Effect of Electric Current and Electrocution Earth (Ground) connected to: Total resistance of path (kW) Measured current

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Effect of Electric Current and Electrocution
Earth (Ground) connected to:
Total resistance of path (kW)
Measured current along path (mA) microx10^-3
Current calculated for 240 V (mA)
Effect expected for calculated 240 V current
Boot
1.1micro = 0.001 ma
Foot (skin)
60.6 mirco=0.0606
Glove
1.1 mirco= 0.001
Hand (skin)
60.6 microa=0.0606
Broken skin (blood point on arm)
0.11MA

Effect Of Electric Current And Electrocution Earth Ground Connected To Total Resistance Of Path Kw Measured Current 1 (188.79 KiB) Viewed 32 times

Purpose of this activity: To understand the probable pathways for current from a mains supply though the human body and the potential for electrocution. Signs of electrocution include burns, respiratory and cardiac failure and shock. A person who has been electrocuted may show none or any of these signs. Never touch a person who has been electrocuted until you are sure that the power is turned off. Physiological effects for various currents through limbs and trunk Current (1s contact) Physiological effect 1 milliampere Threshold of feeling Accepted as maximum harmless 5 milliamperes current 10-20 milliamperes Beginning of sustained muscular contract (“can't let go” current) Pain, possible fainting and 50 milliamperes exhaustion. Heart and respiratory functions continue Ventricular fibrillation, fatal if 100-300 milliamperes continued. Respiration continues. Sustained ventricular contraction followed by normal heart rhythm 6 amperes (utilised in defibrillator). Temporary respiratory paralysis and possibly burns. (Information in table from Nave and Nave: Physics of the Health Sciences, 3rd ed. Philadelphia. W.B. Saunders, 1985) The current will follow the path of least resistance, whether this is on the surface of the body or through it along blood vessels and nerves. Often a victim will show both entry and exit burns where the current has entered and then left the body. A common path of least resistance is along blood vessels; in some circumstances wet skin may offer less resistance. A break in the skin, such as a cut, or a burn caused by high voltage, also reduces resistance. Currents for longer than 1 second may have more severe effects than those in the table above. Resistance in the Body – “Toaster Man” ...or... what happens when the body is connected to mains voltage.
100K 100Ω 10M Heart 10022 100K WW BLOOD SKIN GLOVE "TOASTER" 11 or 12 V DC Power supply 10092 Earth BLOOD 10092 100K SKIN 100K 10M BOOT 10M Imagine - you make some toast - but the toast doesn't pop. So you poke a knife into the toaster to push the toast out... Warning: Never ever do this with the toaster plugged in!! (Probably not a good idea to do this even with the toaster not plugged in, since it can damage the heating elements.) 1. The circuit shown above models the resistances of shoes, skin and blood, etc. Connect one of your multimeters as a milliammeter in the heart position and connect the power supply positive to the “TOASTER”, set at 12 V. This is about 1/20 of the Australian mains voltage (typically 230 V up to 240 V). 2. Use an alligator clip to connect the EARTH (power supply negative) to the left boot position. Measure the current flowing along the path from the TOASTER, through the ammeter and the heart to the EARTH. Add the resistances along this path to find the total resistance. Also, calculate what the current would be if 240 V was being used instead of 12 V. 3. Now connect the EARTH to the left foot (skin). Measure the current flowing along the path from the TOASTER, through the ammeter and the heart to the EARTH. Add the resistances along this path to find the total resistance. Also, calculate what the current would be if 240 V was being used instead of 12 V. Record the information in a table similar to the one below. 4. Repeat the measurement in step 3, but with the EARTH connected to the glove. 5. Repeat the measurement in step 3, but with the EARTH connected to the opposite hand (skin).
6. Repeat the measurement in step 3, but with the EARTH connected to the blood points along the right arm. The 'blood' point illustrates the reduced resistance that would result if the skin were broken by a cut, burn or puncture wound. R=V/I
DC Power supply - 0-30V PROPONE Two multimeters - for measuring voltage and current PLEASE SWITCH CEE AFTER USE OFF OFF 104 COM 44 VIONE CE Membrane circuit - simplfied model of a cell membrane glove "Toasterman" circuit - simplified model of a person getting an electric shock skin blood blood skin boot Wires & alligator clips - for connecting the components of the circuits