ejaasaari/simplewiki-2025-04-01 huggingface dataset:
Electronics is the study of electricity (the flow of electrons) and how to use that to build things like computers. It uses circuits that are made with parts called components and connecting wires to do useful things. The science behind electronics comes from the study of physics and gets applied in real-life ways through the field of electrical engineering. Many people can name several simple electronic components, such as transistors, fuses, circuit breakers, batteries, motors, transformers, LEDs and bulbs, but as the number of components starts to increase, it often helps to think in terms of smaller systems or blocks, which can be connected together to do something useful.  One way of looking at an electronic system is to separate it into three parts: A television set, for example, has as its input a broadcast signal received from an antenna, or for cable television, a cable. Signal processing circuits inside the television set use the brightness, colour, and sound information contained in the received signal to control the television set's output devices. The display output device may be a cathode ray tube (CRT) or a plasma or liquid crystal display screen. The audio output device might be a magnetically driven audio speaker. The display output devices convert the signal processing circuits' brightness and colour information into the visible image displayed on a screen. The audio output device converts the processed sound information into sounds that can be heard by listeners. Analysis of a circuit/network involves knowing the input and the signal processing circuit, and finding out the output. Knowing the input and output and finding out or designing the signal processing part is called "synthesis". History. People started experimenting with electricity as early as 600 B.C.E, when Thales of Miletus discovered rubbing fur on amber would cause them to attract each other. Starting in the 1900s, devices used glass or metal vacuum tubes to control the flow of electricity. With these components a low power voltage can be used to change another. This revolutionized radio, and allowed other inventions. In the 1960s and early 1970s transistors and semiconductors began replacing vacuum tubes. Transistors can be made much smaller than vacuum tubes and they can work using less energy
Scalars are simple numbers. They are used for measuring things. Many things can be measured, and the measure can be explained by only giving the number. Suppose we are measuring a rod. We could give the measured length as 2 metres or 3 cm—depending on the length of the rod under observation. Here, only the figure 2 or 3 along with the unit of measure is enough to transmit information about the rod. Other examples of scalars are:  In other words, mass is measured by scalars, just like distances are measured by scalars. In mathematics, scalars are distinguished from more complex mathematical objects such as vectors and matrices in that they consist of only one number. A scalar formula_1 can also be multiplied to a vector formula_2 or a matrix formula_3, resulting in the vector formula_4 and the matrix formula_5, respectively. For vectors, scalar multiplication produces a new vector of different length in the same or opposite direction of the original vector.
Photons (from Greek φως, meaning "light"), in many atomic models in physics, are particles which transmit light. In other words, light is carried over space by photons. Photon is an elementary particle that is its own antiparticle. In quantum mechanics each photon has a characteristic quantum of energy that depends on frequency: A photon associated with light at a higher frequency will have more energy (and be associated with light at a shorter wavelength). Photons have a rest mass of 0 (zero). However, Einstein's theory of relativity says that they do have a certain amount of momentum. Before the photon got its name, Einstein revived the proposal that light is separate pieces of energy (particles). These particles came to be known as photons.  A photon is usually given the symbol γ (gamma). Properties. Photons are fundamental particles. Although they can be created and destroyed, their lifetime is infinite. In a vacuum, all photons move at the speed of light, c, which is equal to 299,792,458 meters (approximately 300,000 kilometers) per second. A photon has a given frequency, which determines its color. Radio technology makes great use of frequency. Beyond the visible range, frequency is less discussed, for example it is little used in distinguishing between X-Ray photons and infrared. Frequency is equivalent to the quantum energy of the photon, as related by the Planck constant equation, formula_1, where formula_2 is the photon's energy, formula_3 is the Planck constant, and formula_4 is the frequency of the light associated with the photon. This frequency, formula_4, is typically measured in cycles per second, or equivalently, in Hz. The quantum energy of different photons is often used in cameras, and other machines that use visible and higher than visible radiation. This because these photons are energetic enough to ionize atoms.  Another property of a photon is its wavelength. The frequency formula_4, wavelength , and speed of light formula_7 are related by the equation, formula_8, where formula_9 (lambda) is the wavelength, or length of the wave (typically measured in meters.) Another important property of a photon is its
