Short or not?

Discussion in 'Homework Help' started by soumy, Jan 11, 2010.

  1. soumy

    Thread Starter New Member

    Dec 4, 2009
    7
    0
    [​IMG]

    if there's an open between points E and G in the circuit diagram above, shouldn't points D and C become a short circuit? If not, why?

    our prof said that D and C is not short but i believe it's otherwise.
     
  2. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
    282
    Does the open affect points E -H - G, or E - D - G - or even both paths? It makes a difference to the circuit.

    On the other hand, if C & D are connected by a wire, how are they not shorted together? This may be some distinction that equates a short to an accidental or unintended connection, so a deliberate connection is not a short.
     
  3. soumy

    Thread Starter New Member

    Dec 4, 2009
    7
    0
    in the case that the open affect points E -H - G, C and D is short, right? so resistors 2, 3 and 1 will be in series. but if the open only affects points E and D, resistors 4 and 5 will be parallel and they will be in series with resistors 2, 7 and 1. is this correct?
     
  4. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
    282
    Redraw the circuit with those elements left out to see what current paths are left.
     
  5. zgozvrm

    Member

    Oct 24, 2009
    115
    2
    It is and it isn't; depending on your definition of a short.

    1) D and C are shorted if you consider that a short means having no resistance between 2 points.

    2) D and C are not shorted if you consider that the voltage source has a total resistance (load) of greater than 0 ohms.

    (The same goes for points G and F, as well as E and H)
     
  6. zgozvrm

    Member

    Oct 24, 2009
    115
    2
    ... either way, it doesn't affect the outcome of the problem.
     
  7. soumy

    Thread Starter New Member

    Dec 4, 2009
    7
    0
    i mean 1) for short.

    here's the circuit ( there's an open between points E and H )
    [​IMG]

    what's left of the circuit:
    [​IMG]

    to get the total current of the circuit, using ohm's law, i have to get what the total resistance first. what i really want to know is, do i have to include R4 and R5 in the total resistance of the circuit?
     
  8. hobbyist

    Distinguished Member

    Aug 10, 2008
    764
    56
    You can redraw your original circuit by making resistors 4 and 5, (parrallel combo) into one resistor, than you have a curret path to the top of it as well as a path through it, but when you open up point E and G, you now have a dangling resistor, (the parrallel combo), which is not connected to anything at the bottom side of it.
     
  9. hondabones

    Active Member

    Sep 29, 2009
    123
    1
    In the original question the open could occur at points E and D, at points D and G, or both. Thus eliminating resistor 3, 5 or both. I would say there is a number of different ways to look at this problem.
    [​IMG]
    [​IMG]
    [​IMG]
    (images shown respectively)
     
    Last edited: Feb 5, 2010
Loading...