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Newbie - Voltage - shock of 9v battery vs. 12v car battery

Discussion in 'Electronic Basics' started by hdjim69, Nov 1, 2005.

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  1. hdjim69

    hdjim69 Guest

    Hi, I'm just starting out self learning electronics and have a
    question regarding voltage. If a volt is a volt is a volt, that is 1
    volt can push 1 coulomb of electron flow (1 amp) through 1 ohm of
    resistance, than all volts are the same pressure, hence why is a unit
    of measurement. So why is it if I take a new small 9v battery from any
    convenience store and shock myself with it, the shock of this 9v
    battery is MUCH smaller then a shock from a 12v car battery ? It
    can't be the 3v difference. Is it the amount of current ? But then
    since there is not resistance between myself and the battery, the 9v
    would produce 9 amps and the car battery 12 amps again, not that much
    difference but the shock is a huge difference.

    And no, I'm not into shocking myself but it happens...


  2. 1 amp is one coulomb per second.
    They aren't that different. You won't feel either one with dry skin.
    You have to do something like lick the two poles of the battery to
    feel it.
    What can't? I have not gotten a shock from either a 9 volt battery or
    a 12 volt car battery, though I have handled both extensively.
    You have resistance. Hold the leads of an ohm meter to find out how
    much. That resistance is what limits the current from either battery
    that will pass through you.
    Please explain the situation that caused you to be shocked by a 12
    volt battery.
  3. hdjim69

    hdjim69 Guest

    I have worked on my car and have, though my own carelessness forgotten
    to disconnect one of the terminals and have been shocked. I have also
    taken a new 9v battery and have touched it to my tongue. I can tell
    you first hand there is a big difference. I guess that is why we've
    all heard stories of prisoners being tortured using 12v car batteries
    and not 9v toy batteries. Why is the intensity so different ?
  4. Andy Baxter

    Andy Baxter Guest

    hdjim69 said:
    One difference is that a car battery has a much bigger plate surface area
    inside the battery, so the internal resistance will be lower, and hence it
    is capable of passing a much bigger current. If you connect a very low
    resistance load to a small battery, the internal resistance will cause a
    voltage drop, so it won't actually be putting out the rated voltage.

    How much difference this really makes to the 'shock potential' I'm not
    sure - the human body has a fairly high resistance I think.
  5. Guest

    I have handled 12 volt lead acid batteries many times and never felt a
    thing. I admit that I have not bridged 12 volts with my tongue. Is
    this the only kind of shock you are describing, or are you talking
    about being shocked through dry skin?

    The shock sensation goes up dramatically with voltage, but my threshold
    of sensation is around 30 or 40 volts, unless I pierce my skin with a
    sharp point or edge, so the current doesn't have to pass through skin
    resistance (which is most of body resistance). If a wrench slips and
    you skin your knuckles, I guess you might feel 12 volts.

    An automobile also contains an ignition system that pumps the battery
    voltage up to thousands of volts, and that *will* give you a dangerous
    and painful shock.


    You do have resistance.

    When current flows through your tissue, muscles contract and become more
    conductive, more current flows, muscles contract, more current flows etc
    etc. (grab the two probe of an ohm meter on a high Megohm range and flex you

    the higher the voltage the more violent that initial contraction will be.

    Ohms law can be use to calculate the initial current V/R=I

    What you feel is power(Watts), a product of both voltage and current (amps)

  7. Did you get that John? (;-)
  8. I read it but I'm not sure I get it.
  9. hdjim69

    hdjim69 Guest

    I guess I still don't see where the big difference is. Voltage is
    pressure (or potential pressure) or the amount of EMF. The more force,
    the more electrons will flow so the more current or amps there will be.
    The resistance of the human body will be the same for both batteries.
    So why is it, one can be literally tortured with a 12v battery but not
    with a 9v ? The amount of current difference due to the 3v difference
    can't be enough to make one battery a torture device and one a toy.


