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Shorting of Battery terminal

  • 25-11-2008 08:51PM
    #1
    graigavern
    Registered Users, Registered Users 2 Posts: 26 ✭


    I have a question on how does a battery short actually occur??
    We know for a basic circuit we have a battery two cables and a load so our circuit is complete and the load will work.
    Now if we short the terminals they will burn or send the spanner flying why is this??
    What is actually happening to the chemical in side the battery to cause this?

    There is a resistance in any cable with or without a load attached so if this cable is attached without a load it will cause a short, Why?? There is a resistance so the electrons will flow!!
    Any ideas
    Cheers


Comments

  • #2
    Professor_Fink
    Registered Users, Registered Users 2 Posts: 861 ✭✭✭Professor_Fink


    graigavern wrote: »
    I have a question on how does a battery short actually occur??
    We know for a basic circuit we have a battery two cables and a load so our circuit is complete and the load will work.
    Now if we short the terminals they will burn or send the spanner flying why is this??
    What is actually happening to the chemical in side the battery to cause this?

    There is a resistance in any cable with or without a load attached so if this cable is attached without a load it will cause a short, Why?? There is a resistance so the electrons will flow!!


    The short does not stop electron flow, quite the opposite: it enables electrons to more easily flow between the terminals.

    Batteries have an internal resistance. As long as this internal resistance is small compared to the resistance of the rest of the circuit, the energy lost within the battery is tiny. If you short a circuit, you massively reduce the total resistance, and so the internal resistance of the battery becomes dominant. this leads to both the battery and sometimes the wire (depending on its resistivity) rapidly heating.

    Hope this answers your question.


  • #3
    Capt'n Midnight
    Moderators, Recreation & Hobbies Moderators, Science, Health & Environment Moderators, Technology & Internet Moderators Posts: 98,162 Mod ✭✭✭✭Capt'n Midnight


    the current flowing is limited by both the external resistance and the internal resistance

    normally the internal resistance is much lower than any likely external resistance and so it is ignored.

    A car battery of 50 Ah may be capable of 500A cranking power through a starter motor , without the starter motor load there would be an even higher current. If you look at a typical multistrand copper wire 5A would enough to burn out one strand !

    if you shorted out a spanner against battery terminals it would be welded to them by the very high current, then most of the resistance would be inside the battery and it would get hot and possibly boil with the spraying of sulphuric acid and so on and so fourth


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