Does electricity only follow the path of least resistance? (newbie question)

Discussion in 'General Electronics Chat' started by sofakng, Jan 16, 2008.

  1. sofakng

    Thread Starter Member

    Oct 30, 2007
    I'm reading the book on DC at this site and I'm on the electrical safety chapter and I'm confused on the following diagram:


    If the switches are both closed (eg. the circuit is "active" and current is flowing) and the shorting wire is installed, then don't we have a parallel circuit? (eg. current will be flowing through the load and through the shorting wire)

    ...or am I mistaken? I keep remember hearing about "the path of least resistance" and I'm wondering if this is true with the above diagram.

    Would current not flow through the load because it has higher resistance than the shorting wire?
  2. Audioguru

    New Member

    Dec 20, 2007
    The shorting wire is not perfect. It has some resistance so it will have a small voltage across it. Then the load will also have the same small amount of voltage and will pass a small current.
  3. h.d

    Active Member

    Oct 22, 2007
    normaly the current will go through the shorted wire because its resistance abroaches zero and the load is avery high resistance relatively to the wire.
  4. FredM

    Senior Member

    Dec 27, 2005
    Current WILL flow through the load when both switches are closed.. And you DO get a parrallel circuit. Assume the supply can provide enough current so that the voltage does not drop.. if the voltage is 10V, and the load is 10k, 1mA will flow through the load REGARDLESS of what the resistance of the link (or any other resistance in parallel) is.
    Total resistance of the circuit will be 1/((1/R1)+(1/R2)) and total current will be V/R.. If the link has a resistance of 0.1R, current through it will be 100A.. which will dwarf the 1mA through the load, but this 1mA will still be passing through the load.

    >> I keep remember hearing about "the path of least resistance" and I'm wondering if this is true with the above diagram.

    This statement is rarely true! Current flow has no 'intellegence' - it cannot determine the 'optimum' path and choose this. The only example I can think of where this statement is (almost) true is with electrostatics and dielectric breakdown - Here, there are mechanisms wherebye current finds the 'fault line' and primary conduction follows this "path of least resistance"
  5. sofakng

    Thread Starter Member

    Oct 30, 2007
    Thanks for all of the help!

    Are you saying to just treat the circuit as a normal parallel circuit when the shorting wire is installed?

    Also, one other question... how little resistance is required for something to be called "electrically common"? For example, are the two sides of a simple copper switch considered electrically common?

  6. thingmaker3

    Retired Moderator

    May 16, 2005
    A piece of AWG24 wire has a whopping 26 micro-Ohms per foot. Whether both ends of said wire could be considered "common" depends on application, but most applications would count as "common."

    Conductor resistance does become noticeable in such things as building wiring of alarm systems, or circuits with intrinsically low resistance. For most applications, it has a negligible effect and is ignored.
  7. Distort10n

    Active Member

    Dec 25, 2006
    In regards to the current flowing in the 'path of least resistance' I prefer the following statement:

    "The popular notion that current follows the path of least resistance just isn’t true. Current follows the paths of all resistances in proportion to their conductance."