Consider the following diagram:

enter image description here

  1. In the first diagram, the wire is carrying current into the screen. Motion of the wire is downwards (Left Hand Rule)
  2. In the second diagram, the wire is moved downwards, and a current is induced, flowing out of the screen (Right Hand Rule)

In both cases, the direction of motion is the same (downwards) but the direction of Current is opposite.

When we compare the Right and Left Hand Rules, we find that there is always one of the three, either Current, Magnetic Field, or Force (Motion), who's direction is changing. Why does this happen?

  • $\begingroup$ This is essentially a duplicate of Why do we apply Fleming's left hand rule in case of DC motors but use Fleming's right hand rule in case of generators?. $\endgroup$ – John Rennie Nov 10 '14 at 17:08
  • $\begingroup$ But there's no answer posted there. It didn't get much attention. $\endgroup$ – user49111 Nov 11 '14 at 10:33
  • $\begingroup$ I've never used any "left hand rule". I don't really like this kind of rules because the user doesn't usually think about physics while using it. In this case, I really don't understand the figure, sorry. $\endgroup$ – TZDZ Nov 12 '14 at 12:58
  • $\begingroup$ @TZDZ Please don't joke here. The grey and red circle is the wire cross section, and arrows represent the direction of $B$-field $\endgroup$ – user49111 Nov 12 '14 at 13:16
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    $\begingroup$ Here's a 3d view. I couldn't illustrate any better. image $\endgroup$ – user49111 Nov 12 '14 at 15:06

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