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Voltage without knowing current

  1. Apr 12, 2009 #1
    How do you know how much voltage is deadly without knowing the actual current? For example, a stun gun generates a 50kV with only 2 milliamps worth of current. But on the other hand, a small generator can produce 15kV of voltage. Obviously I'm going to say the generator is more deadly, but I don't actually know the current flow. Basically my question is, when reading a voltage rating, how can you really relate the total amount of energy without knowing the current?
  2. jcsd
  3. Apr 12, 2009 #2


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    The short, safe answer, would be to consider any voltage "DEADLY" if you have no information about the current.
  4. Apr 12, 2009 #3


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    . . . because without knowing the current, you really don't know.
  5. Apr 12, 2009 #4
    You need to look at the resistance of your body. Let's say that this is about [itex]3000 \Omega[/itex], you can calculate the current flowing for a given voltage. A current of 30mA is considered deadly, but there are more factors involved, p.e. the resistance varies in case your hands are dry or not, the fact that it is DC or AC (DC is more dangerous because it does not go through zero every 50 or 60 times a second, therefore more difficult to cut), etc.

    As an example consider [itex]U=230V[/itex] and [itex]R=3000\Omega[/itex], you get about [itex]77mA[/itex], so deadly, on the other hand [itex]U=110V[/itex] with the same resistance gives about [itex]37mA[/itex], so lesser change of death, but indeed dangerous. Consider every voltage as dangerous and being carefull is the best remedy.

    best regards,

  6. Apr 12, 2009 #5
    In fact, Edison tried to prove otherwise! Remember the historical debate between Edison and George Westinghouse on DC versus AC ? An elephant lost it's life in the bargain when Edison electrically executed a rogue elephant with AC power to prove to the world the that AC voltages can be fatal. :wink:

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