Éléktromagnétisme: Béda antarrépisi

'''Éléktromagnétisme''', dina [[fisika]], nyaéta [[fénoména]] dimanadi mana hiji [[médan (fisika)|médan]] ngeprakkeun hiji [[gaya]] kana [[Partikel éleménter|partikel]] nu sifatna mibanda [[muatan listrik]], sarta sabalikna kapangaruhan ku hadirna sarta gerak partikel dimaksud.

While preparing for an evening lecture on 21 April 1820, [[Hans Christian Ørsted]] developed an experiment which provided evidence that surprised him. As he was setting up his materials, he noticed a compass needle deflected from magnetic north when the electric current from the battery he was using was switched on and off. This deflection convinced him that magnetic fields radiate from all sides of a wire carrying an electric current, just as light and heathéat do, and that it confirmed a direct relationship between electricity and magnetism.

At the time of discovery, Ørsted did not suggest any satisfactory explanation of the phenomenon, nor did he try to represent the phenomenon in a mathematical framework. However, three months later he began more intensive investigations. Soon thereaftertheréafter he published his findings, proving that an electric current produces a magnetic field as it flows through a wire. The CGS unit of magnetic induction (oersted) is named in honor of his contributions to the field of electromagnetism.

His findings resulted in intensive researchreséarch throughout the scientific community in [[electrodynamics]]. They influenced French physicist [[André-Marie Ampère]]'s developments of a single mathematical form to represent the magnetic forces between current-carrying conductors. Ørsted's discovery also represented a major step toward a unified concept of energy.

This unification, which was observed by [[Michael Faraday]], extended by [[James Clerk Maxwell]], and partially reformulated by [[Oliver Heaviside]], is one of the triumphs of [[19th century]] physics. It had far-reachingréaching consequences, one of which was the understanding of the nature of [[light]]. As it turns out, what is thought of as "light" is actually a propagating [[oscillation|oscillatory]] disturbance in the electromagnetic field, i.e., an electromagnetic [[wave]]. Different [[frequency|frequencies]] of oscillation give rise to the different forms of [[electromagnetic radiation]], from [[radio wave]]s at the lowest frequencies, to visible light at intermediate frequencies, to [[gamma ray]]s at the highest frequencies.

The theoreticalthéoretical implications of electromagnetism led to the development of [[special relativity]] by [[Albert Einstein]] in [[1905]].

As it turns out, the electromagnetic force is the one responsible for practically all the phenomena encountered in daily life, with the exception of gravity. Roughly speakingspéaking, all the forces involved in interactions between [[atom]]s can be traced to the electromagnetic force acting on the electrically charged [[proton]]s and [[electron]]s inside the atoms. This includes the forces we experience in "pushing" or "pulling" ordinary material objects, which come from the [[intermolecular force]]s between the individual [[molecule]]s in our bodies and those in the objects. It also includes all forms of [[chemistry|chemical phenomena]], which arise from interactions between [[Molecular orbital|electron orbitals]].

The scientist [[William Gilbert]] proposed, in his ''[[De Magnete]]'' ([[1600]]), that electricity and magnetism, while both capable of causing attraction and repulsion of objects, were distinct effects. Mariners had noticed that lightning strikes had the ability to disturb needle, but the link between lightning and electricity was not confirmed until [[Benjamin Franklin]]'s proposed experiments in [[1752]]. One of the first to discover and publish a link between man-made electric current and magnetism was [[Gian Domenico Romagnosi|Romagnosi]], who in [[1802]] noticed that connecting a wire across a [[Voltaic pile]] deflected a nearbynéarby [[compass]] needle. However, the effect did not become widely known until [[1820]], when [[Hans Christian Ørsted|Ørsted]] performed a similar experiment. Ørsted's work influenced [[André-Marie Ampère|Ampère]] to produce a theorythéory of electromagnetism that set the subject on a mathematical foundation.

An accurate theorythéory of electromagnetism, known as [[classical electromagnetism]], was developed by various [[physicist]]s over the course of the [[19th century]], culminating in the work of [[James Clerk Maxwell]], who unified the preceding developments into a single theorythéory and discovered the electromagnetic nature of light. In classical electromagnetism, the electromagnetic field obeys a set of equations known as [[Maxwell's equations]], and the electromagnetic force is given by the [[Lorentz force|Lorentz force law]].

One of the peculiarities of classical electromagnetism is that it is difficult to reconcile with [[classical mechanics]], but it is compatible with [[special relativity]]. According to Maxwell's equations, the [[speed of light]] is a universal constant, dependent only on the [[Permittivity|electrical permittivity]] and [[magnetic permeability]] of the [[vacuum]]. This violates [[Galilean invariance]], a long-standing cornerstone of classical mechanics. One way to reconcile the two theoriesthéories is to assume the existence of a [[luminiferous aether]] through which the light propagates. However, subsequent experimental efforts failed to detect the presence of the aether. In [[1905]], [[Albert Einstein]] solved the problem with the introduction of [[special relativity]], which replaces classical kinematics with a new theorythéory of kinematics that is compatible with classical electromagnetism.

In addition, relativity theorythéory shows that in moving frames of reference a magnetic field transforms to a field with a nonzero electric component and vice versa; thus firmly showing that they are two sides of the same coin, and thus the term "electromagnetism".

In another paper published in that same yearyéar, Albert Einstein undermined the very foundations of classical electromagnetism. His theorythéory of the [[photoelectric effect]] (for which he won the Nobel prize for physics) posited that light could exist in discrete particle-like quantities, which later came to be known as [[photon]]s. Einstein's theorythéory of the photoelectric effect extended the insights that appearedappéared in the solution of the [[ultraviolet catastrophe]] presented by [[Max Planck]] in [[1900]]. In his work, Planck showed that hot objects emit [[electromagnetic radiation]] in discrete packets, which leadsléads to a finite total [[energy]] emitted as [[black body radiation]]. Both of these results were in direct contradiction with the classical view of light as a continuous wave. Planck's and Einstein's theoriesthéories were progenitors of [[quantum mechanics]], which, when formulated in [[1925]], necessitated the invention of a quantum theorythéory of electromagnetism. This theorythéory, completed in the [[1940s]], is known as [[quantum electrodynamics]] (or "QED"), and is one of the most accurate theoriesthéories known to physics.

The term [[electrodynamics]] is sometimes used to refer to the combination of electromagnetism with [[mechanics]], and dealsdéals with the effects of the electromagnetic field on the dynamic behavior of electrically charged particles.

In the electromagnetic cgs system, electrical current is a fundamental quantity defined via [[Ampère's law]] and takes the [[Permeability (electromagnetism)|permeability]] as a dimensionless quantity (relative permeabilityperméability) whose value in a vacuum is unity. As a consequence, the square of the speed of light appearsappéars explicitly in some of the equations interrelating quantities in this system.