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How many ways can I flip switch positions to make the motor stop

  1. May 22, 2012 #1

    Femme_physics

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    Last edited by a moderator: May 6, 2017
  2. jcsd
  3. May 22, 2012 #2

    I like Serena

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    There is a total of 16 configurations and only a few of them will let the engine turn.

    Edit: Hmm, I missed the title of your thread before.
    But there are more configurations than you mentioned.
     
    Last edited: May 22, 2012
  4. May 22, 2012 #3

    Ouabache

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    Hi FP :smile: !
    Perhaps it would be a good starting point to determine which positions will allow the motor to start.
    (also ILS alluded to this)
    Once you have that, it should be clearer which positions will shut the motor off.

    hmmm i wonder where ILS got 16 configs? [hint 2 positions, 4 switches]. Perhaps a useful way to represent this problem is with a binary table with switch & position as inputs and output: "motor ON/OFF"
     
    Last edited: May 22, 2012
  5. May 23, 2012 #4

    Femme_physics

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    Oops, you're right!

    Fair enough

    http://img842.imageshack.us/img842/5904/motormode.jpg [Broken]

    How's that? :)
     
    Last edited by a moderator: May 6, 2017
  6. May 23, 2012 #5

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    I like the table. :)

    Let's take a look at the first line where you say the motor is turning.
    That would be with switches 1,2,3 in position 1, and with switch 4 in position 2.

    Can you say how the currents will flow?
     
    Last edited by a moderator: May 6, 2017
  7. May 23, 2012 #6

    Femme_physics

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  8. May 23, 2012 #7

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    Nice drawing. :)

    How about the current through switch 1?
    Which current will be bigger, the current through switch 1 or the current through switch 2?
     
  9. May 23, 2012 #8

    Femme_physics

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    Well the current through the first switch meets no resistance, therefor it will be much higher. Hmm. Short circuit eh?
     
  10. May 23, 2012 #9

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    Yep. Short circuit.
    I don't think there will be current left for the motor to turn. ;)

    (Poor carton board men that are frying.)
     
  11. May 23, 2012 #10

    Femme_physics

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    I agree. :) Is that the only blunder I made?
     
  12. May 23, 2012 #11

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    Well, I haven't checked out all your switch-combinations.
    How many will be left with the motor turning if you remove all short circuits?
     
  13. May 23, 2012 #12

    Femme_physics

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    Last edited by a moderator: May 6, 2017
  14. May 23, 2012 #13

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    And another one bites the dust! ;)
    All correct now.
     
  15. May 23, 2012 #14

    Ouabache

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    Good Job!! :smile:
    As you are learning in solving such questions, analyzing how a circuit functions is most important.
    Once you've determined that, the rest follows more easily.

    Your encoding is easy enough to follow. Another way to encode your table is in standard binary.
    for example: on the input side, position1=0, position2=1. output side: motor off = 0, motor on = 1.
     
    Last edited: May 23, 2012
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