text:
Cookbook:Tartiflette

| Cuisine of France

Tartiflette is a French dish from the Savoy region. It originated in the valley of Aravis, home of reblochon cheese. It is not, however, a traditional dish and was, in fact, invented and launched only in the 1980s by the Reblochon trade union in an attempt to increase sales of the cheese. Different valleys in the region have different methods of producing tartiflette and there is probably more than one recipe per village. All recipes have potatoes, cheese, and some kind of meat such as slab bacon or salt pork. One example of a recipe is shown below.

Ingredients

 * 1¾ pounds Yukon Gold potatoes (5 or 6 medium-sized ones, all the same size) or waxy boiling potatoes
 * 5–6 ounces slab bacon or salt pork, cut into lardons about 1 x ¼ x ¼ inch
 * 2 tablespoons butter
 * 1 ea. (about 6 ounces) medium onion, finely chopped
 * ¼ cup dry white wine or dry vermouth
 * 6 tablespoons (¼ cup plus 2 tablespoons) heavy cream
 * ½ tsp salt, or to taste
 * Pepper, to taste
 * ½ pound reblochon cheese

Procedure

 * 1) Boil potatoes in their skins for exactly 20 minutes, until they’re just beginning to get tender. Do not overcook! Rinse with cold water to stop the cooking.
 * 2) While still warm, peel the potatoes with your fingers, then use a large, very sharp knife to cut them into slices about ⅓-inch thick. Then cut the slices into rough cubes.
 * 3) While the potatoes are cooking, slice the slab bacon or salt pork into slices about ¼-inch thick. Then cut into lardons about ¼-inch across.
 * 4) Melt the butter in a large sauté pan, then cook the lardons over medium-high heat until crisp and golden brown. Remove with a slotted spoon and set aside, leaving the bacon fat in the pan.
 * 5) Preheat the oven to 350 °F.
 * 6) Cook the onions in the bacon fat over medium heat, stirring often, until wilted and slightly golden. Drain in a strainer, pressing with a spoon to remove as much fat as possible, and leave them there.
 * 7) Pour off the fat in the pan, return the bacon and onions, and add the wine. Cook over high heat until the wine is nearly evaporated.
 * 8) Add the diced potatoes and cook for a minute or so, stirring constantly until all the ingredients are well mixed together.
 * 9) Add the cream and salt and pepper to taste. Try using a little more salt than you might think is necessary, at least ½ teaspoon. Stir all the ingredients together for a minute.
 * 10) Lightly butter the inside of an 10–11-inch earthenware baking dish. Add the potato mixture and smooth the surface.
 * 11) Cut the Reblochon in two down across the top so that you have two pieces in the shape of a half-moon. Put one of the pieces away for another use. Use a sharp knife to lightly score the crust of the remaining half-cheese about every inch, including its side. Then, carefully slice horizontally through its center so that you now have two half-moon pieces.
 * 12) Place the two pieces of cheese crust-side-up on top of the potatoes so that they form a circular cheese again.
 * 13) Cover the dish tightly with aluminum foil and bake in the center of the oven for 1 hour.
 * 14) Remove the foil and stir the cheese, including the crust, into the potatoes, mixing well.
 * 15) Place 5–6 inches under the broiler and cook until golden brown on top.

Notes, tips, and variations

 * Use potatoes that are all the same size so that they will cook evenly.

Livre de cuisine/Tartiflette

title: Cookbook:Tartiflette


text:
IB Biology

This guide is currently being updated to the new syllabus effective 2015-2016.

or viewed here on the web.
 * Authorised copies of the IB Syllabus can be obtained from the International Baccalaureate

The following links are useful for the 2014 syllabus, with exams commencing in 2016:
 * IBPal

The link that follow are useful for the remaining section of the 2009 syllabus that will end 2015/2016:

and for assistance with the Internal Assessment go to Lab Banks again by Stephen Taylor.
 * Open Door by Paul Billiet
 * i-Biology by Stephen Taylor
 * by Stephanie Castle is a Youtube series of screen and videocasts
 * for students in a hurry
 * also by Stephen Taylor

Syllabus (2015-2016)

 * Introduction to the Guide
 * How to use this Guide
 * /Study Guide/

Topic 1: /Cell biology/

 * 1.1 Introduction to Cells
 * 1.2 Ultrastructure of cells
 * 1.3 Membrane structure
 * 1.4 Membrane transport
 * 1.5 The origin of cells
 * 1.6 Cell division

Topic 2: /Molecular biology/

 * 2.1 Molecules to metabolism
 * 2.2 Water
 * 2.3 Carbohydrates and lipids
 * 2.4 Proteins
 * 2.5 Enzymes
 * 2.6 Structure of DNA and RNA
 * 2.7 DNA replication, transcription and translation
 * 2.8 Cell respiration
 * 2.9 Photosynthesis

Topic 3: /Genetics/

 * 3.1 Genes
 * 3.2 Chromosomes
 * 3.3 Meiosis
 * 3.4 Inheritance
 * 3.5 Genetic modification and biotechnology

Topic 4: /Ecology/

 * 4.1 Species, communities and ecosystems
 * 4.2 Energy flow
 * 4.3 Carbon cycling
 * 4.4 Climate change

Topic 5: /Evolution and biodiversity/

 * 5.1 Evidence for evolution
 * 5.2 Natural selection
 * 5.3 Classification of biodiversity
 * 5.4 Cladistics

Topic 6: /Human physiology/

 * 6.1 Digestion and absorption
 * 6.2 The blood system
 * 6.3 Defence against infectious disease
 * 6.4 Gas exchange
 * 6.5 Neurons and synapses
 * 6.6 Hormones, homeostasis and reproduction

Topic 7: /Nucleic acids/

 * 7.1 DNA structure and replication
 * 7.2 Transcription and gene expression
 * 7.3 Translation

Topic 8: /Metabolism, cell respiration, and photosynthesis/

 * 8.1 Metabolism
 * 8.2 Cell respiration
 * 8.3 Photosynthesis

Topic 9: /Plant biology/

 * 9.1 Transport in the xylem of plants
 * 9.2 Transport in the phloem of plants
 * 9.3 Growth in plants
 * 9.4 Reproduction in plants

Topic 10: /Genetics and evolution/

 * 10.1 Meiosis
 * 10.2 Inheritance
 * 10.3 Gene pools and speciation

Topic 11: /Animal physiology/

 * 11.1 Antibody production and vaccination
 * 11.2 Movement
 * 11.3 The kidney and osmoregulation
 * 11.4 Sexual reproduction

Option A: /Neurobiology and behavior/

 * A.1 Neural development
 * A.2 The human brain
 * A.3 Perception of stimuli
 * A.4 Innate and learned behaviour
 * A.5 Neuropharmacology
 * A.6 Ethology

Option B: /Biotechnology and bioinformatics/

 * B.1 Microbiology: organisms in industry
 * B.2 Biotechnology in agriculture
 * B.3 Environmental protection
 * B.4 Medicine
 * B.5 Bioinformatics

Option C: /Ecology and conservation/

 * C.1 Species and communities
 * C.2 Communities and ecosystems
 * C.3 Impacts of humans on ecosystems
 * C.4 Conservation of biodiversity
 * C.5 Population ecology
 * C.6 Nitrogen and phosphorus cycles

Option D: /Human physiology/

 * D.1 Human nutrition
 * D.2 Digestion
 * D.3 Functions of the liver
 * D.4 The heart
 * D.5 Hormones and metabolism
 * D.6 Transport of respiratory gases

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

title: IB Biology


text:
User:Tkorrovi

Name: Tarvo Korrovits

Email: tkorrovi@mail.com

title: User:Tkorrovi


text:
World History/A New Millennium

America stands alone
Following the fall of the Communist Bloc in 1989 and the dissolution of the Soviet Union in 1992, the United States remained as the sole global superpower.

Democracy
After the collapse of communism in Eastern Europe, and then in the Soviet Union, many people in the West and in the former communist countries hoped that a new era of democracy would emerge. However, at the beginning of the 21st Century, a number of events and developments quelled this euphoria.

First, the increasing authoritarianism in countries like Russia. Since the movement was only in the opposite direction for some time, this came as a surprise to the West. Most of the former communist countries, especially the western ones, have become free countries with a democratic form of government, according to the American watchdog of liberty, Freedom House. However, Russia made an authoritarian turn with the election of prime minister Vladimir V. Putin. As president, Putin has reasserted the authority of the state over parts of the economy and has been accused of suppressing free speech. There are also very few independent media in Russia, that are not directly or indirectly, under Putin's control.

Second, the September 11th attacks on the United States, which killed almost 3,000 people. People were suddenly reminded of the fact that not the entire world had accepted liberal democracy as a good form, or even as an acceptable form of government. (source?) The countries in the Middle-east have had authoritarian governments since the end of colonialism, many of which had Western support. These attacks made painfully clear that there is a lack of freedom and democracy in the Middle-east.

Bernard Lewis, the famed historian of the Middle-east, has long argued in his many books about Islam, that the support that the West has lent to authoritarian and oppressive regimes in the Middle-east has contributed a great deal to Islamic animosity toward the West. Generally, little attention was paid by important policy-makers in the West to his opinions on his matter, and the West continued to support dictators whose only virtue (in the eyes of the West) was that they secured a steady supply of oil for the West.

After the September 11th attacks, it appeared that president George W. Bush adopted this line of thinking, since he spared Saudi Arabia, where so many of the perpetrators of the attacks came from. However, in many speeches he argued that pushing for democracy in Iraq was one way the West could prevent atrocities such as the ones on September 11th.

It remains to be seen, if the policies of Bush truly represented a watershed in American policies toward the Middle-east. They might not. President Jimmy Carter adopted tough human rights policies toward countries like Iran, Chile and Nicaragua, but this contributed to the fall of the pro-American shah of Iran and the ascendancy of the virulently anti-American Ayatollah Ruhollah Khomeini, who had even less respect for human rights and freedoms than the shah. Carter, therefore, failed to leave a permanent imprint on American foreign policy.

War in Ukraine
Ukraine gained formal independence from the Soviet Union on August 21, 1991. Since then Ukraine and Russia have been at odds over a number of political issues. Notably there has been a dichotomy of people who feel that Ukraine should either align with Western nations or Russia.

