======Lenz’s Law Tubes======


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**Alternative titles:** Falling Magnet in a Tube, Eddy Currents
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====Summary====                   
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====Procedure====  
  - Secure a long aluminum tube vertically using a rod and stand, or hold it over a padded surface such as sandbags.  
  - Drop the non-magnetic aluminum cylinder into the tube and observe that it falls quickly.  
  - Drop the magnetic cylinder into the tube and note that it descends slowly compared to the non-magnetic one.  
  - (Optional) Use two identical aluminum tubes side by side to “race” the magnetic and non-magnetic cylinders for a dramatic comparison.



====Links==== 
Lenz's Law Demonstration - Penn Physics: 
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Demonstration of Lenz's Law - Grand Illusions: 
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📄 Lenz’s Law – Wonder Tubes - UCSC Physics Demonstration Room: [[https://ucscphysicsdemo.sites.ucsc.edu/physics-5c6c-demos/lenzs-law-wonder-tubes/]]\\

====Variations====
  * Try tubes with different wall thicknesses to see how the effect changes.  
  * Use magnets of different strengths to compare the falling times.  
  * Experiment with tubes made of different conductive but non-magnetic metals, such as copper.



====Safety Precautions====
  * Place sandbags or another soft surface under the tube to prevent cracking or chipping of the magnet when it lands.  
  * Do not use iron tubes, as they interfere with the effect by strongly attracting the magnet.  
  * Handle strong magnets with care; they can pinch skin or damage electronic devices.




====Questions to Consider====
  * Why does the magnetic cylinder fall more slowly than the non-magnetic one? (Because eddy currents induced in the aluminum oppose the motion of the magnet according to Lenz’s Law.)  
  * What factors influence how much the magnet slows down? (Magnet strength, tube conductivity, and wall thickness.)  
  * Why doesn’t the non-magnetic cylinder slow down? (No changing magnetic field is produced, so no eddy currents or opposing forces arise.)  
  * How does this demonstration relate to real-world applications? (Eddy currents are used in magnetic braking systems, induction heating, and metal detectors.)