Neodymium

beating a dead horse some more surely you've heard of cobalt being used to make magnets or neodymium or rare earth metal magnets?

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Yah my dad said to use neodymium magnets and i know how we are going to do the project Hey but i'm not gonna get salmon to do the expirement i'll just do with tetras and guppies. And i don't get it how am i gonna get a unit of measurement ...

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... to vary field strength as Mith says, you would need a electro-magnet. http://www.howstuffworks.com/electromagnet.htm As far a regular magnets. Neodymium magnets, also called rare earth magnets are the bomb. Maybe too expensive though, about 2-5 bucks. They can be found at electronic surplus ...

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