Zero tolerance policies in schools

From Wikipedia, the free encyclopedia

https://en.wikipedia.org/wiki/Zero_tolerance_policies_in_schools

A zero-tolerance policy in schools is a strict enforcement of regulations and bans against behaviors or the possession of items deemed undesirable by said schools. Public criticism against the enforcement of such policies has arisen due to potential negative consequences when acts deemed intolerable are done in ignorance, by accident, or under extenuating circumstances, in addition to its connection to educational inequality in the United States. In schools, common zero-tolerance policies concern possession or use of illicit drugs or weapons. Students, and sometimes staff, parents, and other visitors, who possess a banned item for any reason are always (if the policy is followed) to be punished.

In the United States and Canada, zero-tolerance policies have been adopted in various schools and other education venues. Zero-tolerance policies in the United States became widespread in 1994, after federal legislation required states to expel for one year any student who brought a firearm to school, or lose all federal funding.

These policies are promoted as preventing drug abuse and violence in schools. Critics say zero-tolerance policies in schools have resulted in punishments that have been criticized as egregiously unfair against students and teachers, especially in schools with poorly written policies. Consequently, critics describe these policies as "zero-logic policies" because they treat juveniles the way that adults would be treated — or more harshly, given that children are seldom granted full permission to speak up in their own defense to adults with authority over them. Many people have been critical of zero-tolerance policies, claiming that they are draconian, provide little if any benefit to anyone, contribute to overcrowding of the criminal justice system, and/or disproportionately target people of color, particularly people of African-American and Hispanic descent.

Research

There is no concrete evidence that zero-tolerance reduces violence or drug abuse by students. Furthermore, school suspension and expulsion result in a number of negative outcomes for both schools and students. The American Bar Association finds that the evidence indicates that minority children are the most likely to suffer the negative consequences of zero-tolerance policies. Analysis of the suspension rate of students shows that black females and other racial minorities are suspended at a greater rate. The American Psychological Association concluded that the available evidence does not support the use of zero-tolerance policies as defined and implemented, that there is a clear need to modify such policies, and that the policies create a number of unintended negative consequences, including making schools "less safe".

In 2014, a study of school discipline figures was conducted. It was found that suspensions and expulsions as a result of zero-tolerance policies have not reduced school disruptions. The study's author stated that "zero-tolerance approaches to school discipline are not the best way to create a safe climate for learning". Zero-tolerance policies are sometimes viewed as a quick fix solution for student problems. While this seems like a simple action-reaction type of situation, it often leaves out the mitigating circumstances that are often the important details in student incidents. Even civilian judges consider mitigating circumstances before passing judgment or sentencing. If zero-tolerance policies were applied in adult courtroom scenarios, they would be fundamentally unjust and unconstitutional due to neglecting the laws involving due process, along with cruel and unusual punishments.

History

The label of zero-tolerance began with the Gun-Free Schools Act of 1994, when Congress authorized public-school funding subject to the adoption of zero-tolerance policies. Similar policies of intolerance coupled with expulsions for less serious behaviors than bringing a weapon to school had long been a part of private, and particularly religious schools. The use of zero-tolerance policies in public schools increased dramatically after the Columbine High School massacre, with principals declaring that safety concerns made them want zero-tolerance for weapons. These have led to a large number of disproportionate responses to minor, or technical transgressions, many of that have attracted the attention of the international media. These cases include students being suspended or expelled for such offenses as possession of ibuprofen or Midol (both legal, non-prescription drugs commonly used to treat headaches and menstrual cramps respectively) with permission of the students' parents, keeping pocketknives (small utility knife) in cars, and carrying sharp tools outside of a woodshop classroom (where they are often required materials). In Seal v. Morgan, a student was expelled for having a knife in his car on school property, despite his protestations that he was unaware of the knife's presence. In some jurisdictions, zero-tolerance policies have come into conflict with freedom of religion rules already in place allowing students to carry, for example, kirpans.

In the "kids for cash" scandal, judge Mark Ciavarella, who promoted a platform of zero-tolerance, received kickbacks for constructing a private prison that housed juvenile offenders, and then proceeded to fill the prison by sentencing children to extended stays in juvenile detention for offenses as minimal as mocking a principal on Myspace, scuffles in hallways, trespassing in a vacant building, and shoplifting DVDs from Wal-Mart. Critics of zero-tolerance policies argue that harsh punishments for minor offenses are normalized. The documentary Kids for Cash interviews experts on adolescent behavior, who argue that the zero-tolerance model has become a dominant approach to policing juvenile offenses after the Columbine shooting.

In New York City, Carmen Fariña, head of the New York City Department of Education, restricted school suspension by principals in 2015. The Los Angeles Unified school board, responsible for educating 700,000 students, voted in 2013 to ban suspensions for "willful defiance", which had mostly been used against students from racial minorities. A year later, the same school district decided to decriminalize school discipline so that minor offenses would be referred to school staff rather than prosecuted—the previous approach had resulted in black students being six times more likely to be arrested or given a ticket than white students. The district saw suspensions drop by 53%, and graduation rates rise by 12%.

Media attention

Media attention has proven embarrassing to school officials, resulting in changes to state laws as well as to local school policies. One school board member gave this reason for changes his district made to their rigid policy: "We are doing this because we got egg on our face."

• A student at Sandusky High School in Sandusky, Ohio, was suspended for 90 days and failed, after school authorities searched him for drugs in September 1999, and found a broken pocketknife. He had used the knife to clean his golfing cleats.
• The Christina School District in Newark, Delaware, has experienced multiple highly publicized cases of zero-tolerance:
  • After bringing a Cub Scouts dinner knife to school to eat his lunch, a six-year-old boy was ordered to attend an alternative school for students with behavioral problems for nine weeks. After a media uproar, the school board voted unanimously to reduce punishments for kindergartners and first-graders who take weapons to school to a 3-5 day mandatory suspension, retaining the original definition of "weapons".
  • Kasia Haughton, running for fifth-grade mayor at the Leasure Elementary School in Newark, Delaware was suspended and faced possible expulsion after coming to school with a knife to cut the cake. School officials were called in to investigate the incident, and referred to the knife as a "deadly weapon."
  • Other cases include a straight-A student who was ordered to attend "reform school" after a classmate dropped a pocket knife in his lap, and in 2007, when a girl was expelled for using a utility knife to cut paper for a project.
• Earlier in 2009, an Eagle Scout in New York was suspended for 20 days for having an emergency supply kit in his car that included a pocket knife.
• A kindergartner in Grand Rapids, Michigan, was suspended in March 2010 for making a finger gun.
• Another kindergartner, in Pennsylvania, was suspended for 10 days in January 2013 for referring to "shooting" a friend with a Hello Kitty bubble making gun. The suspension was reduced to two days after the parent met with school officials.
• A second-grader in Baltimore, Maryland, was suspended in March 2013 for biting a Pop-Tart into the shape of a mountain, which school officials mistook for a gun.
• 6-year-old Hunter Yelton in Colorado was suspended in 2013 for alleged repeated sexual harassment of a 6-year-old schoolmate, a charge the boy's family disputed. Following widespread negative media coverage and public disapproval, the school agreed to downgrade the suspension caused by "misconduct".
• A freshman at MacArthur High School in Irving, Texas, was suspended for a week in September 2015 after he put a digital alarm clock in a pencil box, and took it to his school to show a teacher. When the device beeped while in one class, the student was suspended and detained on suspicion of creating a hoax bomb.
• In the Escondido school knives case, Brian Capalletti and another student in San Diego were suspended from school for between 2 and 3 weeks and faced criminal charges and possible expulsion after knives were found in their vehicles parked outside their Escondido high school.

