OpenLLM-France/wikimedia huggingface dataset:
# Electrodynamics/Biot-Savart Law
## Biot-Savart Law

The Biot-Savart law relates the magnetic B field to the distances and strengths of magnets in the field. In many respects, it's very similar to Coulomb's law, both in form and concept.
We can state the Biot-Savart Law as:
[Biot-Savart Law]
    $d\mathbf {B} =K_{m}{\frac {Id\mathbf {l} \times \mathbf {\hat {r}} }{r^{2}}}$
Where:
    $K_{m}={\frac {\mu _{0}}{4\pi }}\,$, where $\mu _{0}$ is the magnetic constant
    $I\mathbf$ is the current, measured in amperes
    $d\mathbf {l}$ is the differential length vector of the current element
    $\mathbf {\hat {r}}$ is the unit displacement vector from the current element to the field point and
    $r\mathbf$ is the distance from the current element to the field point
This formula is only true for a steady current, which means that electric charge is not building up anywhere. This is analogous to Coulombs law, which is only true for static charge distributions. When the current is not steady and charge distribution is changing, we have to add correction terms to the Biot-Savart Law. However, the Biot-Savart law is unreasonably robust, more so than Coulomb's Law. This is because most of the errors (the first-order error) will cancel out. Thus, Biot-Savart Law can be applied to cases that are clearly not steady; for example, household currents that alternate at 60 Hz.

## Forms
### General

In the magnetostatic approximation, the magnetic field can be determined if the current density j is known:
    $\mathbf {B} =K_{m}\int {{\frac {\mathbf {j} \times \mathbf {\hat {r}} }{r^{2}}}dv}$
where
    $\mathbf {\hat {r}} ={\mathbf {r} \over r}$ is the unit vector in the direction of r.
    $dv$ = is the differential unit of volume.

### Constant uniform current

In the special case of a constant, uniform current I, the magnetic field B is
    $\mathbf {B} =K_{m}I\int {\frac {d\mathbf {l} \times \mathbf {\hat {r}} }{r^{2}}}$

### Point charge at constant velocity

In the special case of a charged point particle $q\mathbf$ moving at a constant velocity $\mathbf {v}$, then the equation above reduces to a magnetic field approximately of the form:
    $\mathbf {B} =K_{m}{\frac {q\mathbf {v} \times \mathbf {\hat {r}} }{r^{2}}}$
This formula, however, is wrong. This is because a point charge moving in a straight line does not constitute a steady current nor a constant charge distribution, both of which are essential to magnetostatics. In particular, in this case, there is a changing electric field and an induced magnetic field that must be added to correct the above formula. Even though the equation is not precisely correct, it is a very good approximation (unreasonably good, in fact).

### Microscopic Scale

On the microscopic scale, the Biot-Savart law becomes,
    $\mathbf {H} =\epsilon \mathbf {v} \times \mathbf {E}$
and hence,
    $\mathbf {B} =\mathbf {v} \times {\frac {1}{c^{2}}}\mathbf {E}$
# Electrickery

Electrickery is intended to be a lighthearted introduction to the practice of electronics. While electrical theory is covered more than adequately in other works, this exists to entice the novice experimenter to jump right in.
The principles of electronics will be introduced by means of application, in the hopes that the experimenter may desire to learn more.
This book is very much inspired by the "Funway Into Electronics" publications, which took a similar approach to teaching a generation of tinkerers how to build their own gadgets, and in so doing, instilled a passion for hacking in many.
Diagrams in this book are generated using the gEDA suite of electronic design tools, Breadboard diagrams are generated using Fritzing, and the text is written in British English.
If you want to screw around and make visibly satisfying things happen in a relatively short time, this is a good resource to run through before committing to more rigorous study of Electronics.
Electrickery is subdivided into Projects. While one needn't necessarily complete them in order, doing so may prove beneficial.

