Relation Between Electricity And Magnetism Pdf


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As early as the Swiss-born mathematician Leonhard Euler suggested that the same ether that propagates light is responsible for electrical phenomena.

Theory of Electricity and Magnetism

Magnetism is a class of physical phenomena that are mediated by magnetic fields. Electric currents and the magnetic moments of elementary particles give rise to a magnetic field, which acts on other currents and magnetic moments.

Magnetism is one aspect of the combined phenomenon of electromagnetism. The most familiar effects occur in ferromagnetic materials, which are strongly attracted by magnetic fields and can be magnetized to become permanent magnets , producing magnetic fields themselves. Demagnetizing a magnet is also possible. Only a few substances are ferromagnetic; the most common ones are iron , cobalt and nickel and their alloys. The prefix ferro- refers to iron , because permanent magnetism was first observed in lodestone , a form of natural iron ore called magnetite , Fe 3 O 4.

All substances exhibit some type of magnetism. Magnetic materials are classified according to their bulk susceptibility. Paramagnetic substances, such as aluminum and oxygen , are weakly attracted to an applied magnetic field; diamagnetic substances, such as copper and carbon , are weakly repelled; while antiferromagnetic materials, such as chromium and spin glasses , have a more complex relationship with a magnetic field.

The force of a magnet on paramagnetic, diamagnetic, and antiferromagnetic materials is usually too weak to be felt and can be detected only by laboratory instruments, so in everyday life, these substances are often described as non-magnetic. The magnetic state or magnetic phase of a material depends on temperature, pressure, and the applied magnetic field. A material may exhibit more than one form of magnetism as these variables change.

The strength of a magnetic field almost always decreases with distance, though the exact mathematical relationship between strength and distance varies.

Different configurations of magnetic moments and electric currents can result in complicated magnetic fields. Only magnetic dipoles have been observed, although some theories predict the existence of magnetic monopoles.

Magnetism was first discovered in the ancient world, when people noticed that lodestones , naturally magnetized pieces of the mineral magnetite , could attract iron. In ancient China , the earliest literary reference to magnetism lies in a 4th-century BC book named after its author, Guiguzi.

By the 12th century, the Chinese were known to use the lodestone compass for navigation. They sculpted a directional spoon from lodestone in such a way that the handle of the spoon always pointed south.

Alexander Neckam , by , was the first in Europe to describe the compass and its use for navigation. In , Peter Peregrinus de Maricourt wrote the Epistola de magnete , the first extant treatise describing the properties of magnets. In , the properties of magnets and the dry compasses were discussed by Al-Ashraf, a Yemeni physicist , astronomer , and geographer. Written in years near and never published, the treatise had a wide diffusion.

In this work he describes many of his experiments with his model earth called the terrella. From his experiments, he concluded that the Earth was itself magnetic and that this was the reason compasses pointed north previously, some believed that it was the pole star Polaris or a large magnetic island on the north pole that attracted the compass.

James Clerk Maxwell synthesized and expanded these insights into Maxwell's equations , unifying electricity, magnetism, and optics into the field of electromagnetism. In , Albert Einstein used these laws in motivating his theory of special relativity , [11] requiring that the laws held true in all inertial reference frames.

Electromagnetism has continued to develop into the 21st century, being incorporated into the more fundamental theories of gauge theory , quantum electrodynamics , electroweak theory , and finally the standard model. The magnetic properties of materials are mainly due to the magnetic moments of their atoms ' orbiting electrons.

The magnetic moments of the nuclei of atoms are typically thousands of times smaller than the electrons' magnetic moments, so they are negligible in the context of the magnetization of materials. Nuclear magnetic moments are nevertheless very important in other contexts, particularly in nuclear magnetic resonance NMR and magnetic resonance imaging MRI. Ordinarily, the enormous number of electrons in a material are arranged such that their magnetic moments both orbital and intrinsic cancel out.

This is due, to some extent, to electrons combining into pairs with opposite intrinsic magnetic moments as a result of the Pauli exclusion principle see electron configuration , and combining into filled subshells with zero net orbital motion.

In both cases, the electrons preferentially adopt arrangements in which the magnetic moment of each electron is canceled by the opposite moment of another electron.

