Month: June 2016

The F.B.I. and Gang Signs for Physicists

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Those notions which are to be collected by reason . . . will seldom stand forward in the mind, but lie treasured in the remoter repositories of memory, to be found only when they are sought.

— Samuel Johnson, The Rambler, 7 April 1759

Sir John Ambrose Fleming (1849-1945) was the inventor of the thermionic valve, devices that formed the glowing (literally!) and pulsing heart of most electronic circuits until the invention of the transistor in the 1960s and the dawn of the Age of Semiconductors.

His part in most GCSE and A-level courses is small in extent but of significant and perhaps under acknowledged importance: he is the original framer of Fleming’s Left Hand Rule and Fleming’s Right Hand Rule. These respectively predict the direction of the force produced on a current-carrying conductor in a magnetic field (left hand) and the direction of induced current flow when a conductor cuts magnetic field lines (right hand). In short, they summarise the physics of everything from the humble electric motor to the Large Hadron Collider via the rail gun; not to mention the giant spinning generators that produce the humming electrical essence that powers our civilisation.

To use the rules, hold your thumb and first two fingers at right angles to each other. I tell my students that the left hand rule and right hand rule are physicists’ gang sign — it’s not too great a stretch of the imagination, at that. If you have ever invigilated a Physics exam, you can tell the point when the students have reached the Fleming’s Left/Right Hand Rule question . . . just look at their hands!
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But I digress. I began this post because I was taught the following mnemonic for FLHR:

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From: http://www.bbc.co.uk/schools/gcsebitesize/science/triple_aqa/keeping_things_moving/the_motor_effect/revision/3/

And to be honest, I have passed it on without thinking too hard about it. However, a student recently introduced me to the F.B.I. Mnemonic. Start with your thumb and say “F for force”, first finger and say “B for B-field” and then second finger and say “I for current”.

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From: https://en.m.wikipedia.org/wiki/Fleming%27s_left-hand_rule_for_motors

The great advantage of this is that F, B and I are the standard physical symbols for the quantities they represent, unlike the multistage hoop-jumping demanded by the traditional mnemonic.

I don’t know about you, but I think I will be using the FBI mnemonic from now on (which, incidentally, was developed by Robert Van De Graaff (1901-1967), of Van De Graaff generator fame).

The Renaming of Parts; or, Energy is the New Orange

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A PC approach to energy?

Neil Atkin recently wrote a fascinating post about the “New” approach for teaching the concept of energy to secondary school students, and provides some interesting commentary and some very useful links: go read!

I first came across the work of Ogborn and Boohan, on which much of the “New Approach” is based, in the 1990s. I remember embracing it enthusiastically. However, I subsequently returned to the more “traditional” kinetic-chemical-heat-potential-light-sound “naming of parts” model, mostly because many of the resources favoured by our students followed the older convention.

And so it has remained for a number of years, so I was all set to give the “New Approach” a proper rubbishing (as might be gleaned from my selection of the Gary Larson cartoon above) as a specious form of PC — physical correctness as opposed to political correctness, perhaps.

But as I read more about the “New Approach”, I gradually came to the conclusion that it is conceptually sound. More importantly, I think it follows one of the basic principles suggested by Engelmann and Carnine:

[I]f we are to understand how to communicate a particular bit of knowledge . . . we must understand the essential features of the particular concept that we are attempting to convey. Only if we understand what it is and how it differs from related concepts can we design a communication that effectively conveys the concept to the learner.
— The Theory Of Instruction, location 296

In other words, I think the “New Approach” is a more accurate representation of the physics of energy, and less likely to lead to misconceptions and false inferences.

Energy Is The New Orange

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Read Dr Dav’s excellent blog post from 2013 for a clear summary of the arguments in favour of the New Approach, as well as Robin Millar’s excellent paper on the topic.

Rise of the Enoji

One of the suggestions made in the IOP’s Energy 11-14 is to use ideograms or icons to represent different energy stores.

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By analogy with the ubiquitous ’emojis’ I suggest that we should call these energy icons Enojis. Who knows, it could just catch on…

P is for Progressive, T is for Traditionalist, Z is for Zealot

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The change of religion in Scotland, eager and vehement as it was, raised an epidemical enthusiasm, compounded of sullen scrupulousness and warlike ferocity, which, in a people whom idleness resigned to their own thoughts, and who, conversing only with each other, suffered no dilution of their zeal from the gradual influx of new opinions, was long transmitted in its full strength from the old to the young . . .
— Samuel Johnson, A Journey To The Western Islands Of Scotland [1775]

Old Andrew writes of a recent case in Scotland where a teacher was barred from teaching for two years because, for example, she “did not refer to success criteria” and “failed to recap the learning intentions at the end of the lesson”(!)

Well, to some extent I have been there, done that and got the t-shirt. I have been on the receiving end of the ‘support’ that doesn’t feel particularly supportive. However, it has never reached the disciplinary stage; in part, I suppose, because I learned to ‘play the game’ and stick in a few card sorts and the like. Teacher, know thou thy observer!

But I feel I have known what might be termed the “epidemical enthusiasm” of True Believers in the now defunct ‘Axis of Old-style-Ofsted’ model. And, yes, there was indeed a time when it seemed that many who favoured that model conversed “only with each other” and that there was no hope of any dilution of their zeal.

It is depressing to think that these discredited ideas still hold sway in parts of our education system.

That said, it seems to me that this is not automatically a consequence of progressive ideals; rather, it seems to me a consequence of a totalitarian mindset — an inability to trim one’s ideological sails to the winds of empirical reality, especially when one is in a position of power or authority.

And that, I think, is something that each of us — Positive Traditionalist* or Positive Progressivist* alike — needs to guard against.

*See @heymisssmith’s excellent post for further explanation of what I think is a useful expansion of the traditionalist vs. progressivist terminology.