AcharyaChanakya/simple-wikipedia huggingface dataset:
The first science fiction fanzine, "The Comet", was published in 1930. Fanzine printing methods have changed over the decades, from the mimeograph and the ditto machine, to modern photocopying. The number of copies was usually not enough to use commercial printing. Modern fanzines are printed on computer printers or at local copy shops, or they may only be sent as email. The best known fanzine (or "'zine") today is "Ansible". David Langford is the editor and it has won several Hugo awards. Artists working for fanzines have risen to prominence in the field, including Brad W. Foster, Teddy Harvia, and Joe Mayhew; the Hugos include a category for Best Fan Artists. The earliest organized fandom online was the SF Lovers community, originally a mailing list in the late 1970s with a text archive file that was updated regularly. In the 1980s, Usenet groups greatly expanded the circle of fans online. In the 1990s, the development of the World-Wide Web made the online fan community much, much larger. Fans created thousands and then millions of web sites devoted to science fiction and related genres for all media. Most of these websites are small, ephemeral, or about very specific topics. Though sites like SF Site and Read and Find Out give readers a broad range of references and reviews about science fiction.
Fan fiction is non-commercial fiction created by people who love an SF story or world. Fans write stories that take place in the setting of an established book, movie, or television series. Some people call it "fanfic". In some cases, the copyright owners of the books, movies, or television series have instructed their lawyers to issue "cease and desist" letters to fans.
Blaise Pascal (19 June 1623 – 19 August 1662) was a French mathematician, physicist, inventor, philosopher, writer and Catholic theologian.. He was born in Clermont-Ferrand, France. His mother died when he was three years old. His father's name was Étienne. He had two sisters, Jaqueline and Gilberte. Pascal was completely educated by his father.His father was a tax collector. Pascal was considered a child prodigy. Though best known for his works in mathematics, including the creation of Pascal's Triangle, which is named after him, and developments in the field of probability, Pascal was also a scientist. He wrote in support of the scientific method and also contributed to physics. Later he wrote two books about Christianity. Also, the Pascal unit was named after him.
Pascal died in Paris, France at 39. He had several illnesses; it is not known which of them caused his death.
Pascal invented a form of counting machine which helped inventors create the calculator in the 20th century.
Pascal's Triangle is a mathematical triangular array. It is named after French mathematician Blaise Pascal, but it was used in China 3 centuries before his time.
Pascal's triangle can be made as follows. On the first row, write only the number 1. Then, to get the numbers of following rows, add the number that can be seen above and to the left (if any) and the number above and to the right (if any) to find the new value. For example, the numbers 1 and 3 in the fourth row are added to make 4 in the fifth row.
The triangle has many uses in probability. It can also be used in binomial expansions. For example,
Notice the coefficients are the third row of Pascal's triangle: 1, 2, 1.
In general, when a binomial is raised to a positive integer power we have:
where the coefficients "a" in this expansion are precisely the numbers on row "n" + 1 of Pascal's triangle; in other words,
Formally speaking, the way of making the Pascal's Triangle uses Pascal's rule, which states that
for non-negative integers "n" and "k" where "n" ≥ "k" and with the initial condition
Pascal's triangle generalizes readily into higher dimensions. The three-dimensional version is called Pascal's pyramid or "Pascal's tetrahedron". A higher-dimensional analogue is generically called a "Pascal's simplex". See also pyramid, tetrahedron, and simplex.
The first and last number in each row is always 1.
The second number in each row is the row number. In a binomial expansion, this second number is equal to the power. (This makes the 'first' row, 1, actually the zero row).
The rows always read the same forward and backward.
The sum of the numbers in each row is double the sum of the numbers in the row before. The sum of each row is 2.
Antidisestablishmentarianism is a political position. It means "to keep an established church". An official state church is called the "established" church, so a disestablishmentarian is a person who wants to stop the state church. These people say a state church hurts the freedom of religion. These people say the state should be secular, meaning religion and the country are separate. This idea is called disestablishmentarianism. So antidisestablishmentarianism wants to keep the state church.
It is famous because it is one of the longest words in the English language.
The word comes from England in the 1800s. In England, Ireland and Wales, there was an official state church called the Anglican Church. Ireland disestablished in 1871, and Wales disestablished in 1920. England still has the Anglican Church as the state church.
In 2014 Nick Clegg, who was the Leader of the Liberal Democrats at the time, said that he thought the Church of England should no longer be the established church. David Cameron, who was the Prime Minister of the United Kingdom, said the establishment helps the church and state.
Antidisestablishmentarianism is one of the longest words in the English language. It has 28 letters and 12 syllables. It is considered to be the longest word, if you do not count technical terms. For example, "pneumonoultramicroscopicsilicovolcanoconiosis" is a technical term for a lung disease made by people who wanted it to be the longest word.
The word became famous because of a popular television show in the 1950s called "The $64,000 Question", where someone spelled it and won. Duke Ellington, a jazz artist, had a song called "You're Just an Old Antidisestablishmentarianismist". Eminem, a rapper, used the word in his song "Almost Famous".
1193 (MCXCIII) was .