Sometimes, either spontaneously, or owing to an applied external magnetic field—each of the electron magnetic moments will be, on average, lined up. A suitable material can then produce a strong net magnetic field. The magnetic behavior of a material depends on its structure, particularly its electron configuration , for the reasons mentioned above, and also on the temperature. At high temperatures, random thermal motion makes it more difficult for the electrons to maintain alignment.

Diamagnetism appears in all materials and is the tendency of a material to oppose an applied magnetic field, and therefore, to be repelled by a magnetic field. However, in a material with paramagnetic properties that is, with a tendency to enhance an external magnetic field , the paramagnetic behavior dominates. In a diamagnetic material, there are no unpaired electrons, so the intrinsic electron magnetic moments cannot produce any bulk effect.

In these cases, the magnetization arises from the electrons' orbital motions, which can be understood classically as follows:. When a material is put in a magnetic field, the electrons circling the nucleus will experience, in addition to their Coulomb attraction to the nucleus, a Lorentz force from the magnetic field. Depending on which direction the electron is orbiting, this force may increase the centripetal force on the electrons, pulling them in towards the nucleus, or it may decrease the force, pulling them away from the nucleus.

This effect systematically increases the orbital magnetic moments that were aligned opposite the field and decreases the ones aligned parallel to the field in accordance with Lenz's law. This results in a small bulk magnetic moment, with an opposite direction to the applied field.

This description is meant only as a heuristic ; the Bohr—Van Leeuwen theorem shows that diamagnetism is impossible according to classical physics, and that a proper understanding requires a quantum-mechanical description. All materials undergo this orbital response. However, in paramagnetic and ferromagnetic substances, the diamagnetic effect is overwhelmed by the much stronger effects caused by the unpaired electrons.

In a paramagnetic material there are unpaired electrons ; i. While paired electrons are required by the Pauli exclusion principle to have their intrinsic 'spin' magnetic moments pointing in opposite directions, causing their magnetic fields to cancel out, an unpaired electron is free to align its magnetic moment in any direction.

When an external magnetic field is applied, these magnetic moments will tend to align themselves in the same direction as the applied field, thus reinforcing it. A ferromagnet, like a paramagnetic substance, has unpaired electrons. However, in addition to the electrons' intrinsic magnetic moment's tendency to be parallel to an applied field, there is also in these materials a tendency for these magnetic moments to orient parallel to each other to maintain a lowered-energy state.

Thus, even in the absence of an applied field, the magnetic moments of the electrons in the material spontaneously line up parallel to one another. Every ferromagnetic substance has its own individual temperature, called the Curie temperature , or Curie point, above which it loses its ferromagnetic properties. This is because the thermal tendency to disorder overwhelms the energy-lowering due to ferromagnetic order.

Ferromagnetism only occurs in a few substances; common ones are iron , nickel , cobalt , their alloys , and some alloys of rare-earth metals. The magnetic moments of atoms in a ferromagnetic material cause them to behave something like tiny permanent magnets. They stick together and align themselves into small regions of more or less uniform alignment called magnetic domains or Weiss domains.

Magnetic domains can be observed with a magnetic force microscope to reveal magnetic domain boundaries that resemble white lines in the sketch. There are many scientific experiments that can physically show magnetic fields.

When a domain contains too many molecules, it becomes unstable and divides into two domains aligned in opposite directions, so that they stick together more stably, as shown at the right. When exposed to a magnetic field, the domain boundaries move, so that the domains aligned with the magnetic field grow and dominate the structure dotted yellow area , as shown at the left.

When the magnetizing field is removed, the domains may not return to an unmagnetized state. This results in the ferromagnetic material's being magnetized, forming a permanent magnet. When magnetized strongly enough that the prevailing domain overruns all others to result in only one single domain, the material is magnetically saturated. When a magnetized ferromagnetic material is heated to the Curie point temperature, the molecules are agitated to the point that the magnetic domains lose the organization, and the magnetic properties they cause cease.

When the material is cooled, this domain alignment structure spontaneously returns, in a manner roughly analogous to how a liquid can freeze into a crystalline solid. In an antiferromagnet , unlike a ferromagnet, there is a tendency for the intrinsic magnetic moments of neighboring valence electrons to point in opposite directions.

