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| bio | website | sjbyrnes.com |
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| location | ||
| age | ||
| visits | member for | 1 year, 11 months |
| seen | 3 hours ago | |
| stats | profile views | 249 |
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Mar 25 |
comment |
Fermi and Boltzmann distribution of carriers in semiconductor For n-type, the criterion is "When any given conduction-band state has probability << 1 of having an electron in it." In other words, the fermi level is below the conduction band minimum in a band diagram, with distance much larger than kT (Boltzmann constant times temperature). How much larger than kT? Well, the larger it is, the more accurate the Boltzmann approximation is! There is no quantitative criterion that I can tell you: It depends on what you're calculating and how accurate you want the answer to be. |
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Mar 24 |
comment |
Why does higher acceleration minimize a car's fuel consumption? Just so that people don't get the wrong idea --- Even if this observation is true, it is still possible that, all things considered, telling people to accelerate slowly will lead them to better fuel economy, because it indirectly leads them to use lower average speed and/or less braking. Much depends on the situation, e.g. stop-and-go city traffic is very different than accelerating onto an open highway. Anyway, I think this is a very interesting observation and good question! :-) |
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Mar 20 |
answered | What limits the maximum attainable Fermi Energy for a material experimentally? |
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Mar 20 |
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What limits the maximum attainable Fermi Energy for a material experimentally? Structural integrity is compromised when you empty the $\sigma$ orbitals OR fill the $\sigma^*$ orbitals, right? Therefore, it seems to me that you can break the bonds by doping enough either n or p. |
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Mar 19 |
revised |
Multiple measurements of the same quantity - combining uncertainties added 274 characters in body |
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Mar 19 |
comment |
Multiple measurements of the same quantity - combining uncertainties If you're really sure that some measurements are much more accurate then others, then taking the mean of all the measurements is the wrong thing to do. You would want to give extra weight to the more accurate measurements. Granted, the OP asked about the mean. But still, he/she should be guided towards a better analysis method. |
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Mar 19 |
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Multiple measurements of the same quantity - combining uncertainties @dmckee -- Thanks, I changed "standard deviation" to "uncertainty" in the formula. That should be less confusing. |
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Mar 19 |
revised |
Multiple measurements of the same quantity - combining uncertainties change "standard deviation" to "uncertainty" |
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Mar 19 |
answered | Multiple measurements of the same quantity - combining uncertainties |
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Mar 19 |
answered | Fermi and Boltzmann distribution of carriers in semiconductor |
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Mar 11 |
comment |
Using $\frac{1}{A+i\epsilon} = PV\frac{1}{A}-i\pi\delta(A)$ in Feynman Integrals For readers unfamiliar with the equation in the question title, learn more at en.wikipedia.org/wiki/… :-D |
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Feb 22 |
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Ohmic and Non-Ohmic devices Downvoted ... First, under almost all circumstances, $J = \sigma E$ if and only if $V=IR$. So neither is more or less "valid". Second, there are plenty of universal laws in physics. Third, "due to electrical properties" is not an explanation of anything. |
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Feb 22 |
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Ohmic and Non-Ohmic devices If you could be more specific, you would be more likely to get a helpful answer. The reason that a battery doesn't follow Ohm's law is very different than the reason a diode doesn't follow Ohm's law, which in turn is very different than the reason that copper under an extraordinarily high electric field doesn't follow ohm's law, etc. etc. |
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Feb 10 |
awarded | Necromancer |
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Feb 6 |
comment |
In the diode equation, why the exponential $\exp$ and the ideality factor $n$ are there? What do they represent & what is their significance? Have you tried looking up the equation in a book? Or online? If so, which aspects did you find confusing? One of many websites that derive the Shockley diode equation is pveducation.org/pvcdrom (especially chapter 3, see the table of contents on the left side of the screen). |
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Feb 5 |
comment |
How much lift does the average latex helium filled party balloon produce? The helium is under higher pressure than the air, being squeezed by the rubber, but this probably makes a negligible difference. OTOH, I'm not so sure it's OK to neglect the weight of the rubber itself. Is it much less than 14g? I don't know. |
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Feb 1 |
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No magnetic field from a static charge - Is there a simple physical argument to show why? @Chris -- It is not true that "magnetic fields can only be caused by time varying electric fields". One counterexample is a loop of wire carrying a DC current. Another counterexample is an electron at rest (since it's at rest, its electric field is not changing over time). |
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Jan 22 |
revised |
statistics for photon counts in photomultiplier clarify that poisson statistics are almost always correct; add more clearly how probabilities relate to poisson statistics |
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Jan 21 |
answered | statistics for photon counts in photomultiplier |
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Jan 20 |
comment |
Do electrons in multi-electron atoms really have definite angular momenta? It might indeed be small, but why is it small? One naively expects total e-e repulsion to be comparable to e-nucleus attraction, right? (I expect that my question has one answer for lithium and a different answer for uranium.) |
