Re: commercial receptacle limits
Originally posted by ronaldrc: How many horse power does it take to get a 2.5 ton motor vehicle up a 45 degree hill 150, 155,200? If this where the question it would be like letting you change the degree of the hill from 45 degrees to something else that isn't as steep, and that way you can make the horse power fit your answer.
I don?t think this thread is long enough yet, so I?ll throw in my dime?s worth (Hey, I am a consultant, so my two cent?s worth will not come cheap!).
Sorry ronaldrc, but for two reasons this analogy doesn?t help clear up the issue. First, your question cannot be answered. Power (of which ?horsepower? is one unit of measure) involves a force (you gave that ? the weight of the vehicle) that is applied through a distance of travel during a period of time. The question leaves out both the height of the hill and the desired time for the lift.
More to the point, however, is that you propose to change, as the key variable in your analogy, the angle of the hill. This variable would correspond more closely to the resistance of the circuit then to the ?motive force? (the horse, in your analogy, and the voltage source, in a circuit).
It seems to me that an important aspect of this whole question has been missed. What we need to remember is that the ?180 VA? is an artificial number that is provided (for convenience and consistency of calculation) by code, and not a constant value that is established by the laws of physics. Suppose we plug a 16 amp heater into one 20 amp outlet and plug a 16 amp fan into another, and then impose a voltage of 115 on both. For starters, both circuits will draw more than 10 times the 180 VA used to calculate the outlet?s load. Secondly, if you now raise the voltage to 120, current in the heater will go up (more VA!), and current in the fan will go down (constant VA). What happens to the meaning of the 180 VA in this experiment? Nothing! It never really existed, or at least not in a physical sense.
So where does that leave the original question? Let me cite a rule of technical communications: ?It doesn?t say what you think it says. Rather, it says what it says.? The laws of physics would assert that a 120V source can push more energy through a circuit than can a 115V source. True, but irrelevant. The question says 115V, and to answer THAT question, you must use 115V. Go back to post #11 (from Roger): ?Answer the question as asked.? If I were the instructor, I would feel justified in marking as incorrect anything other than ?B.? But then, I would also feel ashamed for having written such a poorly worded question. I prefer to design questions to test a person?s knowledge and understanding, not to test a person?s alertness.
