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LED resistance problem.

  1. Oct 25, 2009 #1
    Hi, I am trying to wire some leds up. There are 5 of them in series VF typ 3.2 V and 30mA. I am using a 9V square battery. 60 Ohm of resistance and an on off switch. Yet it does not light up. Is this because I do not have enough voltage??

    P.S. Yes the switch is on!!


  2. jcsd
  3. Oct 25, 2009 #2


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    Science Advisor

    Well here's a hint, what's 5 times 3.2? It's a lot more than 9 right!

    LED's are very different than say something like a normal light globe in that they don't even start to conduct until the applied voltage is quite close to the rated voltage. So if the LED's nominal operating voltage is 3.2 volts then it's a pretty good bet that the current at say 2.0 volts will be very nearly zero. The result = no light.
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