Sarah McLachlan (born January 28, 1968) is a Canadian singer-songwriter who is known for her emotional music. She was adopted and raised in Halifax, Nova Scotia. She went to the Nova Scotia College of Art and Design, then moved to Vancouver, British Columbia.
Her recording company, Nettwerk, released her first album in 1988. After recording several albums, she organized the all-female music festival Lilith Fair in 1997, 1998, and 1999. Some of the money made from these concerts went to women's charities. McLachlan received the Elizabeth Cady Stanton Visionary Award in 1998 for helping women's music.
She married her drummer, Ashwin Sood, in 1997. They have a daughter, India, born in 2002.
McLachlan has been written about in magazines such as Rolling Stone, Time, and Entertainment Weekly. She has won Grammy and Juno awards for her music.
She funds a Vancouver program that helps poor children learn music. She has played at charity concerts, such as for victims of the December 26, 2004 tsunami and at the 2005 Live 8 concert in Philadelphia, Pennsylvania, USA.
Some of McLachlan's best-known songs include "The Path of Thorns", "Into the Fire", "Possession", "Building a Mystery", "Sweet Surrender", "Adia", "Angel", and "World on Fire".
Albums with only new songs:
Live EPs (shorter albums) were released in 1992 and 2004.
Samuel Langhorne Clemens (November 30, 1835 – April 21, 1910), more widely known as Mark Twain, was a well known American writer born in Florida, Missouri. He worked mainly for newspapers and as a steamboat pilot on the Mississippi River before he became a writer. He married in 1870, and raised his family in Hartford, Connecticut. In later life he invested and lost the money that his writing had made, and toured the world giving lectures that brought him enough money to pay his debt and recover his fortune.
Clemens was best known for his works in fiction, and especially for his use of humour. His first published story, in 1865, was "The Celebrated Jumping Frog of Calaveras County."
"Adventures of Huckleberry Finn" is considered by many to be Clemens' best work. This story of a white boy who helps a black man escape slavery in the southern United States is known for its humanity.
Clemens's style was usually informal and humorous. This made him different from many important 19th century writers whose books he disliked. For example, he greatly disliked Jane Austen's works, such as "Sense and Sensibility" and "Pride and Prejudice", and famously remarked, "She makes me detest (hate) all her people, without reserve."
Actor Hal Holbrook plays Mark Twain on stage in a one-man show called "Mark Twain Tonight".
Halley's Comet appeared in the sky during the year Twain was born and the year he died. This periodic comet comes back every 74 years, which is how long he lived.
Harry Potter and the Prisoner of Azkaban is the third book in the "Harry Potter" series by J. K. Rowling. The book was released on 8 July 1999. It covers Harry Potter's third year at Hogwarts. A movie based on the book was released on 31 May 2004. This is the only book where Lord Voldemort does not make an appearance.
After accidentally inflating his aunt Marge, Harry leaves the Dursleys, and catches a ride on the street on a magical bus called The Knight Bus. Before he begins his way back to Hogwarts, he learns of Sirius Black, a mass murderer, believed to have killed thirteen people with a single curse. Black has escaped from the wizard prison, Azkaban. Meanwhile, upon meeting the Weasleys, Harry learns that, despite accidentally using magic (which is illegal), he has not been expelled. Mr. Weasley tells Mrs. Weasley of Sirius Black's motive to kill Harry when Harry overhears this he is told not to go looking for Black. Later in the book, Harry soon realizes why.
Harry Potter and the Goblet of Fire is the fourth book in the "Harry Potter" series by J. K. Rowling. It was published on 8 July 2000. The original United Kingdom edition had 636 pages, although the US version has 734. It was made into a movie that was released in 2005.
Throughout the three previous novels in the "Harry Potter" series, the main character, Harry Potter, has struggled with the difficulties of growing up and the added challenge of being a famed wizard. When Harry was a baby, Lord Voldemort, the most powerful dark wizard in history, killed Harry's parents but was mysteriously defeated after unsuccessfully trying to kill Harry, though his attempt left a lightning-shaped scar on Harry's forehead. This results in Harry's immediate fame and his being placed in the care of his abusive Muggle (non-magical) aunt and uncle, Petunia and Vernon Dursley, who have a son named Dudley.
On Harry's eleventh birthday, he learns he is a wizard from Rubeus Hagrid, Keeper of Keys and Grounds at Hogwarts School of Witchcraft and Wizardry, and enrols in Hogwarts. He befriends Ron Weasley and Hermione Granger and confronts Lord Voldemort, who is trying to regain power. In Harry's first year, he has to protect the Philosopher's Stone from Voldemort and one of his faithful followers at Hogwarts. After returning to school after summer break, students at Hogwarts are attacked by the legendary monster of the Chamber of Secrets after the Chamber is opened. Harry ends the attacks by killing a Basilisk and thwarting another attempt by Lord Voldemort to return to full strength. The following year, Harry hears he has been targeted by escaped mass murderer Sirius Black. Despite stringent security measures at Hogwarts, Harry encounters Black at the end of his third year and learns Black was framed and is actually Harry's godfather. He also learns that it was his father's old school friend Peter Pettigrew who betrayed his parents.
