Incredibly, The Field Coil Magnet solves this problem.

难以置信的是，励磁磁路解决了这个问题。

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A magnetic resonance imaging apparatus includes a first magnetic field coil (30) and a second magnetic field coil (32).

一种磁共振成像设备包括第一磁场线圈(30)和第二磁场线圈(32)。

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I will post on auction the field coil and iron core magnet on auction later. However, to replace the magnet require technical skill and tool.

我随后会拍卖励磁和导磁柱，但是，改变磁路需要点技术和工具。

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That is we make animation file when you put the current to the coil of the field, getting established magnetic field.

即通过制作动画效果,当你将电流,输送到线圈上，形成磁场。

麻省理工公开课 - 媒体、教育、市场课程节选

For example, one of the experiments we do is measure the magnetic field of current coil, and after we do the experiment, we all have a passive visualization that shows the same experimental set-up, except we add to that.

比如，我们做的一个实验就是,测量电线圈的磁场，在我们做完实验之后，我们都感受到了一个直观化的过程,它展现了同样的实验过程，只是那是我们加的。

麻省理工公开课 - 媒体、教育、市场课程节选

Using a conductive capacitor that is integrated as part of the pen, it connects to an electromagnetic field generated by an excitation coil in the digitizer.

ENGADGET: N-trig's Digital Pencil plays pen and fingertip roles, claims mastery of both

Instead, the coil is pulled through the external magnetic field, which induces a voltage across it.

ECONOMIST: Weighing a kilogram

The coil is suspended in an external magnetic field and the current running through it adjusted so that the attraction between the two magnets balances the gravitational force on the suspended mass.

ECONOMIST: Weighing a kilogram