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____ is the movement if electrons through a circuit
electricity
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three characteristics of an electric circuit are:
- amperage (current)
- voltage (force)
- Resistance (measured in ohms)
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Ohm's Law (Hint: current = ____/____)
current = voltage/resistance
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Resistance
An object's ability to avoid becoming part of an electrical circuit
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Things that have high resistance
rubber, glass, ceramic, thick dry skin
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Things that have low resistance
metal, water, thin wet skin
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Voltage
potential difference between two points within an electrical circuit
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Current
number of electrons flowing within an electrical circuit in 0.1 seconds (measured in amps)
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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
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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
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Extent of injury is proportional to the amount of ____flow through the tissue
Current (amps)
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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)
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_____v is level between high and low voltage
1000v
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High voltage injury vs Low voltage injury
- high voltage injury shows electrothermal damage
- low voltage injury is functional
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The ______of the tissue of the body in contact with the ____will determine whether electrocution will take place.
Resistance, current.
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The resistance of damp skin is less than dry skin. (T/F)
True
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AC is more dangerous than DC (T/F)
True, because AC causes muscle contractions that may prevent the person from releasing the charged wire.
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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
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When the pathway of electrons passes through _____ _____ ____, fatal electrocution may occur
vital body structures
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Time required for most fatal electrocutions is usually only a matter of minutes (T/F)
False, seconds
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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)
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what are the effects of these currents (amps)?
0.001
0.016
0.020
0.100
2.00
20.00
- 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
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The quantity of electrical flow through tissue depends on....
- applied voltage (usually constant)
- time of current flow
- resistance of tissue
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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
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If the path of the current crosses the heart, this causes
ventricular fibrillation (hand to hand, hand to foot)
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If the current passes through the brainstem, this causes
paralysis of cardiorespiratory centers (head to hand, hand to foot)
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High voltage deaths are due to
- electrothermal- severe burns and charring
- complete cardial standstill
- respiratory muscle paralysis
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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
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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
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More than half of low-voltage electrocution victims have burns. (T/F)
False, less than half.
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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
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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
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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
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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
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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
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A Lightning bolt is produced when...
the charged undersurface of a storm cloud discharges its electrical charge to the Earth
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