2. Electrical Safety

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Unformatted text preview: their difference approaches the Let- Go threshold. This protects the user from a deadly electric shock. v༇ The rules of electrical safety are based on the scientific data and common sense; as many other safety rules, they are written with somebody’s blood. Follow them at workplace and at home: remember the hazards of electricity and avoid the danger. © 2013 Alexander Ganago Page 25 of 28 Last printed 2013- 07- 07 12:28 AM File: 2013 EEW 1- 02 Electrical safety.docx Engineering in the Electrical World (EEW) Part 1 Unit 2: Electrical safety End- of- Unit Problems 2- 1. A student who was washing his clothes immersed his hand into the washing machine powered from a 120- V, 3- wire outlet. With his other hand, which was also wet, he was holding a grounded copper pipe. Explain what happens if the insulation fails and the hot wire touches the metal case of the washing machine from inside. 2- 2. An electrician is working in a partly flooded basement where his feet are immersed in water and accidentally touches with pliers a hot wire carrying voltage VH . Assume that the resistance of the hand holding pliers equals 1 kΩ, the resistance of feet immersed in water is 100 Ω (two resistors in parallel) and the resistance of internal organs is 200 Ω. Questions: List the health hazards for voltage VH = 120 V Calculate the maximal voltage VH, MAX , at which the electrician can certainly let go of the hot wire or the pliers. © 2013 Alexander Ganago Page 26 of 28 Last printed 2013- 07- 07 12:28 AM File: 2013 EEW 1- 02 Electrical safety.docx Engineering in the Electrical World (EEW) Part 1 Unit 2: Electrical safety References and further readings [1] Electrical safety handbook by J. Cadick et al., 4th edition, McGraw- Hill, 2012. [2] Web sites of OSHA (Occupational Safety and Health Administrations) [3] Web sites of ESFi (Electrical Safety Foundation International) [3] Web sites such as “All about circuits” © 2013 Alexander Ganago Page 27 of 28 Last printed 2013- 07- 07 12:28 AM File: 2013 EEW 1- 02 Electrical safety.docx Engineering in the Electrical World (EEW) Part 1 Unit 2: Electrical safety Answers to Practice problem and Multiple- Choice Question 4.8 V D © 2013 Alexander Ganago Page 28 of 28 Last printed 2013- 07- 07 12:28 AM File: 2013 EEW 1- 02 Electrical safety.docx...
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This note was uploaded on 12/06/2013 for the course EECS 314 taught by Professor Ganago during the Fall '07 term at University of Michigan.

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