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第 30 章

電磁誘導

誘導
誘導
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 ...
ファラデーの法則
ファラデーの法則
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 ...
レンツの法則
レンツの法則
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 ...
モーションエムフ
モーションエムフ
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 ...
ファラデーディスクダイナモ
ファラデーディスクダイナモ
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 ...
誘導電界
誘導電界
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 ...
誘導電界:応用
誘導電界:応用
An important distinction exists between the electric field induced by a changing magnetic field and the electrostatic field produced by a fixed charge ...
渦電流
渦電流
Since eddy currents occur only in conductors, magnets can separate metals from other materials. For example, in a recycling center, trash is dumped in ...
変位電流
変位電流
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 ...
変位電流の重要性
変位電流の重要性
A displacement current is analogous to a real current in Ampère's law, participating in Ampère's law the same way as the usual ...
電磁界
電磁界
Electric fields generated by static charges, often referred to as electrostatic fields, are characteristically different from electric fields created by ...
マクスウェルの電磁気学の方程式
マクスウェルの電磁気学の方程式
James Clerk Maxwell (1831–1879) was one of the major contributors to physics in the nineteenth century. Although he died young, he made major ...
マクスウェル方程式の対称性
マクスウェル方程式の対称性
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 ...
アンペア・マクスウェルの法則:問題解決
アンペア・マクスウェルの法則:問題解決
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 ...
マクスウェル方程式の微分形式
マクスウェル方程式の微分形式
James Clerk Maxwell (1831–1879) was one of the significant contributors to physics in the nineteenth century. He is probably best known for having ...
発電機:オルタネーター
発電機:オルタネーター
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 ...
DC発電機
DC発電機
An alternator converts mechanical energy into electrical energy that varies sinusoidally, resulting in AC current. Meanwhile, a DC generator converts ...
逆起電力
逆起電力
Generators convert mechanical energy into electrical energy, whereas motors convert electrical energy into mechanical energy. A motor works by sending a ...
磁気ダンピング
磁気ダンピング
Eddy currents can produce significant drag on motion, called magnetic damping. For instance, when a metallic pendulum bob swings between the poles of a ...
超伝導体
超伝導体
A substance that reaches superconductivity, a state in which magnetic fields cannot penetrate, and there is no electrical resistance, is referred to as a ...
超伝導体の種類
超伝導体の種類
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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