Need help for Eddy Currents Motors and Generators (1 Viewer)

[Vizsla]

How do you deduce the direction of an eddy current?

So for example, how would you do it for these two scenarios?

1) http://puu.sh/iXkWf/ef0467331f.png

2) http://puu.sh/iXl1r/7565d2a643.png

Note that 2) is just a magnet going from a region of greater magnetic flux to one of less magnetic flux.

 

[Axio]

I could very well be wrong, but I would have thought:

1 - using right hand, thumb is direction of plate movement facing right, fingers are direction of field lines facing into page, therefore the current is moving upwards (palm) in the magnetic field and then in an anticlockwise direction (so eddy currents are anticlockwise: up in magnetic field, down outside magnetic field)

2 - using right hand, thumb is direction of plate movement facing right, fingers are direction of field lines facing into page, therefore the current is moving upwards (palm) in stronger magnetic field and then in a clockwise direction (so eddy currents are clockwise: up in stronger magnetic field, down in weaker)

 

[anomalousdecay]

Remember that the plate will try to avoid a change in flux (Lens' Law).

So in the case for the first picture, the plate will produce eddy current to avoid the change in flux. Now originally, there was no magnetic flux through the plate. Then it entered a magnetic field that goes into the page. To avoid this change, the eddy currents must produce a magnetic flux that goes out of the page. Using the right hand rule, we obtain anti-clockwise eddy currents.

For the second picture, the original flux threads through the plate. When moved in the direction shown, the plate moves into a magnetic field of less flux density than the original one, but of the same direction. To avoid this change in flux the plate will produce eddy currents that produce a magnetic field into the page as well, to "make up" for the change in flux. Hence, using the right hand rule, we obtain clockwise eddy currents.

 

[Vizsla]

Remember that the plate will try to avoid a change in flux (Lens' Law).

So in the case for the first picture, the plate will produce eddy current to avoid the change in flux. Now originally, there was no magnetic flux through the plate. Then it entered a magnetic field that goes into the page. To avoid this change, the eddy currents must produce a magnetic flux that goes out of the page. Using the right hand rule, we obtain anti-clockwise eddy currents.

For the second picture, the original flux threads through the plate. When moved in the direction shown, the plate moves into a magnetic field of less flux density than the original one, but of the same direction. To avoid this change in flux the plate will produce eddy currents that produce a magnetic field into the page as well, to "make up" for the change in flux. Hence, using the right hand rule, we obtain clockwise eddy currents.

Omg thank you so much. That cleared it up for me

 

[anomalousdecay]

* Lenz's

 

[Mr_Kap]

Remember that the plate will try to avoid a change in flux (Lens' Law).

So in the case for the first picture, the plate will produce eddy current to avoid the change in flux. Now originally, there was no magnetic flux through the plate. Then it entered a magnetic field that goes into the page. To avoid this change, the eddy currents must produce a magnetic flux that goes out of the page. Using the right hand rule, we obtain anti-clockwise eddy currents.

For the second picture, the original flux threads through the plate. When moved in the direction shown, the plate moves into a magnetic field of less flux density than the original one, but of the same direction. To avoid this change in flux the plate will produce eddy currents that produce a magnetic field into the page as well, to "make up" for the change in flux. Hence, using the right hand rule, we obtain clockwise eddy currents.

I don't get it.

where does lenz come into this?