## Projects Listing

* Light up an LED - The "Hello World" of electronics experiments, also introduces Ohm's Law
# Electrodynamics/Conservation Theorems
## Conservation of Momentum

    ${\frac {\partial }{\partial t}}({\mathfrak {p}})=\nabla \cdot \mathbf {\overleftrightarrow {T}}$
# Electrodynamics/Dipoles and Multipoles
## Introduction

In the previous sections of the book, charges and charge distributions have been treated in a general fashion. In this section of the book, we will allow for ordered charge configurations of which molecular matter is actually comprised of. For the most part, ordinary matter is electrically neutral, but it is highly saturated with pairs of charges called dipoles. For us, dipoles will be the building blocks of dielectric and magnetic materials.

## Electric Dipole

An electric monopole is a single charge, and a dipole is two opposite charges closely spaced to each other, or something which looks like that electrically. Dipoles are actually very abundant in nature. For example, a water molecule has a large permanent electric dipole moment. Its positive and negative charges are not centered at the same point; it behaves like like two equal and opposite charges separated by a small distance. Another occurrence happens to uncharged pith balls. In presences of a charged object, the uncharged pith ball will be attracted to the charged object because the little dipoles have responded to the electric field of the rod.

### The Electric Potential due to a Dipole

As it turns out, it is better mathematically to not think of dipoles as a collection of positive and negative charges but as a separate object all together. Take a moment and imagine two opposite charges with magnitude Q and they are separated by a small distance s . The question to ask then is, what is the potential at some distance r away from the configuration?
# History of the National Hockey League/1967–1992/Summit Series/Legacy

The series forced the NHL and the Canadian Amateur Hockey Association to reassess all aspects of how the game was played in North America. Journalist Herb Pinder described the NHL to that point in this way: "The Europeans took our game and evolved it, while we stood still or even went backwards. The Russians had a style, and the Czechs' style was different from that ... There was this hockey world evolving through international competition, and we're back here, stuck, just playing ourselves. It was a business monopoly. And like any monopoly, the NHL got stagnant." Throughout the 1970s and 1980s, Canadian hockey encouraged the adoption of new coaching and training methods used in Europe, and emphasized conditioning and skills development.
In 1975, Soviet club teams began to tour North America in the first Super Series. The Canadiens played Central Red Army to a 3–3 draw on New Year's Eve 1975, in a game that is considered one of the finest ever played. Red Army lost only one of four games against the NHL in the first tour, a 4–1 defeat to Philadelphia, who intimidated them as the Flyers did to their NHL opponents. At one point, Red Army threatened to forfeit the game after Ed Van Impe decked Valery Kharlamov. Red Army was persuaded to complete the game after Alan Eagleson threatened to withhold their appearance fee if the team did not return to the ice. Super Series games continued until 1991, when Soviet players were allowed to enter the NHL after the collapse of the Soviet Union.
The NHL took a greater interest in international play. The Canada Cup, a tournament that featured the top professional players in the world, was held first in 1976, and then four more times until 1991. It was succeeded by the World Cup of Hockey in 1996. Beginning in 1975, Soviet club teams began touring North America, playing NHL clubs in exhibition games that were known as the Super Series. The Calgary Flames and Washington Capitals similarly toured the Soviet Union in 1989 in the first "Friendship Series". The Soviet national team defeated an NHL all-star team in a 1979 challenge series, two games to one, and won Rendez-vous '87, a two-game series held in Quebec City, on aggregate score 8-7.
# History of the National Hockey League/1967–1992/Bobby Orr

In the 1968–69 season, second-year defenceman Bobby Orr scored 21 goals, an NHL record for a defenceman, en route to winning his first of eight consecutive Norris Trophies as the league's top defenceman. At the same time, Orr's teammate, Phil Esposito, became the first player in league history to score 100 points in a season, finishing with 126 points. He was one of three players to break the century mark that year, including Bobby Hull and 41-year old Gordie Howe.
A gifted scorer, Orr revolutionized defencemen's impact on the offensive side of the game, as blue-liners began to be judged on how well they created goals in addition to how well they prevented them. Orr scored the Stanley-Cup-winning goal in overtime of the fourth game against the Blues in 1970, which gave the Bruins their first championship in 29 years. The goal was highlighted by his famous flight through the air after being tripped up following his shot. Orr twice won the Art Ross Trophy as the NHL's leading scorer, still the only defenceman in NHL history to do so. His plus/minus of +124 in 1970–71 is a league record. Orr signed a five-year contract that paid him $200,000 per season in 1971, the first $1 million contract in league history.
Chronic knee problems plagued Orr throughout his career. In 1972, he tore ligaments in his left knee after a hard hit, leading to the first of six knee operations. He played 12 seasons in the NHL before injuries forced his retirement in 1978. Orr finished with 270 goals and 915 points in 657 games and won the Hart Memorial Trophy as the league's Most Valuable Player three times. The customary three-year post-retirement waiting period for entry into the Hockey Hall of Fame was waived as he was enshrined in 1979.
# History of the National Hockey League/1967–1992/Wayne Gretzky

