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Homework Help: Electric Circuit, drawing question

  1. Dec 7, 2004 #1
    I have to simplify this circuit step by step, and I'm stuck on how the first step after the drawing shown should look (how it looks after the resitances labeled 2 & 4 are combined).
     

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  2. jcsd
  3. Dec 7, 2004 #2
    It is the 3 resistances at right which are 'combined ' you must convert the 'pie' to a star ( standard method ) then two arms of the star are combined with the existing arms , this leaves a star of which the right most is redundant the other two gives
    the net resistance, as viewed from the source.
     
  4. Dec 7, 2004 #3

    I didn't really understand any of that...

    I emailed my teacher and he said the resistances 2 & 4 are combined, then I have to figure out the rest. They either combine and resistance2,4 is shown on the far right side, and then is considered parallel to resitance 3, making the circuit a series that can be simplified and solved for. Or, they combine and are next to resistance 1, which combines with it, and forms a series which can be solved.
     
  5. Dec 7, 2004 #4
    That's right. The easy way is to combine resistors 2 and 4 in series (7 + 7 = 14 ohms) Then you have the new combined resistor in parallel with resistor 3 so the resistance of that is (7 * 14) / (7 + 14). Then you can just add the resulting resistor in series with the remaining two (numbers 1 and 5).
     
  6. Dec 7, 2004 #5
    Thank you! I got it!
     
  7. Dec 7, 2004 #6
    I apologise , I over complicated it .
    The two right resistances are combined in 'series ' rt = rx + ry. This result is in parallel with the next one left 1/rt = 1/rx + 1/ry
    ( in this rt is the result of the other two rx , ry whatever they are ).
    the remaining 3 resistances are in series rt = rx + ry + rz
    it takes a little practice but there is no magic.
    Ray.
     
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