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Chapter 30

Electromagnetic Induction

Индукция
Индукция
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 ...
Закон Фарадея
Закон Фарадея
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 ...
Закон Ленца
Закон Ленца
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 ...
Подвижная ЭДС
Подвижная ЭДС
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 ...
Динамо-машина с диском Фарадея
Динамо-машина с диском Фарадея
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 ...
Индуцированные электрические поля
Индуцированные электрические поля
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 ...
Индуцированные электрические поля: приложения
Индуцированные электрические поля: приложения
An important distinction exists between the electric field induced by a changing magnetic field and the electrostatic field produced by a fixed charge ...
Вихревые токи
Вихревые токи
Since eddy currents occur only in conductors, magnets can separate metals from other materials. For example, in a recycling center, trash is dumped in ...
Ток смещения
Ток смещения
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 ...
Значение тока смещения
Значение тока смещения
A displacement current is analogous to a real current in Ampère's law, participating in Ampère's law the same way as the usual ...
Электромагнитные поля
Электромагнитные поля
Electric fields generated by static charges, often referred to as electrostatic fields, are characteristically different from electric fields created by ...
Уравнение электромагнетизма Максвелла
Уравнение электромагнетизма Максвелла
James Clerk Maxwell (1831–1879) was one of the major contributors to physics in the nineteenth century. Although he died young, he made major ...
Симметрия в уравнениях Максвелла
Симметрия в уравнениях Максвелла
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 ...
Закон Ампера-Максвелла: решение проблем
Закон Ампера-Максвелла: решение проблем
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 ...
Дифференциальная форма уравнений Максвелла
Дифференциальная форма уравнений Максвелла
James Clerk Maxwell (1831–1879) was one of the significant contributors to physics in the nineteenth century. He is probably best known for having ...
Электрогенератор: Генератор переменного тока
Электрогенератор: Генератор переменного тока
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 ...
Генератор постоянного тока
Генератор постоянного тока
An alternator converts mechanical energy into electrical energy that varies sinusoidally, resulting in AC current. Meanwhile, a DC generator converts ...
Обратная ЭДС
Обратная ЭДС
Generators convert mechanical energy into electrical energy, whereas motors convert electrical energy into mechanical energy. A motor works by sending a ...
Магнитное демпфирование
Магнитное демпфирование
Eddy currents can produce significant drag on motion, called magnetic damping. For instance, when a metallic pendulum bob swings between the poles of a ...
Сверхпроводник
Сверхпроводник
A substance that reaches superconductivity, a state in which magnetic fields cannot penetrate, and there is no electrical resistance, is referred to as a ...
Типы сверхпроводников
Типы сверхпроводников
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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