In a prologue, which Harry sees through a dream, the three Riddles (who are the parents of Tom Riddle) are murdered, despite not being poisoned or hurt in anyway. They are in perfect health but upon the time of their death, they appear to have petrified faces. Everyone suspects the elderly caretaker Frank Bryce, to be the murder. But he is released. Later on (in Harry's dream) Frank Bryce, Muggle caretaker of an abandoned mansion known as the Riddle House, is murdered by Lord Voldemort after stumbling upon him and Wormtail. Harry is awoken by his scar hurting.
The Weasleys invite Harry and Hermione Granger to the Quidditch World Cup, to which they travel using a Portkey, meeting Cedric Diggory, a Hufflepuff sixth-year, on the way. In the match, Ireland triumph over Bulgaria, despite the skill of Bulgaria's star seeker, Viktor Krum. Various Ministry of Magic employees at the World Cup discuss Bertha Jorkins, a Ministry worker who has gone missing. Her head-of-department, the charismatic Ludovic ¨Ludo¨ Bagman, is unconcerned.
After the match, men wearing the masks of Death Eaters, followers of Voldemort, attack the camp site, causing terror and abusing the Muggle campsite owners. The Dark Mark is fired into the sky, causing mass panic. Harry discovers that his wand is missing. It is later found in the possession of Winky, Barty Crouch's house elf, and the wand is found to have been used to cast the Mark. Although very few believe Winky could have conjured the Mark, Barty Crouch dismisses Winky from his service. Hermione, angry at this injustice, forms a society to promote house elf rights, known as S.P.E.W. (Society for the Promotion of Elfish Welfare).
At Hogwarts, Professor Dumbledore announces that Alastor "Mad-Eye" Moody will be the Defence Against the Dark Arts teacher for the year. Dumbledore also announces that Hogwarts will host a revival of the Triwizard Tournament, in which a champion of Hogwarts will compete against champions from two other European wizarding schools: Beauxbatons Academy, and Durmstrang Institute. The champions are chosen by the Goblet of Fire from names dropped into it. Because Harry is under 17 (the age of majority in the wizarding world), he is disallowed from entering.
At Halloween, the Goblet of Fire picks Fleur Delacour from Beauxbatons Academy, Viktor Krum, the Bulgaria seeker that played at the Quiditch World Cup, from Durmstrang Institute, and Cedric Diggory from Hogwarts to compete in the tournament. Unexpectedly, however, it also chooses Harry as a fourth champion. Despite anger from the Beauxbatons and Durmstrang contingents, Harry's being chosen magically binds him to compete, forcing him to be an unwilling participant in the Tournament. Very few people believe Harry's protests that he did not put his own name in; Ron, envious of Harry again being the centre of attention, accuses Harry of lying and breaks up their friendship.
In their first Defence Against the Dark Arts lesson, Professor Moody introduces the class to the Unforgivable Curses: the Imperius Curse, through which a wizard can be controlled as another wills; the Cruciatus Curse, which causes immense pain; and "Avada Kedavra", the killing curse.
A tabloid-style reporter, Rita Skeeter, starts writing scandalous articles of half-truths and outright fabrications in "The Daily Prophet" about those at Hogwarts, starting with Harry. Because of the Prophet's high readership, her words hold a lot of sway among the wizarding population.
Despite champions not being allowed to know, Hagrid covertly reveals to Harry that the first task is to get past a dragon. Madame Maxime, the headmistress of Beauxbatons, and Professor Karkaroff, headmaster of Durmstrang, also discover this. Sure that they will tell their respective champions, Harry informs Cedric about the dragons in the interest of fairness. Harry struggles to think of a way past a dragon, until Moody suggests flying. Hermione helps him to perfect a Summoning Charm, which he uses to summon his Firebolt broomstick and fly past the dragon to retrieve a golden egg, receiving high marks from the judges. Ron and Harry subsequently reconcile, Ron now understanding the full danger of the tournament. Harry's egg is supposed to contain a clue to the next task, but when opened it merely shrieks loudly.
Hermione infiltrates the school kitchen as part of her house elf welfare campaign (in which she is finding few allies and much resistance). She takes Harry and Ron there to meet Dobby, who now works there after his freeing in Harry's second year. They also find a distraught Winky, who is seriously depressed after being sacked. Dobby is the only known house elf to appreciate his freedom, despite his hardworking nature; the others reject Hermione's idea of payment and holidays, which they find distressing.
The students are informed of the Yule Ball, a Triwizard Tournament tradition, which requires Harry to find a partner with whom to open the dance. He eventually asks Cho Chang, a Ravenclaw fifth-year with whom he is smitten, but she has already agreed to go with Cedric. Ultimately, Harry asks Parvati and Padma Patil to go with him and Ron. Hermione, offended that Ron did not consider her except as a last resort, attends with Viktor Krum, causing intense jealousy in Ron. At the ball, Cedric tells Harry to take the egg into the bath in the prefects' bathroom to work out the clue, but Harry is reluctant to accept the advice because he is jealous over Cho.
Rita Skeeter writes an article revealing Hagrid's half-giant parentage (though it is a mystery how she found out), a taboo in the wizarding world. After Hermione confronts her, Skeeter writes articles painting Hermione as Harry's unfaithful girlfriend. After masses of hate mail, Hermione swears revenge on Skeeter.
