And when that field changes? That’s what induces an emf.

那个领域什么时候改变？这就是诱发电动势的原因。

So an emf is induced in the second coil.

因此在第二个线圈中感应出一个电动势。

And emf, you’ll recall, stands for electromotive force, which is what causes electrons to move and form a current.

电动势，你会记得，代表电动势，这是导致电子移动并形成电流的原因。

So the magnetic flux through the second coil changes, which induces an emf.

因此，通过第二个线圈的磁通量会 发生变化，从而产生电动势。

This means that the magnetic flux through the loops in the coil changes over time, which is what induces an emf.

这意味着通过线圈中的环路的磁通量会随着时间而变化，这就是感应电动势的原因。

And as we'll soon see, the emf depends on the sine of the angle between the coil and the magnetic field.

我们很快就会看到，电动势取决于线圈和磁场之间夹角的正弦值。

So we shorten this to say that the ideal voltage supplied by the battery is its emf.

所以我们缩小范围，说理想电压 由电池提供的是它的电动势。

In maths terms, we’d say that the emf is equal to the negative of the change in flux, over the change in time.

在数学术语中，我们会说电动势等于通量变化随时间变化的负数。

And it's negative, because the induced emf is in the opposite direction of the main current.

它是负的，因为感应电动势 与主电流方向相反。

These days, we call this idea Faraday’s Law of Induction: It says that a changing magnetic field will induce an emf in a loop of wire.

如今，我们将这个想法称为法拉第感应定律：它说变化的磁场会在线圈中感应出电动势。

This induction of an emf that opposes the main current is called self-inductance.

这种与主电流相反的电动势的感应 称为自感。

So, when you measure the actual voltage between the terminals of the battery, you get a value that's less than our ideal emf potential.

因此，当您测量电池端子之间的实际电压时，您会得到低于我们理想电动势电位的读数。

So, when you measure the actual voltage between the terminals of the battery, you get a value that’s less than our ideal emf potential.

因此，当您测量电池端子之间的实际电压时， 您会得到一个低于我们理想的电动势的值。

Now, we can calculate the strength of the emf in a generator using some of the principles we talked about last time.

现在，我们可以使用我们上次讨论的一些原理来计算生成器中电动势的强度。

And this relationship works the opposite way as well, with a changing magnetic flux inducing an emf that opposes the flux.

这种关系也以相反的方式起作用，变化的磁通量会产生与磁通量相反的电动势。

And finally, instead of finding the emf in just one loop of wire, we're finding the emf in a whole coil of wire.

最后，我们不是在一个线圈中找到电动势，而是在一整圈电线中找到电动势。

And when that field changes? That's what induces an emf.

当该领域发生变化时？ 这就是产生电动势的原因。

And you calculate the terminal voltage by subtracting the voltage drop due to internal resistance from the supplied emf voltage, designated by a script E.

然后通过从传递的电动势电压中减去由于内部电阻引起的电压降来计算端电压，用字母 E 表示。

The AC power running through the charging pad induces an emf in your phone's coil, which can use the energy to charge its battery.

流经充电板的交流电源会在手机线圈中感应出电动势，从而可以使用该能量为电池充电。

And that flux seeks to oppose the current with an electromotive force, or emf, in the opposite direction.

并且该通量试图以相反方向的电动势或电动势对抗电流。