50 Questions and Answers on Electrical Safety Knowledge

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50 Questions on Electrical Safety Knowledge 1: What types of equipment can be used to extinguish fires in electrical devices while they are still powered on? Answer: 1211 Carbon dioxide, carbon tetrachloride dry powder (2 correct answers will be accepted). 2. In terms of the frequency of electric shock accidents, which months of the year see the most such incidents? Answer: June to September 3. What is the maximum safe voltage in volts? Answer: 42 volts. 4. What is the specified limit for the direct current that can pass through the human body without posing a safety risk? Answer: 50mA. 5. What is the specified limit for the safe AC current passing through the human body? Answer: 10mA 6. What should be done first in emergency first aid for electric shock? What to do right away then? Answer: Electroshock resuscitation ； Artificial respiration. 7. How many types of protection devices does our factory have to prevent direct lightning strikes? Answer: Lightning rod ； Lightning protection mesh ； Mine counter. 8. When a wire is grounded, the closer a person is to the grounding point, the higher the step voltage; the farther away they are, the lower the step voltage. Under normal circumstances, if the distance from the grounding conductor is sufficient, the step voltage can be considered zero. A: Within 10m B: Beyond 20m C: Beyond 30m Answer: B 9. Low-voltage voltage testers are generally suitable for alternating current and direct current voltages up to ( ) V. A: 220 B: 380 C: 500 Answer: C. 10. What electrical safety measures should be taken for the wiring of lighting fixtures at construction sites? A: Wear insulating gloves. B: Cut off the power supply. C: Stand on an insulating pad. Answer: B. 11. Whether a person who has been electrocuted can be saved depends on ( ). A: The way of electric shock. B: The value of the body’s resistance. C: The voltage level of the electric shock. D: Whether it is possible to disconnect from the power source quickly and provide first aid. Answer: D. 12. What is essential to eliminate static electricity in pipelines? Answer: Grounding 13. What is safe voltage? Answer: Under various environmental conditions, the voltage at which human body tissues (such as the skin, heart, lungs, respiratory organs, and nervous system) are not damaged upon contact with a charged object carrying a certain voltage is referred to as a safe voltage. 14. What are the main factors that affect the degree of harm caused by electric current to the human body? Answer: The main factors include: the magnitude of the current, the resistance of the human body, the duration of electric flow, the frequency of the current, the voltage level, the path taken by the current, and the condition of the human body. 15. After a motor in operation is stopped and then restarted, how many times is a hot start permitted while the motor is still warm? How many consecutive starts are allowed in a cold state? Answer: 1 time ； 2~3 times 16. What protective measures should be taken for electric construction machinery and equipment? Answer: Protective zero connection must be used, along with repeated grounding as well. 17. What are the two parts of electrical safety measures? Answer: Organizational measures and technical measures. 18. What are the main methods of disconnecting from a low-voltage power source? Answer: (1) Cut off the power supply ； (2) Cut the power cable ； (3) Pull the power cable ； (4) Pull the person who has been electrocuted away ； (5) Take appropriate first-aid measures. When taking the above measures, be sure to use insulation tools that are suitable for the corresponding voltage level. 19. What is the sequence for closing the isolating switch during power supply? Answer: Close the busbar side first, then the line side. 20. Can the knife switch in the power distribution box be opened under load? Answer: No. 21. What type of power tools must be used when operating handheld or mobile power tools in areas where there is a risk of explosion and fire? Answer: There are explosion-proof measures in place. 22. What is the safe voltage in volts that should be used when operating hand-held electric tools or lighting devices in humid work environments or inside metal containers? Answer: 12V. 23. When testing the motor, is it okay to press the stop button right away after starting it? Why? Answer: No. The starting current is 6 to 7 times the rated current; stopping it immediately will damage the switch. 24. Most of the motors in our factory are explosion-proof motors. What is the general explosion-proof rating? Answer: dIIBT4 25. Are the explosion-proof motors produced by our factory also waterproof motors? Answer: No, it’s not 26. When the process load is below the rated load, the motor won’t be overloaded, right? Why? Answer: No. Changes in the medium, pump failures, and motor failures can all lead to overload. 