In the latter part of the 1980s, the Oilers won five Stanley Cup titles in seven years, becoming the only team to score 400 or more goals in a season, which they did four times. With future Hall of Famers Grant Fuhr, Paul Coffey, Jari Kurri, Mark Messier, and Glenn Anderson, they established numerous new scoring records.
The Oilers were led by Wayne Gretzky, who remained with the Oilers when they joined the NHL in 1979. At 5 ft 11 in and 170 lb, some observers doubted that Gretzky could match his offensive performance from his lone WHA season. "I heard a lot of talk then that I'd never get 110 points like I did in the WHA," said Gretzky. He proved his critics wrong, scoring 137 points in 1979–80 and winning the first of nine Hart Trophies as the NHL's most valuable player. Over the next several seasons, Gretzky established new highs in goals scored in a season, with 92 in the 1981–82 season; in assists, with 163 in the 1985–86; and in total points, with 215 in 1985–86. He also scored 50 goals in 39 games, the fastest any player had reached the total in a single season. Gretzky scored his 1,000th NHL point in his 424th game, breaking Guy Lafleur's old record of 720 games.
Gretzky's teammates set records of their own. Fuhr's 14 assists in the 1983–84 season set a record for most points by a goaltender in a season. In 1985–86, Coffey set a record for the most goals in a season by a defenceman, with 48. Adding 90 assists, Coffey wound up a point short of tying Bobby Orr's record for most points in a season by a blue-liner.
On August 9, 1988, Oilers owner Peter Pocklington, in financial trouble, traded Gretzky, along with Marty McSorley and Mike Krushelnyski, to the Los Angeles Kings in exchange for Jimmy Carson, Martin Gelinas, US$15 million and three first-round draft picks. Gretzky left Edmonton with a tear-filled news conference, and later said that Edmonton was the only place he ever dreaded playing. Gretzky's trade to the Kings popularized ice hockey in the United States, making hockey "cool" in Hollywood, and shocked fans across Canada. The Kings were the most popular Los Angeles sports team, and Gretzky's fame rivaled that of his peers with baseball's Los Angeles Dodgers and basketball's Los Angeles Lakers.
With the Kings, Gretzky broke Gordie Howe's record for career points. On October 15, 1989, against his former Oilers' teammates, and with Howe in attendance, Gretzky tied the record with a first period assist before notching his 1,851st career point with a third period goal. "An award such as this takes a lot of teamwork and help and both teams here today definitely have a part of the 1,851 [points]." said Gretzky.
# History of the National Hockey League/1967–1992/Entry draft

