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Simple equivalent resistance question

  1. Jan 3, 2014 #1
    1. The problem statement, all variables and given/known data

    how many minimum no of resistances of eash 2Ω resistance can be connected to have an effective resistance of 1.5Ω

    2. Relevant equations



    3. The attempt at a solution

    I tried to put 2 in parallel,series and different combinations.


    After 5-10 mins of relentless trying i could not figure the answer[ I know it now ans=4 ( 3 in series with one in parallel)


    My point being how to really get hold of this "type" of problem very quickly(objective type q).

    and if its not too much could you point out some more similar questions to this on the internet for a grasp on this "Type" of question?

    Thanks
     
  2. jcsd
  3. Jan 3, 2014 #2

    tiny-tim

    User Avatar
    Science Advisor
    Homework Helper

    hi shivam01anand! :smile:
    you're looking for a factor of 3/4

    you only get fractions from parallel, so start with 2 parallel to 1 (doesn't work), then 3 parallel to 1 (does work, in this case), then 4 parallel to 1, then 3 parallel to 2, and so on …

    in fact, why not write out a table of all combinations now, up to say 7, to give you practice and to see how it works? :wink:
     
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