitrogen and oxygen without much error. In this psychrometry section, vapor refers to water vapor. For air at normal (atmospheric) pressure, the saturation pressure of vapor is very low. Also, air is far away from its critical point in those conditions. Thus, the air vapor mixture behaves as an ideal gas mixture. If the partial pressure of the vapor is smaller than the saturation pressure for water for that temperature, the mixture is called unsaturated. The amount of moisture in the air vapor mixture is quantified by its humidity.

The absolute humidity ω is the ratio of masses of the vapor and air, i.e., ω = mv/ma. Now, applying ideal gas equation, pV = mRT for water vapor and for air, we have, since the volume and temperature are the same, ω = 0.622 pv/pa. The ratio of specific gas constants (R in preceding equation) of water vapor to air equals 0.622.

The relative humidity φ is the ratio of the vapor pressure to the saturation vapor pressure at that temperature, i.e., φ = pv/pv,sat.

The saturation ratio is the ratio of the absolute humidity to the absolute humidity at saturation, or, ψ = ω/ωsat. It is easy to see that the saturation ratio is very close to the value of relative humidity.

The above plot shows the value of absolute humidity versus the temperature. The initial state of the mixture is 1, and it is cooled isobarically, and at constant absolute humidity. When it reaches 2, it is saturated, and its absolute humidity is ωa. Further cooling causes condensation and the system moves to point 3, where its absolute humidity is ωb. The temperature at 2 is called the dew point.

It is customary to state all quantities in psychrometry per unit mass of dry air. Thus, the amount of air condensed in the above chart when moving from 2 to 3 is ωb − ωa.

Adiabatic Saturation

Consider an unsaturated mixture entering a chamber. Suppose water was sprayed into the stream, so that the humidity increases and it leaves as a saturated mixture. This is accompanied by a loss of temperature due to heat being removed from the air which is used for vaporization. If the water supplied is at the temperature of exit of the stream, then there is no heat transfer from the water to the mixture. The final temperature of the mixture is called adiabatic saturation temperature.

Wet Bulb Temperature
The relative humidity of air vapor mixtures is measured by using dry and wet bulb thermometers. The dry bulb thermometer is an ordinary thermometer, while the wet bulb thermometer has its bulb covered by a moist wick. When the mixture flows past the two thermometers, the dry bulb thermometer shows the temperature of the stream, while water evaporates from the wick and its temperature falls. This temperature is very close to the adiabatic saturation temperature if we neglect the heat transfer due to convection.

Psychrometric Chart

This chart gives the value of absolute humidity versus temperature, along with the enthalpy. From this chart you can determine the relative humidity given the dry and wet bulb temperatures. We have, from the first law, that for a flow system with no heat transfer, the enthalpy is a constant. Now, for the adiabatic saturation process, there is no heat transfer taking place, so that the adiabatic saturation lines are the same as the wet bulb temperature and the constant enthalpy lines.

Questions

1. The temperature at Phoenix is 35 °C with a relative humidity of 40%. Can a room be cooled using a conventional air cooler?

 * We need to find the wet bulb temperature for the point T = 35°C and φ = 40%. We have, from the psychrometric chart, the wet bulb temperature is between 20 and 25°C.  Thus, you can cool the room down to a comfortable temperature using an evaporative cooler.

2. The temperature of Los Angeles is 37 °C with relative humidity of 83%. To what temperature can a room be cooled using a conventional air cooler?

 * The wet bulb temperature is about 34.2°C for this situation. Thus, you cannot use an ordinary cooler to reduce room temperature in this situation.  You will need to use an air conditioner.

Air Conditioning
The human body can work efficiently only in a narrow range of conditions. Further, it rejects about 60 W of heat continuously into the surroundings, and more during heavy exercise. The temperature of the body is maintained by the evaporation of sweat from the body. Thus, for comfort, both the temperature and the relative humidity should be low.