    I don't know where you got the idea you could be tortured with a 12V

    In order to feel the current from a 12V Battery you would have to have a
    body resistance of about 12K Ohms or less. That is a very small body
  11. ;-)
  12. As you can read here:
    Presuming wet skin, a car battery could theoretically be used to torture
    someone by allowing 12mA of current to flow thru a 1K resistance, but
    OTOH a 9V battery should be able to deliver painful stimulus as well
    since it should have no trouble delivering 9mA. I guess to Hollywood,
    it wouldn't look impressive enough with a small battery no matter how
    much it might really hurt.
  13. (snip)

    Oh, that's easy. One cannot be tortured with a 12 volt battery,
    unless you count making a strange taste on their mouth. They connect
    model T vibrator ignition coils to 12 volt batteries to torture people.
  14. Or you drop one on them.


    Horse pucky!

    The only way I could imagine torturing someone with a 12V car battery would
    be to drip the acid in there eyes or threaten to drop the battery on there
    little toe. Or perhaps applying the electrodes directly to there heart
    muscle. Or perhaps you could wrap there arm in 10ga. wire and direct short
    it across the battery and burn them.

    Typical wet skin 90 -100K Ohms, You would need about 90VDC to feel it.

    Your OSHA Chart concerns AC 60Hz current. DC Current is much less

    However, you can have allot of fun with a 1.5V Battery, A coil and a

    If you can get you body resistance down to 12K you need to cut salt out of
    your diet before you die of high blood pressure.
  16. Sorry, erroneous premise, given your very unscientific presentation.
    You are so far wrong on the idea you're trying to put forth, that it's
    hard to know where to start; especially in view of your complete
    ambivalence toward John's answers to you. If you really want answers,
    sit back and read all the responses again, try then to phrase a decent
    question, and quit believing that you know anything, because you
  17. Not necessarily.
    You mentioned four different methods, and prefaced with "only."
    Inconsistent, at best. I can think of at least two more.
    Now we are talking serious horse pucky. You think you need 90V for
    sensation with wet skin? You are wrong by at least 62 volts.
    Care to theorize on a reason for that assumption?
    A coil, eh? Hmmm.... How much fun can you allot with that? And is
    that 1.5V from a battery, or a cell?
    There are ways. You mentioned one, yourself.
  18. it.

    I can easily feel the 50V DC that my phone line puts out.
    It's also based upon a hand/foot shock path, a fairly long current trace
    IMO. According to Hollywood, your typical drug smuggler/torturer uses a
    much shorter path often involving an anal probe as one end of the
    circuit. Having personally suffered the incredible pain of muscle
    spasms, I can see the "potential" of the method. ;-)

    I know of no technical reason that AC current should be significantly
    more painful than DC.
    Yep, I did allot of that stuff about 30 or so years ago.
    1K w/moist skin


    You mentioned four different methods, and prefaced with "only."

    lol, they just kept coming to me... Curios to know your other two...
    I'll be firing up the bench supply in the morning to see if I can feel
    28VDC, I doubt I can let alone be tortured by it.

    90V "DC" based on 90-100K Ohms..
    Sniped from Wikipedia
    'Let go' current
    With alternating currents there can be a muscular spasm which causes the
    affected person to grip and be unable to release from the current source.
    The maximum current that can cause the flexors of the arm to contract but
    that allows a person to release his hand from the current's source is termed
    the let-go current. For DC, the let-go current is about 75 mA for a 70-kg
    man. For alternating current, the let go current is about 15 mA, dependent
    on muscle mass.

    I can only assume the same would hold true for initial sensation

    Penlight cell, A small vibrating interrupter, and a coil.. the old gadget
    invented a hundred years ago, a box promising goodies inside, you,
    unknowingly place your finger tips on the electrodes to slide open the box.
    doing so you release the vibrator to start the oscillation and you get a
    nice little zap across your hand.


    I can easily feel the 50V DC that my phone line puts out

    I Can't I can feel ring voltage but not battery voltage, unless you are
    putting it in your mouth. Which I suppose would be uncomfortable with a
    12VDC Car battery
    I never considered that... Now I wish you hadden't

    Perhaps a full sweat lather, Licking my index fing fingers and applying an
    Ohm Meter I can't below 90K
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