Promotion

Proponents of punishment- and exclusion-based philosophy of school discipline policies claim that such policies are required to create an appropriate environment for learning. This rests on the assumption that strong enforcement can act as a psychological deterrent to other potentially disruptive students.

The policy assumption is that inflexibility is a deterrent because, no matter how or why the rule was broken, the fact that the rule was broken is the basis for the imposition of the penalty. This is intended as a behavior modification strategy: since those at risk know that it may operate unfairly, they may be induced to take even unreasonable steps to avoid breaking the rule. This is a standard policy in rule- and law-based systems around the world on "offenses" as minor as traffic violations to major health and safety legislation for the protection of employees and the environment.

Disciplinarian parents view zero-tolerance policies as a tool to fight corruption. Under this argument, if subjective judgment is not allowed, most attempts by the authorised person to encourage bribes or other favors in exchange for leniency are clearly visible.

Criticism

Critics of zero-tolerance policies in schools say they are part of a school-to-prison pipeline that over-polices children with behavioral problems, treating their problems as criminal justice issues rather than educational and behavioral problems. Students that may previously have been given short school suspensions before the implementation of policies are now sent to juvenile courts.

Critics of zero-tolerance policies frequently refer to cases where minor offenses have resulted in severe punishments. Typical examples include the honor-roll student being expelled from school under a "no weapons" policy while in possession of nail clippers, or for possessing "drugs" like cough drops and dental mouthwash or "weapons" like rubber bands.

A related criticism is that zero-tolerance policies make schools feel like a jail or a prison. Furthermore zero-tolerance policies have been struck down by U.S. courts and by departments of education.

Another criticism is that the zero-tolerance policies have actually caused schools to turn a blind eye to bullying, resulting in them refusing to solve individual cases in an attempt to make their image look better. The zero-tolerance policy also punishes both the attacker and the defender in a fight, even when the attacker was the one who started the fight unprovoked. In 2017, the Georgia Supreme Court ruled that public schools within Georgia could not have a zero-tolerance policy for violence that does not allow for self-defense.

A particularly dismaying hypothesis about zero-tolerance policies is that they may actually discourage some people from reporting criminal and illegal behavior, for fear of losing relationships, and for many other reasons. That is, ironically, zero-tolerance policies may be ineffective in the very purpose for which they were originally designed.

As schools develop responses to online bullying, schools that have overly harsh approaches to zero-tolerance policies may increasingly police speech of students in their own time that would normally be protected by free speech laws.

The American Bar Association opposes "zero-tolerance policies that mandate either expulsion or referral of students to juvenile or criminal court, without regard to the circumstances or nature of the offense or the students [sic] history."

Critics of zero-tolerance policies also argue that the large numbers of students who are suspended and expelled from school experience negative effects, which can prohibit them from finishing high school. Students who experience suspension, expulsion and arrests pay higher psychological and social costs: such as depression, suicidal thoughts, academic failure, and run the risk of being incarcerated as adults. In a study by Forrest et al., (2000), psychologists identified that a third of youths in juvenile detention centers were diagnosed with depression shortly after being incarcerated. In addition to being diagnosed with depression many youths found themselves having suicidal thoughts (Gnau et al. 1997).

Research found that black, Latino, and white adults with low educational attainment risked a higher propensity of being incarcerated in their lifetime (Pettit & Western 2010). The same study found that the incarceration rate in 2008 was 37% and had risen since the 1980s. That showed that incarceration rates of people with low levels of education were continuing to rise and that students were not completing their high school requirements.

According to kidsdata.org, 21,638 students were suspended and 592 students were expelled from San Diego County schools in 2012. A total of 10.1% of students did not complete their high school diploma.

Despite a decrease in juvenile arrest, suspensions, expulsions, and drop out rates, many still argue that these disciplinary policies have helped contribute to students not completing their high school curriculum. Schools are struggling to keep students within the walls of the educational system rather than the walls of a juvenile detention center.

Reforms to zero-tolerance policies

The American Psychological Association (APA) assembled a Zero-Tolerance Task Force in 2008 that reviewed data and extensive literature on zero-tolerance policies and their effect on student behavior. After synthesizing the evidence, the APA found that zero-tolerance policies do not support child development nor improve school climate or school safety. The APA made several recommendations to reform zero-tolerance policies for serious infractions.

• One reform introduced by the APA was for school staff to consider teacher expertise and allow for greater flexibility when applying zero-tolerance policies. According to the APA, professional school staff need greater discretion when applying zero-tolerance policies because they are often the best mediators when evaluating infractions.
• Similarly, the APA recommended that all offenses be defined and that school officials be adequately trained to handle each offense. The APA affirmed that adequate teacher training will (1) protect teachers from being wrongfully accused of how they applied their school policy and (2) protect students from unfair repercussions.
• Another reform presented by the APA was for schools to evaluate their disciplinary prevention strategies. The APA maintained that schools, after evaluating their existing interventions and programs, would have strategies that have a positive effect on student behavior and school climate.

Alternatives to zero-tolerance policies

For less severe infractions, the American Psychological Association (APA) provided alternatives to zero-tolerance policies to ensure that students are not denied their opportunity to learn.