The new teams were stocked by the NHL's first expansion draft, as each team selected 20 players from the existing franchises. There was much debate over how many players each existing team could protect; the strongest clubs wished to protect more players, while the weaker clubs hoped that protecting fewer players would help improve the balance of competition. Montreal Canadiens manager Sam Pollock's suggestion to allow each team to protect eleven players to start, then add an additional player to their protected list for each player selected in the draft, was ultimately agreed to as a compromise solution. In addition, an "intra-league draft" was held following the 1968 and 1969 seasons to help accelerate the improvement of the expansion teams. Each team protected two goaltenders and fourteen skaters, leaving their remaining players open to be selected by any other team.
Some teams created instant farm systems by buying existing minor league franchises. The Kings bought the Springfield Indians of the American Hockey League the night before the expansion draft, leading the Flyers to purchase the Quebec Aces. Expansion also changed how the amateur draft was handled. The old system, in which franchises sponsored junior teams and players, was abandoned by 1969 when all junior-aged players were made eligible for the entry draft.
During the late 1960s, the concept of sponsoring junior players and teams had been dismantled, meaning that for the 1969 NHL Amateur Draft, every player aged 20 or above was eligible to be selected. The Montreal Canadiens, however, exercised a special "cultural option" that allowed them to select two players of French-Canadian heritage, before any other players were selected. These players counted as Montreal's first two choices. After the Canadiens took Rejean Houle and Marc Tardif, the rest of the league voted to end the rule in 1970, just before future star Gilbert Perreault was selected first in the 1970 expansion draft by the Buffalo Sabres.
In 1974, Sabres general manager Punch Imlach decided to play a joke on the league during the draft. He selected Taro Tsujimoto of the "Tokyo Katanas" with his 11th round pick. Other teams were shocked that the Sabres had scouted for players in Japan, and the league made the pick official. Weeks later, Imlach admitted that he made the player up, choosing the name out of a phone book.
The league reformatted the Amateur Draft into the NHL Entry Draft in 1979 and simultaneously lowered the draft age to 19. It was first opened to the public in 1980, when 2,500 fans attended the draft in the Montreal Forum. The public draft has grown such that it is now held annually in NHL arenas and televised internationally.
# History of the National Hockey League/1967–1992/Expansion years/Broad Street Bullies

The 1970s were associated with aggressive, and often violent, play. Known as the "Broad Street Bullies", the Philadelphia Flyers are the most famous example of this style. The Flyers established league records for penalty minutes—Dave "the Hammer" Schultz's total of 472 in 1974–75 remains a league record—and ended up in courtrooms multiple times when players went into the stands to challenge fans who got involved. One such incident occurred in Vancouver in December 1972, when a fan reached over the glass to pull the hair of Don Saleski, who had a chokehold on Vancouver's Barry Wilkins. Bobby Taylor and several Flyers teammates followed the fan into the stands. The next time Philadelphia went to Vancouver, several players were brought before the courts on charges that ranged from use of obscene language to common assault. Six players were fined, and Taylor received a 30-day suspended sentence. Despite these incidents, the Flyers won: they captured the 1974 Stanley Cup, becoming the first expansion team to win the league championship, and repeated as champions in 1975.
# History of the National Hockey League/1967–1992/Rules and innovations

The early 1980s saw many tie games. The 1982–83 North Stars and Capitals both finished with 16 ties in 80 games, while 17 of 21 teams tied 10 or more games. The season before, the North Stars recorded 20 ties. As a result of the frequent ties, the NHL reintroduced overtime for the 1983–84 season. The effect was immediate, as only seven teams had ten or more ties. Before its discontinuation during World War II, the NHL played a full 10-minute overtime period. The modern overtime format was set as a five-minute, sudden death period; the game ended when either team scored.
The NHL changed its divisional alignment and playoff formats numerous times as it grew. The league's doubling in 1967 also led to the expansion of the playoffs to eight teams from four the previous year. Expansion to 18 teams in 1974 caused the league to realign into two conferences and four divisions, each named after important figures in league history. The teams were split into the Campbell Conference, consisting of the Patrick and Smythe divisions, and the Prince of Wales Conference, consisting of the Adams and Norris divisions. The playoffs were expanded to 12 teams, and each division winner was granted a bye in the first round of the playoffs. The addition of the four WHA teams in 1979 saw the playoffs expanded to 16 teams. Finally, in 1981, the league realigned all teams by geography. Eastern teams played in the Adams and Patrick divisions of the Wales Conference, and Western teams played in the Norris and Smythe divisions of the Campbell Conference. In addition, the playoff format was changed to have the top four teams in each division qualify rather than the top 16 teams overall. The first two playoff rounds were played entirely within each division. This format lasted until 1993.
# History of the National Hockey League/1967–1992/Summit Series

