Why no collector current?

Discussion in 'General Electronics Chat' started by corefinder, Dec 11, 2012.

  1. corefinder

    Thread Starter Member

    Oct 6, 2011
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    0
    Don't know why I _{c} collector current is zero. I have got these reading in ammeter and voltmeter.
     
  2. #12

    Expert

    Nov 30, 2010
    16,276
    6,788
    If the meter on the right was correct, there would be 12 volts across the LED and the 1 ohm resistor...but it isn't correct. If you really built this circuit, the resistor and LED would smoke instantly by trying to survive over 9 amps. If this happened, all the readings become correct because the LED melted and no current passes.

    Sometimes you just can't believe a simulator.
     
  3. corefinder

    Thread Starter Member

    Oct 6, 2011
    55
    0
    Ah, its my mistake the simulator didnt connect it to battery terminal. It didnt consider another ground terminal, so i connected the right ammeter to battery grounded terminal and it worked!!.
    Thanks
     
  4. WBahn

    Moderator

    Mar 31, 2012
    17,736
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    Are you sure the two grounds symbols represent the same node? Sometimes symbols for global node connections let you specify a different global node in order to support multiple supplies and multiple grounds. But, usually, the ground symbol shown like that one will default to node 0, which is the simulator's reference node (for most, if not all, SPICE-based simulators).
     
  5. Audioguru

    New Member

    Dec 20, 2007
    9,411
    896
    The 1 ohm resistor value is much too low. It causes the current in the LED and collector-emitter of the transistor to be much higher than their maximum allowed currents.
    This makes the transistor and LED much hotter than their maximum allowed temperature.
    Then they burn out.

    The transistor has 1V from base to emitter with no resistor to limit the current which which also probably burn out the transistor.
     
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