• The APA encouraged schools to implement preventive strategies that foster student support and a sense of community as an alternative to zero-tolerance policies. In particular, the APA asserted that research-supported preventive strategies improve the school climate and sense of community in schools, whereas zero-tolerance policies result in immediate punishment.
• For students who consistently engage in disruptive behavior, the APA recommended that schools design a list of effective alternatives they can use with students. The APA discussed various options that schools can implement to decrease disruptive behavior, including restorative justice, alternative programs, and community service.
• The APA also promoted increasing culturally relevant training available to teachers. According to the APA, this strategy is important for teachers to integrate culturally responsive management and instruction in their classrooms and, therefore, reduce the disproportionate amount of disciplinary referrals to maximize student learning.

Escondido school knives case

The Escondido school knives case was a collection of school suspensions, possible expulsions, and protests surrounding knives that were found in the cars of two students at San Pasqual High School in Escondido, California.

Discovery and arrests

Brandon Cappeletti, an 18-year-old student at the school, had been on a fishing trip in early January, 2016. He says he had used the knives to cut line and would have used them to prepare fish. After the fishing trip, he left the knives in his truck. Another 16-year-old student had a pocket knife in his glove compartment.

On January 27, police dogs were sniffing vehicles in the school's parking lot. Each student had Advil in the truck. In each case, the dogs alerted on the Advil. Cappeletti was called out of class to unlock the truck. The police found the Advil and the knives. In the case of the 16-year-old, the alert led to the police finding the pocket knife.

Both boys were arrested. Cappeletti was later released to his mother. The 16-year-old's case was referred to the California's juvenile diversion program. Both boys were charged with a misdemeanor for having a knife on school property with a blade longer than two-and-a-half inches. Both were also immediately suspended from classes.

Impact and protests

Cappeletti had already joined the U.S. Marine Corps. Had he been convicted of the misdemeanor, he might not have been able to remain. His mother Amy Cappelletti said, “He's the most patriotic student. He never gets into trouble. These weren't Crocodile Dundee knives.” At a School Board meeting on February 9, 2016, hundreds of people asked the Board not to expel the two students. Tony Coreley, the high school's football coach said that “There are rules and laws that the district has to follow, but this (situation) is unfortunate.” School District spokeswoman Karyl O’Brien said that the rules were the result of California's zero-tolerance policy.

Resolution

On February 11, 2016, the superintendent of the Escondido Union School District stated that the students would not be expelled and that they were expected to be allowed to return to school the following week. Both boys have since been exonerated from misdemeanor citations and juvenile diversion programs.

School-to-prison pipeline

From Wikipedia, the free encyclopedia

https://en.wikipedia.org/wiki/School-to-prison_pipeline 

In the United States, the school-to-prison pipeline (SPP), also known as the school-to-prison link, school-prison nexus, or schoolhouse-to-jailhouse track, is the disproportionate tendency of minors and young adults from disadvantaged backgrounds to become incarcerated because of increasingly harsh school and municipal policies. Additionally, this is due to educational inequality in the United States. Many experts have credited factors such as school disturbance laws, zero tolerance policies and practices, and an increase in police in schools in creating the "pipeline". This has become a hot topic of debate in discussions surrounding educational disciplinary policies as media coverage of youth violence and mass incarceration has grown during the early 21st century.

In recent years, many have started using the term school-prison nexus in place of school-to-prison pipeline to challenge the idea of a unidirectional pipeline that begins in schools in order to show that schools work within a web of institutions, policies, and practices that funnel youth into prisons. Moreover, it may no longer operate as a "pathway" to prison, but instead as a de facto prison.

The current climate of mass incarceration in the United States increases the contact the incarceration system has with the United States education system. More specifically, these patterns of criminalization translate into the school context. Specific practices implemented in United States schools over the past ten years to reduce violence in schools, including zero-tolerance policies and an increase in School Resource Officers have created the environment for criminalization of youth in schools. This results from patterns of discipline in schools mirroring law-enforcement models.

The disciplinary policies and practices that create an environment for the United States school-to-prison link to occur disproportionately affect disabled, Latino and Black students, which is later reflected in the rates of incarceration. Between 1999 and 2007, the percentage of black students being suspended has increased by twelve percent, while the percentage of white students being suspended has declined since the implementation of zero-tolerance policies. Of the total incarcerated population in the United States, 61% are Black or Latino.

History

A graph of the incarceration rate under state and federal jurisdiction per 100,000 population 1925–2008 (omits local jail inmates). The male incarceration rate (top line) is roughly 15 times the female rate (bottom line).

For the half-century prior to 1975 the incarceration rate in the U.S. was fairly constant at roughly 0.1 percent of the population, as indicated in the accompanying figure. The overall incarceration rate in the United States has grown rapidly and steadily since 1972, rising by 6 to 8 percent per year until 2000. Growth rates declined in the first decade of the 2000s and peaked at 506 per 100,000 in 2007 and 2008. From its peak in 2009 and 2010, the population of state and federal prisoners decreased slightly in 2011 and 2012. However, the incarceration rate, including those in jail, in 2012 was 707 per 100,000 people, which was more than four times the rate in 1972.

Causes

See also: Zero tolerance (schools)

Exclusionary disciplinary policies, specifically zero tolerance policies, that remove students from the school environment increase the probability of a youth coming into contact with the incarceration system. Zero tolerance policies have led to the mistreatment of students' situations and strict disciplinary action which greatly impact the students' future, causing them to go to juvenile detention centers or prison.

Approximately 3.3 million suspensions and over 100,000 expulsions occur each year. This number has nearly doubled since 1974, with rates escalating in the mid-1990s as zero tolerance policies began to be widely adopted. Rising rates of the use of expulsion and suspension are not connected to higher rates of misbehaviors. Risky behaviors is something suspended students will most likely engage in. Zero tolerance disciplinary policies have been adopted across the country. Zero tolerance policies are discussed in more detail later in the article, in the Current policies maintaining the link section.

Research is increasingly examining the connections between school failure and later contact with the criminal justice system for minorities. Once a child drops out, they are eight times more likely to be incarcerated than youth who graduate from high school. Studies have found that 68% of all males in state and federal prison do not have a high school diploma. Suspensions and expulsions have been shown to correlate with a young person's probability of dropping out and becoming involved with the criminal justice system. According to the American Civil Liberties Union, "Students suspended or expelled for a discretionary violation are nearly 3 times more likely to be in contact with the juvenile justice system the following year." However, it is unclear if the factors determining the risk of dropping out are not wholly or partially the same as the factors determining the risk of incarceration as an individual likely to enter the criminal justice system is also likely to encounter difficulties within the education system.

