Band Definition and 481 Threads

(To the moderator,please don't shift to the Homework thread list.This thread explores the conceptual part of gear changes) A 2 liter engine has T(max)=185Nm at \omega_e=4500 rpm, has a manual gearbox with the following gear ratios: n1=3.42, n2=2.14, n3=1.45, n4=1.03, n5=0.81, nr=3.46, nd=4.06...

Hi, I want to design an ADC with these specifications: Fin = 20MHz BW= 20MHz ENOB > 4 Power consumption P < 1mW Could anyone suggest me some ADC for this kind? I have searched a lot in IEEE but there are only two ADC with SAR ADC and time-interleaved ADC. The ultralow power consumption...

How does one interpret band structures (i.e. E,k solution pairs for a given Hamiltonian) for a non-primitive cell? I was looking at these slides: http://www.tcm.phy.cam.ac.uk/castep/CASTEP_talks_06/clark2.pdf Slide 9 has the "normal" silicon band structure obtained with a primitive cell...

Why are insulators supposed to possesses a "conduction band", even if usually empty? If you do take the energy to cross the "band gap" and displace an electron, just why should it become delocalized/conductive? Couldn´t it just lose energy rapidly by exciting phonons until it gets trapped...

Homework Statement Hi guys, I'm trying to solve questions from past exams; here comes one. There are 2 possible fundamental equations for the rubber bands: ##S=L_0\gamma \left ( \frac{aU}{L_0} \right ) ^{1/2} -L_0 \gamma \left [ \frac{1}{2} \left ( \frac{L}{L_0} \right ) ^2 + \frac{L_0}{L}...

Does the (intrinsic) Fermi level of an insulator HAVE to lie very near the middle of the band gap? I know it might deviate slightly if electrons and holes have different effective masses, e.g. in Si. But can it be radically different? For example, are there insulators with 5 eV band gaps that...

Can we measure the band energy gap from Fluorescence spectra? If yes, in what way? the excitation spectra or the emission spectra or both Is there a good reference on this subject specifically :smile:

Hello! I'm having my materialphysics exam in a few days, and looking some of the older exams I saw that there are many times questions about band structure and density of states. More specifically there might be a picture of some band structure plus the density of states, like this. Then...

Homework Statement I just have to calculate midband gain for a typical NPN BJT. The transistor model is a 2N3904 Have I calculated something wrong?? My gain is 0.748

Homework Statement Please see attachment. Homework Equations The Attempt at a Solution Not really a homework problem. This is 1 of my exam question which I believe I had the right answer but my professor insists that he has the right one. I started by equating work done, W =...

Hello, I am writing a technical essay on solar cells and I am having trouble finding out exactly what the valance and conduction band actually are. It's a bit elusive, the textbooks I am using simply state the two bands without explaining what they are. If anybody could provide any...

As my title states, I want to understand why electrons in the conduction band can move around so easily in the material. Is it due to the presence of many closely spaced (blurred out) energy levels which make it easy for the electrons to move around? Or are the electrons undergoing some kind...

Hello, Is there an established relationship between the diffraction intensity that a sample produces with its band structure? Thanks

Is there an easy way of designing a band pass filter whose pass band could be varied over a certain band?? The pass band is in MHz range. Thanks

I mean why is it that the eye evolved to detect "visible" light instead of, say, microwaves. What is it about the visible light spectrum?

What are the parameters affects the band gap in a band structure?

The absorption spectra of some materials appear as the absorption bands (for example: TiO2 powder) while the other appear as the absorption peaks (for example: Quantum dots). Please explain why they are different?

Apologies if this is rather trivial. I'm having a hard time wrapping my mind around the mathematics of energy bands and periodic potentials. I understand that an electron in a periodic potential will be of the form \phi_k(r) = e^{ik.r}u_k(r) . This wavefunction has periodicity of the...

Assume that a mass is attached to an elastic band and then allowed to oscillate. Would the formula for the period of oscillation be that as the same of the formula for the period of the oscillation for a spring. T=2∏(√m/k) ?

Boundary of a Mobius band - I think S1 V S1, everyone else says S1?? Hey I am having a huge problem! There are a few problems where I'm using Van Kampen's theorem and for one part of the problem I need to compute the fundamental group of the boundary of the Mobius band. Everyone keeps telling...

Hello , about the band theory I was confused some how seeing the attached image I ask :- 1- when the atoms are far away we take a single atom alone as a system , but when atoms get closer we identify them all as the system , right ?! 2- why do we use the word " splitting" , why...

n is the band index and k is the electron wave vector. Now is energy band specified when for each n , k runs through all the values available that specify periodic boundary conditions ? But in Ashcroft Mermin , it is also given that for a given k , there exists an infinite family of solutions...

Suppose an electron in a crystal(periodic potential) has the Bloch wave function \psi (k_0,x) at t=0. Applying a constant electric field E(at t=0), the electron would still have Bloch-type wave function at any time t with k(t)=-(1/\hbar) eEt+k_0. Now According to this formula for k(t), one can...

Homework Statement What are the color band colors and associated band values for a 1kΩ resistor The Attempt at a Solution resistor color codes are read like so: ab*10^c±tol 1kΩ=10*10^2 a=1, b=0, 10=c Now I get confused. What should the tol be?

A rectangular semiconductor has dimensions of 2x2x1 mm, the unit cell is cubic and has edge length of 2 angstroms. find the number of states in one band of this semiconductor. What I have done: volume of unit cell = (2x10^7)^3 = 8x10^-21 mm^3 volume of semi conductor = 4 mm^3 number of...

