Faraday's Law

法拉第定律

Any change in the magnetic environment of a coil of wire will cause a voltage (emf) to be "induced" in the coil. No matter how the change is produced, the voltage will be generated. The change could be produced by changing the magnetic field strength, moving a magnet toward or away from the coil, moving the coil into or out of the magnetic field, rotating the coil relative to the magnet, etc.

任何改变线圈所处的磁场环境的情况，都会在线圈中引起电压（emf）的'感应'。无论变化是如何产生的，电压都会被生成。这种变化可能是通过改变磁场强度、将磁体向线圈靠近或远离、将线圈移入或移出磁场、将线圈相对于磁体旋转等方法产生的。

Faraday's law is a fundamental relationship which comes from Maxwell's equations. It serves as a succinct summary of the ways a voltage (or emf) may be generated by a changing magnetic environment. The induced emf in a coil is equal to the negative of the rate of change of magnetic flux times the number of turns in the coil. It involves the interaction of charge with magnetic field.

法拉第定律是来自麦克斯韦方程组的一个基本关系。它概括了磁场变化如何通过电磁感应产生电压（或电动势）。线圈中的感应电动势等于磁通量变化率与线圈匝数乘积的负值。它涉及电荷与磁场的相互作用。

Lenz's Law

楞次定律

When an emf is generated by a change in magnetic flux according to Faraday's Law, the polarity of the induced emf is such that it produces a current whose magnetic field opposes the change which produces it. The induced magnetic field inside any loop of wire always acts to keep the magnetic flux in the loop constant. In the examples below, if the B field is increasing, the induced field acts in opposition to it. If it is decreasing, the induced field acts in the direction of the applied field to try to keep it constant.

当感应电动势是由磁通量的变化根据法拉第定律产生时，感应电动势的极性是使得产生的电流的磁场反对产生它的变化。在任何闭合回路中，感应磁场总是作用于保持回路中的磁通量恒定。在下面的例子中，如果B场在增强，感应磁场则与其相反；如果B场在减弱，感应磁场则与施加的场方向相同，以试图保持其恒定。

Magnet and Coil

磁体和线圈

When a magnet is moved into a coil of wire, changing the magnetic field and magnetic flux through the coil, a voltage will be generated in the coil according to Faraday's Law. In the example shown below, when the magnet is moved into the coil the galvanometer deflects to the left in response to the increasing field. When the magnet is pulled back out, the galvanometer deflects to the right in response to the decreasing field. The polarity of the induced emf is such that it produces a current whose magnetic field opposes the change that produces it. The induced magnetic field inside any loop of wire always acts to keep the magnetic flux in the loop constant. This inherent behavior of generated magnetic fields is summarized in Lenz's Law.

当磁体进入线圈时，改变线圈中的磁场和磁通量，根据法拉第定律，线圈中会产生电压。在下面的例子中，当磁体进入线圈时，检流计因磁场增强而向左偏转。当磁体被拉回出去时，检流计因磁场减弱而向右偏转。感应电动势的极性是使得产生的电流的磁场反对产生该变化。在任何线圈内的感应磁场总是作用于保持线圈中的磁通量恒定。这种生成磁场的固有行为总结在楞次定律中。