A vector is a mathematical object that has a size, called the "magnitude", and a direction. It is often represented by boldface letters (such as formula_1, formula_2, formula_3), or as a line segment from one point to another (as in formula_4). For example, a vector would be used to show the distance and direction something moved in. When asking for directions, if one says "Walk one kilometer towards the North", that would be a vector, but if they say "Walk one kilometer", without showing a direction, then that would be a scalar. We usually draw vectors as arrows. The length of the arrow is proportional to the vector's magnitude. The direction in which the arrow points to is the vector's direction. How to add vectors. Adding vectors on paper using the head to tail method. The Head to Tail method of adding vectors is useful for doing an estimate on paper of the result of adding two vectors. To do it: It's called the "Head to Tail" method, because each head from the previous vector leads in to the tail of the next one. Using component form. Using the component form to add two vectors literally means adding the components of the vectors to create a new vector. For example, let a and b be two two-dimensional vectors. These vectors can be written in terms of their components. formula_5 formula_6 Suppose c is the sum of these two vectors, so that c = a + b. This means that formula_7. Here is an example of addition of two vectors, using their component forms: formula_8 formula_9 formula_10 This method works for all vectors, not just two dimensional ones. How to multiply vectors. Using the dot product. The dot product is one method to multiply vectors. It produces a scalar. It uses component form: formula_11 Using the cross product. The cross product is another method to multiply vectors. Unlike dot product, it produces a vector. Using component form: formula_12 Here, formula_13 means the length of formula_14, and formula_15 is the unit vector at right angles to both formula_14 and formula_17. Multiplying by
A soap bubble is a very thin film of soap water. Their shape is a hollow, round ball, or sphere. They have a colorful surface. Soap bubbles do not last very long. Sometimes they break in the air. When they touch something else, they usually break. When people talk about soap bubbles they think about them being pretty but short-lived. So, they are a symbol for other things that are pretty but short-lived or unimportant. Children enjoy playing with bubbles. Sometimes, adults enjoy seeing art done with soap bubbles. They get their colors from iridescence.
A bicycle (or bike) is a small, human powered land vehicle with a seat, two wheels, two pedals, and a metal chain connected to cogs on the pedals and rear wheel. A frame gives the bike strength, and the other parts are attached to the frame. The name comes from these two words - the prefix "bi-" meaning two, and the suffix "-cycle" meaning wheel. It is powered by a person riding on top, who pushes the pedals around with his or her feet. Riding bicycles, which is also called cycling, is an important way to travel in several parts of the world. The most popular type of cycling is Utility cycling. It is also a common recreation, a good form of low-impact exercise, and a popular sport. Road bicycle racing is the second most popular spectator sport in the world. Bicycling uses less energy per mile than any other human transport. Invention. In 1817 a German professor, Baron Karl von Drais, created the first two-wheeled bicycle. It was made of wood and had two wheels. The front wheel could be turned using the handlebars in order to steer the bike. However, it did not have pedals, so the rider would have to push their feet on the ground to make it move. In the 1860s, French inventors added pedals to the front wheel. However, it took a lot of effort to turn the pedals. Later inventors made bikes out of metal only, and made the front wheel very big, giving higher speed. This design was called the penny-farthing bicycle. However, it was difficult to ride, since it could fall easily and the rider would fall far. Several improvements were made in the 1880s and '90s. In 1885, the safety bicycle was invented. This had two wheels the same size so that the rider could sit at a lower height. It was called the safety bicycle because it much easier to ride than the penny-farthing. When stopping, the rider can simply put down a foot instead of completely dismounting. Instead of pedaling and steering with the front wheel, the safety bicycle steers with the front wheel while the pedals
A wheel is a disc or circle-shaped mechanical device. Its main purpose is to allow things to "roll"; in other words, the wheel spins, and object on the wheels moves more easily along the ground. It is a simple machine. The principle behind the wheel is that of mechanical advantage.  Most land vehicles roll on wheels. Wheels are often used in pairs, connected by a rod of wood or metal known as an axle. The wheel and axle turn together. The part of the wheel that attaches to the axle is called the hub.  The wheel with an axle is the basis of many machines, not just vehicles. The potter's wheel, the lathe and the windlass are examples. Many machines have wheels with teeth, known as gears. History. Most experts believe that the ancient Mesopotamians invented the wheel about 4000 BC. People in Asia also discovered it on their own around 3500 BC. The Inca and Maya had wheels on children's toys around 1500 BC, but they did not use wheels for work. Africa south of the Sahara desert and Australia did not have the wheel until people there met people from Europe. Early wheels were solid disks; the spoked wheel was invented around 2000 BC. The earliest documentation of a vehicle with wheels is a painting dated between 33503500 BC. Uses. Today, wheels are used in cars, carts, airplanes, wheelchairs, bicycles, trains, and skateboards, in addition to many more devices.