Conventional air conditioning consists of setting the humidity at an acceptable level, while reducing the temperature. Reducing the humidity to zero is not the ideal objective. For instance, low humidity leads to issues like high chances of static electricity building up, leading to damage of sensitive electronic equipment. A humidity level of 50% is more acceptable in this case.

The most common method of reducing humidity is to cool the air using a conventional air conditioner working on a reversed Carnot cycle. The vapor that condenses is removed. Now, the air that is produced is very cold, and needs to be heated back up to room temperature before it is released back to the air conditioned area.

Common Thermodynamic Cycles
Several thermodynamic cycles used in machines can be approximated with idealized cycles. It was shown previously that a Carnot engine was the most efficient engine operating between two thermal reservoirs. However, due to practical difficulties, Carnot cycle cannot be implemented in all situations. The following sections deal with idealized (non Carnot) systems found in practice.

Rankine Cycle
In the Rankine cycle, also called the standard vapor power cycle, the working fluid follows a closed cycle. We will consider water as a working substance. Other materials can be also used, for example organic one (see Organic Rankine Cycle); properties of the working fluids in use has great influence on the actual process. In the Rankine cycle, water is pumped from a low pressure to a high pressure using a liquid pump. This water is then heated in the boiler at constant pressure where its temperature increases and it is converted to superheated vapor. This vapor is then expanded in an expander to generate work. This expander can be a turbine or a reciprocating (i.e. piston) machine such as those used in older steam locomotive or ship. The output of the expander is then cooled in a condenser to the liquid state and fed to the pump. The Rankine cycle differs from the Carnot cycle in that the input to the pump is a liquid (it is cooled more in the condenser). This allows the use of a small, low power pump due to the lower specific volume of liquid compared to steam. Also, the heat transfer in the boiler takes place mainly as a result of a phase change, compared to the isothermal heating of the ideal gas in the Carnot cycle, so that the efficiency is quite good (even though it is still lower than the Carnot efficiency). The amount of heat transferred as the liquid is heated to its boiling point is very small compared to the heat transfer during phase change. The steam is superheated so that no liquid state exists inside the turbine. Condensation in the turbine can be devastating as it can cause corrosion and erosion of the blades.

There are several modifications to the Rankine cycle leading to even better practical designs. In the reheat cycle there are two expanders working in series, and the steam from the high pressure stage is heated again in the boiler before it enters the low pressure expander. This avoids the problem of moisture in the turbine and also increases the efficiency. The regenerative cycle is another modification to increase the efficiency of the Rankine cycle. In many Rankine cycle implementations, the water enters the boiler in the subcooled state, and also, the large difference in temperature between the one at which heat is supplied to the boiler and the fluid temperature will give rise to irreversibilities which will cause the efficiency to drop. In the regenerative cycle, the output of the condenser is heated by some steam tapped from the expander. This causes the overall efficiency to increase, due to the reasons noted above.

Otto Cycle

The Otto Cycle is the idealization for the process found in the reciprocating internal combustion engines which are used by most automobiles. While in an actual engine the gas is released as exhaust, this is found to be a good way to analyze the process. There are, of course, other losses too in the actual engine. For instance, partial combustion and aspiration problems for a high speed engine. The working material in the idealized cycle is an ideal gas, as opposed to the air fuel mixture in an engine.

 * 1) Heat is transferred at constant volume during 1-2.
 * 2) The gas expands reversibly and adiabatically during 2-3, where work is done.
 * 3) Heat is rejected at constant volume at low temperature during 3-4.
 * 4) The gas is compressed reversibly and adiabatically in 4-1.

