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Chapter 30

Electromagnetic Induction

Induction
Induction
An emf is induced when the magnetic field in a coil is changed by pushing a bar magnet into or out of the coil. emfs of opposite signs are produced by ...
Loi de Faraday
Loi de Faraday
Faraday's law state that the induced emf is the negative change in the magnetic flux per unit of time. Any change in the magnetic field or change in ...
Loi de Lenz
Loi de Lenz
The direction in which the induced emf drives the current around a wire loop can be found through the negative sign. However, it is usually easier to ...
F.Emf mobile
F.Emf mobile
Magnetic flux depends on three factors: the strength of the magnetic field, the area through which the field lines pass, and the field's orientation ...
Dynamo de disque Faraday
Dynamo de disque Faraday
A Faraday disk dynamo is a DC generator, producing an emf that is constant in time. It consists of a conducting disk that rotates with a constant angular ...
Champs électriques induits
Champs électriques induits
The fact that emfs are induced in circuits implies that work is being done on the conduction electrons in the wires. What can possibly be the source of ...
Champs électriques induits : applications
Champs électriques induits : applications
An important distinction exists between the electric field induced by a changing magnetic field and the electrostatic field produced by a fixed charge ...
Courants de Foucault
Courants de Foucault
Since eddy currents occur only in conductors, magnets can separate metals from other materials. For example, in a recycling center, trash is dumped in ...
Courant de déplacement
Courant de déplacement
Ampère's law, in its usual form, does not work in places where the current changes with time and is not steady. Thus, Maxwell suggested including ...
Importance du courant de déplacement
Importance du courant de déplacement
A displacement current is analogous to a real current in Ampère's law, participating in Ampère's law the same way as the usual ...
Champs électromagnétiques
Champs électromagnétiques
Electric fields generated by static charges, often referred to as electrostatic fields, are characteristically different from electric fields created by ...
Équation de Maxwell de l’électromagnétisme
Équation de Maxwell de l’électromagnétisme
James Clerk Maxwell (1831–1879) was one of the major contributors to physics in the nineteenth century. Although he died young, he made major ...
Symétrie dans les équations de Maxwell
Symétrie dans les équations de Maxwell
Once the fields have been calculated using Maxwell's four equations, the Lorentz force equation gives the force that the fields exert on a charged ...
Loi d’Ampère-Maxwell : résolution de problèmes
Loi d’Ampère-Maxwell : résolution de problèmes
A parallel-plate capacitor with capacitance C, whose plates have area A and separation distance d, is connected to a resistor R and a battery of voltage ...
Forme différentielle des équations de Maxwell
Forme différentielle des équations de Maxwell
James Clerk Maxwell (1831–1879) was one of the significant contributors to physics in the nineteenth century. He is probably best known for having ...
Générateur électrique : Alternateur
Générateur électrique : Alternateur
Electric generators induce an emf by rotating a coil in a magnetic field. A simple alternator is an AC generator that creates electrical energy that ...
Générateur DC
Générateur DC
An alternator converts mechanical energy into electrical energy that varies sinusoidally, resulting in AC current. Meanwhile, a DC generator converts ...
Retour EMF
Retour EMF
Generators convert mechanical energy into electrical energy, whereas motors convert electrical energy into mechanical energy. A motor works by sending a ...
Amortissement magnétique
Amortissement magnétique
Eddy currents can produce significant drag on motion, called magnetic damping. For instance, when a metallic pendulum bob swings between the poles of a ...
Supraconducteur
Supraconducteur
A substance that reaches superconductivity, a state in which magnetic fields cannot penetrate, and there is no electrical resistance, is referred to as a ...
Types de supraconducteurs
Types de supraconducteurs
A superconductor is a substance that offers zero resistance to the electric current when it drops below a critical temperature. Zero resistance is not the ...
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