From 1980 to 2008, the number of people incarcerated in the United States quadrupled from roughly 500,000 to 2.3 million people. The graphic to the right shows the uniqueness of this practice in comparison to other countries across the globe, with the United States incarcerating a larger portion of its population than any other country in 2008. The United States holds 25% of the world's prisoners, but only has 5% of the world's population.

Disparities

See also: Youth incarceration in the United States

School disciplinary policies disproportionately affect Black and Latino youth in the education system. Ultimately, this means that they are more likely to be suspended, expelled or arrested; a practice known as the discipline gap. This discipline gap is also connected to the achievement gap. The U.S. Department of Education Office for Civil Rights issued a brief in 2014 outlining the current disparities. Black students are suspended and expelled at a rate three times greater than white students. The Advancement Project found that "In the 2006-2007 school year, there was no state in which African-American students were not suspended more often than white students." On average, 5% of white students are suspended, compared to 16% of black students. Black students represent 16% of student enrollment, and represent 27% of students referred to law enforcement and 31% of students subjected to a school-related arrest. Combined, 70% of students involved in "In-School arrests or referred to law enforcement are Black or Latino." The majority of these arrests are under zero tolerance policies.

Disparities were found in the implementation of zero tolerance policies (ZTPs) in relation to minor offenses. In 2010, in North Carolina black students were punished for the same minor offenses, specifically cell phone, dress code, disruptive behavior and display of affection by more than 15 percent for each category of offense than white students. According to the American Civil Liberties Union, "'Zero-tolerance' policies criminalize minor infractions of school rules, while cops in school lead to students being criminalized for behavior that should be handled inside the school. Students of color are especially vulnerable to push-out trends and the discriminatory application of discipline." Additionally, "The Council of State Governments Report found that black students were more likely to be disciplined for less serious 'discretionary' offenses, and that when other factors were controlled for, higher percentages of White students were disciplined on more serious non-discretionary grounds, such as possessing drugs or carrying a weapon."

A 2009 study reported that the racial disparity in rates of school suspensions could not be explained solely by racial differences in rates of delinquent behavior, and that this disparity in turn was "strongly associated with similar levels of disproportion in juvenile court referrals". Similarly, a 2010 study found that black students were more likely to be referred to the office than students of other races, and that this disparity could be partly, but not completely, explained by student behavior and school-level factors. According to Fordham Law Review Online, "In the juvenile justice system, black girls are the fastest growing demographic when it comes to arrest and incarceration." A 2014 study found that although black students were more likely to be suspended, this disparity "was completely accounted for by a measure of the prior problem behavior of the student", and concluded that "the use of suspensions by teachers and administrators may not have been as racially biased as some scholars have argued." Another 2015 study using a national high school dataset concluded that "misconduct and deviant attitudes were important factors in predicting the receipt of out-of-school suspensions though results indicated that Black students did not generally misbehave or endorse deviant attitudes more than White students did".

These interdisciplinary policies and practices disproportionately impact students from historically disadvantaged backgrounds such as, Latino and Black. It also been noted that students of minority groups were vulnerable to expulsions and that black girls are also highly criminalized for being absent from a schooling context. Dorothy E. Hines and Dorinda J. Carter Andrews have argued that increasing rates criminalization of black girls, disciplinary enforcements such as harsh policies and bans against "various student offenses" can be illuminated through (a) ZTPs including various forms of surveillance measures, (b) policing of their bodies as criminals, and (c) penalizing "bad" girl attitudes."

Schools with a higher percentage of black students are more likely to implement zero tolerance policies and to use extremely punitive discipline, supporting the racial threat hypothesis.

In November 2003, at Stratford High School in Goose Creek, South Carolina, police pointed their guns at students even though the students had not done anything wrong. The police also handcuffed the students, and forced them to kneel while facing the wall. The police claimed they were looking for illegal drugs, but did not actually find any. The police were also accused of racial profiling, due to the disproportionate number of African-American students whom they searched.

Current policies maintaining the link

Zero tolerance policies

Zero tolerance policies are school disciplinary policies that set predetermined consequences or punishments for specific offenses. By nature zero tolerance policies, as any policy that is "unreasonable rule or policy that is the same for everyone but has an unfair effect on people who share a particular attribute" often become discriminatory. The zero tolerance approach was first introduced in the 1980s to reduce drug use in schools. The use of zero tolerance policies spread more widely in the 1990s. To reduce gun violence, the Gun Free Schools Act of 1994 (GFSA) required that schools receiving federal funding "must 1) have policies to expel for a calendar year any student who brings a firearm to school or to school zone, and 2) report that student to local law enforcement, thereby blurring any distinction between disciplinary infractions at school and the law." During the 1996-1997 school year, 94% of schools had zero tolerance policies for fire arms, 87% for alcohol, and 79% for violence.

Over the past decade, zero tolerance policies have expanded to predetermined punishments for a wide degree of rule violations. Zero tolerance policies do not distinguish between serious and non-serious offenses. All students who commit a given offense receive the same treatment. Behaviors punished by zero tolerance policies are most often non-serious offense and are punished on the same terms as a student would be for bringing a gun or drugs to school. In 2006, 95% of out-of-school suspensions were for nonviolent, minor disruptions such as tardiness. In 2006-2007, "out-of-school suspensions for non-serious, non-violent offenses accounted for 37.2% of suspensions in Maryland, whereas only 6.7% of suspensions were issued for dangerous behaviors." In Chicago, the widespread adoption of zero tolerance policies in 1994 resulted in a 51% increase in student suspensions for the next four years and a 3,000% increase in expulsions.

The most direct way these policies increase the probability of a youth coming into contact with the incarceration system is through their exclusionary methods. Suspension, expulsion, and an increased risk of dropping out all contribute to a youth's increased chances of becoming involved with the incarceration system. Suspension removes students from the structure and supervision provided through schooling, providing opportunities for youth to engage in criminal activities while not in the school environment. Other factors may include "increased exposure to peers involved in antisocial behavior, as well as effects on school performance and completion and student attitudes toward antisocial behavior." Suspension can lead to feelings of alienation from the school setting that can lead to students to feel rejected, increasing chances of relationships with antisocial peers. Relationships with peers have strong impacts on student behavior, demonstrated through differential association theory. Students are more than twice as likely to be arrested during months in which they are forcibly removed from school. Students who have been suspended are three times more likely to drop out by the 10th grade than students who have never been suspended. Dropping out makes that student three times more likely to be incarcerated.

