Resistor

Discussion in 'General Electronics Chat' started by mrscrewdriver, Dec 6, 2009.

  1. mrscrewdriver

    Thread Starter New Member

    Dec 2, 2007
    8
    0
    Hi everyone i new at electronics ,i have a question

    i have 8 pieces of 9V battery all of them used. i connect them in series then connect to my DMM it's read 25.40V then i add 2 resistors in parallel, again connect DMM to test the resistors but nothing reading on DMM, i disconnect resistors reading 25.40V what is wrong

    in Theory Total Resistance=2.55ohm Total Current=9.961A is it right?

    also i check cables its working fine

    thanks sorry my bad english
     
  2. dsp_redux

    Active Member

    Apr 11, 2009
    182
    5
    In theory: You have 8x9V(series)=72VDC. You connect your serie of battery in parallel with two paralleled resitors. You should still have 72VDC between one side of the resistor and the ground. If Req = (R1xR2)/(R1+R2) = 2.55Ohm, then I = 72VDC/2.55Ohm = 28.235294A. Your circuit or the way to test your voltage might be wrong.
     
  3. Wendy

    Moderator

    Mar 24, 2008
    20,766
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    Any of those batteries get hot? I suspect you connected some of them backwards, you should have had much more voltage, which is a big dangerous, BTW.
     
  4. Audioguru

    New Member

    Dec 20, 2007
    9,411
    896
    Eight used little 9V batteries that average only 3.175V each are dead.
    Even if they are brand new, eight little 9V batteries cannot drive a load with a resistance as low as only 2.55 ohms. Maybe they can drive 360 ohms (200mA) for a few minutes.
     
  5. Wendy

    Moderator

    Mar 24, 2008
    20,766
    2,536
    I have had 9V go up to an amp, and maintain. It was an accident, I shorted the sucker, but I was also measuring current at the time.
     
  6. Audioguru

    New Member

    Dec 20, 2007
    9,411
    896
    A woman gave a speech. Then she did a dance.
    She danced because the brand new spare 9V battery for her wireless mic was burning her in her pocket when it shorted against a coin.

    Energizer says that a brand new 9V alkaline battery can provide 10A for a few seconds.
     
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