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Very simple circuit question

  1. Mar 15, 2009 #1
    Hello all. I am trying to build a very simple circuit and need some help.

    I want to have an LED connected to a battery, and if a wire is unplugged from the circuit then the LED lights up.

    Does anyone know how I can make this happen?
     
    Last edited: Mar 15, 2009
  2. jcsd
  3. Mar 15, 2009 #2
    Here is a picture of a schematic that gets the job done, but it drains the battery.

    Ok, see the middle wire? While that middle wire is connected the led will not light up because the current will take the path of least resistance. So I would probably put a resistor in front of the LED.

    But if you remove the wire the LED lights up.

    So the LED should typically not be lit, but if I unplug a wire then the LED lights up.

    That's all I need! But without draining the battery of course!
     

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