The word exercise means: Basic modes of physical exercises. People do physical exercises as a part of their healthy lifestyle to get stronger and healthier or stay strong and healthy or to improve their body image. There are three basic modes of physical exercises: Exercises can be an important part of physical therapy, weight loss, or sports performance. Exercise can be fun, but it is important for the exerciser to do what they like and eat enough calories, so when they exercise they are building up muscles, not just breaking them down for fuel. Carbohydrates are muscle-sparing; and if one does not get enough calories overall, there is the risk of burning muscles up with the fat to make up the deficit. Exercise benefits. Benefits of exercise for all ages have been known since antiquity. Marcus Cicero, around 65 BC, stated: “It is exercise alone that supports the spirits, and keeps the mind in vigor.” The CDC recommends that adults should get 150 minutes of physical activity weekly. Regular exercise has been shown to help high blood pressure, obesity, heart disease, diabetes, and depression, among others. Exercise also helps people feel less tired. Regular exercise can have a profoundly positive impact on depression, anxiety, and ADHD. It also relieves stress, improves memory, helps sleep better, and boosts overall mood. Studies show that exercise can treat mild to moderate depression as effectively as antidepressant medication but without the side-effects, of course. References. 7. Why Fitness is famous and necessary?
Percent means "out of one hundred". It is often shown with the symbol "%". It is used even if there are not a hundred items. The number is then scaled so it can be compared to one hundred. Percent is also used to indicate changes in numerical quantities.  For example, we have a bowl of fruit with three apples and one orange. The percentage of apples is 3 out of 4, or 3/4 = 75/100 = 75%.  A percentage is only one way of writing a ratio; one can also write it as a fraction or decimal. There are ways to convert fractions to percentages or decimals to percentages. Uses. Percentages are useful in practice, because it allows one to compare things that are not out of the same number. For example, exam marks are often percentages, which can compare them even if there are more questions on one exam paper than the other.
Writing is the art/act of recording language on a visual medium using a set of symbols. The symbols must be known to others, so that the text may be read. A text may also use other visual systems, such as illustrations and decorations. These are not called writing, but may help the message work. Usually, all educated people in a country use the same writing system to record the same language. To be able to read and write is to be literate. Writing differs from speech because "the readers need not be present at the time". We can read writing from long ago, and from different parts of the world. Text stores and communicates knowledge. Writing is one of the greatest inventions of the human species. It was invented after people settled in towns, and after agriculture started. Writing dates from about 3,300, which is over 5000 years ago, in the Middle East. Writing today is usually on paper, though there are ways to print on almost any surface. Television and movie screens can also display writing, and so can computer screens. Many writing materials were invented, long before paper. Clay, papyrus, wood, slate and parchment (prepared animal skins) have all been used. The Romans wrote on waxed tablets with a pointed stylus; this was popular for temporary notes and messages. The later invention of paper by the Chinese was a big step forward. Writing is traditionally done using a hand tool such as a pencil, a pen, or a brush. More and more, however, text is created by input on a computer keyboard. Definition of writing. There are two schools of thought: Therefore, depending on an author's definition of writing, the term may be used in different ways. With many early systems we do not know what they do convey. The central idea is that "a full writing system must be able to represent anything that might be said in spoken language".p7, 217 From this point of view the invention of the rebus is an essential step. We can only be sure a sign system is full writing if we can translate the symbols into a modern language. In the case of some ancient scripts we cannot do this. History of writing. Writing was invented independently
Plato ( ) was one of the most important philosophers of all time. Born to wealthy parents in Athens, Greece, Plato was a student of Socrates (who did not write) and, later, became the teacher of Aristotle. Plato started a university in Athens called the Academy where he taught. Plato wrote about many ideas in philosophy that are still talked about today, including political philosophy and the philosophy of language. One modern scholar, Alfred North Whitehead, said that all European philosophy since Plato is a series of footnotes to his works. Dialogues. Plato wrote his books in the form of conversations called dialogues. In a dialogue, two or more people talk about ideas and sometimes disagree over them. The "Laws" is Plato's longest dialogue and probably his last. Socrates is usually the main person in Plato's dialogues. Often, Socrates talks with people and tries to see if they believe anything that is illogical. Because of this, some people became angry with Socrates and tried to kill him. In Plato's Apology, Socrates is put on trial by these people and is eventually sentenced to death by drinking poison. Theory of Forms. Plato is famous for developing the theory of forms. This theory says that everything in our world is imperfect but corresponds to a perfect version of itself that exists in another realm.  For example, there are wooden chairs, metal chairs, square chairs, big chairs, small chairs, etc. All the chairs we can ever sit in, according to Plato, are imperfect versions of the perfect form of “chairness,” the ideal chair. The same is true of every other object our senses can perceive: it is imperfect but corresponds to a perfect version of itself.  One simple way to think about Plato's theory is with numbers. The difference between "chairness" and a regular chair is similar to the difference between the number five and having five apples, oranges, pears, etc.  In other words, Plato thought that the world we live in is just a shadow of the real, "intelligible realm," which only a few people will ever understand. He thought that all perfect forms come from perfection itself, which he called "the good.” Plato