In March 2014, Russia annexed the Ukrainian region of Crimea. The resulting conflict lead to an invasion of the Ukrainian mainland on 24 February 2022. The Ukrainian's have been supported by Western nations and at the same time sanctioning Russia. Millions of civilians in Ukraine had became refugees in the weeks following the invasion, many in neighboring countries. The conflict disrupted the global wheat supply (Ukraine supplied about 10% of world grain production in 2021), causing prices to rise as much as 28% in the early stages of the war, before becoming relatively stabile by 2023.

title: World History/A New Millennium


text:
PHP Programming/The foreach Loop

The code
or

Analysis
The foreach loop is a special form of the standard for loop. The example above will print all the values of $array. The foreach structure is a convenient way to loop through an array.

Simple foreach statement
Foreach loops are useful when dealing with an array indexed with arbitrary keys (e.g. non-numeric ones):

To use the classical for structure, you'd have to write:

Basically, an array value can be accessed only from its key: to make sure you get all the values, you first have to make a list of all the existings keys, then grab all the corresponding values. The access to first array value, the previous example does the following steps:

The foreach structure does all the groundwork for you:

Note how the latter example is easier to read (and write). Both will output: My House My Car My Lab

foreach with key values
If you need to use the array's keys in the body of your loop, just add the variable as in the following statement. The phrase '$myKey => $value' makes the value of the key accessible:

Note that this is very useful when constructing a dropdown list in HTML. You can use a foreach-loop to have the $myKey variable inserted into the <tt>value="..."</tt> part and the <tt>$value</tt> as the actual text.

This form mimics the way we used custom keys for $array elements. It will not only assign the elements of $array to $someVar, but also assign the keys of those elements to $i.

Note that, if you change the assigned variable inside the <tt>foreach</tt> loop, the change will not be reflected to the array. Therefore, if you need to change elements of the array you need to change them by using the array key. Example:

title: PHP Programming/The foreach Loop


text:
PHP Programming/Arrays

Arrays are sets of data that can be defined in a PHP Script. Arrays can contain other arrays inside of them without any restriction (hence building multidimensional arrays). Arrays can be referred to as tables or hashes.

Syntax
Arrays can be created in two ways. The first involves using the function array. The second involves using square brackets.

The array function method
In the array function method, you create an array in the scheme of:  For example, to set up the array to make the keys sequential numbers (Example: "0, 1, 2, 3"), you use:

This would produce the array like this:

It is also possible to define the key value:

This would set the array like this:

The square brackets method
The square brackets method allows you to set up by directly setting the values. For example, to make, all you need to do is:

The same applies for setting the key value:

Example #1
This example sets and prints arrays.

Example #2
The following example will output the identical text as Example #1:

Example #3
Using the Example #1 and Example #2 above, now you can try and use arrays the same way as normal variables:

Multidimensional arrays
Elements in an array can also be an array, allowing for multidimensional arrays. An example, in accordance with the motoring examples above, is:

In this example, if you were to use:

The output would be: Toyota

1395

Array functions
There are dozens of array manipulation functions. Before implementing your own, make sure it doesn't already exist as a PHP function in Array functions (PHP manual entry).

Sorting
Examples:

Array traversal
In various circumstances, you will need to visit every array element and perform a task upon it.

The simplest and the most widely used method for this is the foreach operator that loops through the whole array and works individually with each key/item couple. If a more complex way of traversing the array is needed, the following functions operate using the internal array pointer:

 * reset - sets the internal pointer to the first element and returns the first element
 * prev - sets the internal pointer to the previous element and returns it
 * current - returns the current element; does not change the internal pointer
 * next - sets the internal pointer to the next element and returns it
 * each - returns the current element; then sets the internal pointer to the next element
 * end - sets the internal pointer to the last element and returns the last element

Another possibility is defining a function and applying it to each array element via one of the following functions:

 * array_walk - applies a function to each array element
 * array_walk_recursive - same, but if the element is itself an array, it will traverse that array too

title: PHP Programming/Arrays


text:
Talk:PHP Programming/headers and footers

I think out html examples should be xhtml compliant. You know, things like only small letters and solitary tags ending with a slash. -Jeshii 06:24, 30 Jun 2004 (UTC)

I agree, but I think that it is of secondary importance. This is a php book. There already exists an XHTML wikibook. I will personally keep in xhtml compliance, and correct where I catch it, but right now our emphasis needs to be on developing the php book content.

It's a wiki. You can concentrate on writing the narrative and let other people clean up the code after you've done the hard work. If you don't like their changes, change 'em back! --Munin 12:01, 6 Aug 2004 (UTC)


text:
User:Jeshii~enwikibooks

Um, yeah, this is me... Check out my homepage or my wikipedia user page for more info.

title: User:Jeshii~enwikibooks


text:
Cookbook:Peach Cobbler

| Desserts | Cuisine of the United States

Crust

 * 1 cup all-purpose flour
 * ½ cup butter
 * ¼ cup milk

Filling

 * 2 cans (15 oz / 425 g) peaches
 * ½ cup white granulated sugar

Procedure

 * 1) Combine flour, butter, and milk. Cut together to make dough and set aside.
 * 2) Pour peaches in 9x13-inch baking pan. Sprinkle sugar on top.
 * 3) Roll out crust and place on top of peaches.
 * 4) Bake at 350 °F or until top is browned lightly (approximately one hour).

title: Cookbook:Peach Cobbler


text:
Cookbook:Ethics

Many individuals feel that their cooking should reflect their ethics. Note that these ethics are not necessarily universal, and the chef is free to decide which of these is important. Note also that in some cases the efficacy in achieving these goals (such as gathering wild food to avoid buying farmed food) is questionable, or may even run counter to your goals. If you decide you care about these issues, it is up to you to research them.

Treatment of animals
The treatment of animals is important to some cooks. Some may only consume eggs, meat, and dairy from free-range animals. Others will avoid eating any animals (vegetarianism) or will avoid any animal products at all (veganism). Some individuals will eat only seafood that has been caught without harming any dolphins or other marine life.

Sustainability
The issue of sustainability has come up in cooking, especially with regard to climate change and damage to the environment. To achieve this, some individuals will preferentially eat food that is in season and local to their area, or will only eat food that they have hunted or gathered themself. Some also use reusable bags and avoid food with excess packaging in order to reduce the amount of waste they generate. Some vegetarians and vegans avoid animal products, associating a higher carbon footprint with animal husbandry.

Consideration for guests
For some cooks, consideration of the needs of their guests is very important. In these cases, the cooks may take care to consider their guests' dietary needs and requirements, such as food allergies or religious requirements. They may also take care to not get hair, saliva, tears, fingertips, or other parts of themself in the food.

title: Cookbook:Ethics


text:
Cookbook:Oatmeal Raisin Cookies

| Dessert

Ingredients

 * ¾ cup butter, applesauce, equal parts butter and vegetable oil, or shortening
 * 1 ¼ cup brown sugar, firmly packed
 * 1 egg
 * ⅓ cup water or milk
 * 1 ½ tsp vanilla
 * 3 cup raw oats (rolled or quick/old fashioned)
 * 1 cup all-purpose flour
 * ½ tsp baking soda
 * ½ tsp salt
 * ¼ tsp cinnamon
 * 1 cup raisins
 * ¾ cup walnuts, chopped

Procedure

 * 1) Heat oven to 350°F.
 * 2) Lightly grease cookie sheet with oil, shortening, or butter.
 * 3) Combine your choice of fat (butter, apple sauce, butter/vegetable oil mix, or shortening), brown sugar, egg, milk, and vanilla; beat with mixer on high speed to blend well.
 * 4) Combine oats, flour, baking soda, salt and cinnamon; add to shortening mixture and combine until just blended.
 * 5) Stir in raisins and nuts.
 * 6) Drop by rounded tablespoonfuls onto greased cookie sheet, 2 inches apart.
 * 7) Bake for 10–13 minutes, or until lightly browned.

title: Cookbook:Oatmeal Raisin Cookies


text:
User talk:MandyK

Hi MandyK, Welcome to Wikibooks. I saw your comment on the Staff lounge and did some checking. I found that an anon. editor created Cookbook:Apple Pie on June 28. If that was you, and if that's your recipe, thank you for contributing, and I'm sorry if a technical dificulty caused you frustration. If that's not your edit, could you tell me the address of the page you tried to add? Thanks, Gentgeen 22:22, 30 Jun 2004 (UTC)

title: User talk:MandyK


text:
Cookbook:Fresh Broadbeans Salad

| Vegetables | Salads

Quick, simple, refreshing. Just like a salad should be. Use fresh, young broad beans. If you can't find them soft enough to eat raw, cook in boiling water for the shortest time possible, and rinse in cold.

Ingredients

 * Tomatoes
 * Onion
 * Fresh broad beans
 * Olive oil

Procedure

 * 1) Peel the broad beans, and discard any nasty looking peas.
 * 2) Cube tomatoes about 1 cm thick. The volume of cubed tomatoes should be roughly twice that of the peas.
 * 3) Chop onion(s) very finely. The amount depends on how spicy you like your salad.
 * 4) Mix it all together, then sprinkle generously with salt and olive oil.

title: Cookbook:Fresh Broadbeans Salad


text:
General Biology/Glossary

=Glossary= 1. CHEMISTRY a pleasant-smelling, colorless, volatile liquid that is highly flammable. It is used as an anesthetic and as a solvent or intermediate in industrial processes. any organic compound with a structure similar to ether, having an oxygen atom linking two alkyl or other organic groups. plural noun: ethers "methyl t -butyl ether"
 * Autotroph: an organism which can make its own energy
 * Cell: Fundamental structural unit of all living things
 * Ether:noun

