Diamagnetism experiment with copper/lead

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Discussion Overview

The discussion revolves around the concept of diamagnetism, specifically exploring the feasibility of conducting an experiment to repel small pieces of lead or copper using magnets. Participants consider the strength of magnets required, the nature of diamagnetic effects, and the practical challenges of observing these effects in a home experiment.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant expresses interest in performing a simple experiment to repel a small piece of lead or copper, questioning the strength of magnets needed and whether neodymium magnets would suffice.
  • Another participant notes that while diamagnetism is a weak effect, it can be demonstrated with permanent magnets if the setup is sensitive enough to small forces, referencing a rolling soda can as an example.
  • A participant mentions that increasing the strength of the magnetic field can enhance the repulsion of diamagnetic materials, but questions whether a super strong magnet could effectively repel lead.
  • It is pointed out that the force due to diamagnetism in metals like copper and lead is very small, even in large magnetic fields, suggesting that observing this effect at home may be impractical.
  • Another participant introduces bismuth as a material with significantly stronger diamagnetic properties, stating that it can be levitated with strong permanent magnets.
  • Further discussion highlights that the magnetic susceptibility of bismuth is much higher than that of copper and lead, allowing for observable effects at lower magnetic field strengths.

Areas of Agreement / Disagreement

Participants generally agree that diamagnetism is a weak effect and that observing it with lead or copper in a home experiment may be challenging. However, there is a divergence regarding the practicality of using different types of magnets and the comparative effectiveness of bismuth versus copper and lead.

Contextual Notes

Participants note the limitations of the diamagnetic effect in common metals and the dependence on the strength of the magnetic field. There is also an acknowledgment of the challenges in directly observing these effects without specialized equipment.

JoeSalerno
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I'm new to the concept of diamagnetism, but it seems very fascinating, and I'd like to try a simple experiment. Say I wanted to repel a small piece of lead (or copper, both are readily available to me) about 3.5 grams, how strong of a magnet would I need? Could I just use small neodymium magnets or would a more serious electromagnet be needed? Is there a way to calculate the needed magnetic field strength and compare it to the magnetic susceptibility value of lead or copper? Excuse me if I've made any fundamental errors, as I've only really read about it a bit on the internet.
 
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It is a weak effect, but you can demonstrate it with permanent magnets if you have a setup that reacts to small forces. Here is an example with a rolling soda can.
 
mfb said:
It is a weak effect, but you can demonstrate it with permanent magnets if you have a setup that reacts to small forces. Here is an example with a rolling soda can.
From what I've read, you can't increase the diamagnetic strength of an object, but increasing the strength of the magnetic field it is present in pushes it away harder. If you theoretically had a super strong permanent or electromagnet, would you be able to repel the small sample of lead?
 
Every moving magnet will lead to a force, stronger magnets just lead to stronger forces. There is no threshold.
 
In case it is not obvious: the force due to diamagnetism in metals such as copper and lead is so small that the effect is tiny even in very large fields. The force is small that it is not something one needs to think about even when dealing with say 14T superconducting magnets.
Note that the famous levitating frog was in the bore of a 16T magnet.

Directly seeing the effect in experiment that can be done at home would most likely be impossible
 
Bismuth's diamagnetism is so strong that you can levitate it with strong permanent magnets. You can buy pieces of bismuth and do it at home.
 
mfb said:
Bismuth's diamagnetism is so strong that you can levitate it with strong permanent magnets. You can buy pieces of bismuth and do it at home.

Indeed, but the susceptibility of bismuth is something like 20 higher than that of of copper and lead (which means the effect can be seen at ~1T which is the field you get from a strong RE magnet).
 

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