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May
3
answered Microscopic picture of an inductor
Apr
29
answered How does a force on electrons produce a force on a metal plate
Apr
26
comment What is the reasoning behind hole carriers being able to carry heat?
I wrote a more detailed explanation of what holes are at physics.stackexchange.com/questions/10800/… - that may help answer your question.
Apr
26
answered Is light red shifted in optical tweezers?
Apr
25
answered Integrating factor $1/T$ in 2nd Law of Thermodynamics
Apr
16
answered To which real densities do carrier densities in the semi-classical model of a crystal correspond?
Apr
16
comment To which real densities do carrier densities in the semi-classical model of a crystal correspond?
Why do the density of electrons and holes depend on the corresponding effective masses? Are you assuming that the total mass of all electrons is equal to the total mass of all holes? Because that's not true.
Apr
16
awarded  Nice Answer
Apr
15
revised Physics Equations for Grad School / Physics GRE Prep
added 291 characters in body
Apr
15
comment Physics Equations for Grad School / Physics GRE Prep
An example of why this isn't true: From high school until right before the GRE, I never bothered to remember whether it's B = mu H or H = mu B. Then I memorized it for the GRE, and I've never had to look it up again. It just took a bit of mental effort -- very worthwhile. Knowing things like that is very very useful, because if you're calculating or thinking through something, you don't want to have to keep stopping to look up dumb things like that. Even if it only takes 20 seconds to look it up, that's enough to lose your train of thought.
Apr
15
answered Physics Equations for Grad School / Physics GRE Prep
Apr
12
comment Why isn't temperature measured in Joules?
You can define temperature as "The temperature of a body is the energy of an ideal 1D classical simple harmonic oscillator in thermal equilibrium with that body." Then there is no "per degree of freedom" in the definition -- we're just talking about an energy.
Apr
12
comment Why isn't temperature measured in Joules?
I disagree. You imply that if two things are measured in the same unit, then they have to be exactly the same thing. Therefore, you say, a unit system that measures temperature in J is not "correct". Well, I think that a knowledgeable person can understand that temperature is not exactly the same thing as total energy content, but can still measure both in J. (The advantage of using kelvin IMHO is not that it's more "correct", but to reduce the frequency of stupid confused mistakes and miscommunications -- which is still worthwhile!!)
Apr
10
answered Effects of surface roughness on specularity
Mar
25
answered Indirect band gap semiconductor for LEDs?
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.
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! :-)
Mar
20
answered What limits the maximum attainable Fermi Energy for a material experimentally?
Mar
20
comment 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.
Mar
19
revised Multiple measurements of the same quantity - combining uncertainties
added 274 characters in body