2. literary the clear sky; the upper regions of air beyond the clouds. "nasty gases and smoke disperse into the ether" 1. a flowering plant's unit of reproduction, capable of developing into another such plant. synonyms:	pip, stone, kernel; ovule "apple seeds" a quantity of these. "grass seed" the cause or latent beginning of a feeling, process, or condition. "the conversation sowed a tiny seed of doubt in his mind" synonyms:	genesis, source, origin, root, starting point, germ, beginnings, potential (for); More archaic (chiefly in biblical use) a person's offspring or descendants. synonyms:	descendants, heirs, successors, scions; More a man's semen. a small crystal introduced into a liquid to act as a nucleus for crystallization. noun: seed crystal; plural noun: seed crystals a small container for radioactive material placed in body tissue during radiotherapy. 2. any of a number of stronger competitors in a sports tournament who have been assigned a specified position in an ordered list with the aim of ensuring that they do not play each other in the early rounds. "he knocked the top seed out of the championships" verb verb: seed; 3rd person present: seeds; past tense: seeded; past participle: seeded; gerund or present participle: seeding 1. sow (land) with seeds. "the shoreline is seeded with a special grass" sow (a particular kind of seed) on or in the ground. cause (something) to begin to develop or grow. "severance payouts that help seed their new businesses" place a crystal or crystalline substance in (something) in order to cause crystallization or condensation (especially in a cloud to produce rain). 2. (of a plant) produce or drop seeds. "mulches encourage many plants to seed freely" 1. the seed-bearing part of a plant, consisting of reproductive organs (stamens and carpels) that are typically surrounded by a brightly colored corolla (petals) and a green calyx (sepals). synonyms:	bloom, blossom, floweret, floret "blue flowers" a brightly colored and conspicuous example of the flower of a plant together with its stalk, typically used with others as a decoration or gift. "I stopped to buy Bridget some flowers" the state or period in which a plant's flowers have developed and opened. "the roses were just coming into flower" 2. the finest individuals out of a number of people or things. "the flower of college track athletes" synonyms:	best, finest, pick, choice, cream, crème de la crème, elite "the flower of the nation's youth" antonyms:	dregs the period of optimum development. "a young policeman in the flower of his life gunned down" verb verb: flower; 3rd person present: flowers; past tense: flowered; past participle: flowered; gerund or present participle: flowering 1. (of a plant) produce flowers; bloom. "these daisies can flower as late as October" induce (a plant) to produce flowers. 2. be in or reach an optimum stage of development; develop fully and richly. "it is there that the theory of deconstruction has flowered most extravagantly"
 * Eukaryote: an organism with a nucleus
 * Exoenzyme: an enzyme used to break down organic molecules outside the body
 * Glycerol: noun; a colorless, sweet, viscous liquid formed as a byproduct in soap manufacture. It is used as an emollient and laxative, and for making explosives and antifreeze.
 * Heterotroph: an organism which can not make its own energy
 * Hydrocarbon: an organic compound that contains carbon and hydrogen only.
 * Lipid: fatty acid esters which form the basis of cell membranes
 * Nucleus: Membrane-bound organelle which contains the chromosomes
 * Prokaryote: an organism with no nucleus
 * Seed: noun
 * Flower: noun
 * Tracheid: a type of water-conducting cell in the xylem that lacks perforations in the cell wall.
 * Haploid: A cell with a single set of chromosomes (23 in humans), in humans this is usually in gametes. This is commonly represented by n.
 * Diploid: A cell with two sets of chromosomes (46 in humans). This is commonly represented by 2n.
 * Sporangium: (in ferns and lower plants) a receptacle in which asexual spores are formed.

title: General Biology/Glossary


text:
User:Alsocal

Allen Lew is a Los Angeles, California area technologist. He currently works as a Quality Assurance Engineer for the Rubicon Project, whose "mission [is] to automate the $65 billion global online advertising industry." He is also a part time technology consultant for a variety of clients.

Education and Work
Previously, Allen worked for the Los Angeles Urban League, a nonprofit agency dedicated "to enabling African Americans and other minorities to secure economic self-reliance, parity, power and civil rights through advocacy activities and the provision of programs and services in our uniquely diversified city and region."

Allen is a graduate of the University of California, Berkeley, known to some as UC Berkeley, Berkeley, or Cal. There he majored in Molecular and Cell Biology with an emphasis in Immunology. His involvement on campus began with Alpha Delta Phi Fraternity-California Chapter, where he has held a variety of positions from Secretary to Philanthropy Chair. He was employed as a Computer Resource Specialist by the College Writing Programs of UC Berkeley, assisting faculty and staff in anything related to computers or technology. Allen also serves as the current director and news editor of Berkeley's student portal, One.Berkeley.edu, and a writer for Calstuff, a blog devoted to news and opinion on UC Berkeley. He also kept a personal blog at the Berkeley Open Computing Facility.

He has also spent two summers (2003 and 2004) keeping the grounds for the Hollywood Bowl. In the summer of 2005, he worked for US News & World Report as a Web Intern.

Allen was born and raised in Los Angeles, CA, where most of his family is living today. He is the oldest of three children.

Places I've worked at:

 * Hollywood Bowl-Summer of 2003 and 2004
 * U.S. News and World Report-Summer of 2005
 * UC Berkeley-Fall of 2005 until March 2007
 * Los Angeles Urban League- March 2007 to present.

I'm also on

 * Wikipedia
 * Wikiquote
 * Wiktionary
 * Commons
 * Wikia

title: User:Alsocal


text:
Puzzles/Logic puzzles/Knights, Knaves & Spies/Solution

Puzzles | Logic puzzles | Knights, Knaves & Spies | Solution

A - Knight B - Spy C - Knave

Reasoning
B is not the knight, since if he is, then A would also be the knight.

C is not the knight, since his statement would then be a lie. Therefore A is the knight.

Hence C is the knave, and B is the spy.


text:
Talk:Guitar/Intervals and Power Chords

Umm...you sure a "double-stop" can be played on a piano? --Furrykef 07:07, 1 Jul 2004 (UTC)

Yup - if a double stop is simply playing two notes at the same time, you just push down two keys on the piano.... hey presto, a double stop! Dave

 * Double stopping doesn't just mean two notes played at the same time. On guitar, double stopping means holding down (stopping) two strings onto the fretboard at any position (except open) in order to produce a 'dyad' or 'interval' when the strings are played. Double stopping doesn't apply to piano playing.

 * And if it did just mean playing two notes at the same time, it certainly wouldn't be restricted to string instruments (xylophones, bagpipes, pipe organs, and harmonicas are just a few non-string instruments that can play more than one note at a time). 151.200.237.145 04:36, 8 May 2007 (UTC)

 * I would agree here. Double stopping only happens when ONE string is stopped in two placed, if done correctly, you amplify certain harmonics and produce a two-tone effect.  This is not the same as just plucking two strings at once. (stestagg) 86.140.72.186 21:30, 1 September 2007 (UTC)

a pussle
Make of these a pussle. Delete the name of the songs and set the solution of the discusions-page. Maby you will find some new one, and we (the german wikibooks-team) will borrow them --Mjchael 22:16, 1 November 2007 (UTC)

E    F     F#    G     G#    A     Bb    H     C     C#   D    D#   E e|-|-|-|-|-|-|-|-|-|-||--- -|| h|-|-|-|-|-|-|-|-|-|-||--- -|| G|-|-|-|-|-|-|-|-|-|-||--- -|| D|--2--|--3--|--4--|--5--|--6--|--7--|--8--|--9--|-10--|-11--|-12-|-13 -|-14-| A|--2--|--3--|--4--|--5--|--6--|--7--|--8--|--9--|-10--|-11--|-12-|-13 -|-14-| E|--0--|--1--|--2--|--3--|--4--|--5--|--6--|--7--|--8--|--9--|-10-|-11 -|-12-|

A    Bb    H     C     C#    D     D#    E     F    F#    G    G#   A e|-|-|-|-|-|-|-|-|-|-||--- -|| h|-|-|-|-|-|-|-|-|-|-||--- -|| G|--2--|--3--|--4--|--5--|--6--|--7--|--8--|--9--|-10--|-11--|-12-|-13 -|-14-| D|--2--|--3--|--4--|--5--|--6--|--7--|--8--|--9--|-10--|-11--|-12-|-13 -|-14-| A|--0--|--1--|--2--|--3--|--4--|--5--|--6--|--7--|--8--|--9--|-10-|-11 -|-12-| E|-|-|-|-|-|-|-|-|-|-||--- -||

solution

 * Song 1 = Wild Thing
 * //: E - E - - A A A B - B- - A A A :// (0 5 7 )

 * Song 2 = Smoke on the Water
 * //: G Bb C - G Bb Db C - ; G Bb C - Bb G :// (3 1 3 - 3 1 4 3 ...)

 * Song 3 = With or Without you
 * //: C C C C C C C C G G G G G G G G A A A A A A A A F F F F F F F F :// (3 ... 3... 5... 1... )
 * or: You're Beautiful (James Blunt);
 * so lonley (police) ;
 * let it be (beatles)

 * Song 4 = Carlifornia Dreaming (the Mama & the Papas)
 * //: A A G G F F G G E4 E4 E4 E4 E E E E :// (the E is a simple chord ( 5 5 3 1 1 3 3 0 0...)

 * Song 5 = Sympathie for the Devel oder: let me entertaint you
 * //: D D D D D D D D | C C C C C C C C | G G G G G G G G | C C C C C C C C :// (5.... 3 .....)

 * Song 6 = Child in time (Deep Purple)
 * //: G G A - | G G A - | F F G - | G G A - :// (3 3 5........... 1 1 3...)

 * Song 7 = Hit the Road Jack
 * //: A | G | F | E :// (5 3 1 0 ) (one of 30 possible songs)
 * Ebenso möglich: Year 2525 oder Dicke (Westernhagen) (German)

 * Song 8 = She's f*** hates me
 * //: E E E E | A A A A | F# F# F# F# | H H H H :// ( 0 0 2 2 ) oder (0 5 2 7)

 * Song 9 = boulevard of broken dreams
 * //: E G D A :// ... //: C G D E :// ... B7

 * Song 10 = Westerland (die Ärzte) (German)
 * //: G / G / G /D :// (2x)
 * C / C / G / C / C / D / D
 * //: G D E C :// 3x
 * A D G G

 * Song 11 = Hey Joe (Jimi Hendrix)
 * //: C | G | D | A | E-A -E :// ( 3 3 5 5 0)

 * Song 12 = Skandal im Sperrbezirk (German)
 * //: D D C C G G A A :// (5 3 3 5)

 * Song 13 = I'm Free (The Who)
 * //: E E - G G - A A - A A A - F# F# - A A - B B - B B B :// (0..3..0...2..0..2..) or (0..3..5....2..5..7....)