Internationally, Canada had long been protesting the Soviet Union's use of "professional amateurs" at the World Championships and the Olympic Games, which were amateur events. Canada withdrew from international competition in 1969 and boycotted the 1972 Olympic hockey tournament. As an alternative, NHL Players' Association executive director Alan Eagleson negotiated a deal with Soviet authorities to hold an eight-game series between the Soviet national team and Canada's top professionals.
The tournament was the NHL's response to the defection of players to the WHA. Bobby Hull was barred from playing, as was any other player who signed a contract with the rival league, which was a heavily criticized move. Prime Minister Pierre Trudeau sent a telegram to NHL president Clarence Campbell, expressing his "intense interest which I share with millions of Canadians ... that Canada should be represented by its best hockey players, including Bobby Hull". Echoing the feelings of the public, Hull called the decision "crazy", and stated that "I'm a Canadian and I want to play for my country. I don't know why the NHL has to be so petty over this. I want to do this for Canada." The NHL did not relent.
Here's a shot. Henderson makes a wild stab for it and falls. Here's another shot. Right in front. They score! Henderson scores for Canada!
The series was tied at three wins and a tie apiece entering the eighth and deciding game, with millions of Canadians watching "the game of the century". With the game tied at five late in the third, the Soviets were met with a concerted Canadian attack in the final seven minutes. With 34 seconds remaining in the game, Esposito took a shot at Vladislav Tretiak from 12 feet out. Paul Henderson scooped up the rebound and put it past the fallen Soviet goalie to score the goal that won the game, 6–5, and the series. Later, Alexander Yakolev, the former Soviet ambassador to Canada, argued that the Summit Series planted the seeds of glasnost and perestroika in the Soviet Union, as it was one of the first times that the Soviet people had seen so many foreigners who had not come to do harm, but to share in the game.
# Environmental Health Engineering Theory and Practice/Communities

A community is a social unit (a group of living things) with commonality such as norms, religion, values, customs, or identity. Communities may share a sense of place situated in a given geographical area (e.g. a country, village, town, or neighbourhood) or in virtual space through communication platforms.

## Useful Off-site Resources

* United States Centers for Disease Control: Community Health
# Environmental Health Engineering Theory and Practice/Conclusions

By the end of this wikibook, our hope is that you find Environmental Health Engineering Theory and Practice a helpful resource to learn more about this unique healthcare profession. Remember, the environment - natural or human-made - is the space around or between objects; health is not only the absence of disease, but it is also much more the promotion of wellness; and engineering is the design and deployment of technology to meet the needs of humanity.
This wikibook began with an introduction to the theory of environmental health engineering grounded in the modified toxicological paradigm and supported by examples from practice described by the National Environmental Health Association and others. Emerging areas and case studies provided both an opportunity to consider the future of environmental health engineering as well as an opportunity to learn by doing - or, at least to learn by reading, discussing, and reflecting on case studies.
As set-out in the introduction, and again encouraged in the conclusion, Environmental Health Engineering Theory and Practice is meant to be alive and interactive. Fix the problems you encounter, add where you feel more information is needed, and debate actively where you disagree. You are encouraged to consume the knowledge provided, and to take professional responsibility for improving our profession through active stewardship of this wikibook. YOUR participation is vital!

## Useful Off-site Resources

* Biological markers in environmental health research. Committee on Biological Markers of the National Research Council, (1987)
* A niche for infectious disease in environmental health: rethinking the toxicological paradigm, (2010)
* NEHA: National Environmental Health Association
# Environmental Health Engineering Theory and Practice/Drinking Water

Drinking water, also known as potable water, is water that is safe to drink or to use for food preparation.

## Useful Off-site Resources

* NEHA: Water Quality
# Environmental Health Engineering Theory and Practice/Early Biologic Effect

Toxicodynamics, termed pharmacodynamics in pharmacology, describes the dynamic interactions of a toxicant with a biological target and its biological effects.

## Useful Off-site Resources

* Biological markers in environmental health research. Committee on Biological Markers of the National Research Council, (1987)
# Environmental Health Engineering Theory and Practice/Climate Change

The effects of global warming include its effects on human health. The observed and projected increased frequency and severity of climate related impacts will further exacerbate the effects on human health. This article describes some of those effects on individuals and populations.

## Useful Off-site Resources

* World Health Organization: Climate Change and Human Health