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I Need explanation about magnetic forces

  1. Jun 14, 2017 #1
    Hi,

    I saw this video and I can't explain why the magnet is propelled to the end of the coil with such a huge force. Can someone explain it in clear terms. I also tried to use Flemings left hand (or right hand) rule but it did not give me a satisfactory answer.



    Thanks,
    SM
     
  2. jcsd
  3. Jun 14, 2017 #2

    Bandersnatch

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    Magnets are typically coated in conductive metal, like nickel, for extended durability. Even if themselves not conductive, their metallic coating will conduct electricity from the battery to the copper coil. The current will flow between + and - through the coil, creating a magnetic field in the process:
    electricity-navy-basics-97-jpg.jpg
    The induced magnetic field will interact with the permanent magnets, propelling the battery assembly forward.
     
  4. Jun 14, 2017 #3

    sophiecentaur

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    Well, the car has the whole of its motor on board and needs to get power via the braid 'brushes' (contacts). That limits the current available to the motor. The magnet (solenoid) is much less subtle; it can have very fat wire for its coils and be supplied with a lot of current without the problem of brushes. Also the force is applied direct to the magnet and no gears / transmission system is there to affect the efficiency. It is, perhaps, not a fair fight. :smile:
     
  5. Jun 15, 2017 #4

    CWatters

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    Some batteries can deliver quite a lot of power into a low resistance load.
     
  6. Jun 15, 2017 #5

    CWatters

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    I think the car is wind-up (aka clockwork)?
     
  7. Jun 15, 2017 #6

    davenn

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    yes ... there is no magnetic field or batteries involved in the car .... you can see him winding up the spring
    at around 2 min20sec

    just the battery and magnets in the copper tube example
    and @Bandersnatch has explained how that works
     
  8. Jul 8, 2017 #7

    Thanks. That makes a lot of sense and also explains why an initial nudge is required to start the mechanism that propels the magnet all the way to the other end.
     
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