Unexpected Magnetic Experiment Results

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Discussion Overview

The discussion centers around an experimental investigation into the effects of a steel cup on the magnetic attraction of a neodymium magnet. Participants explore the unexpected result that the presence of the cup appears to reduce the magnet's pull, contrary to initial expectations. The scope includes experimental methodology and technical considerations related to magnetism.

Discussion Character

  • Experimental/applied
  • Technical explanation

Main Points Raised

  • Bill reports that his experiment showed a reduction in magnetic attraction when a steel cup was placed on one end of a neodymium magnet.
  • One participant suggests that the hole diameter in the cup is too small, potentially shorting out the magnet, and recommends increasing the hole size to improve magnetic pull.
  • Another participant questions how Bill managed to remove the neodymium magnet from the cup and suggests a larger hole diameter for better results.
  • Bill confirms he included a tapped hole in the bottom of the cup to facilitate removing the magnet, acknowledging the potential issue of the magnet being stuck otherwise.

Areas of Agreement / Disagreement

Participants present differing views on the design of the cup and its impact on the magnet's performance. There is no consensus on the optimal dimensions or the reasons behind the observed reduction in magnetic attraction.

Contextual Notes

Participants express varying assumptions about the design and material properties of the cup, as well as the configuration of the magnet. The discussion does not resolve the underlying reasons for the unexpected experimental results.

Who May Find This Useful

Individuals interested in experimental magnetism, DIY physics experiments, or those exploring the effects of materials on magnetic fields may find this discussion relevant.

wmingin
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Hello All!

I read that placing a steel cup on one end of a permanent magnet will increase the "pull" at the opposite end. Having far too much time on my hands, I decided to perform my own test, to see how much the pull is increased. I found a neodymium cylinder magnet, 1 inch diameter and one inch long. I then machined a cup 2" diameter, 1-1/2" long, with a 7/8" deep x 1" diameter hole in one end. This gave me a steel cup with 1/2" wall and 1/2" floor. I attached a small steel rod to the strain gauge and measured the results with a 3/8" air gap steel to magnet. Here are the results...

Magent with no cup: 3lbs / 5oz.

Magnet with cup: 2lbs / 8oz.

The cup seems to have REDUCED the attraction!

What gives?

Cheers!

Bill
 
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You made your hole diameter to small. It is shorting out your magnet. Make your hole 1- 1/4" in diameter. You will also need a bushing to keep the magnet in the center of the hole. Make your bushing out of plastic, wood, copper, aluminium, or anything else that is not attracked by the magnet. This will increase the pull of the magnet. Good Luck.
 
How did you get the neodymium magnet out of the cup? I would have suggested a 1" deep by 1 1/2" or 1 3/4" dia hole. The cross section of the outer shell should be at least the cross section of the neodymium magnet, 0.785 square inches..
Bob S
 
Hi Bob!

Thanks for the reply! When I milled the cup, I included a 1/4-20 tapped hole in the bottom to provide a means to push the magnet out. You're right, If not for the tapped hole, the magnet would still be in the cup (maybe forever).

I'll try your suggestions. Thanks Again!

Cheers!

Bill
 

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