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Very Naïve Question About Electric Circuits

  1. Jul 16, 2012 #1
    Hi all,

    I’m deeply ignorant about how electricity works. I just wanted to confirm that the following was possible:

    I have a button on one end of a wire. The wire stays unified for about 3 feet, then forks into a right section and a left section, each of which is about 3 feet long, and each of which is connected to a different light-bulb. Pressing the button closes a circuit that causes current to travel to both light-bulbs and illuminate them. One day, there is a short in the right fork of the wire. So now when I push the button the light-bulb connected to the left fork of the wire illuminates but the light-bulb connected to the right fork of the wire does not illuminate.

    Is that what would happen with the short in the right hand fork of the wire? I thought it was, but in my ignorance I wasn’t sure if this could screw up the circuit on the left hand of the fork, and I wasn’t sure if this sort of Y-shaped circuit was even possible.

    Thanks so much,
    Howard
     
  2. jcsd
  3. Jul 16, 2012 #2

    CWatters

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    What you describe sounds more like an open circuit/broken wire than a short circuit.

    Normally light bulbs are wired in parallel and a short circuit of the type you describe wouldn't cause one to work and the other not. Instead it would most likely stop both bulbs working and blow a fuse in the power supply.

    If the bulbs are wired in series (eg two 6V bulbs connected to a 12V battery) then a short might cause the symptoms you describe.

    Hard to say really as it depends not only on the electrical circuit but the physical layout. If this were house wiring the short might not even be within the circuit but between this and another circuit.
     
  4. Jul 16, 2012 #3
    Hi CWatters,

    Thank you very much! Yes, I think I meant a broken wire / open circuit, and I think I had in mind them being wired in series, e.g. by both being connected to the same battery.

    So if it's just a broken wire - i.e. if there was a break in the right fork of the wire but not the left - would it matter whether the bulbs were wired in series or parallel? Would in both cases the switch turn on both bulbs before the break, but only the bulb connected to the left fork of the wire after the break?

    Thanks again!
    Howard
     
  5. Jul 16, 2012 #4

    CWatters

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    Thinking about it some more, the symptoms you describe are most likely consistent with

    a) Parallel connection and a break

    and less likely to be (with reason)..

    b) Series connection and a short (the good bulb would be brighter than normal or fail due to over voltage).
    c) Series connection and a break (both lamps would go out)
    d) Parallel connection and a short (fuse would blow)

    Whichever the fault is most likely to be in the leg that's not lit. Check the bulb first :-)
     
  6. Jul 17, 2012 #5
    electricity won't travel through a short/ground or open circuit to find the path of least resistance, as (air is highly resistant to electricity)

    it illuminates a bulb like water pressure on a water wheel/mill (to perform power) but/through a wire
     
    Last edited: Jul 17, 2012
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