plugin-2011 W 314 HW 1 p1

plugin-2011 W 314 HW 1 p1 - EECS 314 Student’s name

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: EECS 314 Student’s name ___________________________ Discussion section # _______ (Last, First, write legibly, use ink) (use ink) Instructor is not responsible for grading and entering scores for HW papers lacking clear information in the required fields above Winter 2011 Homework set 1 Problem 1 Dangers of Electricity; Safety Measures (30 points = 1 point per question) In order to answer the questions below, read: • • • “Safety lecture notes” posted on CTools “From Electrical Safety Handbook” posted on CTools The document online: http://sound.westhost.com/articles/electrocution.htm (sections “What can kill you” and the following). 1. What current levels are generally considered deadly (check all that apply): a. 50 A b. 5 A c. 500 mA d. 50 mA e. 5 mA f. 500 µA g. 50 µA 2. If the current stops someone’s heart completely, will the heart restart itself? a. Never happens b. May happen but don’t count on it c. Most certainly, yes. 3. An electric shock across one hand (finger to finger or finger to thumb) is… (check all that apply): a. Impossible b. Deadly c. Painful but usually not lethal d. May hurt and burn. 4. An electric shock that throws a person across the room is… a. Impossible, except if a lightning bolt hits the person directly b. Quite likely if the current flows from hand to foot c. Unavoidable, even if the person wears shoes with insulating soles. d. None of the above. © 2011 Alexander Ganago Last printed 1/6/11 7:00 PM Page 1 of 6 File: 2011 W 314 HW 1 p1.doc EECS 314 Student’s name ___________________________ Discussion section # _______ (Last, First, write legibly, use ink) (use ink) Instructor is not responsible for grading and entering scores for HW papers lacking clear information in the required fields above 5. A telephone circuit has voltages up to … a. 90 V b. 48 V c. 24 V d. 12 V 6. The ringing tone in the telephone circuit … (check all that apply): a. Carries the highest voltage. b. Has killed many people, which is common knowledge. c. Cannot be even felt as a tingle. d. Is more dangerous near the Let‐Go limit than continuous voltage. e. Allows the victim to let go of the wire during intervals between the beeps. 7. Amplifiers … (check all that apply): a. Are among the safest devices to work with: they never hurt anyone. b. Can easily kill you, especially Class D. c. May be relatively safe but still require safe working practices. d. Are not discussed in the text. 8. Any power source capable of supplying more than 30 mA has the potential to kill you… (check all that apply): a. Regardless of the voltage b. Only if the voltages are above 120 V c. Never, if the current remains below 50 mA d. None of the above. 9. The author of the text on electrocution recalls that the shock he got from a 12‐V car battery was … a. Almost unnoticeable b. Quite nasty c. Very mild. 10. A 12 V car battery … (check all that apply): a. Can never create a current through the human body, which is high enough to cause any damage or pain. b. Can provide very high currents, up to 300 A. c. If the skin is cut or punched,a 12‐V battery is capable of sending through a human body a current that hurts a lot. © 2011 Alexander Ganago Last printed 1/6/11 7:00 PM Page 2 of 6 File: 2011 W 314 HW 1 p1.doc Winter 2011 Homework set 1 EECS 314 Student’s name ___________________________ Discussion section # _______ (Last, First, write legibly, use ink) (use ink) Instructor is not responsible for grading and entering scores for HW papers lacking clear information in the required fields above 11. A pair of telephone lines at 48 V… (check all that apply): a. May carry high currents that can cause electric arc. b. If a metal tool falls on such lines, nothing happens. c. If a metal tool falls on such lines, it may vaporize splattering molten metal all around. d. In case of an arc discharge, present the danger of extreme heat and may cause eye damage due to UV radiation. e. In case of an arc discharge, only the extreme heat is dangerous. 12. The mains (household) supply voltages around the world… (check all that apply): a. Are all at 120 V. b. Vary from one country to the other. c. Are up to 240 V. d. Are much safer at 220 V than at 240 V. e. At 110 V, are totally safe. 13. Metal watch bands or rings remain cool if caught across the terminals of a 12‐V car battery … a. Are safe. b. Get warm but not too hot to burn the skin. c. Can be easily melted into flesh. 14. The survivors’ tales about minor electric shocks, after which they could not let go of a hot wire… (check all that apply): a. Are nothing but exaggeration. b. Can be explained by the structure of the muscles in the human hand. c. Are true but unexplainable. d. Teach us that panic increases the chance of dying. 15. If, lacking proper equipment, you have to touch a wire to determine whether it is hot (live, carrying voltage and current)… (check all that apply): a. Very carefully touch it with your fingertip. b. Never use your fingertip, because it can get dirty. c. Never use your fingertip, because you may grab the wire and be unable to let it go. d. Use the back of your hand. e. Do not use the back of your hand, because the skin there is very insensitive. © 2011 Alexander Ganago Last printed 1/6/11 7:00 PM Page 3 of 6 File: 2011 W 314 HW 1 p1.doc Winter 2011 Homework set 1 EECS 314 Student’s name ___________________________ Discussion section # _______ (Last, First, write legibly, use ink) (use ink) Instructor is not responsible for grading and entering scores for HW papers lacking clear information in the required fields above 16. If you see someone who fell after being shocked with a hot wire, which he cannot let go, the wisest course of action is… a. Don’t bother: he’ll recover in a few minutes and would do everything himself; your uninvited help might only embarrass him. b. First, turn the power off; then help the person. c. Help him stand up and explain where the main switch is, so he can turn the power off when needed. d. Help him stand up, then walk to the main switch to turn off the power. e. Not to be scared of anything, just help him the best you can. f. Call 911; even if they arrive half anhour later, nothing happens. 