Eddy Current (1 Viewer)

[Alice3357]

Two aluminum tubes, one is complete, the other has a vertical cut.
When dropping a magnet through the tubes respectively, the magnet fell much faster in the tube with the vertical cut.

Why would this happen? eddy current would also be formed in the tube with the cut to exert a force against the fall of the magnet, wouldn't it?

Could anyone please explain?


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[mysterymarkplz]

Yes you're right both tubes will experience eddy currents which their direction will be in such a way to generate a magnetic field that opposes the direction of motion of the falling magnet. The reason the magnet falls down the vertical cut tube faster than the complete tube is because the vertical cut tube has less volume than the complete cut, therefore less eddy currents can form in the vertical cut tube, and the less eddy currents there are the weaker the magnetic field they will generate, so basically the magnetic field in the vertical cut tube is weaker than the magnetic field in the complete tube, thus the magnet falling down the vertical cut tube will be resisted less, thus will fall first.

 

[QZP]

Yes you're right both tubes will experience eddy currents which their direction will be in such a way to generate a magnetic field that opposes the direction of motion of the falling magnet. The reason the magnet falls down the vertical cut tube faster than the complete tube is because the vertical cut tube has less volume than the complete cut, therefore less eddy currents can form in the vertical cut tube, and the less eddy currents there are the weaker the magnetic field they will generate, so basically the magnetic field in the vertical cut tube is weaker than the magnetic field in the complete tube, thus the magnet falling down the vertical cut tube will be resisted less, thus will fall first.

surface area

 

[mysterymarkplz]

my bad, thank you!

 

[Alice3357]

Thanks a lot!


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[bongoli]

Both tubes do experience eddy currents. However in the copper tube, there is a greater retarding force (more eddy currents) which allows the opposition of motion (Lenz's Law). As a result of Lenz's law, the magnet dropped through the copper tube is slowed down. The tube with the vertical cut, would drop faster as less eddy currents can form within the volume of the tube. Thus the tube with the slit make the magnet fall faster than the copper tube.