 * Song 14 = Proud Mary
 * C C C A --- (2x) C C C A G F F F G G | (333 5 | 333 5 3 111 33)
 * D --- A B (A) G | D --- G D (557(5)3|5---35)

 * Song 15 = Locomotive Breath - JETHRO TULL
 * E G D (5x) B D
 * E G D (5x) G A --- B-

 * Song 16 = VENUS - Shocking Blue u.a.m.
 * B = Intro
 * B | E A (8x) A E (4x) C H

 * Song 17 = "You really got me"
 * only intro
 * F | GGFG --- G | GGFG --- F (1 3313-3| 3313-3)

 * Song 18 =( Sittin' On ) The Dock Of The Bay - Otis Redding
 * (1 chord = 1x 4/4)
 * G H C A (2x) G E G E G A G E (3 2 3 0 - 3 0 3 0 3 5 3 0 )
 * C A (3 0) can be played as C B Bb A ( 3 2 1 0 )

 * Song 19 = Bad Moon rising
 * DD AG D-- (4x) G D A G D (2x)

 * Song 20 = Narcotic (Liquido)
 * original one Fred higher
 * C C C C | D D D D | F F F F | C C C G (3 5 1 3,3)

 * Song 31 = Smells like teen spirit (Nirvana)
 * F F Bb Bb Ab Ab Db Db (1 1 1 1 4 4 4 4)

title: Talk:Guitar/Intervals and Power Chords


text:
User:LouMarini

Trovo questo progetto interessante, sopratutto per espandere e condividere alcune delle mie aree di interesse:
 * formazione personale
 * coaching
 * pnl programmazione neuro linguistica
 * psicologia
 * ipnosi ericsoniana

sto producendo qualche piccolo testo, che presto condividerò

Ciao

title: User:LouMarini


text:
Talk:Chinese (Mandarin)/Pinyin Pronunciation

Incorrect pronunciation?
By following the rules for manipulating rhymes to pronounce them, don't we get for example that yin is pronounced without the initial y sound, which is not accurate? (yi doesn't have an initial y sound, but yin does.) similarly, we would not have an initial w sound for wu, which it does have.

It is also confusing/wrong to define the initial as the non-vowels at the beginning and then say some syllables have no initial, when all syllables have a non-vowel seciton at the beginning. Perhaps define the initial as what you get after manipulating the non-vowel section at the beginning.

 * I updated table and lists to reflect versions in Wikipedia pinyin articles. This includes removing w and y from the list of initials and rearranaging list to "conventional" pinyin order.  Also added a bit of explanation when y and w are used.  Hope that helps...  --  Murdocke January 10, 2005 09:27 UTC

Quick note to author(s):
Could use explanations of the use of accents in pinyin to illustrate tones.

 * I have added a small section on tones and some text examples. Like the comment below suggests, it would be cool to have links to a Mandarin speaker demonstrating the tones.

Audio files would be cool (can we do that yet?)

Why isn't this lesson 1? Learning the structure etc counts as a lesson to me.

Also, I need a login.

Audio samples?
I've started following the course, but I've got some problems with the pronunciation part. I've got no chance of visiting China in the near future to meet a native speaker, English isn't my native language and the descriptions of mouth and tongue positions are also Chinese to me.

In short, it would be really helpful if you could provide some example sound files... Azertus 20:44, 9 Feb 2005 (UTC)

 * I'm sure everyone envisages some sort of audio integration in the future, especially for the pinyin lessons, but we're not there yet. Chinese: Fundamentals of the language really needs a ton of work and audio samples before anyone could learn good pronunciation from it, but there are already some sites further along.

 * If you don't have any Chinese friends that could help you, Conversational Chinese Online has a good guide. You could also look for language tapes or CDs at your library to get the pronunciation. -Everlong 02:35, 14 Feb 2005 (UTC)

Third tone duration
It's been my observation (for English speakers), that third tone also has the characteristic of lengthing the vowel sound, similar to Sanskrit / Hindi short and long matras (vowels). I'm just a beginner in learning Chinese and I don't claim this is academically "correct" or proven, however. I've never seen this pointed out on any pronunciation site, but the "trick" always works when I show it to others. If I pronounce a vowel as 2-3 times a regular vowel sound, it gets heard as third tone, even when I keep the tone as flat as possible. 14:41, 3 October 2005 (UTC) Stephan Hodges

 * I was also told to do this by my Chinese 101 instructor. And now that I look, there isn't much explanation of the tone pronunciation on the Tones page. I'll add the missing paragraph, including your useful hint. --Everlong 07:25, 12 May 2006 (UTC)

Help!
I've been studying Chinese for about a month and have looked at many descriptions of pronunciation, but this page is way more confusing than anything I've seen. I don't understand the value of (i.e., need for) the initials and finals, am overwhelmed by the sheer mass of material here, and on top of it all, what software do you need to play an OGG file? Thank you. Alan Nicoll 00:18, 15 January 2006 (UTC)

More whining: if this is meant to be part of a textbook for beginners, it will scare away more users than it will help. It's put together like the ultimate reference to Mandarin pronunciation, not the user-friendly introduction that beginners need. Also, some of my characters are showing up as boxes, which is warned about, but how does one go about fixing the problem? Alan Nicoll 00:29, 15 January 2006 (UTC)

"The Mandarin syllable" section could use some diagrams
To show an example of which part is the tone, which part is the initial, which part is the final, and perhaps an exception. --Kakurady (discuss • contribs) 15:19, 28 December 2016 (UTC)
 * For example: in  d ua ̀ n , d is the initial, uan is the final, and ˋ is the tone. --Kakurady (discuss • contribs) 15:28, 28 December 2016 (UTC)


text:
Genealogy/Getting started

Please select a topic above.

title: Genealogy/Getting started


text:
User:JYOQ~enwikibooks

よろしく.

change to wikisource >> my page

title: User:JYOQ~enwikibooks


text:
User:Wcrowe

I live in Oklahoma City and run my own computer support business. I specialize in the IBM AS400/iSeries, but also program in Visual Basic, Perl, PHP, Javascript, manage Linux systems, and do webpage and networking support. I've been at this for over twenty years (my first computer was a Heathkit and my first programming language was Fortran). I've worked as an electronics technician, programmer, systems analyst, MIS director, and have taught at the college level.

All in all, I think I liked computers better when I was the only guy I knew who had one.

title: User:Wcrowe


text:
Catalan/Numerals

Numerals i ordinals
All numbers in a downloadable file for learning with the computer

title: Catalan/Numerals


text:
User:Sekicho

Comprehensive texts

 * US Copyright Law
 * US Patent Law
 * US Trademark Law

Projects in progress

 * Federal Rules of Evidence
 * Japanese Law and Government
 * US Corporate Law
 * US Income Tax

To do

 * US Aviation Law
 * US Securities Law

title: User:Sekicho


text:
IB Mathematics (HL)/Group Theory

The aims of this option are to provide the opportunity to study some important mathematical concepts, and introduce the principles of proof through abstract algebra. For this topic, you do not need any background knowledge of a core topic.

Naive Set Theory
Sets can be used as a foundation for constructing all the rest of mathematics. This is called axiomatic set theory. But axiomatic set theory is a very formal theory, too cumbersome for everyday mathematical use. On the other hand, sets are too useful a mathematical construct to be reserved for specialists investigating the foundations of mathematics. Naive set theory refers to using the framework of sets without formally defining them. This in what we will be doing.

A set is defined (informally) as any collection of things
Ex: The set of primary colors, the set of my siblings, the set of positive integers.

Some sets can be described by listing the things in them
We list the things separated by commas, and use curly braces to indicate that the belong to a set.

Ex: {red, yellow, blue}, {Donna, Linda, Bobbi, Julie, Steve}

If we can completely list (enumerate) all the things in a set, the set is said to be finite. The set of primary colors and the set of my siblings are finite sets. If a set isn’t finite, it is said to be infinite. The set of all positive integers is an infinite set.

Some sets can be described by a rule for enumerating them
The set of positive even integers is infinite, so we can’t list them all. But, we can write it as {2, 4, 6, …}. The “…” says that there is a rule for constructing a list that contains every member of the set, even though the list can't be completed in a finite amount of time.

Problem:

1. Explicitly state a rule for constructing the set of positive even integers.

An interesting aside: some infinite sets are so “big” that it isn't possible to write a rule that constructs a list of all its members. The set of real numbers is one such set.

Some common mathematical sets
Here are some common mathematical sets you are familiar with. You need to be able to recognize the symbols.
 * $$\mathbb{N}$$
 * the set of positive integers, $$\{1, 2, \ldots\}$$

 * $$\mathbb{Z}$$
 * the set of integers

 * $$\mathbb{Z}^+$$
 * the set of positive integers, $$\{1, 2, 3, \ldots\}$$

 * $$\mathbb{Q}$$
 * the set of rational numbers

 * $$\mathbb{Q}^+$$
 * the set of positive rational numbers

 * $$\mathbb{R}$$
 * the set of real numbers

 * $$\mathbb{R}^+$$
 * the set of positive real numbers

 * $$\mathbb{C}$$
 * the set of complex numbers

The “things” in a set are called elements of the set
If something (say “x”) is in some particular set (say “S”), we say “x is an element of S.” To say this concisely, we write

 * $$x \in S$$

Mathematicians often use the word member as a synonym for element. For example, you’ll hear things like “2 is a member of the set of positive integers”.

Definition of equality for sets
Two sets S and T are equal if every element of S is also an element of T and every element of T is also an element of S. Not surprisingly, we write this as

 * $$S \mathbf= T$$

Here are some implications of this definition.

The ordering of elements in a set is not important

The set {red, yellow, blue} equals (i.e. is the same as) the set {yellow, blue, red}. Why? Look at the definition of equality. Every element in the first set is an element of the second, and every element in the second set is an element of the first. So the two sets are equal.

Something is either an element of a set or not; it doesn’t make any difference if you list it multiple times

The set {red, red, yellow, blue, red} is the same as (i.e. is equal to) the set {red, yellow, blue}, even though “red” is listed multiple times in the first set. Don’t take my word for it; check the definition of equals.

Definition of subsets
What would happen if we broke up the definition of equal sets into its two parts? Suppose we required only that every element of S is also an element of T, without requiring the “vice versa”? For example, every element of the set {red, yellow, blue} is in the set {red, orange, yellow, green, blue, purple}, but not vice versa. This kind of thing happens often enough that we give it a name. We say that S is a subset of T if every element of S is also an element of T. To say this concisely, we write

 * $$S \subseteq T$$

Not surprisingly, we’ll also make up a definition for the “vice versa” part. That is, we say that S is a superset of T if every element of T is an element of S. We write this as

 * $$S \supseteq T$$

Notice the similarity between the symbols $$\subseteq$$ and $$\supseteq$$, which are defined for sets, and $$\le$$ and $$\ge$$, which are defined for numbers. This is not an accident. The subset relation between sets is not the same thing as the less-than-or-equal relation between the integers, but the two relations do have many similarities. (How many can you think of?) Good mathematical notation will often be suggestive of such similarities.