The trio secretly meet Sirius at Hogsmeade, who tells them that Barty Crouch was fanatical about catching dark wizards, often stooping to the same level to punish them. This culminated in Crouch sending his own son to Azkaban. His son later died there. Sirius suspects that someone is attempting to attack Harry through the Tournament and make it look like an accident. He suspects Karkaroff, who is a former Death Eater who walked free.
Finally acting on Cedric's tip, Harry takes the egg to the prefects' bathroom by night, where with help from Moaning Myrtle he listens to the egg underwater. There, the shrieks become the words of a song, which tells Harry that the task is to recover something dear to him from Merpeople at the bottom of the lake in the grounds. While sneaking back to Gryffindor Tower under his invisibility cloak, he sees Barty Crouch in Snape's office on the Marauder's Map, despite Crouch supposedly being too ill to judge the Triwizard Tournament. While investigating, Harry falls into a trick step and drops the egg, which shrieks loudly and attracts Filch, Snape (who has had potion ingredients stolen), and Moody. Moody's magical eye sees Harry stuck in the stair under his cloak, but Moody covers for him, then borrows the Marauder's Map.
Harry, Ron, and Hermione are unable to find a way to survive underwater for the second task, leaving Harry panic-stricken. He is rescued on the morning of the task by Dobby, who gives him some Gillyweed that he heard Moody and Professor Sprout talking about. The Gillyweed gives Harry flippers and gills and allows him to find Ron at the bottom of the lake. However, he refuses to leave the hostages belonging to the other champions behind, and insists on rescuing Fleur's sister when Fleur does not arrive. Although Harry finishes last, the judges (apart from Karkaroff) still award him high marks for 'moral fibre.'
One month before the final task, Harry and Krum are talking near the Forbidden Forest when they encounter Barty Crouch, who stopped appearing to work at the Ministry several months ago. Although insane, in moments of clarity he confesses to have done 'something terrible,' that Bertha Jorkins is dead, and begs for Dumbledore. Leaving Krum with Crouch, Harry fetches Dumbledore but returns to find Krum stunned and Crouch gone, Krum claiming that Crouch attacked him from behind. Moody gives chase but does not find Crouch.
During a Divination lesson, Harry experiences another dream involving Voldemort punishing Wormtail for a 'mistake.' Harry tells Dumbledore about this, and stumbles upon a memory-keeping device in Dumbledore's office, a Pensieve. Inside the Pensieve, he discovers that Ludo Bagman was accused and acquitted of Death Eater activity, and that Barty Crouch's son was sent to Azkaban for supposedly helping to torture Neville Longbottom's parents into insanity.
Harry prepares for the final task, a hedge maze filled with dangerous creatures and obstacles, the goal being to reach the Triwizard Cup at the centre. Inside the maze, Harry stuns Krum, who was using the Cruciatus Curse on Cedric. Helping each other, the two reach the Cup. They agree to touch it at the same time and become joint winners. However, on touching it they discover that it is a Portkey that transports them to a graveyard. There, Wormtail appears, kills Cedric using Voldemort's wand, and ties up Harry. Wormtail uses Harry's blood, Tom Riddle Sr.'s bone, and his own hand to restore Lord Voldemort to a body.
Voldemort, alive again, summons his Death Eaters, berates them for believing him dead, and mentions that he has a single 'faithful servant' concealed at Hogwarts, who has led Harry to the graveyard for the resurrection. He tortures Harry, then challenges him to a duel to prove his prowess. However, when he and Harry fire spells at each other, their wands connect unexpectedly, causing echoes of Voldemort's previous magic to appear, including manifestations of Cedric and Harry's parents. These echoes provide a distraction for Harry, who escapes with Cedric's body to the Cup, which takes him back to Hogwarts.
Under the panic caused by his arrival, Moody takes a traumatised Harry to his office. He reveals himself to be Voldemort's 'faithful servant.' He explains that he put Harry's name into the Goblet of Fire under a different school and has been guiding him through the tournament to ensure he would touch the Cup first: he gave him the hint about flying, staged a conversation about Gillyweed in front of Dobby, cursed obstacles from outside the hedge maze, and used the Imperius Curse on Krum to force him to curse Cedric. As Moody prepares to kill Harry, Professors Dumbledore, McGonagall, and Snape intervene and stun Moody. Slowly, Moody changes appearance to become Barty Crouch Jr., the supposedly long-dead son of Barty Crouch Sr., who was using Polyjuice Potion to impersonate Moody.
Using Veritaserum, a truth potion, they learn that Barty Crouch Sr. rescued his son from Azkaban as a favour to his dying wife: the Crouch Jr. who died in Azkaban was his mother, disguised under Polyjuice Potion. Crouch Jr. was kept imprisoned at home. Winky convinced Crouch Sr. to allow Crouch Jr. to see the Quidditch World Cup, where he stole Harry's wand, escaped, and conjured the Dark Mark. Wormtail, meanwhile, had captured Bertha Jorkins, who had once seen Crouch Jr. at home and been bewitched to forget. This allowed Voldemort to discover Crouch Jr.'s whereabouts, then formulate a plan to install Crouch at Hogwarts and lead Harry to him. Crouch Sr. was imprisoned by Wormtail, and when he escaped to Hogwarts, Crouch Jr. killed him.