A book is now a set of printed sheets of different kinds of paper held together between two covers. The sheets of paper in a book are called pages. The pages have words written in them and maybe illustrations drawn. The first books were not printed, but written by hand in ink.  The book is a more flexible format than the earlier idea of the scroll. The change from scrolls to books began in the Roman Empire and took many centuries to become complete. A writer of a book is often called an author. Someone who draws the pictures in a book is called an illustrator. Books can have more than one writer or illustrator. A book can be a text that is a part of a larger collection of texts. A section of a text may be published as a book so that it only has one writer or only focuses on one subject area. Books written in this way can be understood without reading whole collection of writings. Examples are the Iliad, Odyssey, Bible, Quran and Torah. Encyclopedias often have separate articles written by different people, and are published as separate volumes. Each volume is a book. "Hardcover" books have hard covers made of cardboard that is covered in cloth or leather and sewn together. "Paperback" books have covers made of stiff paper that is glued together. A small book is a "booklet" and may be stapled together. The words in books can be read aloud and recorded. These are called "audiobooks". Books may be borrowed from a library or bought from a bookstore. People can make their own books and write in them, and add family photos and drawings. Some books are empty inside, like a diary, an address book, or photo album. These books are meant to be written in. Usually, the word "book" means that the pages inside have words, and often pictures. Some books are written just for children, some are for entertainment, and some are textbooks for studying something in school, such as math or history. Etymology. It is thought that the earliest Indo-European writings may have been carved on beech wood. The Latin word , means a book in the modern sense (bound and with separate leaves). It originally meant
A sundial shows the current solar time during the day. It does this because the sun appears to move through the sky. At different times in the day when the sun is shining, a shadow is cast in different places on the dial. A person marks the dial with the time at a certain shadow. This lets users easily see the time. There are a few commonly seen designs, such as the 'ordinary' or standard horizontal garden sundial. However, sundials can be designed for any surface where a fixed object casts a predictable shadow. They may be horizontal or vertical or tilted.  Ancient Egypt had sundials. Other cultures developed them further, including the Greeks and Romans.
A peninsula is a region of land that sticks out in a body of water. It is also defined as a piece of land with water on three sides. Many countries are on peninsulas, and may either take up part of a peninsula (such as Portugal) or all of it (such as India). Parts of a country may also be on a peninsula. For example, Jutland is a peninsula, as is Baja California in Mexico. If Eurasia is considered a continent then the continent of Europe is technically a peninsula. In this case, the great peninsulas of Europe, the Iberian, Italian, and Balkan peninsulas would technically be peninsulas within peninsulas. The area of the European Peninsula, comprised of Europe minus Russia, Fennoscandia, and any islands, is roughly 4.4 million square kilometers. The Arabian Peninsula is usually cited as the largest peninsula in the world with an area of 3,237,500 square kilometers.
Combinatorial game theory, also known as CGT is a distinct branch of mathematics and theoretical computer science that studies combinatorial games, and is distinct from "traditional" or "economic" game theory. CGT arose in relation to the theory of impartial games, the two-player game of Nim in particular, with an emphasis on "solving" certain types of combinatorial games. A game must meet several conditions to be a combinatorial game. These are: Combinatorial Game Theory is largely confined to the study of a subset of combinatorial games which are two player, finite, and have a winner and loser (i.e. do not end in draws.) These combinatorial games can be represented by trees, each vertex of which is the game resulting from a particular move from the game directly below it on the tree. These games can be given game values. Finding these game values is of great interests to CG theorists, as is the theoretical concept of game addition. The sum of two games is the game in which each player on her/his turn must move in only one of the two games, leaving the other as it was.  Elwyn Berlekamp, John Conway and Richard Guy are the founders of the theory. They worked together in the 1960s. Their published work was called "Winning Ways for Your Mathematical Plays". Definitions. In the theory, there are two players called "left" and "right". A game is something that allows left and right to make moves to "other games". For example, in the game of chess, there is a usual starting setup. One could also, however, think of a chess game after the first move as a different game, with a different setup. So each position is also called a game. Games have the notation {L|R}. formula_1 are the games the left player can move to. formula_2 are the games the right player can move to. If you know chess notation, then the usual chess setup is the game  The dots "..." mean there are many moves, so not all are shown. Chess is very complex. It is better to think of easier games. Nim, for example, is much
Nim is a simple game used for examples in combinatorial game theory. The rules of nim are simple: There is a simple mathematical strategy to play the game perfectly. If both players play perfectly, the winner is determined by the initial setup.