27 October 2011 at 10:13 #15881
Here is an Excel file of statements I edited down. I think they only went from 220ish to 180ish but an awful lot of them had to be unpacked into three or so simpler statements, so I think it should be much more user friendly this way now.
One chief thing I did was re-order the sub-sub domains going for three groupings, Fundamental, Classroom and Technological.
Fundamental – charge, current, resistance, V=IR, electromagnetism, energy and power
Classroom – circuits, components and practical (these subdivide quite a bit too, mind)
Technology – mains electricty and national grid stuff, doping of semiconductors
The other thing I did was learn just why the statement
Voltage is electrical ‘push’.
always grated on me so much. It isn’t. The force eE where E=spatial-derivative-of(V) is electrical push. Anything else is setting up a conceptual disaster. I think I’m suggesting bringing in the Drude model as the primary model (raised to the status of ‘truth’?) from much earlier in the teaching. Other models can be referred to as analogies, but not this one…
28 October 2011 at 10:27 #15883
I have always taught the Drude classical eelctron gas model at AS level as a beautiful example of 19th century physics which also happens to lead elegantly both into Ohm’s law (why is V proportional to I?) and resistivity (as the geometric parts also appear naturally in the model). Of course it is limited – it cannot explain superconductors for a start and it is purely classical so gives no handle on semiconductors either – but I think it helps to ‘see’ what is happening in a conductor nicely.
30 October 2011 at 16:39 #15884
I was wondering what would happen if you introduced a proto-quantitative version of Drude just after you’d done solids liquids and gases through kinetic particle theory.
Why do we reserve this ‘scientific’ model for Higher Tier GCSE students? Why not just give it straight to the Year 7 students? I reckon a good few of them would cope with it, certainly as well as they do with pizza delivery models.
As for superconductors, yes you’re right. It doesn’t do that, but that’s pretty rare pre 19 isn’t it? As for semiconductors, can it be fudged quite simply by explaining the links between the ‘atoms’? Not sure. Getting quite detailed now on just one bit of the map, I suppose.
31 October 2011 at 08:50 #15885
To be honest, the failure to deal with super/semi conductors is in many ways a strength – it shows how physical models grow and develop. The Drude model works extremely well up to a point and then falls over. Is it wrong? Limited? Right in certain respects? Helpful? All really good questions about the philosophy of science…
You must be logged in to reply to this topic.