Dumbledore explains that Harry's and Voldemort's wands connected because they share a core of a feather from the same phoenix, coincidentally Dumbledore's own phoenix Fawkes.
Dumbledore announces Lord Voldemort's return to the school. However, many people, including Minister for Magic Cornelius Fudge, refuse to believe it. Fudge hastily has the Dementor's Kiss performed on Crouch Jr., who is thus unable to give testimony proving Voldemort's return. Dumbledore puts his own anti-Voldemort plans into action.
Hermione discovers Rita Skeeter is an unregistered Animagus who can take the form of a beetle, allowing her to eavesdrop on secrets. She blackmails Skeeter to force her to stop writing her libelous stories. Not wanting his tournament winnings, Harry gives all one thousand Galleons to Fred and George to start their joke shop, and returns home with the Dursleys.
Crohn's disease is a disease that causes the intestines to become swollen. It is a type of inflammatory bowel disease (IBD). The intestines may also develop ulcers. People with Crohn's disease often have pain in the stomach, diarrhea, vomiting, and weight loss. Crohn's can also cause skin rashes, arthritis, and swollen eyes. It is named after Burrill Bernard Crohn, who described cases in 1932. It was first
described by Giovanni Battista Morgagni (1682–1771) in the 18th century.
Nobody knows exactly what causes Crohn's disease. In the disease, the person's body attacks itself. The immune system attacks healthy parts of the digestive tract. This causes swelling in the digestive tract.
Though Crohn's is an immune-related disease, it is not an autoimmune disease (the immune system is not triggered by the body itself). The exact underlying immune problem is not clear. Crohn's disease seems to be connected to the person's genes. People whose brothers or sisters have the disease are the most likely to get it. Men and women can both be affected by Crohn's disease.
Managing Crohn's disease includes both lifestyle changes and various kind of medication. It is a chronic condition for which there is no cure. Certain parasitic intestinal worms appear to make the bowel less inflamed. It is supposed that the worms modify the immune reactions in the parts of the intestine where they live.
Alternative medicine of various kinds has been tried, with uncertain results.
Pet door
Pet doors, also known as cat doors, dog doors, doggie doors, or in the United Kingdom, cat flaps, are small doors for pets. They are usually built in regular doors, but can also be in windows or walls. They usually have the hinge on the top, with no latch, so the animal can push their way in and out. Newer models sometimes only let the pet go outside, but not inside. Others have a latch and something that can be put on the pet that makes the latch open when the pet gets close to the door. They are most commonly used for pet cats, but can also be used for dogs, miniature pigs, or other small pets.
The pet door was developed by Isaac Newton.
Mount Rainier is a mountain 54 miles (87 kilometres) southeast of Seattle, Washington, in the United States. The volcano is the highest mountain in the Cascade Range, at 14,410 feet (4,392 metres). The top of the mountain is mostly covered by snow and glaciers. Rainier is an active volcano, but has not had an eruption for more than 100 years. Some describe Rainier as dormant or inactive.
On March 2, 1899, U.S. President William McKinley made the mountain and area around it Mount Rainier National Park. It was the country's fifth national park.
Fort Knox
Fort Knox is an U.S. Army post in Kentucky. Named after Henry Knox, the fort is now the site of the U.S. Bullion Reservatory (where the United States keeps its gold). The fort's fortifications were built in 1862 during the American Civil War; however, after the war the camp became abandoned until 1917.
It is named for Henry Knox, a general in the American Revolutionary War.
Maxwell's equations
Maxwell's equations describe how electric charges and electric currents create electric and magnetic fields. They describe how an electric field can generate a magnetic field.
In the 1860s James Clerk Maxwell published equations that describe how charged particles give rise to electric and magnetic force per unit charge. The force per unit charge is called a field. The particles could be stationary or moving. These, and the Lorentz force equation, give everything one needs to calculate the motion of classical particles in electric and magnetic fields.
The first equation allows one to calculate the electric field created by a charge. The second allows one to calculate the magnetic field. The other two describe how fields 'circulate' around their sources. Magnetic fields 'circulate' around electric currents and time varying electric fields: Ampère's law with Maxwell's extension, while electric fields 'circulate' around time varying magnetic fields: Faraday's law.
where the following table provides the meaning of each symbol and the SI unit of measure:
where formula_4 is the "free" electric charge density (in units of C/m), not counting the dipole charges bound in a material, and formula_5 is the electric displacement field (in units of C/m). This equation is like Coulomb's law for non-moving charges in vacuum.
The next integral form (by the divergence theorem), also known as Gauss' law, says the same thing:
formula_7 is the area of a differential square on the closed surface A. The surface normal pointing out is the direction, and formula_8 is the free charge that is inside the surface.
In a "linear material", formula_5 is directly related to the electric field formula_10 with a constant called the permittivity, formula_11 (This constant is different for different materials):
You can pretend a material is linear, if the electric field is not very strong.
