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Is there current even with huge resistances?

  1. Sep 28, 2013 #1
    If I had a AA battery hooked up to both my hands, positive to my right hand and negative to my left hand, I would expect the resistance to be huge, maybe in the millions of ohms?

    According to Ohm's Law, if you have a voltage, and the resistance is not infinite, then there is a current, no matter how miniscule. Is there something else that needs to be taken into account in the case of my question? Maybe an energy threshold is required to be overcome, so the electricity can "make a path".
     
  2. jcsd
  3. Sep 28, 2013 #2

    mfb

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    There is always a current - even if you don't connect anything to the battery, the casing and even the air conduct tiny currents.

    Millions of ohms is a good estimate for dry skin (two connections) - something like 1-20 MOhm. That gives nA to µA, and it is possible to measure that current with good ammeters.
     
  4. Sep 28, 2013 #3
    This might be completely wrong, but would that mean that if I am near an electric circuit, or even kilometres away, that some of that current would be going through me, as I am in parallel with it?
     
  5. Sep 28, 2013 #4
    At some point you're going to have to make a determination about how many individual electrons flowing in what amount of time you consider to be a current.

    Is an average 1 electron per hour a very small current or a collection of discrete events separated by an average interval? In the case where the circuit is very distant you may find that there is a calculable probability of a single electron from that circuit finding a path through your body over the entire course of the batteries discharge cycle. At what probability do you consider yourself part of the circuit? These determinations are going to depend on the design and purpose of your circuit.
     
  6. Sep 29, 2013 #5
    Ok, thankyou both for your help and explanations, it is still weird to think that a AA battery has any affect on me though... Thanks again.
     
  7. Sep 29, 2013 #6

    UltrafastPED

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    Don't worry ... the AA battery has no effect on you. Your nerves are electrical connections and conduct their own currents all of the time.

    If you want to test this (and feel very weird!) try walking through a zone with extremely strong magnets - like at a particle accelerator - the induced currents will effect your nerves. This is probably not a good idea, but graduate students have been known to do this and lots of other dumb things ...
     
  8. Sep 29, 2013 #7

    mfb

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    MRI devices are a safer method to test this. The big experimental magnets are usually switched off when you are allowed to go there, and there are just a few magnets powerful enough to feel anything.

    The dumbest thing I have seen in this context was done by a professor. He used a steel tool while the magnetic field was on. He was aware of the risk, of course, and switching the field off and on again would have costed something like an hour. Well, it was an interesting experience to hold something where the force did not go down, but towards the magnet (and much stronger than gravity).
     
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