Problems:

1) Is $$\mathbb N\supseteq\mathbb Z$$? Is $$\mathbb Z \supseteq\mathbb N$$? Is $$\mathbb Z \subseteq\mathbb Z^+ $$? Is $$\mathbb Z\subseteq\mathbb Z$$?

2) If S, T and U are sets with
 * $$S \subseteq T$$

and
 * $$T \subseteq U$$,

what can you say about the relationship between S and U? Show it using the definition of $$\subseteq$$. Do you remember what this property is called?

3) Put as many as you can of the common mathematical sets listed above into a single order of subsets, that is
 * ? $$\subseteq$$ ? $$\subseteq$$ ? $$\subseteq$$ …

The relationship between subsets, supersets and equality
Reviewing the definitions, we see that for two sets $$S$$ and $$T$$,

 * $$S \mathbf= T$$

is true whenever both

 * $$S \subseteq T$$ and $$S \supseteq T$$

are true. Problems:

1) What is the analogous statement for $$\leq$$ and $$\geq$$ with respect to real numbers? Is this statement true?

2) For x and y in $$\mathbb N$$, either x $$\leq$$ y or x $$\geq$$ y. Does the same hold true for $$\subseteq$$ and $$\supseteq$$ with respect to sets?

“Proper” subsets
Sometimes we have $$S \subseteq T$$ and we want to rule out the possibility that $$S \mathbf= T$$. To do this, we write

 * $$S \subset T$$

i.e. we omit the bar below the $$\subset$$. To say this in words, we say that S is a proper subset of T. The use of the word “proper” here is kind of funny. It doesn’t mean that there is something more accurate, or more polite, about being a proper subset. It is just the term that mathematicians have come to use to avoid having to say, “S is a subset of T but it isn’t equal to T.” Similarly,
 * $$S \supset T$$

is read “S is a proper superset of T ” and is a shorter way of writing

 * $$S \supseteq T$$ and $$S \neq T$$

Problems:

1. For any set S, which of the following are true?

 * $$S \subseteq S$$
 * $$S \subset S$$
 * $$S \mathbf= S$$
 * $$S \supseteq S$$
 * $$S \supset S$$

2. Suppose S = {2, 4, 6}. For each of the following sets T, list all the relationships that hold between S and T.

 * T = {6, 4, 2}
 * T = {2, 4, 4}
 * T = {2, 6, 10}
 * T = {2, 4, 6, 10}
 * T = {1, 3, 5}

The smallest possible set
Is there a set X that is a subset of every possible set S? Yes. We can have a set with no elements at all. The definition of subset says that X is a subset of S if every element of X is also an element of S. If X has no elements, this statement is true regardless of what elements S contains.

We call the set containing no elements the null set. It sometimes is written as

 * { }

but more often we write it as

 * $$\empty$$

Again, note the similarity between the notations for the set $$\empty$$ and the number 0. Just as $$0 \le n$$ for any natural number n, $$\empty \subseteq S$$ for any set S.

Combining sets: union and intersection
So far, we have defined various relations on pairs of sets $$(=, \subset, \subseteq, $$etc.) in terms of membership. It is also useful to define operations that take two sets and form a third set. Once again, we will define these operations in terms of membership.

We’ll start by defining the intersection of two sets S and T to be the set containing anything that is both an element of S and an element of T. We’ll write the intersection operation as

 * $$S \cap T$$

Similarly, we’ll define the union of two sets S and T to be the set containing anything that is either an element of S or an element of T. We’ll write the union operation as
 * $$S \cup T$$

If you have any trouble getting mixed up between $$\cap$$ and $$\cup$$, try remembering that $$\cup$$looks like U, which stands for Union.

Problems:

1. If S = {1, 2, 3} and T = {2, 3, 4}, what is $$S \cap T$$? What is $$S \cup T$$?

2. Are the following statements true for any sets S and T?

 * $$S = (S\cap S)$$
 * $$S \subseteq (S\cup S)$$
 * $$S \subseteq (S\cup T)$$
 * $$S \subset (S\cap T)$$
 * $$S \supset (S\cup T)$$

Is so, explain why. If not, give a counter-example.

Venn diagrams
When doing math, it is often useful to draw a picture to help visualize a problem. For elementary set operations, there is a conventional method of drawing pictures called Venn diagrams, named after the British mathematician John Venn. To draw a set S, we simply draw a circle, with the name of the set inside the circle.

 * [[Image:Trivial_Venn_Diagram.png]]

The intent of this drawing is that the inside of the circle represents all the elements in S. The outside of the circle represents everything that isn’t in the set S. There isn’t any significance to the fact that we use circles in Venn diagrams. We could just as well draw

 * Image:Trivial_Elliptical_Venn_Diagram.PNG or [[Image:Trivial Pentagonal Venn Diagram]]

Now, to represent an operation on two sets, we draw two overlapping circles, like this:

 * [[Image:Simple Venn Diagram]]

If you have colored pencils, you could color the inside of S red and the inside of T blue, like this:

 * [[Image:Colored Simple Venn Diagram]]

We can now describe all the area that is colored as. The purple overlap between the circles represents. If you don’t have colored pencils, you can draw the circles and shade in the area you want to describe. For example, you can draw something like to represent. To represent, you would shade in only the overlap of the two circles. (I would show this, but the word processor I am using to write this can’t do this easily.) If we never combined more than two sets, Venn diagrams wouldn’t be useful enough to bother learning about. But they are very useful when we want to illustrate relationships between three sets. In this case, we draw three overlapping circles, like this: Problems: Illustrate the following set operations by drawing 3 overlapping circles for S, T and U and then shading in only the area described

Once we get more than three sets, Venn diagrams aren’t so useful. The problem is that we can’t simply draw four circles that show every possible combination of intersections. So Venn diagrams are mostly an introductory learning tool. Problems: Draw a Venn diagram (not limited to circles) that depicts every possible combination of intersections between four sets. What is the best you can do?

Set complement (first try)
There is one more operation we want to define for sets – the complement. This operation is a unary operation, meaning it takes only one set as an argument. (Intersection and union are called binary operations, because they take two sets as arguments.) The idea behind the complement of a set S is that it should contain exactly those elements that the set S doesn’t contain. We’ll write the complement of S as	S′ (Another notation that you’ll often see is .) Thus, we might try to define the complement of S as “the set of all elements that are not elements of S”. For example, if S were the set of odd integers, than the complement of S would include all the even integers. But according to our definition, the complement of S would also contain my sister Donna, the color red and Valentine’s Day, since they aren’t in S either. So the complement is going to have all kinds of useless junk in it. If this were an everyday discourse, we could just dismiss the junk as being irrelevant to our conversation and ignore it. But in mathematics, we like to be more precise than that. Our solution will be to introduce the notion of a “universal set”.

Universal set
A set consisting of all elements under consideration is called the universal set.It is usually by the capital English Letter U. The universal set is simply the set of all things that we are currently talking about. The name “universal set” is misleading. It is not a set that contains everything in the universe. Nor is it universal in the sense that everyone has agreed to use it. Perhaps a better term would be “universe of discourse”. If we are making statements about the real numbers, then we say our universal set is the set of real numbers. If, on the other hand, we were discussing the natural numbers, our universe of discourse would be the set of all natural numbers. Another way to think of this is with a Venn diagram. We can draw the set S as where the shaded area represents the elements in S. But how would we shade the diagram to represent the complement of  S?  We would want to shade the outside of the circle. But where would we stop? A “little ways” out? To the edge of the paper? Maybe the back of the paper as well? The universal set makes it clear where to stop:

Keep in mind that the only reason for defining a universal set is to remove ambiguity when we’re taking a set complement. If we’re not going to be using set complements, we don’t need to worry about what our universal set is.

Set complement (the real thing)
Now that we have the concept of a universal set, we’ll give the real definition for set complement: The complement of a set T is the set of all elements that are in the universal set but not in T. Problems: Assume that R, S, and T are subsets of some universal set U. Draw Venn Diagrams to determine whether the following statements are always true.

(You had this last problem before, in the section titled Combining sets: union and intersection. Did you get the same answer this time?  If not, did the Venn diagram mislead you? You have to be careful when interpreting Venn diagrams with proper subsets.)

DeMorgan’s laws
In mathematics, the term “law” describes a statement that can be proved from more fundamental mathematics. There are a number of synonyms: postulate, theorem, corollary, etc. The term “law” is often used in conjunction with statements that were discovered a long time ago, typically before that area of mathematics was formalized. DeMorgan’s laws, named after Augustus De Morgan, are and Note the symmetry between these two statements. If you take one and interchange the  and , you get the other. DeMorgan’s laws are important because they provide a method for moving the complement from the “outside” to the “inside” of a complex expression. By applying DeMorgan’s laws repeatedly, we can transform any complex expression containing complements into an equivalent expression that has only complements of simple sets. Ex: In the last step, we made use of the fact that taking the complement a second time returns us to the original set, i.e. for any set S, Problems: Use Venn diagrams to show that DeMorgan’s laws are true. Use DeMorgan’s laws to transform these expressions into equivalent expressions that have complements only of basic sets.

Other useful laws
There are numerous laws relating various combinations of intersection, union and complement operations. Laws of the form X = Y are especially useful because we can use them for translating an expression into other, equivalent expressions. Here are some useful laws of this having this form. To the right of each law is a verbal description. union is commutative intersection is commutative When operations are commutative, we don’t have to be concerned about the order of the operands. union is associative intersection is associative When operations are associative, we can remove unnecessary parentheses. For example, we can write  because there is no difference between   and. intersection distributes over union This is analogous to the fact that for real numbers, multiplication distributes over addition. That is,. If we exchange  for * and   for +, we get the law above. Notice also that union does not distribute over intersection, such as addition does not distribute over multiplication for real numbers. The next two laws include U, the universal set. law of the excluded middle This is called the law of the excluded middle because any element in the universal set either is an element of S or isn’t an element of S. There is no middle ground. universal set is an identity for intersection This says that taking the intersection with the universal set makes no change, just as multiplying a real number by 1 makes no change. Problems: Verify each of the above laws using Venn diagrams.