The permittivity of free space is called formula_13, and is used in this equation:
Here formula_10 is the electric field again (in units of V/m), formula_16 is the total charge density (including the bound charges), and formula_13 (approximately 8.854 pF/m) is the permittivity of free space. One can also write formula_11 as formula_19. Here, formula_20 is the permittivity of the material when compared to the permittivity of free space. This is called the relative permittivity or "dielectric constant".
See also Poisson's equation.
formula_22 is the magnetic flux density (in units of tesla, T), also called the magnetic induction.
This next integral form says the same thing:
The area of formula_7 is the area of a differential square on the surface formula_25. The direction of formula_7 is the surface normal pointing outwards on the surface of formula_25.
This equation only works if the integral is done over a closed surface.
This equation says, that in every volume the sum of the magnetic field lines that go in equals the sum of the magnetical field lines that go out. This means that the magnetic field lines must be closed loops. Another way of saying this is that the field lines cannot start from somewhere.
This is the mathematical way of saying: "There are no magnetic monopoles".
Here formula_30
This is what the symbols mean:
Φ is the magnetic flux that goes through the area A that the second equation describes,
E is the electric field that the magnetic flux causes,
s is a closed path in which current is induced, for example a wire,
v is the instantaneous velocity of the line element (for moving circuits).
The electromotive force is equal to the value of this integral. Sometimes this symbol is used for the electromotive force: formula_31, do not confuse it with the symbol for permittivity that was used before.
This law is like Faraday's law of electromagnetic induction.
Some textbooks show the right hand sign of the integral form with an "N" (N is the number of coils of wire that are around the edge of "A") in front of the flux derivative. The "N" can be taken care of in calculating "A" (multiple wire coils means multiple surfaces for the flux to go through), and it is an engineering detail so it's left out here.
The negative sign is needed for conservation of energy. It is so important that it even has its own name, Lenz's law.
This equation shows how the electric and magnetic fields have to do with each other. For example, this equation explains how electric motors and electric generators work. In a motor or generator, the field circuit has a fixed electric field that causes a magnetic field. This is called fixed excitation. The varying voltage is measured across the armature circuit.
Maxwell's equations are used in a right-handed coordinate system. To use them in a left-handed system, without having to change the equations, the polarity of magnetic fields has to be made opposite (this is not wrong, but it is confusing because it is not usually done like this).
H is the magnetic field strength (in units of A/m), which you can get by dividing the magnetic flux B by a constant called the permeability, μ (B = μH), and J is the current density, defined by:
J = ∫ρvdA
v is a vector field called the drift velocity. It describes the speeds of the charge carriers that have a density described by the scalar function ρ.
In free space, the permeability μ is the permeability of free space, μ, which is "exactly" 4π×10 W/A·m, by definition. Also, the permittivity is the permittivity of free space ε. So, in free space, the equation is:
The next integral form says the same thing:
"s" is the edge of the open surface "A" (any surface with the curve "s" as its edge is okay here), and "I" is the current encircled by the curve "s" (the current through any surface is defined by the equation: "I" = ∫"J·dA)."
If the electric flux density does not change very fast, the second term on the right hand side (the displacement flux) is very small and can be left out, and then the equation is the same as Ampere's law.
There are only two covariant Maxwell Equations, because the covariant field vector includes the electrical and the magnetical field.
"Mathematical note: In this section the abstract index notation will be used."
In special relativity, Maxwell's equations for the vacuum are written in terms of four-vectors and tensors in the "manifestly covariant" form. This has been done to show more clearly the fact that Maxwell's equations (in vacuum) take the same form in any inertial coordinate system. This is the "manifestly covariant" form:
The second equation is the same as:
Here formula_38 is the 4-current, formula_39 is the field strength tensor (written as a 4 × 4 matrix), formula_40 is the Levi-Civita symbol, and formula_41 is the 4-gradient (so that formula_42 is the d'Alembertian operator). (The formula_43 in the first equation is implicitly summed over, according to Einstein notation.) The first tensor equation says the same thing as the two inhomogeneous Maxwell's equations: Gauss' law and Ampere's law with Maxwell's correction. The second equation say the same thing as the other two equations, the homogeneous equations: Faraday's law of induction and the absence of magnetic monopoles.
formula_38 can also be described more explicitly by this equation: formula_45 (as a contravariant vector), where you get formula_38 from the charge density ρ and the current density formula_47. The 4-current is a solution to the continuity equation:
In terms of the 4-potential (as a contravariant vector) formula_49, where φ is the electric potential and formula_50 is the magnetic vector potential in the Lorentz gauge formula_51, "F" can be written as:
which leads to the 4 × 4 matrix rank-2 tensor:
The fact that both electric and magnetic fields are combined into a single tensor shows the fact that, according to relativity, both of these are different parts of the same thing—by changing frames of reference, what looks like an electric field in one frame can look like a magnetic field in another frame, and the other way around.
Using the tensor form of Maxwell's equations, the first equation implies
(See Electromagnetic four-potential for the relationship between the d'Alembertian of the four-potential and the four-current, expressed in terms of the older vector operator notation).
Different authors sometimes use different sign conventions for these tensors and 4-vectors (but this does not change what they mean).
formula_39 and formula_56 are "not" the same: they are related by the Minkowski metric tensor formula_57: formula_58. This changes the sign of some of "F"'s components; more complex metric dualities can be seen in general relativity.
