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| how exactly resistor works |
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| ArthurDent:
“The exceptions merely form the basis for the entire modern world as we know it.” Here we have the difference between the academic and real world. Ask any practicing engineer how many times they use complex equations to solve simple problems. Application is far different than research and development or theoretical research. If I’m planning a trip from Boston to NYC and ask someone the distance, I don’t think I really need to know the diameter of the earth to calculate great circle distance and how it isn’t a perfect sphere, or that the distance could be different depending on whether I go from Boston to NYC instead of NYC to Boston because of the effects of relativity and rotational speed of the earth, and whether my reference point is earth or the center of the universe. I’m into precise time and frequency and realize that talking to the average person about leap seconds or 5ns drift rates isn’t going to be a conversation starter. If someone asks me the time I look at my watch, which is synced to WWVB, and give them the approximate time. I believe the answer the OP wants is also a practical explanation, even if it isn’t to 12 decimal places. Yes, running a lot of current through a resistor generates heat which is what makes electric space heaters possible. They also have kind of an aura or field emanating from them. |
| rstofer:
--- Quote from: djacobow on September 29, 2018, 06:52:45 pm ---This is a beginners forum, so I understand that it is not a good idea to answer more than what was asked. But in giving a limited answer, I think it is important not to say something that is fundamentally wrong, least it become a fundamentally wrong building block for their entire understanding of electricity for their whole lives. --- End quote --- In EE school, we worked with Ohm's Law, Kirchhoff's Laws and the other simple Theorems beginning in the first semester. I'm not sure but I think Maxwell's Equations didn't come up until 4 years later. Notably because it took 4 years of progressive math courses to get to a point where curl and divergence made any sense at all, mathematically. Yes, Maxwell's Equations can be hand-waved but sooner or later somebody wants to use numbers. Ohm, Kirchhoff, Norton and other Laws/Theorems are good enough for all practical purposes and certainly sufficient for a beginner. |
| djacobow:
--- Quote from: ArthurDent on September 29, 2018, 07:58:08 pm ---“The exceptions merely form the basis for the entire modern world as we know it.” Here we have the difference between the academic and real world. Ask any practicing engineer how many times they use complex equations to solve simple problems. Application is far different than research and development or theoretical research. If I’m planning a trip from Boston to NYC and ask someone the distance, I don’t think I really need to know the diameter of the earth to calculate great circle distance and how it isn’t a perfect sphere, or that the distance could be different depending on whether I go from Boston to NYC instead of NYC to Boston because of the effects of relativity and rotational speed of the earth, and whether my reference point is earth or the center of the universe. I’m into precise time and frequency and realize that talking to the average person about leap seconds or 5ns drift rates isn’t going to be a conversation starter. If someone asks me the time I look at my watch, which is synced to WWVB, and give them the approximate time. I believe the answer the OP wants is also a practical explanation, even if it isn’t to 12 decimal places. Yes, running a lot of current through a resistor generates heat which is what makes electric space heaters possible. They also have kind of an aura or field emanating from them. --- End quote --- You guy are killing me, so I think I'm just going to give up after this post. But you're still wrong as hell. Ohm's "Law" is misleading. It's as simple as that. It doesn't help to teach it as a "Law" even to a preschooler. There are cases where a simplification is helpful, there are cases where a simplification is necessary, because the truth is too complex. This is not one of those cases, because you do not have to explain the complex reality, only hint at its existence. This is actually very useful information for a student because it puts the seed into his or her head that E=IR is telling your something about the material under consideration, NOT about the universe. It's funny, you make a distinction between an academic and an engineer. As it happens, I'm an engineer and I'm happy to use simplest equations I can get away with. But I'm also often called on to teach, and I have a responsibility not to fill my students' heads with bullshit. Some of those students will continue on to more advanced learning, some will not, but regardless, it's nice to not tell them false stories. Hence, I always qualify Ohm's Law because it is perfectly trivial to explain to a day-one beginners of average intelligence that this equation, while generally useful, does not describe reality in many important circumstances and exactly describes reality in absolutely no circumstances. Engineering students definitely "get" this and it trips up nobody. The same goes for all the much worse crutch/analogies about water, drips, pipes, valves, pressure, flow, ball bearings, screens, hills, obstacles, etc, every single one of which ultimately becomes a hindrance to understanding electricity -- usually long before an undergraduate has finished his or her EE program. Finally, let me just state for the record that the OP's original question "how, exactly a resistor works" was absolutely an invitation for a nitpicky explanation. To borrow from your analogy above, the OP literally asked "how, exactly, do airplanes work?" and the answer he got was "you buy a ticket and it takes you where you want to go." |
| taydin:
--- Quote from: rstofer on September 29, 2018, 08:16:15 pm ---Ohm, Kirchhoff, Norton and other Laws/Theorems are good enough for all practical purposes and certainly sufficient for a beginner. --- End quote --- Yep, that's what it comes down to. The word "law" is always used more or less loosely. If you take "law" in its most strict, absolute sense, for example, "every human will die" would be a law (fits observation, and there are no recorded exceptions of it ;D ). But there are very, very few things in life that are this certain, so it wouldn't be useful as a scientific categorization. |
| rstofer:
If somebody wants to call some kind of referendum to downgrade Ohm's Law to Ohm's Suggestions, go for it! I suspect that static inertia will preclude any change in the name or categorization. |
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