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Why don't all lights turn off when connected in parallel

  1. Jan 21, 2016 #1
    1. The problem statement, all variables and given/known data
    When the filament of a light is broken why do others continue to light?

    2. Relevant equations
    Parallel: U=U1=U2=U3
    I=I1+I2+I3+...

    3. The attempt at a solution
    Is it because there are some nodes? How can you explain this simply?
     
  2. jcsd
  3. Jan 21, 2016 #2

    CWatters

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    So what happens (for example) to U2 and I2 if Bulb 1 or 3 fails?
     
  4. Jan 21, 2016 #3
    U2 doesn't change and I2 ... I don't know, it becomes greater?
     
  5. Jan 21, 2016 #4

    cnh1995

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    Consider three bulbs in parallel and U1=U2=U3. If bulb 1 fails, how will it affect U2 and U3?
     
  6. Jan 21, 2016 #5
    U2 will continue being equal to U3 and won't change.
     
  7. Jan 21, 2016 #6

    cnh1995

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    Right. Hence, the remaining bulbs continue to light.
     
  8. Jan 21, 2016 #7
    The lights are connected in parallel, so power doesn't need to go through one bulb in order to get to the others. It's like ties on a railroad track - you can remove one tie, and the others still touch both sides of the track.

    The exception to this is strings of lights for a christmas tree. These are too small to individually accept 120/240 volts, and so are usually connected in series to reduce voltage.
     
  9. Jan 21, 2016 #8

    CWatters

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    The voltage on bulb 2 is the same but the current doesn't increase.

    Remember Ohms law says V=IR so

    I=V/R

    The voltage stays the same, what about the resistance?
     
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