Henry Knox
Henry Knox (1750-1806) was a military leader for the Americans during the American Revolutionary War. Originally from Boston, Massachusetts, he was appointed Chief Artillery Officer of the Continental Army. He is best known for transporting cannons and other artillery from Fort Ticonderoga to Boston through icy conditions using oxen. Later, George Washington named him the first Secretary of War.
Fort Knox in Kentucky & Maine are named after him.
American Revolutionary War
The American Revolutionary War was a war fought between Great Britain and the original Thirteen Colonies in North America from 1775 to 1783. Most of the fighting was in North America and other places. The Continental Army, the rebel army, was led by George Washington and helped by France and Spain. They defeated the British Army after the British moved their attention to other matters. This happened as the British had far more lucrative colonies whilst America at the time had very little of value so they let America have it's independence so they could focus on what were richer colonies.
After the war ended, the Thirteen Colonies became independent, which meant that the British Empire was no longer in charge of them. They became the first 13 states of a new country, which they called the United States of America.
The war started after years of problems between the British Empire and the colonists of North America after the French and Indian War (also called the Seven Years' War). People in the Thirteen Colonies disliked many of the actions of the British government, such as the Intolerable Acts. For many years, the British government decided the countries that could trade with the colonies instead of letting the colonies decide for themselves. Many colonists wanted free trade.
In 1765, the British Parliament needed money to pay back the debt for the French and Indian War. They passed a Law called the Stamp Act. This law said that colonists had to buy stamps for legal papers, newspapers, and even playing cards, as other British people did. The money from the stamps went to the King. The colonies did not follow this law. The colonies kept refusing to do what the King wanted. The Boston Tea Party and Boston Massacre caused people to become more angry about the situation. The British sent more soldiers (who were called Red Coats by the colonists to insult them) to keep control of the colonies and they sometimes had to fight. In 1774, the British passed the Intolerable Acts to punish the colonists in Boston for the Boston Tea Party.
Not all colonists wanted to leave the British Empire. The "Loyalists", or Tories, stayed loyal to Great Britain. They were not going to change their views. The "Patriots", or Whigs, wanted independence. Before the Revolutionary War, most people in America were Loyalists; but after it, most people were Patriots.
Many colonists wrote letters showing how they felt. Thomas Paine wrote "Common Sense", a famous pamphlet about independence from Britain. Other colonial leaders, such as Benjamin Franklin, John Adams, and Thomas Jefferson wanted independence.
The first battles of the American Revolutionary War were Lexington and Concord. One of the first major battles was the Battle of Bunker Hill in 1775. Then, the British controlled Boston. Soon, the Second Continental Congress sent an Olive Branch Petition to King George III, which he rejected, and named George Washington head of the army. Early in 1776, Washington's army drove the British out of Boston.
A few months later, the Continental Army and the British troops under William Howe fought the New York and New Jersey Campaign. During the New York battles, the British started using Hessian troops, who were from Germany. Though the colonists lost New York, which the British would hold it for the rest of the war, Washington was able to hold onto most of his army. Over Christmas, 1776, Washington crossed the Delaware River and defeated the Hessians at Trenton and the British at Princeton.
In 1777, the British attacked Philadelphia, which was the American capital. Two battles were fought over Philadelphia: Brandywine and Germantown. Again, the Americans lost a major city, but Washington was able to keep most of his army. Around then, the thw marquis de Lafayette joined the American Army from his native France. In 1778, the British left Philadelphia.
Between 1778 and 1781, most battles between Washington and the British were inconclusive and had no major effect militarily.
One of the most important battles was the Battle of Saratoga in 1777. American soldiers under Horatio Gates forced a British surrender under John Burgoyne. That led to France and Spain joining the war on the side of Americans, who they thought would win. Both powerful countries fought the British around the world. From 1778 to 1780, there was fighting in the West.
The Scottish commerce raider John Paul Jones also won several naval battles for the Americans over the British, but the French Navy did most of the fighting at sea. The Americans tried to capture Canada several times but failed.
In 1779, the main fighting shifted to Georgia and South Carolina. As the fighting spread northward, General Nathanael Greene led the rebels' campaign. He caused many people in the South to be Patriots instead of Loyalists and won several battles against the British.
In 1781, Washington and French General Jean Rochambeau led an offensive against British troops at Siege of Yorktown in Virginia. When their soldiers lost this battle, the British surrendered to the Americans. However, the British continued to fight the French and Spanish for two years and won in India, Gibraltar and elsewhere.
The American Revolution came to an end in 1783 when a peace treaty was signed in Paris, France. In the Treaty of Paris, British King George III accepted the independence of the colonies and recognized the newly-created nation as the United States of America.
The treaty also gave all the land Britain claimed to own west of the Appalachians as far as the Mississippi River to the new country. The land would eventually become part of the United States and lead to the creation of 35 new states (some of them later rebelled as part of the Confederate States of America) that now make up the contiguous United States. Many Loyalists fled to Canada.
