# magnetism with aluminum

**URL:** <https://boards.straightdope.com/t/magnetism-with-aluminum/692>\
**Category:** Cecil's Columns/Staff Reports\
**Created:** [February 20, 2000, 10:58pm UTC](https://boards.straightdope.com/t/magnetism-with-aluminum/692 "2000-02-20T22:58:00Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![biondoli](https://avatars.discourse-cdn.com/v4/letter/b/9dc877/32.png) [@biondoli](https://boards.straightdope.com/u/biondoli)\
**Post date:** [February 20, 2000, 10:58pm UTC](https://boards.straightdope.com/t/magnetism-with-aluminum/692/1 "2000-02-20T22:58:00Z")

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There was something I didn’t see addressed which I feel definately needs attention. The explanation on electron polarity is great but missing something. Metals are generally conductors which means that electrons flow freely throughout the material depending on outside electomagnetic pulls. We all know that aluminum conducts electricity as we use it daily on computers. In this way you create a large, overall polarity in the object…but not in aluminum…why?

Ciao  
Vince

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**Author:** ![JillGat](https://avatars.discourse-cdn.com/v4/letter/j/9fc29f/32.png) [@JillGat](https://boards.straightdope.com/u/JillGat)\
**Post date:** [February 20, 2000, 11:27pm UTC](https://boards.straightdope.com/t/magnetism-with-aluminum/692/2 "2000-02-20T23:27:00Z")

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Please add a link to the column you are discussing.

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**Author:** ![Cabbage](https://avatars.discourse-cdn.com/v4/letter/c/f07891/32.png) [@Cabbage](https://boards.straightdope.com/u/Cabbage)\
**Post date:** [February 20, 2000, 11:36pm UTC](https://boards.straightdope.com/t/magnetism-with-aluminum/692/3 "2000-02-20T23:36:00Z")

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This is probably it:  
[http://www.straightdope.com/classics/a3\_339.html](http://www.straightdope.com/classics/a3_339.html)

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**Author:** ![biondoli](https://avatars.discourse-cdn.com/v4/letter/b/9dc877/32.png) [@biondoli](https://boards.straightdope.com/u/biondoli)\
**Post date:** [February 20, 2000, 11:38pm UTC](https://boards.straightdope.com/t/magnetism-with-aluminum/692/4 "2000-02-20T23:38:00Z")

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Yes, that was it…sorry.

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**Author:** ![JonF](https://avatars.discourse-cdn.com/v4/letter/j/cab0a1/32.png) [@JonF](https://boards.straightdope.com/u/JonF)\
**Post date:** [February 21, 2000, 1:01pm UTC](https://boards.straightdope.com/t/magnetism-with-aluminum/692/5 "2000-02-21T13:01:00Z")

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I’m not sure I understand the question. The fact that electrons move easily through metals tends to {i]destroy\* rather than create a polarity.

When electricity is flowing through aluminum, there is an associated magnetic field. Many years ago I took my VW speedometer apart. It was a “bicycle-bell” shaped aluminum housing, to which was mounted the needle, and a spring that pushed the needle towards zero. Just inside the aluminum bell was a magnet mounted to a flexible shaft connected to some axle. When the wheels turned, the shaft and magnet spun, inducing “eddy currents” in the aluminum bell, creating a magnetic field, which interacted with the magnet so the aluminum housing tried to follow the magnet. The position of the aluminum bell (and, therefore, the needle) depended on the return spring force and the speed at which the magnet spun. I suppose some other speedometers work the same way.

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jrf