Скачать или смотреть 20.1 Faraday's Law and Lenz's Law | General Physics

Chad provides a comprehensive lesson on Faraday's law and Lenz's law. The lesson begins with an introduction to magnetic flux in which it is shown to be directly analogous to electric flux learned previously. Ultimately, the magnetic flux depends upon the strength of the magnetic field, the area of the loop, and the angle of the magnetic field with respect to the normal of the plane of the loop. The relevance is that there is an induced emf in a loop of wire provided there is a change in magnetic flux. Faraday's law provides the magnitude of this induced emf and Lenz's law provides the direction. This change in magnetic flux could be due to a change in the strength of the magnetic field, a change in the area of the loop, or a change in the orientation of the magnetic field with respect to the plane of the loop. Examples of all three are considered in the lesson.

Lenz's law shows how to determine the direction of the induced emf and induced current in a loop of wire experiencing a change in magnetic flux. Ultimately, the induced current results in an induced magnetic flux, and Lenz's law states that the induced magnetic flux opposes the change in the external magnetic flux. This can be especially tricky when the change in the external magnetic flux points in the opposite direction of the external magnetic flux, and Chad shows how to solve several examples.

The lesson concludes with a special application of Faraday's law termed motional emf. As a conducting rod connected to a loop is moved in the plane perpendicular to a magnetic field, there is a change in magnetic flux and an induced emf. Chad shows how the expression for the potential difference for this motional emf is derived from Faraday's law and also show the application of Lenz's law to determine the direction.

00:00 Lesson Introduction
00:51 Magnetic Flux
03:28 Faraday's Law
04:59 Lenz's Law
13:50 Application of Lenz's Law
25:13 Faraday's Law and Motional Emf

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