As Is usual for 18th-century wars, casualty figures (killed/wounded/missing/captured) for the American Revolution are poorly known. Unlike American Civil War casualties, which were published in newspapers, Revolutionary War casualty reports are found in local town histories; total casualties of the Revolution are rough estimates.
Continental Army
The Continental Army was the fighting force of the thirteen British colonies in the American Revolutionary War. It was created in 1775 by the First Continental Congress. Most of the army was disbanded in 1783 after the conclusion of the war. The army was officially closed by a resolution of Congress in 1784. A Legion of the United States partly replaced it in 1792, and the United States Army replaced it in 1796.
Congress elected George Washington as the commander-in-chief of the Continental Army when it was formed. He led the army until it was disbanded.
Cream cheese
Cream cheese is a soft, mild-tasting, white cheese. Sometimes, it is given extra flavor by adding additional seasonings such as puréed garlic, chopped dill, or chopped olives; as well, some cream cheese has small pieces of fruit or other sweet food blended into it. Cream cheese is different from other cheese in that it is not allowed time to mature. It is either made by cream or a mixture of milk and cream.
Cream cheese is often spread on toasted bagels. Waffles with cream cheese and salsa is eaten in some areas of the United States.
Cream cheese is used to make cheesecake, a sweet, rich cake that is served for dessert.
Shrewsbury is the county town of Shropshire, a county of England. It is located 9 miles (14 km) east of the Welsh border and serves as the commercial centre for Shropshire and mid-Wales.
The town is very old. It was started around 700 AD. The town centre has almost the exact same medieval street plan and over 660 listed buildings. Many of these buildings have timber framing from the 15th and 16th centuries. There is also Shrewsbury Castle, which was built in 1074, and Shrewsbury Abbey, which was built in 1083. The town centre is almost completely surrounded by the River Severn.
Charles Darwin was born in Shrewsbury and lived there for 27 years.
The population of Shrewsbury is just over 71,000, making it the second largest town in Shropshire, the biggest being Telford.
The town has a railway station and a professional football club, Shrewsbury Town, who compete in League One.
Shrewsbury is twinned with Zutphen, Netherlands.
Shrewsbury Abbey is the setting of the Brother Cadfael Chronicles by Ellis Peters (Edith Pargeter). The books were later made into a television show. The story is about a 12th-century monk who solves mysteries. In 2013, the Abbey honoured Pargeter on the 100th anniversary of her birth.
Telford
Telford is a large town in the county of Shropshire, England. It is in the borough of Telford and Wrekin.
It is a new town and building began in the 1960s. It is known for its large shopping centre in the town centre. It also has an ice rink and a large park.
The population of Telford is just over 140,000. It is the largest town in Shropshire, however the county town is Shrewsbury.
The town has a railway station, Telford Central. The town also has a football club, A.F.C. Telford United.
Ludlow is a town in Shropshire, a county of England. The town is very old and dates back to around 800 AD. There is a large castle and many other historic buildings.
There are just over 10,000 people living in the town.
It is the largest town in the South Shropshire area.
The town, though not large, is important in its area, which includes the Welsh Marches, Wales and South Shropshire. Its parish church, St Laurence's, is the largest in the county.
The A49, A4117, B4361 and B4365 roads pass through or go near Ludlow.
Ludlow has a train station.
South Shropshire
South Shropshire is an area of Shropshire in England.
It is very hilly and has few people living there. The only large town is Ludlow.
The area has many castles and other ancient features, such as stone circles.
Battle of Yorktown (1781)
The Battle of Yorktown, also called the Siege of Yorktown, fought from September 28-October 19, 1781. It is considered the last major land battle of the American Revolutionary War. The Continental Army, led by General George Washington, won a decisive victory against the British Army, led by General Lord Charles Cornwallis. Cornwallis was forced to surrender after being surrounded by Washington's army.
The Americans were assisted by the French, led by the Comte de Rochambeau. The battle took place in Yorktown, Virginia, near the York River. After the French fleet defeated a British fleet, Cornwallis was cut off and had to surrender to the French and the Continental Army. Eventually, it led to the Treaty of Paris in 1783, two years later.
British General Lord Cornwallis had fought against the Americans in 1776 and 1777. He was convinced the Americans could not defeat a British army in the field. In 1778 he returned to England to care for his wife who died in February of 1779. After a few months he returned to America to continue the fight. While he was gone, there was a change in British strategy. Before, the British had concentrated on defeating and destroying Washington's army. Now, since the French had joined the Americans, it was no longer just a rebellion but a world war. Earlier, the French had been helping the Americans with loans and war supplies. Now France and Spain were fighting against the British, who had to move troops from North America to defend other places. The new strategy was to win back the Southern colonies beginning with Georgia. The British thought that as many as 50 percent of the population in the South was loyal to Britain. They would start with Georgia and move north through The Carolinas to the Virginia Colony.
On his arrival in New York City, Cornwallis was made second-in-command to General Henry Clinton. The two generals did not trust each other. Clinton was convinced Washington would attack him in New York. He was afraid of sending troops home and having to depend more on Loyalist militia. Cornwallis was ready to go ahead with what troops he had. Clinton was suspicious Cornwallis' return from England was to get a command for himself. In fact, Cornwallis had secured a commission to replace Clinton if Clinton repeated his threats to resign.