Policing in schools

Zero tolerance policies increase the number of School Resource Officers (SRO) in schools, which increases the contact a student has with the criminal justice system. Students may be referred by teachers or other administrators but most often zero tolerance policies are directly enforced by police or school resource officers. The practice of increasing the number of police in schools contributes to patterns of criminalization. This increase in SROs has led to contemporary school discipline beginning to mirror approaches used in legal and law enforcement. Zero tolerance policies increase the use of profiling, a very common practice used in law enforcement. This practice is able to identify students who may engage in misbehavior, but the use of profiling is unreliable in ensuring school safety, as this practice over identifies students from minority populations. There were no students involved in the 1990s shootings who were Black or Latino and the 1990s school shootings were the main basis for the increase in presence of police in schools. Data shows that people of color with disabilities are the most affected by the school-to-prison pipeline.

A Justice Policy Institute report (2011) found a 38% increase in the number of SROs between 1997 and 2007 as a result of the growing implementation of zero tolerance policies. In 1999, 54% of students surveyed reported seeing a security guard or police officer in their school, by 2005, this number increased to 68%. The education system has seen a huge increase in the number of students referred to law enforcement. In one city in Georgia, when police officers were introduced into the schools, "school-based referrals to juvenile court in the county increased 600% over a three year period." There was no increase in the number of serious offenses or safety violations during this three-year period. In 2012, forty-one states required schools to report students to law enforcement for various misbehaviors on school grounds. This practice increases the use of law enforcement professionals in handling student behavior and decreases the use of in-classroom (non-exclusionary) management of behaviors.

In 2014, the United Nations Human Rights Committee (HRC) expressed concern with increasing criminalization of students in response to school disciplinary problems, and recommended that the US government "promote the use of alternatives to the application of criminal law" to address such issues. The HRC also noted its concern with the use of corporal punishment in schools in the US. In the second Universal Periodic Review of the United States' human rights record, the government avowed taking "effective measures to help ensure non-discrimination in school discipline policies and practices."

In March 2010, at the Carver Primary School on the Far South Side of Chicago, several first grade students were handcuffed, and told that they were going to prison and would never see their parents again, after they talked in class.

In November 2011, at Orange River Elementary School in Florida, an assistant principal called the police after a girl kissed a boy.^[

In February 2010, the principal of a junior high school in Forest Hills, New York, called police after a 12-year-old student used a green magic marker to write, "I love my friends Abby and Faith. Lex was here 2/1/10 :)" on a desk. A police officer handcuffed the girl, and took her to the police station.

In October 2010, at Southern Lee High School in Lee County, North Carolina, a 12th grade honors student, who was taking college-level classes, was charged with misdemeanor possession of a weapon on school grounds, and suspended for the rest of the school year, after she brought a paring knife to school. The student had mistakenly taken her father's lunch box to school, which looked the same as her own lunch box. The school found the knife while searching the lunch box for illegal drugs, which the student did not have.

In 2014, in Lynchburg, Virginia, an 11 year-old black autistic boy was charged with a misdemeanor disorderly contact for kicking a trash can. A few later, this same kid was walking to join other students, and the same officer that reprimanded him for the trash can grabbed him, pushed him to the floor, and arrested him. As a result, the officer charged him with felony assault on a police officer.

Robbins v. Lower Merion School District

Further information: Robbins v. Lower Merion School District

In Rosemont, Pennsylvania, Harriton High School lent students laptop computers by way of their One-to-One initiative program. Over 2,000 students were given these laptops for school and home usage. Unbeknownst to the students and parents, the school district had webcams installed on each computer that were utilized to take images of students' activities while on the computer. The school district used these photos to attempt to incriminate students. In November 2009, the school's assistant principal falsely accused a student of selling illegal drugs after a school employee saw the student holding Mike and Ike candy while the student was at home.

Events affecting school to prison pipeline

1. A large factor of the school to prison pipeline is the disproportionate disciplinary actions taken against students of color. In recent years, the media has reported about some of these experiences.
2. Examples of zero tolerance policies and its role in school-to-prison pipeline statistics.

In Spring 2018, a 14-year-old black boy came to school with a new haircut. The haircut featured a design made with a razor. The student was pulled out of class one day at Tenaya Middle School in Fresno, California, because of his haircut, which the school claimed violated their dress code. The child's mother claimed, "The vice principal told my son that he needed to cut his hair because it was distracting and violated the dress code". The child's mother claims she agreed to get her son a new haircut; she also said she was unable to immediately get an appointment due to a lack of black barbers in her area. When her son arrived at school the next day, according to the child's mother, the school explained to her that he would face in-school suspension after returning with his haircut. The mother claims, "I requested that my son is issued a warning, to allow time to grow out his hair."

In Spring 2018, a black male student at Apache Junction High School in Arizona wore a blue bandana to school, which violated the dress code. His teacher called the police on him for not removing his bandana. He was then arrested and suspended for nine days.

In the summer of 2018, an 11-year-old black girl, Faith Fennidy, was sent home from a private Roman Catholic school in Louisiana because she had hair extensions. The young girl had been wearing extensions to school for two years before a new policy was added. The policy prohibits extensions, clip-ins, and/or weaves. The child would have to adhere to the policy to attend school. The family chose to withdraw the student from the school; the student was not suspended or expelled.

In 2012, at Creekside Elementary School in Milledgeville, Georgia, a six-year-old student, Salecia Johnson, was crying and flailing on the floor of her principal's office. The principal said she was inconsolable, had thrown various items, and had damaged school property during a tantrum. Salecia was handcuffed and transported to a police station. The child was initially charged as a juvenile with simple battery of a school teacher and criminal damage to property, but it was later decided the girl would not be charged because of her age.

Impact of COVID-19 pandemic

On March 11, 2020, the World Health Organization (WHO) declared the COVID-19 disease a global pandemic, resulting in school shut-downs across multiple countries, including the United States. Based on a report by UNICEF, approximately 94% of all countries enacted forms of remote learning to continue education for children in response to government closures caused by the COVID-19 pandemic. Likewise, as a result of the pandemic, in the United States, state and federal legislation either closed public schools and transferred to virtual instruction or offered hybrid learning, a mixture of face-to-face instruction and online learning. As school districts in the US encountered difficulty navigating requirements to provide education in remote settings, disciplinary practices continued to reflect aspects of the school-to-prison pipeline with zero-tolerance policies just as harmful as those before the COVID-19 pandemic. Since the nation's transition to remote learning, punishments including out-of-school suspension, juvenile detention, and police involvement have been enacted for minor infractions that have occurred in virtual learning environments.

