A choice 1 b choice 2 c both choices 1 and 2 are

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A. Choice 1 B. Choice 2 C. Both choices 1 and 2 are correct D. Both choices 3 and 4 are correct E. All listed choices are good. Book Page 111
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EE for 21 st century 1-2 Avoid electrocution 1-2-2 Resistance of the human body © 2015 Alexander Ganago Page 13 of 13 Last printed 2015-07-24 1:06 PM File: 2015 1-2-2 Human R.docx S UMMARY ü Higher voltages are more dangerous, because they can induce higher currents through the human body. ü Electric resistance of the human body depends on many factors, including the conditions of the skin, the type of contact (finger touch vs. palm touch, etc.). Compared to dry, healthy skin, the resistance of internal organs is very low. ü High electric resistance of dry, healthy skin protects the human body against the harmful effects of external electric currents. ü Wetting of the skin significantly lowers its electric resistance and thereby greatly increases the risk of electric shock. ü Sweat is an excellent conductor of electric current because it is rich in ions; open wounds or skin pierced with a wire provide direct access to the internal organs whose electric resistance is very low. ü In industry, any voltage above 30 V is considered potentially dangerous. ü Combination of electricity and water is potentially deadly. Never use any electric appliance when sitting in a bathtub! ü Remove all jewelry before you start working with electricity! ü Never keep working with a tool that has given you a shock! ü Mild electric shocks , which do not involve muscle paralysis, present an indirect danger because they may cause the person to jerk, drop a tool, fall from a ladder, etc. ü High voltages eliminate the main protection of the human body against electric shock because they may puncture the skin. ü A shock circuit involves the human body and may cause an electric shock. ü When working on a circuit that can be connected to a source of voltage or current, use only one hand and keep the other hand in a pocket or behind your back. ü The path of electric current from hand to hand might be the most usual case. This connection is dangerous because the current flows through the chest where it can affect the heart, lungs, and other vital organs. ü Hand-to-foot electric shock may take place due to operating power tools with faulty insulation. If the current exceeds the Let-Go threshold, the danger is mortal. ü The electric potentials created on the surface of the ground by a thunderbolt or a fallen high- voltage wire may cause a lethal electric shock due to the foot-to-foot connection. The best survival strategy is to minimize the potential difference between the feet. L ITERATURE [1] Electrical safety handbook by J. Cadick et al., 4 th edition, McGraw-Hill, 2012.
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  • Fall '07
  • Ganago
  • Electric charge, Alexander Ganago

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