What is the main purpose of a standard fuse or circuit breaker?
- To keep the voltage steady when loads change
- To provide a path to ground for fault current
- To protect conductors and equipment from overcurrent
- To protect workers from shock at any current level
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C. To protect conductors and equipment from overcurrent
Overcurrent devices open the circuit when current exceeds the rating of the conductors or equipment, preventing overheating and fire. They trip at many amperes, far above the fraction of an ampere that can kill a person, so they are not shock protection.
Reference: 29 CFR 1910.304(f)
A worker with wet hands touches a 120-volt conductor. If the resistance of the path through the body is 1,000 ohms, how much current flows through the worker?
Answer in milliamperes.
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120 milliamperes
I = V / R = 120 V / 1,000 ohms = 0.12 A. 0.12 A x 1,000 = 120 mA.
Reference: Ohm's law; OSHA electrical safety training (effects of current on the body)
Which use of a flexible extension cord is prohibited?
- Running it through a hole in a wall to feed the next room
- Unplugging it by pulling on the plug body instead of the cord
- Plugging a portable drill into it for a short repair job
- Using a three-wire cord with a grounded power tool
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A. Running it through a hole in a wall to feed the next room
Flexible cords may not be used as a substitute for fixed wiring, run through holes in walls, ceilings or floors, or run through doorways and windows. Powering a portable tool for a temporary job is exactly what a cord is meant for.
Reference: 29 CFR 1910.305(g)(1)(iv)