Union-of-intersections form
A good start in determining how two set expressions are related is to reduce them both to union-of-intersections form. This is an expression of the form (? ? … ?) (? ? … ?) (? ? … ?) … (? ? … ?) where all the question marks are either a named set or its complement. For example, the expression is in union-of-intersections form. This is analogous to the sum-of-products form for expressions over R, such as or, following the common conventions for omitting multiplication symbols and extra parentheses, Question: What mathematical properties and/or notational conventions are needed to get the previous line from the one before it? Here’s a general technique for transforming any set expression into union-of-intersections form, Apply DeMorgan’s laws repeatedly to move all complements to named sets. Apply the distributive law repeatedly to change intersection of unions into unions of intersections. Make free use the associative laws to get rid of unnecessary parentheses and the commutative laws to put things in a nice order. Here’s a simple example. (I had originally intended to take this topic farther, that is to develop a complete algorithm for deciding whether two set expressions were equivalent (or had a subset relationship). But I decided it was going to get into too many details, so I’m just going to stop here. Problems: Determine whether each of the following relationships is always true. Start by transform both sides of the expression into union-of-intersections form.

Sets of sets
At the beginning of this topic, I said that sets could be used for constructing all of mathematics. This is possible because the elements of sets can be sets themselves. For example, consider the set S = {1, {1}, {1, {1}}}. This set has three elements, the number 1, the set {1}, and the set {1, {1}}. When dealing with sets of sets, it is important not to get confused between a element of the set and a subset of the set. For example, if S = {1, {1}, {1, {1}}}, then the number 1 is an element of S, and not a subset of S. On the other hand, the set {1} is both an element of S and a subset of S.  How can this be? Let me write each of the elements of S in a different color. S = {1, {1}, {1, {1}}} Now {1} is clearly an element of S.  But in addition, {1} is a subset of S, but for a different reason. Questions: Is the set {1, {1}} an element of S? A subset of S? Problems: Is the set {1, {1, {1}}} an element of S? A subset of S? How many subsets does the set S have? List them. Suppose we start with nothing but the null set, Ø. If that is the only thing in the mathematical universe, what other sets could we possibly build out of it? There is only one possibility, and that is to put it into a set, i.e. {Ø}. Is Ø really different than {Ø}? How many elements does Ø have. How many elements does {Ø} have? So now we have two sets, Ø and {Ø}. What new sets can we build from these? Well, one possibility would be to have a set containing only {Ø}, that is. (The sets and {Ø} each have just one element; how can we be sure that they aren’t the same set?  Hint: use the definition of set equality.)  But from Ø and {Ø}, we can also build the set (Ø, {Ø}}.  This is clearly a new set, because it has two elements – our biggest set yet! Problems: How many new sets can you build by making sets of the four sets we know about so far, i.e. Ø, {Ø},  and (Ø, {Ø}}? List them. Make up a procedure that will take any set (including the null set) and produce a new (different) set. Starting with the null set, write the first 6 sets your procedure produces if you repeatedly apply it to the previously produced set. Will your procedure ever produce the same set a second time? If so, write a second procedure that never repeats. If your first procedure never repeats, write a second one that does. Constructing the natural numbers from sets It probably will come as a surprise to you, but you constructed the natural numbers in the previous problem set! You probably didn’t recognize them because you wrote them in an unfamiliar notation. But how we write (or pronounce) numbers doesn’t have any effect on their meaning. In English, we say “zero, one, two, three, …” while in French, we say “zéro, un, deux, trois, …”, but the numbers aren’t any different. Similarly, we could use different mathematical notations, say 0, 1, 2, 3, … or , I, II, III, …, and the underlying numbers themselves wouldn’t be any different. What is important is what properties the numbers have. For the natural numbers, the important properties are: For any n N, there is a function (we’ll call it a “successor” function and write it as succ) whose value is another natural number. There is a single n N that is not the successor of any other natural number. We’ll call this number “zero” and write it as “0”. For any n N that isn’t 0, there is only one m N such that n = succ(m). That’s it. Any set of objects satisfying those properties is essentially the natural numbers. (Later, we’ll get more precise about what we mean as “essentially”.) Everything else you know about the natural numbers (the properties of addition, multiplication, …) follow as a natural consequence. Cool, huh? We’re not going to actually show this right now, but we will later in the Discrete Math topic.

Russell’s paradox
Russell’s paradox, named after philosopher/mathematician Bertrand Russell is the standard example of how naïve set theory can get into trouble by accepting anything as a set. To see this, let’s let our universal set U be the set of all sets, and we’ll consider those sets that don’t contain themselves as members. (Interlude: None of the sets we have seen so far contain themselves as members. In fact, it isn’t possible for a finite set to contain itself as a member.  But what about the infinite set	Ц = …… This is an infinite set, the limit of the sequence Ø, { Ø },, , … .  Every set in this sequence has only one element.  In the case of Ц, it’s element is	…… which is just Ц.  So Ц  Ц which is to say that Ц contains itself. End of interlude.) Let’s call sets that don’t contain themselves to be “reasonable” sets. Clearly, there are lots of reasonable sets. We’ll define R to be the set of all the reasonable sets. (You can’t get much more reasonable than that. ) So. But it turns out that R embodies a contradiction. To see this, ask yourself the question Is R a reasonable set?” If your answer is “yes”, then R contains R because we defined R as the set of all reasonable sets. On the other hand, R does not contain R by the definition of reasonable. It doesn’t do any good to answer “no” to the question. You’ll still conclude both that R contains R and R does not contain R. Axiomatic set theory resolves this paradox by being more careful about defining what a set is. It turns out that the “set of all sets” is not something that can be constructed in axiomatic set theory.

title: IB Mathematics (HL)/Group Theory


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Electronics/Charge and Coulomb's Law

Two atoms are walking down the street. The first atom says to the second atom "I think I lost an electron!" The second says "Are you sure?" To which the first states "I'm positive!"

Basic Understanding

 * Conductors : Materials which contain movable charges that can flow with minimal resistance.

 * Insulators : Materials with few or no movable charges, or with charges which flow with extremely high resistance.

 * Semiconductors : Materials whose behavior ranges between that of a conductor and that of an insulator under different conditions. Their conducting behavior may be heavily dependent on temperature. They are useful because we are able to change their conducting behavior to be dependent on many other factors.

 * The Atom : An atom contains a positively charged nucleus and one or more negatively charged electrons. The atom exists in three states: neutral, positively charged, and negatively charged.  A neutral atom has the same number of electrons and protons, a positively charged atom has more protons than electrons and a negatively charged atom has more electrons than protons.

 * (+) and (-) Ions : An ion is an atom that has an unequal number of electrons and protons. Ions are formed when a neutral atom gains or loses electrons during a chemical reaction. In a battery, the positive side has + ions, means there are fewer electrons than protons, giving it an overall positive charge, and -ve side, more electrons than protons, giving it an overall negative charge. +ve and -ve charge will attract each other, and it is the use of such an attractive force that allows the battery to do work.

Note: Electric current is not the same as electron flow as is widely mistaken. Firstly, the total current has the opposite direction compared to electron flow. This is a lucky "mistake" on our forefathers' part to put it this way. It is also because of this lucky legacy that we are reminded that electricity can flow in materials other than metals alone. For example, in water, it is not electrons that flow, it is ions, and the +ve ions and -ve ions flow in opposite directions, contributing half of the total current each.

Balance of Charge
Atoms, the smallest particles of matter that retain the properties of the matter, are made of protons, electrons, and neutrons. Protons have a positive charge, Electrons have a negative charge that cancels the proton's positive charge. Neutrons are particles that are similar to a proton but have a neutral charge. There are no differences between positive and negative charges except that particles with the same charge repel each other and particles with opposite charges attract each other. If a solitary positive proton and negative electron are placed near each other they will come together to form a hydrogen atom. This repulsion and attraction (force between stationary charged particles) is known as the Electrostatic Force and extends theoretically to infinity, but is diluted as the distance between particles increases.

When an atom has one or more missing electrons it is left with a positive charge, and when an atom has at least one extra electron it has a negative charge. Having a positive or a negative charge makes an atom an ion. Atoms only gain and lose protons and neutrons through fusion, fission, and radioactive decay. Although atoms are made of many particles and objects are made of many atoms, they behave similarly to charged particles in terms of how they repel and attract.

In an atom the protons and neutrons combine to form a tightly bound nucleus. This nucleus is surrounded by a vast cloud of electrons circling it at a distance but held near the protons by electromagnetic attraction (the electrostatic force discussed earlier). The cloud exists as a series of overlapping shells / bands in which the inner valence bands are filled with electrons and are tightly bound to the atom. The outer conduction bands contain no electrons except those that have accelerated to the conduction bands by gaining energy. With enough energy an electron will escape an atom (compare with the escape velocity of a space rocket). When an electron in the conduction band decelerates and falls to another conduction band or the valence band a photon is emitted. This is known as the photoelectric effect.

A laser is formed when electrons travel back and forth between conduction bands emitting synchronized photons.

 * 1) When the conduction and valence bands overlap, the atom is a conductor and allows for the free movement of electrons. Conductors are metals and can be thought of as a bunch of atomic nuclei surrounded by a churning "sea of electrons".
 * 2) When there is a large energy level gap between the conduction and valence bands, the atom is an insulator; it traps electrons. Many insulators are non-metals and are good at blocking the flow of electrons.
 * 3) When there is a small energy level gap between the conduction and valence bands, the atom is a semiconductor. Semiconductors behave like conductors and insulators, and work using the conduction and valence bands. The electrons in the outer valence band are known as holes. They behave like positive charges because of how they flow. In semiconductors electrons collide with the material and their progress is halted. This makes the electrons have an effective mass that is less than their normal mass. In some semiconductors holes have a larger effective mass than the conduction electrons.

Electronic devices are based on the idea of exploiting the differences between conductors, insulators, and semiconductors but also exploit known physical phenomena such as electromagnetism and phosphorescence.

Conductors
In a metal the electrons of an object are free to move from atom to atom. Due to their mutual repulsion (calculable via Coulomb's Law ), the valence electrons are forced from the centre of the object and spread out evenly across its surface in order to be as far apart as possible. This cavity of empty space is known as a Faraday Cage and stops electromagnetic radiation, such as charge, radio waves, and EMPs (Electro-Magnetic Pulses) from entering and leaving the object. If there are holes in the Faraday Cage then radiation can pass.

