Month: October 2009

Secrets of the Van der Graff

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The philosopher of science Michael Polyani referred to it as ‘personal knowledge’, sociologist of science Harry Collins called it ‘tacit knowledge’ and your local gardener would simply know it as ‘green fingers’. It is the knowledge which we possess as experts in any given field but which is difficult to articulate. A certain ‘je ne sais quoi’ if you will. I suppose it’s why these cookery programs are so popular. All these wonderful chefs giving the impression that ‘there’s nothing to it’ is music to our ears – until we try to repeat the exercise ourselves.

In fairness to cookery programs, they are so much better than cookery books because there are so many vital steps which would never appear in print, partly because the chef simply can’t think of everything, but also perhaps because some of the essential steps would be considered ‘too obvious’ by the expert.

Needless to say, the same applies to teaching, and even more so when teaching a practical subject.

So with this caveat, here are a few tips when using the Van der Graff generator in a physics lesson.

  1. Don’t make the mistake of waiting for a sunny summer’s day. Yes the air needs to be dry to prevent the machine discharging into the air, but if you think about it there is likely to be less moisture in the air in a cold, dry winter’s day than in a warm dry summer’s day (warm air holds more moisture).
  2. I say that like it’s the most natural thing in the world for a physics teacher to know, yet it was only pointed out to me last year. You see you don’t need to know everything to be an expert – you only need to know a little more than your neighbour.
  3. You must have a hair-dryer to hand. Ideally have a student spend 10 minutes warming up all the belt in advance of any demonstration, and if necessary continue to use it on and off throughout (but obviously have it off while speaking).
  4. You will also need to hair dryer when trying the hair-raising demo with a volunteer student. There isn’t any danger here (unless the student has a pace-maker!) and greatest chance of accident is if someone gets a shock accidently and falls and bangs their head.
  5. Here you will need to give the student a helping hand. Again it’s the hair-dryer to the rescue – use another student to help here (if the volunteer is a girl then the person with the hair-dryer should also be a responsible female, for obvious reasons). Get her to use the hair-dryer to ‘fluff-up’ the volunteer’s hair and the Van der Graff should keep it up there.
  6. Volunteer needs to be well insulted – standing on plastic box usually does the trick.
  7. Have another student hold up a mirror so the volunteer can see herself – it adds to the fun.
  8. Remember that not only can the volunteer be touched, but the electrons can ‘jump’ through the air, so you can’t even come close to her.
  9. When discharging, ask her to simply touch the wooden bench and she will discharge sufficiently slowly to prevent shock. The effect is most noticeable if there is contrast between the hair and the background, so ideally have the lights on and dark blinds on the windows.
  10. Don’t forget to try some of the other old reliable like aluminium trays, fluorescent light bulbs and even blowing bubbles at the dome.

Hope this helps.
Have fun!

Physics notes – now with a full set of solutions

I may have mentioned that puting together the Junior Cert notes took rather a long time. Well it wasn’t much compared to how long it took to update the Leaving Cert notes.
For these I took all the exam papers from 2002 to 2009 at both higher level and ordinary level and broke up each question into the smallest chunks possible.
I then arranged these questions by topic, in the order in which the concepts appear in the notes themselves, so we’re left with a pretty comprehensive bank of questions.

Oh, and I typed up full solutions for these also.

This will hopefully be beneficial not only to students, but also to teachers (particularly new teachers) who want to make sure that they have all the material covered, and at the correct depth.

While it may have taken all Summer to put together, updating it each year shouldn’t prove too onerous.
Again, the intention is to see if it’s possible to publish this online for anyone to download as a booklet rather than coughing up beaucoup de moolah in these somewhat troubled times.  This would also involve replacing the odd copyright image with a more legimate substitute and problably sticking in some sample questions in most chapters also.

All in good time.

I also dug out some (okay – all) of the comments which teachers and students have sent my way over the last couple of years and put a link to it on the homepage – it is really is hugely rewarding to receive these, so if that’s you then thanks!
www.thephysicsteacher.ie

Nice resources for atomic bonding

A rather unorthodox approach to revising atomic bonding:


 
It dovetails nicely with one of the many free resources from absorblearning – in this case an animation of an oxygen atom bonding (covalently) with two hydrogen atoms to form a water molecule.

There are over 100 other free resources like this from the same site (you can see more on the right-hand side of the pages).
It would be ideal if one could link directly to the resourse but instead you have to click on the icon on the top left to arrive at the required distination. Just as well it’s worth the trip.
The plan is put links to most of these in the relevant junior chemistry page of thephysicsteacher.ie

Annnnnd we’re back

It’s taken a while (actually all Summer) but thephysicsteacher.ie now contains student notes on all topics on the Junior Cert Science syllabus.

Each chapter contains a copy of the relevant points from the syllabus at the beginning. This gives the student an overview of what the chapter is about and also acts as a check for both student and teacher to ensure we have everything covered before we finish.

There is then the main body which contains the notes in a relatively condensed form.

Next come the questions; here we have included every relevant question which has appeared on an exam paper at higher or ordinary level. These have been arranged to follow the order of the concepts in the notes themselves.

Each question has a reference to the year when the question appeared. Some questions come up repeatedly and this is readily apparent by noting the numbering of years at the top.

Next come the solutions. These are not just the answers but where necessary fully worked out solutions.

Finally there is a bank of miscellaneous questions which rounds of the chapter.

So what next?

Because it’s my first year using this approach it will take at least the year to road-test it and fine tune as I go along. This time next year it should be closer to a polished product.

I teach second- and third-years and so far we have never needed to look at a text-book. The hope is that next year we can spare parents the expense of purchasing science text-books for Junior Science.

Of course the notes still need to be photocopied and distributed, but at least we cut down considerably on paper by using narrow margins, reducing size by printing two pages onto one A4 and photocopying back to back, with the result that most chapters are on one double-sided page. Students seem to have little trouble with this approach although they do have to invest in a plastic folder to contain the notes.

It would be nice to think that we could work in a paperless classroom, but this would require all students to have their own laptop in class so I’m not holding my breath.

The wonderful people at CESI have been helping with the presentation and I can’t see any reason why the notes can’t be published as an online book after we have road-tested it.

It can be updated every year both to improve the quality and add extra exam questions as they appear. In particular I would like to develop the questions to include a lot more ‘higher order’ thinking rather than just simple recall.

It needs to be in ‘editable’ format to allow other teachers to adapt it to their own needs.

I also need to add interactive links to the Junior Chemistry and Junior Biology pages of the website; currently I have over one hundred waiting patiently in the wings; they range from average to priceless.

It’s all freely available to download. In fact to save teachers and/or students the trouble of downloading 45 different chapters I can’t see any reason why I can’t copy them to cd and post them – at least initially.

The website already contains a guide to teaching Junior Cert Physics by topic; it would be nice if this could be expanded to include Chemistry and Biology, but this would involve a contribution from a more knowledgeable source than I.

And what I really want to do is to have evolution permeate the entire Biology section  – after all could there be anything more ridiculous than teaching Biology without reference to the underlying template upon which all life is built?

That, and the fact that it’s only the greatest story ever told.

That’ll do for now.

Junior Cert Physics      Junior Cert Biology         Junior Cert Chemistry