Lecture 7

  1. ____ is the movement if electrons through a circuit
  2. three characteristics of an electric circuit are:
    • amperage (current)
    • voltage (force)
    • Resistance (measured in ohms)
  3. Ohm's Law (Hint: current = ____/____)
    current = voltage/resistance
  4. Resistance
    An object's ability to avoid becoming part of an electrical circuit
  5. Things that have high resistance
    rubber, glass, ceramic, thick dry skin
  6. Things that have low resistance
    metal, water, thin wet skin
  7. Voltage
    potential difference between two points within an electrical circuit
  8. Current
    number of electrons flowing within an electrical circuit in 0.1 seconds (measured in amps)
  9. Alternating current (Ac)
    • electric current alternates direction in the circuit in regular intervals (Hertz-cycles per second)
    • household current is 60 hetz
    • ventricular fibrillation occurs between 40 to 150 hertz
  10. Direct current (DC)
    • electrical current that flows in one direction within a circuit
    • DC is less dangerous than AC
    • DC is used in battery operated systems
  11. Extent of injury is proportional to the amount of ____flow through the tissue
    Current (amps)
  12. What is a Volt?
    • force required to produce 1 amp of current to flow through a resistance of 1 ohm
    • (volt the more common terminology instead of amp)
  13. _____v is level between high and low voltage
  14. High voltage injury vs Low voltage injury
    • high voltage injury shows electrothermal damage
    • low voltage injury is functional
  15. The ______of the tissue of the body in contact with the ____will determine whether electrocution will take place.
    Resistance, current.
  16. The resistance of damp skin is less than dry skin. (T/F)
  17. AC is more dangerous than DC (T/F)
    True, because AC causes muscle contractions that may prevent the person from releasing the charged wire.
  18. How does electrocution occur?
    • the victim's body must become incorporated into the circuit.
    • the source of electricity must have suficient force (volts) to overcome the resistance of the body
    • a low resistance pathway to ground muct be present
    • the current tends to take the shortest route between the point of entry and best exit to ground
  19. When the pathway of electrons passes through _____ _____ ____, fatal electrocution may occur
    vital body structures
  20. Time required for most fatal electrocutions is usually only a matter of minutes (T/F)
    False, seconds
  21. What is the most important factor in human electrocution?
    amount of current flow

    (The amount of tissue damage is proportional to the quantity og electricity flowing through the tissue)
  22. what are the effects of these currents (amps)?
    • Current: Effect
    • 0.001 small tingle
    • 0.016 "hold on" current
    • 0.020 muscular paralysis
    • 0.100 ventricular fibrilation
    • 2.00 ventricular standstill
    • 20.00 household fuse blows
  23. The quantity of electrical flow through tissue depends on....
    • applied voltage (usually constant)
    • time of current flow
    • resistance of tissue
  24. Resistance of body tissue in Ohms

    Dry skin of palm
    dry thin skin
    wet skin of palm
    wet thin skin
    internal organs
    • Dry skin of palm -100,000
    • dry thin skin- 30,000
    • wet skin of palm- 1,000
    • wet thin skin- 100
    • internal organs 500
  25. If the path of the current crosses the heart, this causes
    ventricular fibrillation (hand to hand, hand to foot)
  26. If the current passes through the brainstem, this causes
    paralysis of cardiorespiratory centers (head to hand, hand to foot)
  27. High voltage deaths are due to
    • electrothermal- severe burns and charring
    • complete cardial standstill
    • respiratory muscle paralysis
  28. Autopsy findings in low voltage deaths
    • -may be no evidence of injury of body or clothing
    • -skin hairs may be singed
    • -traces may be transferred from a metal conductor to the skin (metallization)
    • -characteristic electrocution mark
  29. What is a characteristic electrocution mark of a low voltage death?
    - firm depressed center surrounded by a ring of pallow and then a ring of erythema
  30. More than half of low-voltage electrocution victims have burns. (T/F)
    False, less than half.
  31. Electrical burns:
    • Occur on skin at points of entrance and exit
    • -tiny white dots representing minute blisters
    • - collapsed blister with raised border and depressed center
    • - white to red-black lesions with raised border and depressed center
    • -peripheral zone of blanched skin is characteristic of an electrical injury
  32. Internal characteristics of electrical injury
    • -usually no changes to the internal organs
    • -microscopic changes can be helpful
    • -skin sections may show "streaming of nuclei" as an inficator of heat effect
    • -nuclei at base of the epidermis are thin, elongated, and lie parallel to eachother
  33. Characteristics at autopsy of victims of High voltage electrocution
    • -all victims will have burns
    • -charing and carbonization of tissue may occur
    • -may be multiple pitted small burns if current "dances" or arcs accross the body
    • -heat generated in the body may cause explosive type injuries such as rupture of organse
  34. Loss of conciousness occurs immediately in elecectrocutions. (T/f)
    False, it may not occur immediately. Victim may yell,move or talk, or unplug the offending object
  35. Unusual aspects: Current marks may be hidden in _____ or in the ______
    Mouth- children put live wires into their mouths, or drinking from a water fountain in contact with electric current

    urethra-from urinating on a high tension wire. because of its high electrolyte content, urine is a good conductor
  36. A Lightning bolt is produced when...
    the charged undersurface of a storm cloud discharges its electrical charge to the Earth
Card Set
Lecture 7