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

那领域什么时候改变？这就是诱发动势的原因。

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

因此，通线圈的磁通量会 发生变化，从而产生动势。

Yeah, but the EMF's no good. - Why?

没有 EMF不能用 - 怎么会？

Well, no traces of EMF, that's for sure.

没有动势反应 这点很确定。

I just swept the Telesca house with the EMF. It's clean.

我用EMF把特莱斯卡的房子扫视 没什么发现。

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

动势，你会记得，代表动势，这是导致子移动并形成流的原因。

So an emf is induced in the second coil.

因此在线圈中感应出动势。

The magnetic flux through the loop changes, which induces an emf.

通环路的磁通量发生变化， 从而产生动势。

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，我们会说动势等于通量变化随时间变化的负数。

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

这意味着通线圈中的环路的磁通量会随着时间而变化，这就是感应动势的原因。

The strength of the emf is equal to negative of the change in the magnetic flux, over the change in time.

随着时间的变化，动势的强度等于磁通量变化的负值。

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动势或动势对抗流。

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

这种与主流相反的动势的感应 称为自感。

First, in the early 1800s, Michael Faraday showed us how a changing magnetic field induces an electromotive force, or emf, resulting in an electric current.

首先，在 19 世纪初，迈克尔·法拉向我们展示了变化的磁场如何产生动势或动势，从而产生流。

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，我们将这想法称为法拉感应定律：它说变化的磁场会在线圈中感应出动势。

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.

流经充板的交流源会在手机线圈中感应出动势，从而可以使用该能量为池充。

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动势。

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，当您测量池端子之间的实际压时， 您会得到低于我们理想的动势的值。

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

它是负的，因为感应动势 与主流方向相反。

And to calculate an induced emf, you just take the change in current over time and multiply it by negative L.

要计算感应动势，只需将流随时间的变化乘以负。