One of the interesting things to do with conductors is demonstrate the transfer of charge between metal spheres. Start by taking two identical and uncharged metal spheres which are each suspended by insulators (such as a pieces of string). The first step involves putting sphere 1 next to but not touching sphere 2. This causes all the electrons in sphere 2 to travel away from sphere 1 to the far end of sphere 2. So sphere 2 now has a negative end filled with electrons and a positive end lacking electrons. Next sphere 2 is grounded by contact with a conductor connected with the earth and the earth takes its electrons leaving sphere 2 with a positive charge. The positive charge (absence of electrons) spreads evenly across the surface due to its lack of electrons. If suspended by strings, the relatively negatively charged sphere 1 will attract the relatively positively charged sphere 2.

Insulators
In an insulator the charges of a material are stuck and cannot flow. This allows an imbalance of charge to build up on the surface of the object by way of the triboelectric effect. The triboelectric effect (rubbing electricity effect) involves the exchange of electrons when two different insulators such as glass, hard rubber, amber, or even the seat of one's trousers, come into contact. The polarity and strength of the charges produced differ according to the material composition and its surface smoothness. For example, glass rubbed with silk will build up a charge, as will hard rubber rubbed with fur. The effect is greatly enhanced by rubbing materials together.

 * Van de Graaff Generator: A charge pump (pump for electrons) that generates static electricity. In a Van de Graaff generator, a conveyor belt uses rubbing to pick up electrons, which are then deposited on metal brushes. The end result is a charge difference.

Because the material being rubbed is now charged, contact with an uncharged object or an object with the opposite charge may cause a discharge of the built-up static electricity by way of a spark. A person simply walking across a carpet may build up enough charge to cause a spark to travel over a centimetre. The spark is powerful enough to attract dust particles to cloth, destroy electrical equipment, ignite gas fumes, and create lightning. In extreme cases the spark can destroy factories that deal with gunpowder and explosives. The best way to remove static electricity is by discharging it through grounding. Humid air will also slowly discharge static electricity. This is one reason cells and capacitors lose charge over time.

Note: The concept of an insulator changes depending on the applied voltage. Air looks like an insulator when a low voltage is applied. But it breaks down as an insulator, becomes ionised, at about ten kilovolts per centimetre. A person could put their shoe across the terminals of a car battery and it would look like an insulator. But putting a shoe across a ten kilovolt powerline will cause a short.

Quantity of Charge
Protons and electrons have opposite but equal charge. Because in almost all cases, the charge on protons or electrons is the smallest amount of charge commonly discussed, the quantity of charge of one proton is considered one positive elementary charge and the charge of one electron is one negative elementary charge. Because atoms and such particles are so small, and charge in amounts of multi-trillions of elementary charges are usually discussed, a much larger unit of charge is typically used. The coulomb is a unit of charge, which can be expressed as a positive or negative number, which is equal to approximately 6.2415×1018 elementary charges. Accordingly, an elementary charge is equal to approximately 1.602×10-19 coulombs. The commonly used abbreviation for the coulomb is a capital C. The SI definition of a coulomb is the quantity of charge which passes a point over a period of 1 second ( s ) when a current of 1 ampere (A) flows past that point, i.e., C = A·s or  A = C/s. You may find it helpful during later lessons to retain this picture in your mind (even though you may not recall the exact number). An ampere is one of the fundamental units in physics from which various other units are defined, such as the coulomb.

Force between Charges: Coulomb's Law
The repulsive or attractive electrostatic force between charges decreases as the charges are located further from each other by the square of the distance between them. An equation called Coulomb's law determines the electrostatic force between two charged objects. The following picture shows a charge q at a certain point with another charge Q at a distance of r away from it. The presence of Q causes an electrostatic force to be exerted on q.

The magnitude of the electrostatic force F, on a charge q, due to another charge Q, equals Coulomb's constant multiplied by the product of the two charges (in coulombs) divided by the square of the distance r, between the charges q and Q. Here a capital Q and small q are scalar quantities used for symbolizing the two charges, but other symbols such as q1 and q2 have been used in other sources. These symbols for charge were used for consistency with the electric field article in Wikipedia and are consistent with the Reference below.

$F = \frac {k q Q}{r^2}$

F = magnitude of electrostatic force on charge q due to another charge Q r = distance (magnitude quantity in above equation) between q and Q k = Coulomb's constant = 8.9875×109  N·m2/C2 in free space

The value of Coulomb's constant given here is such that the preceding Coulomb's Law equation will work if both q and Q are given in units of coulombs, r in metres, and F in newtons and there is no dielectric material between the charges. A dielectric material is one that reduces the electrostatic force when placed between charges. Furthermore, Coulomb's constant can be given by:

$k = \frac {1}{4 \pi \epsilon }$

where $$\epsilon \,$$ = permittivity. When there is no dielectric material between the charges (for example, in free space or a vacuum),

$\epsilon _0\,$ = 8.85419 × 10-12 C2/(N·m2).

Air is only very weakly dielectric and the value above for $$\epsilon _0\,$$ will work well enough with air between the charges. If a dielectric material is present, then

$\epsilon = \kappa \epsilon _0\,$

where $$\kappa $$ is the dielectric constant which depends on the dielectric material. In a vacuum (free space), $$\kappa = 1$$ and thus $$\epsilon = \epsilon _0$$. For air, $$\kappa = 1.0006$$. Typically, solid insulating materials have values of $$\kappa > 1$$ and will reduce electric force between charges. The dielectric constant can also be called relative permittivity, symbolized as $$\epsilon_r$$ in Wikipedia.

Highly charged particles close to each other exert heavy forces on each other; if the charges are less or they are farther apart, the force is less. As the charges move far enough apart, their effect on each other becomes negligible.

Any force on an object is a vector quantity. Vector quantities such as forces are characterized by a numerical magnitude (i. e. basically the size of the force) and a direction. A vector is often pictured by an arrow pointing in the direction. In a force vector, the direction is the one in which the force pulls the object. The symbol $$\vec {F}$$ is used here for the electric force vector. If charges q and Q are either both positive or both negative, then they will repel each other. This means the direction of the electric force $$\vec {F}$$ on q due to Q is away from Q in exactly the opposite direction, as shown by the red arrow in the preceding diagram. If one of the charges is positive and the other negative, then they will attract each other. This means that the direction of $$\vec {F}$$ on q due to Q is exactly in the direction towards Q, as shown by the blue arrow in the preceding diagram. The Coulomb's equation shown above will give a magnitude for a repulsive force away from the Q charge. A property of a vector is that if its magnitude is negative, the vector will be equal to a vector with an equivalent but positive magnitude and exactly the opposite direction. So, if the magnitude given by the above equation is negative due to opposite charges, the direction of the resulting force will be directly opposite of away from Q, meaning the force will be towards Q, an attractive force. In other sources, different variations of Coulombs' Law are given, including vector formulas in some cases (see Wikipedia link and reference(s) below).

In many situations, there may be many charges, Q1, Q2, Q3, through Qn, on the charge q in question. Each of the Q1 through Qn charges will exert an electric force on q. The direction of the force depends on the location of the surrounding charges. A Coulomb's Law calculation between q and a corresponding Qi charge would give the magnitude of the electric force exerted by each of the Qi charges for i = 1 through n, but the direction of each of the component forces must also be used to determine the individual force vectors, $$\vec {F_1}, \vec {F_2}, \vec {F_3}, ...., \vec {F_n}$$. To determine the total electric force on q, the electric force contributions from each of these charges add up as vector quantities, not just like ordinary (or scalar) numbers.

$\vec {F_e} = \vec {F_1} + \vec {F_2} + \vec {F_3} + ..... + \vec {F_n}$

The total electric force on q is additive to any other forces affecting it, but all of the forces are to be added together as vectors to obtain the total force on the charged object q. In many cases, there are billions of electrons or other charges present, so that geometrical distributions of charges are used with equations stemming from Coulomb's Law. Practically speaking, such calculations are usually of more interest to a physicist than an electrician, electrical engineer, or electronics hobbyist, so they will not be discussed much more in this book, except in the section on capacitors.

In addition to the electrostatic forces described here, electromagnetic forces are created when the charges are moving. These will be described later.

Reference(s):

 * College Physics Volume 2  by Doug Davis, Saunders College Publishing, Orlando, FL, 1994

 * Coulomb's Law

 * Dielectric constant

 * GCSE Science/Static Electricity
 * GCSE Science/Advanced static electricity topics

Next: Voltage, Current, and Power Return to: Electronics Outline

title: Electronics/Charge and Coulomb's Law


text:
User:Laudaka

Hi, I'm currently not active at Wikibooks. For a little about me see my Wikipedia user page: http://en.wikipedia.org/wiki/User:Laudaka Greetings, Paulus/laudaka - Hoi, Op dit moment ben ik niet actief bij Wikibooks. Voor wat meer info over mij zie mijn gebruikerspagina van Wikipedia: http://nl.wikipedia.org/wiki/Gebruiker:Laudaka Met vriendelijke groet, Paulus/laudaka

title: User:Laudaka


text:
Portuguese/Contents/Days, Months, Seasons

<< Portuguese:Contents


text:
Portuguese/Contents/Common adjectives

<< Portuguese:Contents

Size

 * Large - grande
 * Huge - enorme
 * Small - pequeno
 * Tiny - minúsculo

Appearance

 * Beautiful/Handsome - bonito
 * Pretty - lindo
 * Ugly - feio

Age

 * Young  - novo / jovem
 * Old    - velho
 * Ancient - antigo

Colors

 * red - vermelho
 * green - verde
 * yellow - amarelo
 * brown - castanho (In Portugal) marron (In Brazil)
 * black - preto
 * white - branco
 * blue - azul
 * purple - roxo
 * pink - rosa

adjectives

 * Smart/Intelligent - inteligente
 * Stupid - estúpido / burro
 * High/tall - alto
 * Low/short - baixo
 * Long - longo
 * Short - curto
 * Thin - magro
 * weak - fraco
 * Fat - gordo
 * Hot - quente / calor
 * Cold - frio
 * Frozen - congelado
 * New - novo
 * delicious - delicioso
 * bitter - amargo
 * soft - suave
 * hard - duro
 * horrible - horrível
 * perfect - perfeito
 * possible - possível
 * calm - tranquilo
 * good - bom
 * bad - mau
 * awful - ruim
 * excellent - excelente
 * wide - largo
 * narrow - estreito
 * heavy - pesado
 * light (weight) - leve
 * light (color) - claro
 * bright - brilhante
 * happy - feliz
 * sad - triste
 * proud - orgulhoso
 * embarrassed - envergonhado / com vergonha

title: Portuguese/Contents/Common adjectives


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Talk:Electronics/Charge and Coulomb's Law

Practically all of this infomation came from Electronics/Charge, before I added a major section on Coulomb's Law on July 13.

