Magnetism

Resources for teaching Magnetism

This week with Form 6 it was Magnetic Fields.

One of the concepts I try to emphasise is that this is a 3-dimensional phenomena, as opposed to the 2-dimensional pattern that you get from sprinkling iron filings on a page.

Some of these help:

I got the ferrofluid from teachersource.com

For bonus points, on this next video can you guess why the clips are only standing up sometimes as opposed to all the time?

Magnetic Movie from Semiconductor on Vimeo.

And no discussion on Magnetism could be complete without a mention of the man who gives his name to the unit of Magnetic Field Density; the Tesla.
http://theoatmeal.com/comics/tesla

All these links are available from the Magnetism page of the website.

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Teaching Magnetism

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?

Junior Cert Science: Unusual demonstration of magnetic fields

This week we looked at a concept called ferromagnetism which allows us to demonstrate the 3-dimensional nature of magnetic fields.

Thanks to my first years for being so co-operative 🙂

Here’s another way of illustrating the idea (which we didn’t do)

The mystery of magnetism
Floating rings used to demonstrate magnetic repulsion
Floating rings used to demonstrate magnetic repulsion

Sometimes the most basic question can be the hardest to answer. “How do magnets work?” is one such question. If you’re a teacher like me you’ll probably end up using fancy terms like “North and South Poles” and “Opposite Poles Attract”, and may even go on to demonstrate it using the floating magnets above.

Or if it’s a senior class you might talk about the material having “Magnetic Domains” which are usually randomly oriently but in a magnet are all lined up parallel.
And this invaribly works.
But there’s usually one student (quite often it’s someone who is not great academically, and consequently may remain in the background for much of the time) who’s not happy with this. 
But how does one magnet know that the other magnet is there?

And that, my friends, is a great moment. It means that at least one person in my class managed to avoid all the ‘education’ that I stuff down their throats, and maintained his ability to think for himself. ‘Course that won’t help him (or her) much when it comes to exam time, but at least in my mind it counts for a lot.

A former student once sent me a card on which he wrote “Thanks sir, I was in your class for two years and in that time I learnt nothing”. It was one of the nicer compliments I have received. Cheers Luke.

I hope to be teaching more Junior Cert Science this year and need to remember to avoid the temptation of throwing in jargon as a substitute for deeper explanations. For that matter, when the apple falls from the tree how does it ‘know’ which way is down?

Or here’s one for leaving cert students: why is the charge of a proton (which is composed of three quarks) the same as the charge of an electron if they are completely seperate particles?

Here’s a lovely article taken from the  science magazine Discover detailing how the author realises that nobody actually understands how magnetism works.

As teachers, we need to become comfortable discussing the limitations of what we know.