Discussion in 'Homework Help' started by cobra commander, Aug 25, 2005.

  1. cobra commander

    Thread Starter New Member

    Aug 25, 2005
    Question I need help for in Digital Electronics:

    Current over what rating can start to injury a human being.
    A) .1mA
    B.) .001mA
    C.) .015mA
    D.) 0.15mA
  2. Dave

    Retired Moderator

    Nov 17, 2003
    Your answer is all of them!

    From 0 to 0.5 mA - no sensation

    1 mA - threshold of perception

    From 1 to 3mA - weak sensation

    From 3 to 10 mA - painful sensation

    10 mA - threshold of muscular contraction in the arms

    30 mA - threshold of respiratory paralysis

    75 mA to 100 mA - threshold of cardiac fibrillation (probability 0.5%)

    250 mA - cardiac fibrillation with 99.5% probability (for an exposure time of 5 seconds)

    4A - threshold of cardiac paralysis (sudden stoppage of the heart)

    5A - burning of organic tissues

    The magnitude of the applied voltage necessary to produce dangerous current values depends on, amongst other things, the conditions in which the shock occurs and the resistance of the body, where body resistance varies between wide limits. Between hand and foot, for example, assuming good electrical contact, the resistance is about 500 Ohms , excluding skin resistance. The skin resistance varies from about 1000 Ohms /cm^2 for wet skin to about 3 x 10^5 Ohms /cm^2 for dry skin.