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Electricity is confusing!

  1. Jul 27, 2010 #1
    Well I guess it's pretty simple, I know E = IR, but I've been thinking of some situations lately that have been confusing me so I decided to ask here. The first one is how does a high voltage stun gun not create high currents? The highest I've seen is 4.5 million volts. I think they simply can't kill you because it is 4.5 million volts rated between the two prongs so the electricity only travels an inch or two correct? My finger reads 7 million Ohms over an inch, which would mean if I stuck that stun gun there it would create .65 Amps right?

    The second questions is since when you add resistors in series, the total resistance drops, why couldn't you just keep adding resistors until you have an extremely low resistance and create high currents off of low voltages? And how does it make sense that adding more resistors drops overall resistance anyways?
  2. jcsd
  3. Jul 27, 2010 #2
    Dunno from stun-guns. Maybe the spec'd voltage is the un-loaded, before you unload on someone's butt, value. There could be just a few electrons even at 4.5MV, so the current would be minimal.

    But to the resistors. Firstly, resistors in _parallel_ decrease the total resistance. You can imagine it as increasing the number of paths for current to flow. As you keep adding resistors, more current flows. However you are not "creating" current flow. The voltage (think of it as pressure) is creating the flow, and the source will always have a limit on how much it can push. As you approach that limit the voltage will begin to drop, or your resistors will melt, whichever happens first.
  4. Jul 27, 2010 #3
    Okay that makes sense now, sorry I mistyped that I meant to say in parallel.
  5. Jul 27, 2010 #4
    I don't get where the confusing part is.

    The stun guns have capacitors which hold very little charge, its not an infinite power source so the V drops exponentially. It would start at 650mA or whatever you got, but drop very quickly, that's why it won't kill you (most likely).

    I heard of cases where stun guns killed, but maybe its the police brutality propaganda or what not.
  6. Jul 27, 2010 #5
    What do you mean it would drop? I thought it would just carry 650 milliamps constantly through wherever on your body it was touching.
  7. Jul 27, 2010 #6
    lololol no no no no. Its not an ideal voltage source. The 4.5 million volts is for an instant, and drops sharply.

    When you rub your cat with a balloon you have a potential of about 10 million volts or so on the balloon, but it never kills you. The amount of CHARGE is very small (learn about charge, unit is coulomb) and the energy is small also.
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