H Padleckas 11:05, 2 Jul 2004 (UTC) H Padleckas 17:26, 13 Jul 2004 (UTC)

Should we put Electric Field in here?
I'm just about done with this module for now. As a low priority, I may someday put in a picture of forces on q due to multiple point charges. There are a couple things that the Electronics regular authors may want to consider now.

 * This module isn't too long. In the next module Electronics/Voltage, Current, and Power (most of which I wrote), there is a section called "Electric Field."  That module seems longer and a little more material may be added to it under Voltage and Current and more under Circuit.  Should we move the "Electric Field" section into this module or should we keep it where it is?  Eventually, I plan to move it to the "Charge and Coulomb's Law" module and rename the module "Electronics:Charge, Coulomb's Law, and Electric Field."  But if I'm told the consensus is that it should stay where it is, then we won't move it and I'll keep the Electronics/Voltage, Current, and Power name unchanged, because it's a rather small, less important part of a bigger module covering numerous other topics.

 * A number of books don't go into the dielectric correction when first presenting Coulomb's Law. As an afterthought, I added equations on it separately, because I think it's important to mention it.  For simplicity or brevity, if any of the Electronics authors care to undertake the task of combining all the permittivity equations with Coulomb's Law into one equation but keeping the same information, I would have no objection.

 * Under "Balance of Charge" section, there seems to be "loose" bullet statement about laser. If anybody wants to do something about that, go ahead.

On a low priority basis, I might someday copy some of the information in this module over to the first module of Electromagnetism in the "Modern Physics" book.

H Padleckas 19:12, 15 Jul 2004 (UTC)

Electronics?
Should this be Electronics:Charge and Coulomb's Law, or is it being used by other books, etc. I don't want to put a TOC in if it is shared.

Name of this module
Before I learned about moving modules, I copied and pasted Electronics/Charge into this module and then added the section on Coulomb's Law. A better thing to have done would have been to move Electronics/Charge to this module when it was new, essentially renaming it. This way the history of Electronics/Charge would have been preserved, giving User:Wanderer credit for writing the first part on charge (up to but not including Quantity of Charge, which I wrote). This Electronics/Charge and Coulomb's Law module is being used only by the Electronics book. Wanderer has copied the Electronics/Charge information into Physics in English:Charge for his "Physics in English" book (Coulomb's Law section is not included). I also copied practically all of the Coulomb's Law section from this Electronics/Charge and Coulomb's Law module and the Electric Field section in the next module into a new module called Modern Physics:Coulomb's Law and the Electric Field for the Modern Physics book. I plan to leave things the way they are in this Electronics/Charge and Coulomb's Law module for a little while to get a feel for whether the Electronics regulars want to include the Electric Field section in here or not. When this issue is decided, I plan to move Electronics/Charge to new module, insert Electric Field from the next module if so decided, and call the new module either Electronics/Charge and Coulomb's Law or Electronics/Charge, Coulomb's Law, and Electric Field. After that the Electronics/Charge and Coulomb's Law module can then be deleted by administrators.

H Padleckas 14:09, 24 Jul 2004 (UTC)

when did everything get bolded?
i mean do we really need to bold every other word? - Omegatron

overcomplicated
this isn'y really usable to teach people about electronics as most teachers would teach ohms law first and resistor color band codes, then (after introducing a lot of components and circuits) introduce all of the theories on this page when it gets to the point that could be applied to their work, you're not going to remember it if you never use it. also there's no hands on experience in this entire book. Someone please organize this into a usable textbook form.

 * Another user has started a more hands-on text called LearnElectronics - Aya T E C 17:46, 15 August 2005 (UTC)

Is this correct?
In the second paragraph of the first section it says "Atoms only gain and lose protons and electrons through fusion, fission, and radioactive decay." I don't want to change it myself, because I don't really know much about physics (that is why I am reading this), but I think it should say "Atoms only gain and lose protons and neutrons through fusion, fission, and radioactive decay." Earlier in that same paragraph it had said that atoms can lose electrons, which causes them to become ions.

 * You are correct. You could also change "radioactive decay" to "radioactive alpha-decay". Beta and gamma radiation do not affect the nucleus. - Aya T C 16:00, 13 August 2005 (UTC)

 * See the section right above this. - Omegatron 03:13, 15 August 2005 (UTC)

A Better use of your time...
would be to disregard this wikibook and check out http://www.ibiblio.org/obp/electricCircuits/ I believe this book is far more accurate. But then again, who among you reading this discussion can remember where the local LIBRARY is, to go check out a few books (Understanding Physics vol. i, ii, iii by Isaac Asimov).

 * Of course, you can get the one I have; same text, but combined into one volume. But the publishers were only interested in pushing up Asimov's book count and making money without doing any work--so they just used the same plates, with the page numbers in volumes 2 and 3 renumbered.  But they had so little concern for the reader that they didn't update the zillions of internal links to those pages so that they told you where to go.  The books also have as many annoying little errors as the poorer books on Wikibooks.  Metric1000 11:31, 27 September 2005 (UTC)

probably incorrect
in the section on conductors it says: "This causes all the electrons in sphere 2 to travel away from sphere 1 to the far end of sphere 2." That can't be right.

I'm sure all are "pushed", but they can't all go to the other side. That would create an insanely strong electromagnetic force.

Hopefully someone more knowledgeable than me can fix this.

Also I noticed towards the second half of the page the term "electric force" is used without much explanation. I wonder if some more specific term should be used (such as perhaps "electrostatic force") or if this is the correct term and it should be defined/explained.

Thank you. Best regards -- Jason Woofenden

Focus
This chapter is called Charge and Coulombs Law. So where is Q=It is there is the SI defininition. That is the most important point of the chapter. I have a cell/battery with 3600 Coulombs of charge or 1 Ampere hours so I can draw a current of 1 Ampere from it for an hour or a current of 0.1 A for 10 hours.--IKnowNothing 18:58, 26 February 2006 (UTC)

+ve and -ve
The "(+) and (-) Ions" section suddenly starts talking about +ve and -ve, what are these supposed to mean? Jeffrey.Rodriguez (talk) 18:29, 16 November 2010 (UTC)

 * I believe it means positive and negative, but I find it (and the rest of that paragraph) very confusing. Perhaps relying less on text and a bit more on a diagram of some kind could clear that paragraph up. 213.119.131.169 (discuss) 16:33, 15 July 2015 (UTC)

Photoelectric effect incorrect
I believe the explanation about photoelectric effect to be incorrect. What the text claims to be the photoelectric effect (absorbing an electron and emitting a photon) is the exact opposite of what the photoelectric effect is (absorbing photons and emitting electrons). The process of emitting a photon when an excited electron falls back is called fluorescence. See the wikipedia articles on fluorescence and the photoelectric effect. -- 213.119.143.106 (discuss) 17:11, 15 July 2015 (UTC)


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User talk:193.112.136.21

Please don't vandalise wikibooks. Any deletions you make can very simply be reverted by myself (or any other wikibook editor) with one click of a button.

If you want to start making regular edits, instead of deleting pages, then you are very welcome to do so. Theresa knott 14:26, 2 Jul 2004 (UTC)

title: User talk:193.112.136.21


text:
User:Lzap

$$Insert formula here$$--200.60.249.121 16:02, 2 Jul 2004 (UTC)

title: User:Lzap


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Talk:Electronics/DC Voltage and Current

KVL analogies
From the article:

 * Kirchoff's laws can be described with a sentence as "What comes in, must go out". It's that simple.

Not really. KCL works for "what goes in comes out", but KVL is more like "what goes up comes down", but not really. - Omegatron

 * Yes really: Voltage is exactly analagous to height in a gravitational situation.

 * Yeah, but it's not an exact analogy to KVL, is it? KVL is more like "if you go up 5 stairs and go down some stairs and are on the ground, you must have gone down 5 stairs."

 * Here is a better description of it:

 * "Applying KVL is analogous to taking a walk while paying attention to increases and decreases in altitude. If you walk in a loop (ie. you end your walk where you started) the net change in altitude is zero.  This is true for any path that you take for your walk. " - Omegatron 18:28, 2 Jul 2004 (UTC)

I agree, but maybe we could make it even simpler:
 * Kirchoff's laws can be described in 2 sentences: "What comes in, must go out". "What goes up, must come down". It's that simple.

I like the way those sentences hint that the KVL is not *always* true. (because we know "what goes up, must come down" is also not *always* true).

In a very few situations, I need the full equation:

sum( forces on a block of wood ) = mass * change in velocity / time

sum( voltages around a loop ) = area of loop * change in magnetic field / time

In most circuits the magnetic field does not change significantly. In most buildings, bridges, dams, etc., the velocity does not change significantly.

For practical circuit design, I generally assume that

sum( voltages around a loop ) = 0 (not exactly true, but close enough for circuit design)

in the same way that when I design a truss, I generally assume that

sum( forces on a block of wood ) = 0 (not exactly true, but close enough for bridge design).

-- DavidCary 14:17, 3 Jul 2004 (UTC)

Removed from article
In parallel voltage...

 * you can't have ideal voltage sources in parallel, if this is what is meant by this statement. it is equivalent to saying 3=5.  With source impedances, like real cells, they can be in parallel, but that would be silly...

The flow a circuit is that of a potential drop.

 * what??

de-emphasize current divider?
Voltage dividers are important to know. The idea of a voltage divider equation is used in many different circuits -- bandpass filters, power loss in power lines, etc. Is the current divider really that important? What is it used for? If it's not that important, perhaps we could de-emphasize it. Make it a "study problem" to practice Ohm's law? (or perhaps Thevenin or Norton equivalent circuits)? --DavidCary 04:09, 28 Jun 2005 (UTC)

 * I agree that voltage dividers are more often used. But this does not mean that current dividers are unimportant in electronic circuit analysis involving current sources it is easier to use current divider than voltage divider.  Currently I would say that voltage dividers are already more emphasised than current dividers.  I am not aware of any practical use of it.  The only use I can think of is if you wanted to have two different currents flowing in two different branches of the circuit.  But it is a useful in circuit analysis especially when there are current sources instead of voltage sources. --IKnowNothing 18:46, 28 Jun 2005 (UTC)

title: Talk:Electronics/DC Voltage and Current