What is infinite resistance?

Discussion in 'General Electronics Chat' started by Gdrumm, Feb 9, 2009.

  1. Gdrumm

    Thread Starter Distinguished Member

    Aug 29, 2008
    I'm trying to solve a series circuit question from my DC Circuits class homework, and I can't seem to recall what infinate resistance means.

    Here is the info I have on the circuit.
    E=40v, R1=5ohms, R2=10ohms, R3= Infinate ohms.

    I see the answer in the back of the book, but I don't know how they got it.

    I'm solving for E Total, I Total, R Total, and P Total.

    I'm guessing that infinate resistance means there is a short?
    Thanks, Gary
  2. KL7AJ

    AAC Fanatic!

    Nov 4, 2008
    Nope...infinite resistance means the component (resistor) does not exist. You may safely remove it from your schematic with no danger of punishment
  3. Gdrumm

    Thread Starter Distinguished Member

    Aug 29, 2008
    But I'm still curious, because in the answer section of my workbook, it shows Total I=0 amps, meaning that R3 in effect neutralized R1 and R2.

    So, does this look accurate?
    ET = 40v
    IT = 0A
    RT = 00 ohms
    PT = 0 watts

    What does "fail open" mean?
    I found that on this site, Vol 1, Chapter 5/7.
    It implies that a resistor might "fail open", increasing it to near infinate levels.
    Thanks, Gary
    Last edited: Feb 9, 2009
  4. mik3

    Senior Member

    Feb 4, 2008
    If the resistors are connected in series then no current will flow due to the infinite resistance (open circuit).

    if the resistors are connected in parallel then current will flow only through R1 and R2.
  5. flat5

    Active Member

    Nov 13, 2008
    "fail open" means resistor has been destroyed. It has failed.
    In this case, "fail open", it does not pass any current anymore.
    It is a dead resistor. Don't try to return it to the store where you bought it.

    See "Monty Python Dead Parot Sketch".
  6. thingmaker3

    Retired Moderator

    May 16, 2005
    I=E/R, so as R increases, I diminishes. As R increases without bound, I approaches zero. Once R is a few zillion yotta-Ohms, I is a few zillionths of a yocto-Ampere.
  7. blhoward

    New Member

    Feb 4, 2009
    Infinite resistance is open circuit (burnt resistor in real life) no current will flow, zero ohms is short circuit.
    Lets not confuse.