• In May 2020, a fifteen-year-old Black female student with ADHD in Michigan was sent to a juvenile detention center for not turning in her online homework. The juvenile court concluded that her failure to submit her homework violated her probation and sentenced her to seventy-eight days in juvenile detention. She was later released after an adverse reaction from the public.

• In August 2020, Isaiah Elliot, a twelve-year-old Black student with ADHD attending virtual school in Colorado was punished after being seen on his computer camera picking up a toy NERF gun. Isaiah was suspended for five days by the school, which later contacted police to conduct a welfare check before notifying his parents.

As before the pandemic, the "virtual" school-to-prison pipeline continues to disproportionately impact racial minorities, predominantly African American and Hispanic students from low-income backgrounds, and students with disabilities. There are more than 48,000 youth confined in facilities in the United States on any given day. According to a report by the NAACP, as of 2020, "African American children represent 32% of children who are arrested, 42% of children who are detained, and 52% of children whose cases are judicially waived to criminal court." Additionally, students with disabilities account for 8.6% of the student population in the United States but represent 36% of incarcerated youth. Because students of color and students with disabilities are disproportionately incarcerated, they represent a large number of youth at risk for contracting COVID-19 and other infectious diseases. On that note, infectious diseases are severely concentrated in both adult and juvenile correctional facilities. The Marshall Project reported that most juvenile prison facilities have more than 80% infection rates. Moreover, approximately "15% of jail inmates and 22% of prisoners – compared to 5% of the general population – are reported having tuberculosis, Hepatitis B and C, HIV/AIDS, or other STDs."

Controversy over efforts to reduce racial disparities

In 2014 the Obama administration issued guidance that urged schools to reduce the number of suspensions and expulsions, especially of minority students, thereby stemming the school-to-prison pipeline. During the Trump administration, in December 2018, Education Secretary Betsy DeVos rescinded these guidelines. In doing so, she cited research by John Paul Wright and four coauthors that purported to show that the disparate rates of suspensions and expulsions were due not to racism, but rather to prior poor behavior by black students.

Lead author John Paul Wright has advocated for the fringe view that black people evolved to be genetically inferior to white people. In the study cited by DeVos, Wright et al. assumed that teachers' reporting of behavior was accurate and unbiased. They concluded that "the racial gap in suspensions was completely accounted for by a measure of the prior problem behavior of the student --- a finding never before reported in the literature." However, other scholars have found implicit bias and racial discrimination in teachers' interpretation of behavior of black students as more threatening than similar behavior by white students.

Education researcher Francis Huang found other methodological flaws in the study by Wright et al., such as sample bias (comparison between a sample of 4,101 students and a reduced sample of 2,737 students who were not representative of the earlier sample) and their use of the Social Skills Rating Scale as a proxy for evaluating prior behavior. Correcting for sample bias in the study by Wright et al. led Huang to conclude that their data confirmed what earlier researchers had found regarding racial disparities in punishment that could not be accounted for by actual differences in behavior.

Alternative approaches

Restorative justice

The use of restorative justice in schools began in the early 1990s with initiatives in Australia. Restorative justice models are used globally and have recently been introduced to school disciplinary policies in the United States as an alternative approach to current punitive models, such as zero tolerance. The focus is on ensuring that students understand and learn from their behavior as well as take responsibility for their actions and participate in steps that aim to repair the harm done to relationships between the student and the school environment. Programs, such as restorative circles, restorative meetings, restorative youth courts, and peer mediation, are being used as alternatives to zero tolerance policies and harsh disciplinary practices. The idea behind these programs is that students should be encouraged to participate in their punishments and school administration should refrain from using suspensions and expulsions for minor offenses. The goal of restorative programs is to keep students in school and to stop the flow of students from schools to the criminal justice system.

Some challenges to the use of restorative justice in schools are lack of time and community support. It requires balancing the time needed for mediation with the other demands of education in one school day. Scholars acknowledge that to achieve proper, unbiased mediation, it will require training, support, and review. It is also crucial that an entire community— students, parents, teachers, staff, coaches, etc. are convinced it is a better alternative and willing to work together.

Steven Teske, a juvenile court judge in Clayton County, Georgia, created the School-Justice Partnership model in 2003, known as the "Clayton County Model" or informally, "The Teske Model", to reduce the arrests of students involving minor offenses by using a collaborative agreement between schools, law enforcement, and the courts. The model has three main components: identifying minor offenses not subject to referral to the court; defining the roles of school police and school administrators to avoid using police as disciplinarians; and creating restorative practices and education programs in lieu of arrests. It took aim at zero tolerance policies which do not consider situational context or individual circumstances. The model's application in his county resulted in a 67 percent decline in referrals to juvenile court. Despite concerns by some that a softer approach would yield school safety issues, the data shows an increase in graduation rates of approximately 20 percent and an 8 percent decline in suspensions. The method has spread across the United States with some notable cities such as Birmingham, Alabama, and Wichita, Kansas, seeing similar improvements.

Editorial policies of major media

See also: United States incarceration rate § Editorial policies of major media

Beginning especially in the 1970s, the mainstream commercial media in the U.S. increased coverage of the police blotter, while reducing coverage of investigative journalism.

Advertising rates are set based on the audience. Because "if it bleeds, it leads", the media were able to accomplish this change without losing its audience.

Beyond this, the growth of private prisons increased the pool of major advertisers who could be offended by honest reporting on incarcerations and the school-to-prison pipeline: It makes financial sense to report on this only to the extent that such reporting is needed to maintain an audience.

Media constructions have contributed to hysteria over youth violence and mass incarcerations. TV overrepresents violent crime and people of color as offenders. This creates a "culture of fear" and "mean world syndrome" that particularly works against black or Latino males.

Mental health relating to the school to prison pipeline

Where there are undetected and untreated child mental health concerns, this can lead to unwanted suspensions and expulsions. When teachers include strategies to address the concerns found in students, it leads to students wanting to pursue their own academic achievement and success.

Students with diagnosable mental health problems suffer under zero tolerance policies. Such policies aim to create safer classrooms by removing potential disruptions, but many in mental health, social services, courts, or other related fields believe they fail in this goal and may result in less safe schools and communities. School is considered a protective factor against "delinquent conduct" and removing students from such an environment harms their ability to succeed.

An American Psychological Association Zero Tolerance Task Force report found that "students with disabilities, especially those with emotional and behavioral disorders, appear to be suspended and expelled at rates disproportionate to the representation in the population."

Zero tolerance policies also fail to account for neurological development in youths. Studies show that the brain is still "under construction" until about age 21. Youth are more likely to take risks, act impulsively, and exercise poor judgment. When these actions result in their involvement with the criminal justice system, they are punished rather than taught how to develop.