When all atoms are arranged in a substance so that each neighbor is anti-parallel, the substance is antiferromagnetic. Antiferromagnets have a zero net magnetic moment, meaning that no field is produced by them. Antiferromagnets are less common compared to the other types of behaviors and are mostly observed at low temperatures. In varying temperatures, antiferromagnets can be seen to exhibit diamagnetic and ferromagnetic properties.

In some materials, neighboring electrons prefer to point in opposite directions, but there is no geometrical arrangement in which each pair of neighbors is anti-aligned. This is called a spin glass and is an example of geometrical frustration. Like ferromagnetism, ferrimagnets retain their magnetization in the absence of a field. However, like antiferromagnets, neighboring pairs of electron spins tend to point in opposite directions.

These two properties are not contradictory, because in the optimal geometrical arrangement, there is more magnetic moment from the sublattice of electrons that point in one direction, than from the sublattice that points in the opposite direction. Most ferrites are ferrimagnetic. When a ferromagnet or ferrimagnet is sufficiently small, it acts like a single magnetic spin that is subject to Brownian motion. Its response to a magnetic field is qualitatively similar to the response of a paramagnet, but much larger.

An electromagnet is a type of magnet in which the magnetic field is produced by an electric current. Electromagnets usually consist of a large number of closely spaced turns of wire that create the magnetic field. The wire turns are often wound around a magnetic core made from a ferromagnetic or ferrimagnetic material such as iron ; the magnetic core concentrates the magnetic flux and makes a more powerful magnet.

The main advantage of an electromagnet over a permanent magnet is that the magnetic field can be quickly changed by controlling the amount of electric current in the winding. However, unlike a permanent magnet that needs no power, an electromagnet requires a continuous supply of current to maintain the magnetic field.

Electromagnets are widely used as components of other electrical devices, such as motors , generators , relays , solenoids, loudspeakers , hard disks , MRI machines , scientific instruments, and magnetic separation equipment. Electromagnets are also employed in industry for picking up and moving heavy iron objects such as scrap iron and steel. As a consequence of Einstein's theory of special relativity, electricity and magnetism are fundamentally interlinked.

Both magnetism lacking electricity, and electricity without magnetism, are inconsistent with special relativity, due to such effects as length contraction , time dilation , and the fact that the magnetic force is velocity-dependent.

However, when both electricity and magnetism are taken into account, the resulting theory electromagnetism is fully consistent with special relativity. Thus, special relativity "mixes" electricity and magnetism into a single, inseparable phenomenon called electromagnetism , analogous to how relativity "mixes" space and time into spacetime. All observations on electromagnetism apply to what might be considered to be primarily magnetism, e.

If the field H is small, the response of the magnetization M in a diamagnet or paramagnet is approximately linear:. In a hard magnet such as a ferromagnet, M is not proportional to the field and is generally nonzero even when H is zero see Remanence. The phenomenon of magnetism is "mediated" by the magnetic field. An electric current or magnetic dipole creates a magnetic field, and that field, in turn, imparts magnetic forces on other particles that are in the fields.

electricity and magnetism pdf

Electromagnetism is a branch of physics involving the study of the electromagnetic force , a type of physical interaction that occurs between electrically charged particles. The electromagnetic force is carried by electromagnetic fields composed of electric fields and magnetic fields , and it is responsible for electromagnetic radiation such as light. It is one of the four fundamental interactions commonly called forces in nature , together with the strong interaction , the weak interaction , and gravitation. Electromagnetic phenomena are defined in terms of the electromagnetic force, sometimes called the Lorentz force , which includes both electricity and magnetism as different manifestations of the same phenomenon. The electromagnetic force plays a major role in determining the internal properties of most objects encountered in daily life. The electromagnetic attraction between atomic nuclei and their orbital electrons holds atoms together. Electromagnetic forces are responsible for the chemical bonds between atoms which create molecules , and intermolecular forces.

Electricity and magnetism are separate yet interconnected phenomena associated with the electromagnetic force. Together, they form the basis for electromagnetism , a key physics discipline. It is responsible for the interactions between atoms and the flow between matter and energy. The other fundamental forces are the weak and strong nuclear force , which govern radioactive decay and the formation of atomic nuclei. Since electricity and magnetism are incredibly important, it's a good idea to begin with a basic understanding of what they are and how they work.

