http://www.livescience.com/38059-magnetism.html
http://www.livescience.com/30430-earth-magnetosphere-magnetic-field.html
http://school.discoveryeducation.com/curriculumcenter/magnetism/activity2.html
References
http://www.windows2universe.org/physical_science/magnetism/magnetic_field.html
http://education.jlab.org/qa/electromagnet.html
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