Analysis
Heat is transferred at constant volume in 1-2, so that Q1-2 = m cv(T2 − T1). Similarly, the heat rejected in 3-4 is Q3-4 = m cv (T3 − T4). The thermal efficiency of the Otto cycle is thus

ηth = (Q1-2 − Q3-4)/Q1-2

ηth = 1 − Q3-4/Q1-2

ηth = 1 − (T3 − T4)/(T2 − T1)

Since 2-3 and 4-1 are reversible adiabatic processes involving an ideal gas, we have,

T2/T3 = (V3/V2)γ − 1

and

T4/T1 = (V1/V4)γ − 1

But,

V1 = V2

and

V3 = V4

So, we have

T2/T3 = T1/T4

Thus,

ηth = 1 − (T3/T2)(1 − T4/T3)/(1 − T1/T2)

Or

ηth = 1 − T3/T2

If we introduce the term rc = V3/V2 for the compression ratio, then we have,

ηth = 1 − rc1 − γ

As can be seen, increasing the compression ratio will improve thermal efficiency. However, increasing the compression ratio causes the peak temperature to go up, which may cause spontaneous, uncontrolled ignition of the fuel, which leads to a shock wave traveling through the cylinder, and is called knocking.

Diesel Cycle

The Diesel cycle is the idealized cycle for compression ignition engines (ones that don't use a spark plug). The difference between the Diesel cycle and the Otto cycle is that heat is supplied at constant pressure.

 * 1) Heat is supplied reversibly at constant pressure in 1-2.
 * 2) Reversible adiabatic expansion during which work is done in 2-3.
 * 3) Heat is rejected reversibly at constant volume in 3-4.
 * 4) Gas is compressed reversibly and adiabatically in 4-1.

Analysis
Heat is transferred to the system at constant pressure during 1-2 so that

Qin = m cp (T2 − T1)

Heat is rejected by the system at constant volume during 3-4:

Qout = m cv (T3 − T4)

Thus, the efficiency of the Diesel cycle is

ηth = (Qin − Qout)/Qin

ηth = 1 − Qout/Qin

ηth = 1 − (cv (T3 − T4))/(cp (T2 − T1))

ηth = 1 − (1/γ) (T3 − T4)/(T2 − T1)

$$ \eta_{th} = 1 - \frac{1}{\gamma}\frac{T_4}{T_1} \left( \frac{\frac{T_3}{T_4} - 1}{\frac{T_2}{T_1} - 1} \right) $$

We define the cutoff ratio as rt = V2/V1, and since the pressures at 1 and 2 are equal, we have, applying the ideal gas equation, T2/T1 = rt. Now, for the adiabatic processes 2-3 and 4-1 we have,

$$ \frac{T_2}{T_3} = \left( \frac{V_3}{V_2} \right)^{\gamma - 1} $$

$$ \frac{T_1}{T_4} = \left( \frac{V_4}{V_1} \right)^{\gamma - 1} $$

Since V3 = V4, we have

$$ \frac{T_2}{T_1}\frac{T_4}{T_3} = \left( \frac{V_1}{V_2} \right)^{\gamma - 1} $$

$$ \frac{T_4}{T_3} = \left( \frac{V_1}{V_2} \right)^{\gamma} $$

$$ \eta_{th} = 1 - \frac{1}{\gamma}\frac{1}{r_c^{\gamma - 1}} \left( \frac{r_t^\gamma - 1}{r_t - 1} \right) $$

Dual Cycle

The dual cycle is sometimes used to approximate actual cycles as the time taken for heat transfer in the engine is not zero for the Otto cycle (so not constant volume). In the Diesel cycle, due to the nature of the combustion process, the heat input does not occur at constant pressure.

Gas Turbine Cycle (or Joule-Brayton Cycle)
Gas turbines are rotary internal combustion engines. As the first stage air is drawn in from outside and compressed using a compressor. Then the fuel is introduced and the mixture is ignited in the combustion chamber. The hot gases are expanded using a turbine which produces work. The output of the turbine is vented outside as exhaust.

The ideal gas turbine cycle is shown above. The four stages are

 * 1) Heat input at constant pressure during 1-2.
 * 2) Reversible adiabatic expansion during 2-3, where work is done.
 * 3) Heat rejection at constant pressure during 3-4.
 * 4) Reversible adiabatic compression during 4-1 where work is consumed.

Large amount of work is consumed in process 4-1 for a gas turbine cycle as the working material (gas) is very compressible. The compressor needs to handle a large volume and achieve large compression ratios.