The Relationship Between Electricity and Magnetism

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Together, these two phenomena form the basis for electromagnetism

 А это не так? - спросил Беккер холодно, глядя на ее припухший локоть. - Конечно, нет! - возмущенно ответила девушка. Она смотрела на него невинными глазами, и Беккер почувствовал, что она держит его за дурака.  - Да будет. На вид вы человек состоятельный. Дайте немножко денег, чтобы я могла вернуться домой.

Мидж покачала головой. - В Космополитене пишут, что две трети просьб потереть спинку кончаются сексом. Бринкерхофф возмутился. - У нас ничего такого не случалось. - Вот.  - Она едва заметно подмигнула.

Electromagnetism

Джабба облегченно вздохнул.

 - Прости, не мог позвонить раньше, - успел сказать. Подумал, не рассказать ли ей. Но решил этого не делать.

 Я пробовал, - прошептал Стратмор еле слышно. Ей еще не приходилось слышать, чтобы он так. - Что значит - пробовал. Стратмор развернул монитор так, чтобы Сьюзан было .

Как кот, пойманный с канарейкой в зубах, святой отец вытер губы и безуспешно попытался прикрыть разбившуюся бутылку вина для святого причастия. - Salida! - крикнул Беккер.

Сьюзан осталась стоять. - Коммандер, если вы все еще горите желанием узнать алгоритм Танкадо, то можете заняться этим без. Я хочу уйти. Стратмор глубоко вздохнул.

Открыть дверь и вызвать сотрудников отдела систем безопасности, я угадал. - Совершенно. Будет очень глупо, если вы этого не сделаете.

Беккер грохнулся на пол возле двери.

К несчастью для того, кто это придумал, коммандер Стратмор не нашел в этой выходке ничего забавного. Два часа спустя был издан ставший знаковым приказ: СОТРУДНИК КАРЛ ОСТИН УВОЛЕН ЗА НЕДОСТОЙНЫЙ ПОСТУПОК С этого дня никто больше не доставлял ей неприятностей; всем стало ясно, что Сьюзан Флетчер - любимица коммандера Стратмора. Но не только молодые криптографы научились уважать Стратмора; еще в начале своей карьеры он был замечен начальством как человек, разработавший целый ряд неортодоксальных и в высшей степени успешных разведывательных операций. Продвигаясь по служебной лестнице, Тревор Стратмор прославился умением сжато и одновременно глубоко анализировать сложнейшие ситуации. Он обладал почти сверхъестественной способностью преодолевать моральные затруднения, с которыми нередко бывают связаны сложные решения агентства, и действовать без угрызений совести в интересах всеобщего блага.

Не успел он набрать международный код, как в трубке раздался записанный на пленку голос: Todos los circuitos estan ocupados - Пожалуйста, положите трубку и перезвоните позднее. Беккер нахмурился и положил трубку на рычаг. Он совсем забыл: звонок за границу из Испании - все равно что игра в рулетку, все зависит от времени суток и удачи. Придется попробовать через несколько минут.

 - Почему же так долго. - Ты явно не в себе, - как ни в чем не бывало сказал Хейл.  - Какие-нибудь проблемы с диагностикой.

5 Comments

Avice C.
17.04.2021 at 04:04 - Reply

Maxwell's equations say that electricity and magnetism are related. 1. Changing electric fields produce magnetic fields. 2. Changing magnetic fields produce.

Armand L.
17.04.2021 at 11:18 - Reply

Magnetism is a class of physical phenomena that are mediated by magnetic fields.

Silvio G.
18.04.2021 at 16:28 - Reply

No enrollment or registration.

Katherine R.
19.04.2021 at 11:37 - Reply

Electricity is a form of energy that is transmitted through the wires especially copper wires for operating the various machines and devices such as lights, fans, refrigerator, computers, television, air conditioner, washing machines, etc.

Ronnie H.
23.04.2021 at 01:45 - Reply

What is the ratio of the gravitational force to the electrostatic force acting on the electron due to the nucleus? Data: Page 4. 4. G = χ N.m.

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