I started Magnetism with First Years today. They seem to be an enthusiastic bunch but let’s face it; if you can’t make Magnetism fun then you’re just a crap teacher. Anyway, after giving them a pair of magnets they were sent off to come up with as many unprompted observations as they could. It worked very well and some of their observations included the following:
(i) Sometimes magnets attract each other, sometimes they repel.
(ii) Magnets attract some materials but not others.
(iii) The only materials that they were attracted to magnets were metals.
(iv) They were attracted to some metals but not others.
(v) It was not possible to distinguish why it was attracted to these particular metals.
(vi) The metals seem to be more attracted to the poles than to the middle.
(vii) When one nail was hanging at the end, it in turn became a magnet and attracted other nails.
(viii) When the first nail was removed from the magnet, the second nail quickly lost its magnetism.
On the basis of these observations they were given the following puzzler for bonus marks homework.
Given only a bar-magnet and another similar-looking non magnetic metal, how could you tell which one was magnetic?