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Battery circuit, but using ground rather than negative pole?

  1. Feb 18, 2015 #1
    New to the forum :)

    We were (trying to) discussing this at work the other day. Consider a simple battery powered circuit, with a resistor and an LED. With a battery, current is "chemically produced" in the battery and flows from the positive to the negative pole, passing through the LED (limited by the resistor) and "returning" (?) to the battery's negative pole. This is a correct summary?

    f80630a6e7b03b2e1149aef632014c703997ecf8.png

    But what if we disconnect the battery's negative pole, and connect the LED's cathode to "ground/earth" instead? Like, a big ol' iron pole into the ground. Theoretically, this should make no difference in terms of the curcuit, but would current still flow from the battery? If so, would we somehow destroy the battery?


    Joakim
     
  2. jcsd
  3. Feb 18, 2015 #2

    Bystander

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    So long as you connect the battery to another "big ol' iron pole into the ground."
     
  4. Feb 18, 2015 #3
    So, the circuit would work because current goes down into pole 1.
    And the battery would be saved, since it can suck up fresh electrons from pole 2?

    :)
     
  5. Feb 18, 2015 #4
    Love this forum already ;)
     
  6. Feb 18, 2015 #5

    Bystander

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    The battery is open circuited until you complete the circuit with the second ground. It will not magically push electrons through the circuit without that completion.
     
  7. Feb 18, 2015 #6

    davenn

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    then you have an open circuit ... that is the circuit isn't complete ... so no current can flow

    if you do as Bystander said, and connect the negative of the battery to the ground as well and there isn't too much ground resistance between the 2 earth stakes,
    then the LED may still light up

    BTW ... electrons flow from negative terminal to the positive terminal
    what you were referring to is known as conventional current flow .... this direction was decided before people knew electrons existed
    But that is another whole topic and has been discussed many times on PF


    Dave
     
  8. Feb 18, 2015 #7
    Right. Flow is from - to +, I knew that :-)
    But, I realize the battery circuit has to be closed for current to flow, and the LED to light, but I guess the original question was: does this really require current to flow between pole 1 and 2 (through ground)? Since I got the flow the wrong way, I guess that sort of explains why this really makes no sense.

    The question -- does current HAVE TO "return" to the battery, specifically; can't it go somewhere else "after" lighting the LED -- makes no sense if we have to do the switching at the + pole of the battery. I can't think of any ground-like "equivalent" of +

    Thanks for playing along with my odd question :)
     
  9. Feb 18, 2015 #8
    ... ehh, other than maybe connecting the resistor to the anode (+) of another battery... hehe.
    Still, before you pounce on me, I get it: that leaves us with two open circuits (and no current flowing). Right?
     
  10. Feb 18, 2015 #9

    Bystander

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    Yes.
     
  11. Feb 18, 2015 #10

    jim hardy

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    Many people think "ground" has some magical affinity for electric current.
    I think that comes from the "Water Analogy" .
    Water runs out the end of our garden hose and is pulled to ground by gravity. And when we lift water above ground we increase its graviational potential energy.

    Electric charge is (so far as i know) unaffected by gravity .

    "Ground" (i much prefer to call it Earth) is, for circuits, nothing but another wire that happens to go almost everywhere.
    If current can get back to its source by going through ground, Kirchoff's Laws say it probably will.
    But it has no reason to prefer that path homeward over a copper wire.

    Your flashlight is oblivious to whether it's resting on the ground or hung from a skyhook.
    There's a lot to be learned from the humble flashlight, and we've had long threads about it before.
     
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