One issue in improving mental health services in school and interrupting the school to prison pipeline is that schools are unequipped to identify disorders and provide help for them.

Electromagnetic induction

From Wikipedia, the free encyclopedia

https://en.wikipedia.org/wiki/Electromagnetic_induction 

Alternating electric current flows through the solenoid on the left, producing a changing magnetic field. This field causes, by electromagnetic induction, an electric current to flow in the wire loop on the right.

Electromagnetic or magnetic induction is the production of an electromotive force across an electrical conductor in a changing magnetic field.

Michael Faraday is generally credited with the discovery of induction in 1831, and James Clerk Maxwell mathematically described it as Faraday's law of induction. Lenz's law describes the direction of the induced field. Faraday's law was later generalized to become the Maxwell–Faraday equation, one of the four Maxwell equations in his theory of electromagnetism.

Electromagnetic induction has found many applications, including electrical components such as inductors and transformers, and devices such as electric motors and generators.

History

Faraday's experiment showing induction between coils of wire: The liquid battery (right) provides a current that flows through the small coil (A), creating a magnetic field. When the coils are stationary, no current is induced. But when the small coil is moved in or out of the large coil (B), the magnetic flux through the large coil changes, inducing a current which is detected by the galvanometer (G).

 

A diagram of Faraday's iron ring apparatus. Change in the magnetic flux of the left coil induces a current in the right coil.

Electromagnetic induction was discovered by Michael Faraday, published in 1831. It was discovered independently by Joseph Henry in 1832.

In Faraday's first experimental demonstration (August 29, 1831), he wrapped two wires around opposite sides of an iron ring or "torus" (an arrangement similar to a modern toroidal transformer). Based on his understanding of electromagnets, he expected that, when current started to flow in one wire, a sort of wave would travel through the ring and cause some electrical effect on the opposite side. He plugged one wire into a galvanometer, and watched it as he connected the other wire to a battery. He saw a transient current, which he called a "wave of electricity", when he connected the wire to the battery and another when he disconnected it. This induction was due to the change in magnetic flux that occurred when the battery was connected and disconnected. Within two months, Faraday found several other manifestations of electromagnetic induction. For example, he saw transient currents when he quickly slid a bar magnet in and out of a coil of wires, and he generated a steady (DC) current by rotating a copper disk near the bar magnet with a sliding electrical lead ("Faraday's disk").

Faraday explained electromagnetic induction using a concept he called lines of force. However, scientists at the time widely rejected his theoretical ideas, mainly because they were not formulated mathematically. An exception was James Clerk Maxwell, who used Faraday's ideas as the basis of his quantitative electromagnetic theory. In Maxwell's model, the time varying aspect of electromagnetic induction is expressed as a differential equation, which Oliver Heaviside referred to as Faraday's law even though it is slightly different from Faraday's original formulation and does not describe motional EMF. Heaviside's version (see Maxwell–Faraday equation below) is the form recognized today in the group of equations known as Maxwell's equations.

In 1834 Heinrich Lenz formulated the law named after him to describe the "flux through the circuit". Lenz's law gives the direction of the induced EMF and current resulting from electromagnetic induction.

Theory

Faraday's law of induction and Lenz's law

Main article: Faraday's law of induction

 

A solenoid

 

The longitudinal cross section of a solenoid with a constant electrical current running through it. The magnetic field lines are indicated, with their direction shown by arrows. The magnetic flux corresponds to the 'density of field lines'. The magnetic flux is thus densest in the middle of the solenoid, and weakest outside of it.

Faraday's law of induction makes use of the magnetic flux Φ_B through a region of space enclosed by a wire loop. The magnetic flux is defined by a surface integral:

$${\displaystyle \Phi _{\mathrm {B} }=\int _{\Sigma }\mathbf {B} \cdot d\mathbf {A} \,,}$$

where dA is an element of the surface Σ enclosed by the wire loop, B is the magnetic field. The dot product B·dA corresponds to an infinitesimal amount of magnetic flux. In more visual terms, the magnetic flux through the wire loop is proportional to the number of magnetic field lines that pass through the loop.

When the flux through the surface changes, Faraday's law of induction says that the wire loop acquires an electromotive force (EMF). The most widespread version of this law states that the induced electromotive force in any closed circuit is equal to the rate of change of the magnetic flux enclosed by the circuit:

$${\displaystyle {\mathcal {E}}=-{\frac {d\Phi _{\mathrm {B} }}{dt}}\,,}$$

where ${\displaystyle {\mathcal {E}}}$ is the EMF and Φ_B is the magnetic flux. The direction of the electromotive force is given by Lenz's law which states that an induced current will flow in the direction that will oppose the change which produced it. This is due to the negative sign in the previous equation. To increase the generated EMF, a common approach is to exploit flux linkage by creating a tightly wound coil of wire, composed of N identical turns, each with the same magnetic flux going through them. The resulting EMF is then N times that of one single wire.

$${\displaystyle {\mathcal {E}}=-N{\frac {d\Phi _{\mathrm {B} }}{dt}}}$$

Generating an EMF through a variation of the magnetic flux through the surface of a wire loop can be achieved in several ways:

1. the magnetic field B changes (e.g. an alternating magnetic field, or moving a wire loop towards a bar magnet where the B field is stronger),
2. the wire loop is deformed and the surface Σ changes,
3. the orientation of the surface dA changes (e.g. spinning a wire loop into a fixed magnetic field),
4. any combination of the above

Maxwell–Faraday equation

See also: Faraday's law of induction § Maxwell–Faraday equation

In general, the relation between the EMF ${\displaystyle {\mathcal {E}}}$ in a wire loop encircling a surface Σ, and the electric field E in the wire is given by

$${\displaystyle {\mathcal {E}}=\oint _{\partial \Sigma }\mathbf {E} \cdot d{\boldsymbol {\ell }}}$$

where dℓ is an element of contour of the surface Σ, combining this with the definition of flux

$${\displaystyle \Phi _{\mathrm {B} }=\int _{\Sigma }\mathbf {B} \cdot d\mathbf {A} \,,}$$

we can write the integral form of the Maxwell–Faraday equation

$${\displaystyle \oint _{\partial \Sigma }\mathbf {E} \cdot d{\boldsymbol {\ell }}=-{\frac {d}{dt}}{\int _{\Sigma }\mathbf {B} \cdot d\mathbf {A} }}$$

It is one of the four Maxwell's equations, and therefore plays a fundamental role in the theory of classical electromagnetism.

