Magnetic Field: Find the Right Magnet for a Foot Away

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Discussion Overview

The discussion revolves around finding a suitable magnet that can attract objects from at least a foot away, with participants exploring the characteristics and types of magnets that might meet this requirement. The conversation includes considerations of magnet geometry, pull force, and specific applications for personal projects.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Homework-related

Main Points Raised

  • One participant expresses a need for a magnet that can attract from at least a foot away, questioning whether the size of the magnet determines the strength of the magnetic field.
  • Another participant discusses the concept of a uniform magnetic field produced by an infinite current sheet, suggesting that larger sheets could extend the range of attraction.
  • A participant explains that the design of a hook magnet confines its magnetic field, resulting in a quick drop-off in strength, and recommends using a bar magnet for a more extended range.
  • There is mention of a major supplier indicating that a magnet meeting the specified requirements would need to be custom made and could be expensive.
  • Participants inquire about specific requirements and applications for the desired magnet, including the need for a solenoid that can eject a metal rod without using an electromagnet.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the best type of magnet for the specified distance, with multiple viewpoints and suggestions presented. The discussion remains unresolved regarding the optimal solution.

Contextual Notes

Participants express varying levels of understanding of the concepts discussed, with some referencing advanced topics that may not be accessible to all contributors. There are also indications of specific requirements that may not have been fully articulated.

Who May Find This Useful

This discussion may be of interest to individuals working on personal projects involving magnets, students learning about magnetism, and those seeking practical applications for magnetic materials.

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I'm engaged in a project that requires a magnet that can attract from at least a foot away. I mistakenly thought that a larger pull force would also mean a larger field and wasted $15 on a hook magnet with 130lbs pull force but only attracts from abut 2 inches away.

So what kind of magnet would fit my need? Is it the dimension that determines the size of the field?
 
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As with electric charge, you will find that the field of an infinite current sheet is uniform and independent of the distance a point is from the sheet.
Check out:
http://en.wikipedia.org/wiki/Current_sheet
Of course you cannot hope to make an infinitely big sheet but a larger sheet will result in a larger range.
 
Thanks for the reply LHarriger but that is way ahead of my current level. That seems like collage stuff and I'm only in 11th grade.
 
Your hook magnet confines the fields to a small annulus between the magnet disk at center and the steel cup it's mounted in. This field drops quickly if your metal object isn't right up against the assembly. Why is it done that way? By confining the field to a tiny volume, its strength (hence pull force) goes way up.

To pull from a distance you need a magnet with "open" geometry, that is the fields extend away from the body. The most open geometry is a bar magnet (technically it's called a dipole), so look for the combination of biggest and strongest bar magnet. Beware that the pull force 1 foot away will be tiny.
 
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What are those tubular magnets called that when you put a metal rod inside it will shoot the rod out. I heard they are used in car locks.
 
What are your desired specs, and what are you trying to accomplish?
 
marcusl said:
What are your desired specs, and what are you trying to accomplish?

I need a magnet the will pull from at least 9" away or a solenoid that will shoot something outwards, but WITHOUT an electromagnet. It's for a personal project.
 

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