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Help with Induction motor interview lesson

Discussion in 'Science' started by lejames82, Mar 14, 2012.

  1. I have been asked to deliver a 20 minute interview lesson on the induction motor as part of an interview. Having not taught the exam board in question before (OCR Advancing Physics) I was wondering if anyone had any bright ideas. I have been told they have only just started chapter 15 but induction motors seem to be some way in looking at the resources. Does anyone have any nice ideas, 20 minutes doesn't seem a long time and I'm not sure what to include and miss out. Any help greatly appreciated or suggestions welcome. Thanks
     
  2. I have been asked to deliver a 20 minute interview lesson on the induction motor as part of an interview. Having not taught the exam board in question before (OCR Advancing Physics) I was wondering if anyone had any bright ideas. I have been told they have only just started chapter 15 but induction motors seem to be some way in looking at the resources. Does anyone have any nice ideas, 20 minutes doesn't seem a long time and I'm not sure what to include and miss out. Any help greatly appreciated or suggestions welcome. Thanks
     
  3. Do you have long before you have to do this? An opportunity to try things out is always good.
    I haven't taught AP but was a keen user of Nuffield, on which AP is based. However, that was almost 30y ago, and my memory cells are weakening [​IMG]
    One of the major demo/pracs was a spinning metal can, supported on a vertical pin. Motive power was provided from 2 coils wrapped on iron C cores, mounted side-by-side close to the rim of the can. Both were in an ac parallel cicuit, with the phase of the current delayed to one of them using a capacitor. This means that the magnetic fields (which constantly change) is "behind" in one of them so the can rotates to follow the field. However, getting this to work needs a bit of time, so can't be done "cold" during 20min slot.
    I'd be tempted to go for a recapitulation exercise (show dc motor with brushes & commutator - ask for concise description of its functioning: look for LH Rule as well as commutator action; also query if it would work on ac) followed by a discussion of sparking and electrical interference. Then I'd pass round an induction motor (noting how heavy it is) and showing that it doesn't have brushes and requires ac. (I'm assuming the school will have these things).
    Alternatively, I might go with some simple induction experiments eg swinging metal (Al) sheet between magnetic poles, dropping magnet down plastic & copper pipes, spinning bar magnet above an aluminium disc which is free to move. The thing to stress here is that the metals are all non-magnetic - induced currents create magnetic fields which try to oppose the motion.
    In all cases, I'd be interested in your demeanor, relationships, confidence more than anything else.
    Good luck and please report back.
     

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