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Can you figure this out? Bragging rights to first one to find without cheating. — Parallax Forums

Can you figure this out? Bragging rights to first one to find without cheating.

mctriviamctrivia Posts: 3,772
edited 2010-04-24 22:02 in General Discussion
attachment.php?attachmentid=69704

All resisters are 1 ohm. Bragging rights goes to the first person to find the resistance of this network without using spice or similar simulation software.

Hint answer is less then 2 ohms.

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Lots of propeller based products in stock at affordable prices.

Comments

  • Martin HodgeMartin Hodge Posts: 1,246
    edited 2010-04-24 01:41
    The answer is .42
  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2010-04-24 01:55
    Well thanks a lot mctrivia. My lawn needs cutting, and I decided to do it only if I came across an even less fun alternative. 'Didn't think it was possible, but now I've gotta go mow.

    -Phil
  • ScopeScope Posts: 417
    edited 2010-04-24 02:30
    Looks like a quilt Aunt Martha used to have on the back of her couch.
  • bill190bill190 Posts: 769
    edited 2010-04-24 06:25
    And how would you go about solving that?

    I was thinking perhaps removing everything except the bare minimum, then adding on one small section at a time. Then it would be just a series or parallel addition to the circuit?

    And with resistors, with series they would double, and parallel they would half.

    Or perhaps you could break it down into sections?

    (Two one ohm resistors in series would be 2 ohms, parallel .5 ohms.)
  • LeonLeon Posts: 7,620
    edited 2010-04-24 13:29
    A well-known similar problem is a cube of resistors - calculate the resistance across two opposite corners. I thought that mctrivia's network might be a hypercube, when I first saw it, but it isn't.

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    Leon Heller
    Amateur radio callsign: G1HSM
  • sylvie369sylvie369 Posts: 1,622
    edited 2010-04-24 13:51
    .833 Ohms, or 5/6ths.
  • mctriviamctrivia Posts: 3,772
    edited 2010-04-24 15:32
    Only way I know to do this is analyse every current path. But there are a lot of them.

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    Lots of propeller based products in stock at affordable prices.
  • LeonLeon Posts: 7,620
    edited 2010-04-24 16:11
    Here is how it's done for a cube:

    www.physics.ucsb.edu/~lecturedemonstrations/Composer/Pages/64.42.html

    Doing it the hard way one would have to solve a large number of simultaneous equations.

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    Leon Heller
    Amateur radio callsign: G1HSM

    Post Edited (Leon) : 4/24/2010 4:16:33 PM GMT
  • JohnBJohnB Posts: 10
    edited 2010-04-24 21:24
    What I want to know is how to cheat. That may come in handy someday.
    john
  • W9GFOW9GFO Posts: 4,010
    edited 2010-04-24 21:34
    Is this being treated as no connection?

    attachment.php?attachmentid=69734

    Rich H

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    The Simple Servo Tester, a kit from Gadget Gangster.

    Post Edited (W9GFO) : 4/24/2010 9:40:47 PM GMT
    connection.jpg
    102 x 66 - 3K
  • LeonLeon Posts: 7,620
    edited 2010-04-24 21:47
    JohnB said...
    What I want to know is how to cheat. That may come in handy someday.
    john

    Use SPICE.

    Here is the schematic for a SPICE simulation of the cube problem:

    www.leonheller.com/Designs/Cube.pdf

    The current through the cube is 6A, giving the resistance as 5/6 ohms.

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    Leon Heller
    Amateur radio callsign: G1HSM

    Post Edited (Leon) : 4/24/2010 10:17:24 PM GMT
  • mctriviamctrivia Posts: 3,772
    edited 2010-04-24 22:01
    Yes that is no connectin

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Lots of propeller based products in stock at affordable prices.
  • MikeKMikeK Posts: 118
    edited 2010-04-24 22:02
    0.68 ohms

    Post Edited (MikeK) : 4/25/2010 7:03:14 PM GMT
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