Interesting article from SciAm on transforming a rubberband into a trefoil knot and how math in the knot world of zero thickness says no but the real world says yes. http://www.scientificamerican.com/article.cfm?id=mathematical-impressions-can-you-turn-rubber-band-into-knot

Homework Statement Describe the ”conduction band” in Na metal. Why it is half-filled and non-magnetic? The Attempt at a Solution Na has electron configuration: [Ne]3s^1 the 3s band is highest in energy and is the conduction band for Na. since Na has 1 electron in the 3s band, and...

Homework Statement A person performs an exercise where he pulls a rubber band stuck in a wall to later return it to its resting position. The two movements forward and backward, is equivalent to one practice cycle. They both happen in a horrizontal plane with a constant velocity of v=0.5ms-1...

I've been looking on journals and textbook, as well as internet. Does anybody know if there is an equation to find out the value of direct optical band gap and indirect optical band gap? What is the difference of optical band gap, direct optical bandgap and indirect optical bandgap? also...

In n-type semiconductor, Can electron stay between donor energy level and valence band? Can I say that the donor energy level here refer to the Fermi level? Thank you

Electrons in the conduction band of metal will be attracted by the nucleus of atom? I wonder why there can be electron in the conduction band of metal at 0K .At 0K , all electron should lose its energy as(3/2)kT=0. Thank you

Hi, Does anyone have an intuitive idea of why it is always the valence bands split under spin/orbit coupling, but not conduction band? (or a much smaller splitting than valence band) I know through tight-binding calculations, if I plug in numbers correctly, conduction bands always have...

the 2 signals shown are used for modulating ( DSB-SC) a carrier with frequency fc. Now i need to find the similarities and differences between their time domain representation. Clearly the both will have same envelope. Now i tried for the difference part but could not find it. One possibility...

Can a hole go to conduction band? In p-type, the hole is above the fermi level, lower than conduction band, higher than valence band, how can this be happened? And will this happen when the p-type is at 0K

This is regarding youngs elastic modulus I need help as I am trying to figure out the stress and strain of an elastic band when a force has been applied - in youngs modulus. Does anyone know how to go about this?

Please link to execrable songs by musicians that should have known better. Some "songs" like "I'm so glad" by Cream appear to be album-fillers instead of serious music. Clapton has gold records on his wall, but this stinker causes me to change the channel or hit "next" on the CD player...

I am a little bit confused about the upward band bending in a n-type Si which is in contact with a metal. Suppose that electrons flow from Si to the metal to align the chemical potentials such that positive donor levels become depleted. In equilibrium one ends up with a negative charge density...

Okay, I am working on my physics lab, and I have a few questions regarding it. First, we are asked to make a prediction: "Predict how you think the presence of a rubber band will affect the force felt by the force probe from the rubber band compared to masses hung directly from the hook?" My...

hello, is there anyone who can help me in the band gap calculation. my situation is that: I can calculate the band gap of sigle crystalline graphene, because i know the high symmetrical pionts of the first Brillouin zone of an hexagonal crystalline(M-G-K-M). But the problem is that...

Homework Statement The first vibrational band in the absorption spectrum of H2CO is at 28871 cm-1. The first two bands in the emission spectrum (from v'=0 level) lie at 27021 cm-1 and 24687 cm-1. Explain these observations. Determine the band origin of the electronic transition and the...

I search it on google, books, articles, everyone cite it but no one explain fully what it is. If you can: bibliography please! Thanks a lot!

In a metallic system, the Fermi level is crossed either from the conducting zone into the non-conducting zone or vice versa. Is there an interpretation one can give to the direction of the crossing? In other words, if the 1D band gap diagram shows the fermi line is crossed from the...

Hi, I am trying to model a type II GaSb/InAs superlattice through the 8 band k.p method in MATLAB...I have studied general quantum mechanics but have no background in coding. I need to calculate the bandstructure and the CB,VB wavefunctions...can anyone provide me with a sample code for better...

In band theory of solids, when an electron's wave vector lies at the first brillouin zone border, it satisfies the bragg condition and there is some forbidden region for that wave vector. I like to know what happens for such these electrons that they can not have some energies in the forbidden...

As we know, in intrinsic semiconductors the fermi level is halfway between the valence and conduction band. and The fermi level is the level in which the most energetic electron settles at T=0. but my question: How can the fermi level be in a forbidden region in intrinsic semiconductors? or...

I need some help with FREQ. on the MHz Band and the kHz Band? If I am on a Radio that displays the FREQ 909.5 MHz I know I would write this out as 909,500,000 Hz and this is 9 Hundred and 9 Thousand 5 Million Herts Am I right?

I am new to solid state physics, having been in computational chemistry (quantum mechanics) for the larger part of my career. Hence have a lot of newbie like questions that are not easily answered by google/wikipedia searching. 1)In viewing a 1-dimensional band gap diagram, crossing the...

I was reading about electronic band structure in wiki and I didn't understand why the conduction bands are necessary for flowing current in a material. If all the atoms in a solid shares valence band and all its eletrons, then these electrons may travel through the solid. I didn't get why the...

Hi, I'm studying for a course in semiconductor devices, involving pn-diodes, schottky-diodes and mosfet transistors. Just wondering if there's any good online resource that demonstrates specifically how to draw energy band diagrams for the various devices in various situations (applied...

Hello everyone, I have finished high school not long ago, and haven't start my uni. So I take this time to read some physics. I have no one teachs me, the only book I have is 'Giancoli's PHYSICS'. Its a good book (discriptive but not mathematical, which suits me as I haven't done much...