What is a short?

Discussion in 'General Electronics Chat' started by nanobyte, Dec 6, 2006.

  1. nanobyte

    Thread Starter Senior Member

    May 26, 2004
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    Can someone give me simple definition for what a short circuit or short is? Most of the definitions I have seen so far seems to be too complicated. I am looking for a definition of short that can be used for someone whose knows very little or nothing about electronics.
     
  2. Dave

    Retired Moderator

    Nov 17, 2003
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    Hi nanobyte,

    Put simply, a short is a low resistance path between two or more nodes in a circuit. Your definition of low resistance will be dependant upon the circuit within which the short occurs.

    Dave
     
  3. wireaddict

    Senior Member

    Nov 1, 2006
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    It should probably be added that shorts are almost always unintentional &/or undesirable
     
  4. pfofit

    Member

    Nov 29, 2006
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    For these laypeople I say that
    A short is when the "electricity" takes a different path (a shortcut) from the the path it was designed to take....normally caused by defective components or corroded/cut wire insulation and sometimes by human error

    cheers
     
  5. sci-3d

    Well-Known Member

    Aug 22, 2006
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    Short is hight current condition when the resistant is very small, consider

    I = V/R

    when lim R --> 0, lim I -- > Infinity.
     
  6. thingmaker3

    Retired Moderator

    May 16, 2005
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    I like to say "small impedence" instead of "resistance." We are occasionally plagued by capacitive shorts in our high-frequency cables - these don't show up on an ohm-meter but do show up on the spectral analiser.
     
  7. Dave

    Retired Moderator

    Nov 17, 2003
    6,960
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    Hi Lee,

    Whilst you are completely right about shorts due to capacitive effects, Average-Joe isn't going to understand the concept of capacitance or impedance. I can imagine it now:

    Question 1: What is a short?

    Question 2: What is a short again? :D

    The best way of tackling this question is to say you don't really know!

    Dave
     
  8. nomurphy

    AAC Fanatic!

    Aug 8, 2005
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  9. m4yh3m

    Senior Member

    Apr 28, 2004
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    Instead of electricity... think of a car...
    Instead of circuit boards... think roads...
    Now... replace "short circuit" with "driving on the sidewalk" --
    It's a lot faster since there's no cars on the sidewalk... buuut you also manage to kill a whole bunch of idiots err components.

    -----


    basically, if you have a circuit with 5 resistors and you attatch a metal wire that starts right before the first resistor and connects to the circuit right after the last resistor, electricity is going to flow quicker through the wire than it is the resistors. the resistors are there to lower the voltage/current. if you bypass that and send a higher amount to the next component... you're going to fry it. it takes the SHORTest path of least resistance.
     
  10. gt4awd

    New Member

    Nov 19, 2006
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    This is not true. Are you saying spark gaps are useless? Spark gaps include ignition coils, power switching devices, and they are used to prevent a voltage surge from damaging equipment. Radio would of probably never been invented without spark gaps.

    A short is an arc between two points of differnt electrical potential.

    The above definition of a short is good, and correct in my opinion, but would not be easy for a person that knows very little of electricity to understand.

    An example that might work is to first explain to the person that lightning is infact a short. The earth and the clouds both build up a charge, this charge is separated by the air until one side obtains enough energy to jump to the other. Lightning is a giant short.
     
  11. wireaddict

    Senior Member

    Nov 1, 2006
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    I did say that shorts are almost always unintentional &/or undesirable &, incidentally, I'm standing by that premise.

    I wasn't referring to intentional conductive devices like various contacts, jumpers, PC board artwork, wiring or even spark gaps as a "short" nor did I say they're useless. Actually, however, a spark gap is a high Z device until the voltage across it becomes high enough to cause the current to arc across it.
     
  12. alim

    Senior Member

    Dec 27, 2005
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    I think wireaddict is given a practical understanding of a 'short' and should not be dismissed as done by gt4awd.It is valid.
     
  13. kubeek

    AAC Fanatic!

    Sep 20, 2005
    4,670
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    I don´t think that a short doesn´t necesarily have to involve sparks. Without air there will be no sparks, but the short can still exist.
     
  14. Dave

    Retired Moderator

    Nov 17, 2003
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    But isn't the essence that "a short" is a shorter route around a particular current path intentional or otherwise - we understand that this is basically a low resistance path in a circuit. However I would agree from a personal perspective that shorts are generally unintentional.

    Dave
     
  15. pfofit

    Member

    Nov 29, 2006
    25
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    Agreed, most shorts do not start out as sparks, but some quickly evolve into a light show.

    A common intentional short is a SCR crowbar circuit designed to intentionally short out a supply and blow a fuse.

    cheers
     
  16. Ron H

    AAC Fanatic!

    Apr 14, 2005
    7,050
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    Yeah, and a crash can also be intentional, as in a destruction derby, but they are generally unintentional. The key word here is "generally".
     
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