Dropping magnet through vertical aluminum tube

In summary, a well-known physics experiment involves dropping a magnet through a vertical aluminum tube. The magnet slows down noticeably before passing through, as electrical current is induced in the tube, creating an opposing magnetic flux. There are questions about whether current is also induced in the magnet and whether the Right Hand Motor Rule or Left Hand Generator Rule applies. Additionally, a similar problem is posed about calculating the de-acceleration of a magnetized object moving through a conductive material without any other forces involved. The experiment is explained by Lenz's law, where the induced current opposes the change causing it.
  • #1
dougettinger
26
1
A well known physics experiment is dropping a magnet through a vertical aluminum tube.
The magnet slows noticably before passing completely through the tube. Electrical current is created in the aluminum tube thereby creating a magnet thereby creating an opposing magnetic flux to slow down the falling magnet.

My question is whether, theoretically, current is also induced in the magnet and/or forces are exerted on the magnet about its axis ?

Another question is whether the Right Hand Motor Rule or the Left Hand Generator Rule can be applied to this experiment ?

Thoughtfully, Doug Ettinger
 
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  • #2
The basic rule is Lenz's law.
The falling magnet causes a changing magnetic flux linkage in the Aluminium tube which causes an emf and a resulting induced current.
The induced current opposes the change causing it... the falling magnet... currents circulate around the aluminium tube to effectively try to 'repel' the falling magnet.
 
  • #3
A problem similar to the subject experiment is posed. How is the de-acceleration calculated for a magnetized object of mass, m, and velocity, v, moving through a conductive material (assume an aluminum tube)? No other force fields including gravity are involved.

The magnetized body has a magnetic field intensity of H = B/u where B = magnetic induction and u = permeability of the medium.

Need help, Doug Ettinger
 

1. How does dropping a magnet through a vertical aluminum tube work?

When a magnet is dropped through a vertical aluminum tube, it creates a changing magnetic field. This changing magnetic field induces eddy currents in the aluminum tube. These eddy currents generate their own magnetic field that opposes the motion of the magnet, causing it to slow down and ultimately come to a stop inside the tube.

2. Why does the magnet slow down when dropped through the tube?

The slowing down of the magnet is due to the generation of eddy currents in the aluminum tube. These eddy currents create a magnetic field that opposes the motion of the magnet, causing it to experience a drag force. This drag force is what slows down the magnet as it falls through the tube.

3. Does the strength of the magnet affect the rate at which it falls through the tube?

Yes, the strength of the magnet does affect the rate at which it falls through the tube. A stronger magnet will induce stronger eddy currents in the aluminum tube, resulting in a greater opposing force and a slower rate of falling. However, other factors such as the size and shape of the magnet also play a role in the rate of falling.

4. Can the dropping speed of the magnet be controlled?

The dropping speed of the magnet can be controlled by altering the properties of the aluminum tube. For example, a thicker or longer tube will result in a slower rate of falling due to the increased resistance to the eddy currents. Additionally, the strength of the magnet and the angle at which it is dropped can also affect the speed at which it falls through the tube.

5. Are there any real-world applications of this experiment?

Yes, there are several real-world applications of this experiment. One example is in braking systems for roller coasters and trains, where eddy currents are used to slow down and stop the vehicles. Another application is in electromagnetic braking for vehicles, where the motion of a metal disc or wheel through a magnetic field generates eddy currents that help slow down the vehicle. This experiment also has applications in electricity generation, as eddy currents can be used to convert kinetic energy into electrical energy.

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