# Lecture 7

 ____ is the movement if electrons through a circuit electricity three characteristics of an electric circuit are: amperage (current)voltage (force)Resistance (measured in ohms) Ohm's Law (Hint: current = ____/____) current = voltage/resistance Resistance An object's ability to avoid becoming part of an electrical circuit Things that have high resistance rubber, glass, ceramic, thick dry skin Things that have low resistance metal, water, thin wet skin Voltage potential difference between two points within an electrical circuit Current number of electrons flowing within an electrical circuit in 0.1 seconds (measured in amps) Alternating current (Ac) electric current alternates direction in the circuit in regular intervals (Hertz-cycles per second)household current is 60 hetzventricular fibrillation occurs between 40 to 150 hertz Direct current (DC) electrical current that flows in one direction within a circuitDC is less dangerous than ACDC is used in battery operated systems Extent of injury is proportional to the amount of ____flow through the tissue Current (amps) 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) _____v is level between high and low voltage 1000v High voltage injury vs Low voltage injury high voltage injury shows electrothermal damage low voltage injury is functional The ______of the tissue of the body in contact with the ____will determine whether electrocution will take place. Resistance, current. The resistance of damp skin is less than dry skin. (T/F) True AC is more dangerous than DC (T/F) True, because AC causes muscle contractions that may prevent the person from releasing the charged wire. 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 bodya low resistance pathway to ground muct be presentthe current tends to take the shortest route between the point of entry and best exit to ground When the pathway of electrons passes through _____ _____ ____, fatal electrocution may occur vital body structures Time required for most fatal electrocutions is usually only a matter of minutes (T/F) False, seconds 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) what are the effects of these currents (amps)? 0.001 0.016 0.020 0.100 2.00 20.00 Current: Effect0.001 small tingle0.016 "hold on" current0.020 muscular paralysis0.100 ventricular fibrilation2.00 ventricular standstill20.00 household fuse blows The quantity of electrical flow through tissue depends on.... applied voltage (usually constant)time of current flowresistance of tissue 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 -100,000dry thin skin- 30,000wet skin of palm- 1,000wet thin skin- 100internal organs 500 If the path of the current crosses the heart, this causes ventricular fibrillation (hand to hand, hand to foot) If the current passes through the brainstem, this causes paralysis of cardiorespiratory centers (head to hand, hand to foot) High voltage deaths are due to electrothermal- severe burns and charringcomplete cardial standstillrespiratory muscle paralysis 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 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 More than half of low-voltage electrocution victims have burns. (T/F) False, less than half. 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 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 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 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 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 A Lightning bolt is produced when... the charged undersurface of a storm cloud discharges its electrical charge to the Earth Authormlhayes ID17353 Card SetLecture 7 DescriptionElectricity Updated2010-05-03T01:47:22Z Show Answers