Demonstration experiments(演示实验) Dof the electromagnetic induction Coil线圈 magnet G G cO Date: 10. 1 Date:10.17 ×××x× ×××××× A conductor IS G x×××× moving in a magnetic field ⅹ×××b×
Demonstration experiments( 演示实验 )of the electromagnetic induction. Date: 10.1 Date: 10.17 A conductor is moving in a magnetic field. a b G G Coils线圈 magnet
A current appears only if there is relative motion between Relative motion the coil and the magnet( one must move relative to the other); the current disappears when the relative motion between them ceasest(终,停止)。 The induced emf( electromotive force E动势)and induced current in these experiments are apparently caused when something changes--but what is that something?. Faraday knew!
A current appears only if there is relative motion between the coil and the magnet( one must move relative to the other); the current disappears when the relative motion between them ceases(终，停止）。 The induced emf(electromotive force电动势） and induced current in these experiments are apparently caused when something changes--but what is that something?. Faraday knew!! Relative motion
2 Faraday' s Law of induction法拉第电磁感应定律 Faraday's law of induction, stated in terms of above experiments, is this: An emf is induced in the loop(coils)when the number of magnetic field lines (magnetic flux m that pass through the loop is changing B changing
2.Faraday’s Law of Induction法拉第电磁感应定律 Faraday’s law of induction, stated in terms of above experiments, is this: An emf is induced in the loop(coils) when the number of magnetic field lines (magnetic flux )that pass through the loop is changing. m B m changing
With the notion of magnetic flux, we can state Faradays law in a more quantitative(定量的)and useful way. As you will see in the following, the induced emf tends to oppose the flux change, so Faradays law is formally written as (SI) at
With the notion of magnetic flux, we can state Faraday’s law in a more quantitative(定量的） and useful way: dt dm As you will see in the following, the induced emf tends to oppose the flux change,so Faraday’s law is formally written as dt dm = − (SI)
The minus sign(负号) indicates that opposition: n B B increasing decreasing
The minus sign(负号） indicates that opposition: B m increasing n dl B m decreasing n dl