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B Effect of number of coils on current in a generator?

  1. Jun 4, 2016 #1
    Hello everyone and thank you for your replies in advance. I am currently doing a physics project where I am testing to see how the number of coils of wire effects the current generated when a magnet is run through the coil. I am currently just dropping the magnet through the coil from a constant height (the coils are around a paper towel tube) but I am finding it difficult to get consistent readings. Based on the readings I have gotten, doubling the number of coils (one tube has 100 coils and the other has 100 coils and 100 more on top of those) does not double the current produced. I assume this is because the wire has greater resistance since it is much longer. I am just wondering if these are the results I should be getting, or have I completely messed up? Thank you again for all your replies.
     
  2. jcsd
  3. Jun 4, 2016 #2
    The induced emf. depends on the change of magnetic flux. For every coil, the emf. can be accumulated. Hence the more the coils you equip, the more emf. you will generate, hence the more current. However simultaneously you need more power to initiate the generator.
     
  4. Jun 4, 2016 #3
    So more current will be produced if I add more coils, but the current will not double if I double the number of coils without changing the speed of the magnet?
     
  5. Jun 4, 2016 #4
    The speed of the magnet shouldn't have to be changed. I mean you have to have more power to maintain the same speed.
    That's the result you get from your experiment?
     
  6. Jun 4, 2016 #5
    If u r just dropping the magnet then the speed of the magnet is not constant throughout the drop. It will be less in first half and as compared to second half. So the rate of change of magnetic flux is not the same through the two coils(assuming the coils are one above the other) . Apart from this the coils should be exactly identical in terms of size (diameter) ,material etc.
     
  7. Jun 4, 2016 #6
    The result I get is (though I am finding it hard to get accurate measurements), when I have 100 coils of copper wire around the tube and I drop a magnet through, the current produced is about 0.07 A. However when wrap 100 more coils on top of the 100 coils that are already there, and then I drop a magnet through from the same height, the current generated is about 0.085 A. However, I am having a difficult time measuring the current since it happens so quickly, so I am wondering if they should both be the same current, if the one with 200 coils should be higher but not doubled, or if the one with 200 coils should produce double the current?
     
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