Analysis
The heat input in a gas turbine cycle is given by Qin = m cp (T2 - T1) and the heat rejected Qout = m cp (T3 - T4). Thus the thermal efficiency is given by

$$ \eta_{th} = 1 - \frac{Q_{out}}{Q_{in}} $$

$$ \eta_{th} = 1 - \left(   \frac{T_3 - T_4}{T_2 - T_1}  \right) $$

$$ \eta_{th} = 1 - \frac{T_4}{T_1} \left(   \frac{\frac{T_3}{T_4} - 1}{\frac{T_2}{T_1} - 1}  \right) $$

Since the adiabatic processes take place between the same pressures, the temperature ratios are the same

$$ \eta_{th} = 1 - \frac{T_4}{T_1} = 1 - \frac{1}{ \left(   \frac{p_1}{p_4}    \right)^{\frac{\gamma - 1}{\gamma}}} $$

Or

$$ \eta_{th} = 1 - \frac{1}{r_p^{\frac{\gamma - 1}{\gamma}}} $$

Where rp is the pressure ratio and is a fundamental quantity for the gas turbine cycle.

Refrigeration Cycles
The ideal refrigeration cycle is reverse of Carnot cycle, working as a heat pump instead of as a heat engine. However, there are practical difficulties in making such a system work.

The gas refrigeration cycle is used in aircraft to cool cabin air. The ambient air is compressed and then cooled using work from a turbine. The turbine itself uses work from the compressed air, further cooling it. The output of the turbine as well as the air which is used to cool the output of the compressor is mixed and sent to the cabin.

The Rankine vapor-compression cycle is a common alternative to the ideal Carnot cycle. A working material such as Freon or R-134a, called the refrigerant, is chosen based on its boiling point and heat of vaporization. The components of a vapor-compression refrigeration system are the compressor, condenser, the expansion (or throttling) valve, and the evaporator. The working material (in gaseous form) is compressed by the compressor, and its output is cooled to a liquid in the condenser. The output of the condenser is throttled to a lower pressure in the throttling valve, and sent to the evaporator which absorbs heat. The gas from the evaporator is sent to the compressor, completing the cycle.

Standard refrigeration units use the throttling valve instead of a turbine to expand the gas as the work output that would be produced is not significant to justify the cost of a turbine. There are irreversibilities associated with such an expansion, but it is cost effective when construction costs are considered.

title: Engineering Thermodynamics/Applications


text:
File:Diesel Engineering Thermodynamics.png

diesel cycle

Metapost
prologues := 2; beginfig(1); numeric u; u := .4cm; drawarrow (0, 0) -- (10u, 0); label.bot("V", (10u, 0)); drawarrow (0, 0) -- (0, 10u); label.lft("p", (0, 10u)); vardef arrowhead expr p = save A,u,a,b; pair A,u; path a,b; A := point length(p)/2 of p;   u := unitvector(direction length(p)/2 of p); a := A{-u}..(A - ahlength*u rotated 30); b := A{-u}..(A - ahlength*u rotated -30); (a & reverse(a) & b & reverse(b))--cycle enddef; pair p, q, r, s; p := (4u, 8u); q := (9u, 3u); s := p shifted -(2u, 0); r := q shifted -(0, 1.5u); dotlabel.lft("1", s); drawarrow s .. p; dotlabel.rt("2", p); drawarrow p .. controls (((p + q)/2) shifted -(.5u, .5u)) .. q; dotlabel.rt("3", q); drawarrow r .. controls (((s + r)/2) shifted -(.5u, .5u)) .. s; dotlabel.bot("4", r); drawarrow q .. r; currentpicture := currentpicture scaled 2; currentpicture := currentpicture shifted -llcorner currentpicture; endfig; end;