Faraday's law and relativity

Faraday's law describes two different phenomena: the motional EMF generated by a magnetic force on a moving wire (see Lorentz force), and the transformer EMF this is generated by an electric force due to a changing magnetic field (due to the differential form of the Maxwell–Faraday equation). James Clerk Maxwell drew attention to the separate physical phenomena in 1861. This is believed to be a unique example in physics of where such a fundamental law is invoked to explain two such different phenomena.

Albert Einstein noticed that the two situations both corresponded to a relative movement between a conductor and a magnet, and the outcome was unaffected by which one was moving. This was one of the principal paths that led him to develop special relativity.

Applications

The principles of electromagnetic induction are applied in many devices and systems, including:

• Current clamp
• Electric generators
• Electromagnetic forming
• Graphics tablet
• Hall effect meters
• Induction cooking
• Induction motors
• Induction sealing
• Induction welding
• Inductive charging
• Inductors
• Magnetic flow meters
• Mechanically powered flashlight
• Near-field communications
• Pickups
• Rowland ring
• Transcranial magnetic stimulation
• Transformers
• Wireless energy transfer

Electrical generator

Rectangular wire loop rotating at angular velocity ω in radially outward pointing magnetic field B of fixed magnitude. The circuit is completed by brushes making sliding contact with top and bottom discs, which have conducting rims. This is a simplified version of the drum generator.

 

Main article: Electric generator

The EMF generated by Faraday's law of induction due to relative movement of a circuit and a magnetic field is the phenomenon underlying electrical generators. When a permanent magnet is moved relative to a conductor, or vice versa, an electromotive force is created. If the wire is connected through an electrical load, current will flow, and thus electrical energy is generated, converting the mechanical energy of motion to electrical energy. For example, the drum generator is based upon the figure to the bottom-right. A different implementation of this idea is the Faraday's disc, shown in simplified form on the right.

In the Faraday's disc example, the disc is rotated in a uniform magnetic field perpendicular to the disc, causing a current to flow in the radial arm due to the Lorentz force. Mechanical work is necessary to drive this current. When the generated current flows through the conducting rim, a magnetic field is generated by this current through Ampère's circuital law (labelled "induced B" in the figure). The rim thus becomes an electromagnet that resists rotation of the disc (an example of Lenz's law). On the far side of the figure, the return current flows from the rotating arm through the far side of the rim to the bottom brush. The B-field induced by this return current opposes the applied B-field, tending to decrease the flux through that side of the circuit, opposing the increase in flux due to rotation. On the near side of the figure, the return current flows from the rotating arm through the near side of the rim to the bottom brush. The induced B-field increases the flux on this side of the circuit, opposing the decrease in flux due to r the rotation. The energy required to keep the disc moving, despite this reactive force, is exactly equal to the electrical energy generated (plus energy wasted due to friction, Joule heating, and other inefficiencies). This behavior is common to all generators converting mechanical energy to electrical energy.

Electrical transformer

Main article: Transformer

When the electric current in a loop of wire changes, the changing current creates a changing magnetic field. A second wire in reach of this magnetic field will experience this change in magnetic field as a change in its coupled magnetic flux, d Φ_B / d t. Therefore, an electromotive force is set up in the second loop called the induced EMF or transformer EMF. If the two ends of this loop are connected through an electrical load, current will flow.

Current clamp

A current clamp

 

Main article: Current clamp

A current clamp is a type of transformer with a split core which can be spread apart and clipped onto a wire or coil to either measure the current in it or, in reverse, to induce a voltage. Unlike conventional instruments the clamp does not make electrical contact with the conductor or require it to be disconnected during attachment of the clamp.

Magnetic flow meter

Main article: Magnetic flow meter

Faraday's law is used for measuring the flow of electrically conductive liquids and slurries. Such instruments are called magnetic flow meters. The induced voltage ε generated in the magnetic field B due to a conductive liquid moving at velocity v is thus given by:

${\displaystyle {\mathcal {E}}=-B\ell v,}$

where ℓ is the distance between electrodes in the magnetic flow meter.

Eddy currents

Main article: Eddy current

Electrical conductors moving through a steady magnetic field, or stationary conductors within a changing magnetic field, will have circular currents induced within them by induction, called eddy currents. Eddy currents flow in closed loops in planes perpendicular to the magnetic field. They have useful applications in eddy current brakes and induction heating systems. However eddy currents induced in the metal magnetic cores of transformers and AC motors and generators are undesirable since they dissipate energy (called core losses) as heat in the resistance of the metal. Cores for these devices use a number of methods to reduce eddy currents:

• Cores of low frequency alternating current electromagnets and transformers, instead of being solid metal, are often made of stacks of metal sheets, called laminations, separated by nonconductive coatings. These thin plates reduce the undesirable parasitic eddy currents, as described below.
• Inductors and transformers used at higher frequencies often have magnetic cores made of nonconductive magnetic materials such as ferrite or iron powder held together with a resin binder.

Electromagnet laminations

Eddy currents occur when a solid metallic mass is rotated in a magnetic field, because the outer portion of the metal cuts more magnetic lines of force than the inner portion; hence the induced electromotive force is not uniform; this tends to cause electric currents between the points of greatest and least potential. Eddy currents consume a considerable amount of energy and often cause a harmful rise in temperature.

Only five laminations or plates are shown in this example, so as to show the subdivision of the eddy currents. In practical use, the number of laminations or punchings ranges from 40 to 66 per inch (16 to 26 per centimetre), and brings the eddy current loss down to about one percent. While the plates can be separated by insulation, the voltage is so low that the natural rust/oxide coating of the plates is enough to prevent current flow across the laminations.

This is a rotor approximately 20 mm in diameter from a DC motor used in a CD player. Note the laminations of the electromagnet pole pieces, used to limit parasitic inductive losses.

Parasitic induction within conductors

In this illustration, a solid copper bar conductor on a rotating armature is just passing under the tip of the pole piece N of the field magnet. Note the uneven distribution of the lines of force across the copper bar. The magnetic field is more concentrated and thus stronger on the left edge of the copper bar (a,b) while the field is weaker on the right edge (c,d). Since the two edges of the bar move with the same velocity, this difference in field strength across the bar creates whorls or current eddies within the copper bar.

High current power-frequency devices, such as electric motors, generators and transformers, use multiple small conductors in parallel to break up the eddy flows that can form within large solid conductors. The same principle is applied to transformers used at higher than power frequency, for example, those used in switch-mode power supplies and the intermediate frequency coupling transformers of radio receivers.