27. Why aren’t fire permits issued, and why isn’t it allowed to connect temporary electricity without such permits? Answer: Temporary electricity use involves electricity that can generate sparks, which increases the risk of electric shock accidents as well as fires and explosions. It is necessary to obtain relevant permits and temporary electricity usage permits, and certain safety measures must be implemented at the construction site before temporary electricity can be used. 28. For electrical equipment connected to indoor lighting circuits, what should be the maximum total capacity of each circuit in kW? (1) 1 ； (2) 2 ； (3) 3. Answer: (2) 29. The capacity of a socket should correspond to the electrical load; how many appliances are allowed to be connected to each socket? Answer: 1, 30. When the relative humidity at the workplace is greater than 75%, such an working environment is considered a high-risk environment for electric shock: (1) Dangerous ； (2) Particularly dangerous ； (3) General answer: (1) 31. To prevent accidents caused by static electricity sparks, all metal pipes and non-conductive material pipes used for processing, storing, and transporting various flammable gases, liquids, and powders must (1) have a sufficiently high resistance ； (2) Have a sufficiently low resistance ； (3) Grounding: 332. For the power leads of power tools, the yellow-green dual-colored wire should be used as the ground wire. (1) Phase ； (2) Working neutral wire ； (3) Protective grounding. Answer: (3) 33. The most effective measure to ensure the personal safety of electrical maintenance personnel is. (1) Hang a signboard ； (2) Place the barrier ； (3) Ground and short-circuit the equipment under maintenance. Answer: (3) 34. From a safety perspective, there must be a clear indication when the equipment loses power. (1) Signboard: (2) Grounding point ； (3) Disconnect point. Answer: (3) 35. To confirm that a device or circuit is de-energized, indicators should be used as a basis. (1) Voltmeter ； (2) Electroscope ； (3) Disconnect the signal. Answer: (2) 36. It is not allowed in the vicinity of various electrical equipment such as distribution panels/cabinets, switches, and transformers. (1) Place the fire extinguisher ； (2) Set up fencing ； 3) Storing flammable, explosive, damp, and other items that affect operation. Answer: (3) 37. For ordinary residential and office buildings, where the main purpose is to prevent electric shock, a leakage protection switch with a leakage operating current of mA should be used. (1) 6 ； (2) 15 ； (3) 30. Answer: (3) 38. The power cords for mobile electric tools and their switchboards (cabinets) must be of this type. (1) Double-layer plastic insulated copper core wire ； (2) Two-strand copper core plastic flexible wire ； (3) Flexible wires with copper core and rubber insulation sheath or copper core and polyvinyl chloride insulation sheath. Answer: (3) 39. The length of the power cord lead for portable electric tools should generally not exceed a certain number of meters. (1) 2 ； (2) 3 ； (3) 4. Answer: (2) 40. For hand-held electric tools that have been left unused for a long time, it is necessary to measure their insulation resistance before use; for Class I hand-held electric tools, the insulation resistance between the live parts and the casing must be no less than M Ω. (1) 2 ； (2) 0.5 ； (3) 1. Answer ； (2) 41. What is a short circuit? Answer: A short circuit occurs when, in an electrical circuit, the phase wires come into contact with each other, or with the neutral wire or ground, without going through a load or with very low resistance, resulting in a significant increase in current in the electrical circuit. 42. What are the disadvantages of a short circuit? Answer: The short-circuit current causes the point of the short circuit and even the entire circuit to overheat, which can ignite the insulation layer of the wires and set fire to combustible materials in nearby buildings. 43. Under what circumstances should electrical equipment such as fans, lighting fixtures, and mobile welding machines be moved? Answer: Turn off the power. 44. Any electrical equipment should be assumed to be live until it is confirmed to be de-energized, and must not be touched blindly. Answer: There is electricity. 45. What is the surface temperature of a 1kW iodine-tungsten lamp tube? 500~800 degrees Celsius. 46. Why do incandescent lamps tend to break when turned on? Answer: When the filament is cold, its resistance is low; at the moment power is applied, the current is high (about 10 times higher). Over time, this can lead to damage to the filament. 47. If the two ends of a fluorescent light are red and not bright, can it still be used continuously? Why? Answer: No. At this time, the current is greater than the rated current, which will cause (1) the filament to age and get damaged quickly ； (2) Excessively high ballast temperature can cause a fire. 48. Between alternating current and direct current with the same voltage, which one causes more harm to humans? Answer: Alternating current. Especially alternating current at 50~60Hz. 49. What is the first measure that must be taken in case of a fire in electrical equipment? : Power outage. 50. What is the approximate daily electricity consumption of our company? Or what is our company’s average daily electricity consumption? 51. During the production process, temporary maintenance work involving open flames must not be carried out near cable trenches. Why? Answer: To prevent explosions caused by flammable gases in the trench. 52. Under what circumstances during the operation of electrical equipment should operators take emergency measures, start up the backup units, shut down the faulty units, and notify professionals to conduct inspections and repairs? Answer: (1) The load current suddenly exceeds the specified value or a phase loss condition is confirmed ； (2) The motor or switch suddenly becomes very hot or starts to smoke ； (3) The motor or other equipment generates noise or sparks due to friction caused by loose components ； (4) The mechanical load suffers from a serious failure or poses a threat to electrical safety.