how do you work out the direction of an eddy current? =/ (1 Viewer)

[nerdiichic]

I find it very difficult to work out the direction of the eddy current, can someone please explain the steps in working out the direction of it please?

Thank You

 

[Aindan]

An eddy current is generated due to Lenz's law, so teh current will produce a magnetic field in order to oppose the change that created it right.
So for example, You move a metal sheet into a magnetic field, a current will be created so as to OPPOSE this force moving it into the field. So the force that the eddy current creates will be to the left. Using your right hand palm rule. Fingers point into the page since magnetic field is into the page, and palm points to the left....so your thumb points up. Now eddy currents whirl around in a circle, so imagine the current like a circle. Your thumb pointing up means that the current is going anticlockwise.

You may get confused as to whether your thumb is pointing up at the 3 o clock position or the 9 o clock position of the circle. But since the metal sheet is moving from left to right, it is the 3 o clock position that the current is pointing up in...Hopefully you can understand my retarded explanation.

_____________
| --------------- | x x x x x x
|---------------- | ---> x x x x x x
|-----------------| x x x x x x
|_____________|

 

[OmmU]

I have a trick, since the moving magnet will induce a current and magnetic field which oppose's the original change in magnetic flux. It is almost like in the picture bellow, the conductor acting as a south pole (because south and south repel). From this we can draw an S on the end of the coil that the magnet is being inserted into and a little trick shows the direction of the induced current (or eddy current) [see 1]

See the trick with additng the arrows to the S that show the direction of the eddy current? This is the same with the N [see 2]

 

[nerdiichic]

thanks guys, you have been really helpful i get it now LOL just in time for my half yearlies

 

[khorne]

Or just think of it logically, using lenz's law. If, say, field lines are going into the page and a metal sheet, then it's as if a north pole is "set up" above the sheet, so if the metal is being moved out, a south pole will be induced, while if it is moving in a north will. then use thumb hand whatever rule to find direction of circular current.

 

[jamesfirst]

You must note that eddy currents are induced in metals. So think beyond the solenoid ones that OmmU has provided