text:
File:Brayton Engineering Thermodynamics.png

brayton cycle

prologues := 2; beginfig(1); numeric u; u := .4cm; drawarrow (0, 0) -- (10u, 0); label.bot("V", (10u, 0)); drawarrow (0, 0) -- (0, 10u); label.lft("p", (0, 10u)); pair p, q, r, s; p := (4u, 8u); q := (9u, 3u); s := p shifted -(2u, 0); r := q shifted -(1.5u, 0); dotlabel.top("1", s); draw s .. p; dotlabel.top("2", p); draw p .. controls (((p + q)/2) shifted -(.5u, .5u)) .. q; dotlabel.bot("3", q); draw r .. controls (((s + r)/2) shifted -(.5u, .5u)) .. s; dotlabel.bot("4", r); draw q .. r; currentpicture := currentpicture shifted -llcorner currentpicture; endfig; end;


text:
File:Dual Engineering Thermodynamics.png

dual cycle

prologues := 2; beginfig(1); numeric u; u := .4cm; drawarrow (0, 0) -- (10u, 0); label.bot("V", (10u, 0)); drawarrow (0, 0) -- (0, 10u); label.lft("p", (0, 10u)); pair p, q, r, s, t; p := (4u, 8u); q := (9u, 3u); s := p shifted -(2u, 0); r := q shifted -(0, 1.5u); t := s shifted -(0, 2u); dotlabel.lft("1", t); draw t .. s; dotlabel.lft("2", s); draw s .. p; dotlabel.rt("3", p); draw p .. controls (((p + q)/2) shifted -(.5u, .5u)) .. q; dotlabel.rt("4", q); draw r .. controls (((t + r)/2) shifted -(.5u, .5u)) .. t; dotlabel.bot("5", r); draw q .. r; currentpicture := currentpicture shifted -llcorner currentpicture; endfig; end;


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Template:EngTherm

Engineering Thermodynamics  | Thermodynamic Systems | First Law | Second Law | Applications /Templates

title: Template:EngTherm


text:
Cookbook:Cuisine of Vietnam

| South-East Asian cuisines

These recipes are considered to be a part of the culinary tradition of Vietnam:

 * Phở – rice noodle soup
 * Phở gà – with chicken
 * Phở bò – with beef
 * Bún măng – rice noodle soup with bamboo shoots
 * Ca kho to – catfish in clay pot
 * Canh chua cá – sour fish soup
 * Bánh mì – colorful Saigon sandwich on French bread
 * Bánh Xèo – crêpe-like pancake
 * Nem – fried spring rolls
 * Nước mắm pha - Fish Sauce
 * Gỏi Cuốn – summer rolls
 * Bún bò Huế – spicy beef soup
 * Mực nhồi thịt – stuffed squid in clay pot
 * Com chien – fried rice

Vietnamese cuisine (cuisine translates to ẩm thực in Vietnamese: ẩm: drink and thực: food) is known for its common use of fish sauce, soy sauce and hoisin sauce. Vietnamese recipes use many vegetables, herbs and spices, including lemon grass, lime, and kaffir lime leaves. Throughout all regions the emphasis is always on serving fresh vegetables and/or fresh herbs as side dishes along with dipping sauce. The Vietnamese also have a number of Buddhist vegetarian dishes. The most common meats used in Vietnamese cuisine are pork, beef, prawns, various kinds of tropical fish, and chicken. Duck and goat/lamb are used much less widely.

title: Cookbook:Cuisine of Vietnam


text:
Talk:Dichotomous Key/Animalia

Echinodermata have radial symmetry, and so under this key would be classes as Cnidaria or Ctenophora. I don't know how to fix this, however, without introducing more technical characters.

 * I made it no longer incorrect, but it is still technical -- not such a big deal, I think, for one of the high level taxa like Animalia. Can always be simplified later... TUF-KAT 18:37, 20 Mar 2004 (UTC)

 * This is only a superficial symmetry. If one considers e.g. the madreporite, then echinoderms are clearly bilateral symmetric. Lycaon 08:51, 27 November 2005 (UTC)

title: Talk:Dichotomous Key/Animalia