17. Mains outlets (household voltage)… (check all that apply): a. Have killed people but only in UK, Australia, and other countries where the mains carry 240 V b. Are totally safe at 120 V (US standard). c. Require extreme care, regardless of the voltage. d. In the US, can be repaired even under applied voltage. e. May cause electrocution, but such events are highly unlikely. 18. Metal rings, jewelry, etc. …. (check all that apply): a. Are neat things to wear, especially when you work on high voltage power supplies. b. Can be worn casually, because they present no danger. c. May lead to trouble if they get caught by metal parts and do not allow you to withdraw your hand from the source of electric shock. d. Help you divert the current from your body, because their electric resistance is lower. Even if a high current flows through it, the ring itself remains cool. e. May get extremely hot in the case of an arc discharge even at low voltages. f. May get extremely hot in the case of an arc discharge but only at voltages above 400 V. g. Make you especially attractive when you work on an electric system of a vintage car, and are quite safe because it is only 12 V. 19. Microwave ovens are deadly. True / False 20. Capacitors can retain a lethal charge for a long time. True / False © 2011 Alexander Ganago Last printed 1/6/11 7:00 PM Page 4 of 6 File: 2011 W 314 HW 1 p1.doc Winter 2011 Homework set 1 EECS 314 Student’s name ___________________________ Discussion section # _______ (Last, First, write legibly, use ink) (use ink) Instructor is not responsible for grading and entering scores for HW papers lacking clear information in the required fields above 21. To make sure that capacitors in the power supply of your PC are discharged, do the following… (check all that apply): a. Turn off the switch; you may start working on the guts of the PC right away. b. Turn of the switch and wait for 3 – 5 minutes. c. Disconnect the power cord from the wall outlet; you may start working on the guts of the PC right away. d. Disconnect the power cord from the wall outlet; hold the power button pressed for several seconds; watch for the fan of the power supply to stop. e. Don’t worry: they never get charged thus are always harmless. 22. Car ignition system will most likely kill you. True / False 23. If you are in a vehicle that comes in contact with a live power line (very high voltage, possibly ~ 500 kV or more)… (check all that apply): a. Remain in the vehicle until you are sure that the power line is no longer live (high voltage has been disconnected from it). b. Get out of the vehicle as soon as possible, regardless of how exactly you step out of it. c. If you must get out of the vehicle, make sure that you jump so that your body does not touch the vehicle and the ground at the same time. d. Do not touch any metal parts inside your vehicle, because they will be at the high voltage that may shock you. 24. If you are caught in the middle of a thunderstorm, … (check all that apply): a. Don’t panic; walk as usual. b. Make long strides: you’ll get home sooner without putting yourself in unnecessary danger. c. Crouch low. d. Shorter steps are safer, becausethe voltage difference between your feet gets smaller and less dangerous. 25. The resistance of damp leather boots is only 50% higher than that of a foot immersed in water. True / False © 2011 Alexander Ganago Last printed 1/6/11 7:00 PM Page 5 of 6 File: 2011 W 314 HW 1 p1.doc Winter 2011 Homework set 1 EECS 314 Student’s name ___________________________ Discussion section # _______ (Last, First, write legibly, use ink) (use ink) Instructor is not responsible for grading and entering scores for HW papers lacking clear information in the required fields above 26. The person most responsible for your own personal safety is …. a. You b. Your boss c. Your advisor d. Your Department Chair e. Your Dean. f. None of the above. 27. Higher voltages (above 400 V) cause the same damage as low voltages, because only the current magnitude counts. True / False 28. The reading material includes the example where the current from a faulty electric drill through the worker’s body is calculated as 21 mA. This case is… (check all that apply): a. Harmless, because this current level does not stop neither breathing nor heartbeat. b. Awkward, because the worker cannot move farther than the power cord of the electric drill extends. c. Potentially lethal, because if the current flows through the body for a long time, it heats the tissue, reducing its resistance thus increasing the current magnitude and aggravating its effects on the human. d. Overly pessimistic, because the authors used the minimal values of resistances in their calculations of the current magnitude. e. Conservative, or describing the worst possible scenario (due to the lowest resistance), which is prudent for outlining safety measures. 29. Assuming that the worker in the example above stands on dry concrete and wears dry shoes with leather soles, the current through his body is calculated as… a. Well below 1 mA, which is harmless. b. Around 1.2 mA, which is harmless. c. Around 12 mA, which is harmless. d. Around 1.2 mA, which is extremely dangerous. 30. The recommended safety credo is: If it cannot be done safely, …. a. Ask your boss for clarification and advice. b. Only a brave person should dare do it. c. It need not be done. d. Call 911. © 2011 Alexander Ganago Last printed 1/6/11 7:00 PM Page 6 of 6 File: 2011 W 314 HW 1 p1.doc Winter 2011 Homework set 1 ...
View Full Document

Ask a homework question - tutors are online