Gap Definition and 267 Threads

1. Homework Statement As shown above Homework Equations *Not too sure if they are relevant. Pretty sure there's more. We have textbooks from the library as references but we still can't quite figure it out :/ Φ = BcAc = BgAg B = Φ/Ac = (Ni/R)/Ac R = lc/(Ac.μ) The Attempt at a Solution...

I've tried to summarise the explanation my professor gave. Is it correct or have I misunderstood? It's a highly simplified view of things anyway, but here goes: Taking the simplest 1D case, there are two possibiities for an electron in the lattice: it may be scattered and move back the way it...

Homework Statement Two parallel metal sheets of length 10 cm are separated by 20 mm in a vacuum. A narrow beam of electrons enters symmetrically between them as shown. When a PD of 1000 V is applied between the plates the electron beam just misses one of the plates as it emerges. Calculate...

Does phonon required a minimum energy in the absorption process of an indirect band gap, and why?

I graduated with a Bachelor of Electrical Engineering degree in 2015, and am right now in teacher's college until April of 2018. Within these two years, I plan to keep up to date with electronics projects that I can do on my own time. Ultimately, I plan to go back to Engineering right after my...

Hi, everyone! I'm doing a research in gap conduction calculation models in popular nuclear fuel performance codes. I want to make a sensitive analysis in their behaviors, but unfortunately, I just have access to FRAPCON package. is there anyone who can help me to gather some of the codes...

http://www.usnews.com/news/articles/2016-09-20/black-white-pay-gap-climbing-due-to-discrimination

For quite a long time now I'm having some trouble to bridge the gap between two different approaches to Special Relativity. The first approach is the traditional one. It is the approach that Einstein presented in his paper and that is taught in most of the basic textbooks. In this approach...

I am a junior in college studying physics, math, and computer science who has been heavily involved in research, year round, for the past 2 years and have already started taking graduate classes. I feel like before I start a phd program I would really like a year or two off. How do professors...

So I will be starting an undergraduate MSci degree in Physics/Theoretical Physics in 2017, for the time being I am on a gap year. What's the best way to mentally prepare for a theoretical physics degree? I am not just talking about being familiar with the topics discussed, but also improving my...

Hi all, I am currently taking a year off after graduating with my bachelors in physics. Hence I have a year to either work (really need to make money) or travel. I have a feeling that if I applied to a full-time job and left after a year, it would be a form of betrayal. Is it wise to...

I am trying to calculate the flux density of an air gap in an electromagnet. I am following this page that calculates the flux density in a C core with an air gap. My confusion is that I am using 50Hz AC instead of DC I have control over the voltage amplitude since I would be using a variac to...

Error is like " no PSPICE template for 2N6798 ， spark gap switch how to find the .ilb of spark gap switch and 2N6798? thank for your help.

Hi everyone How can I determine the optical band gap of a cobalt ferrite film deposited on a glass substrate using its absorption, transmittance and diffuse reflectance spectrum (knowing that I don't know the thickness of this film)

I've been admitted to UT Arlington with 100% tuition scholarship. However, even after the scholarship, the living expenses are quite a bit for me (however, with on campus jobs and all, I believe my family will be able to manage so I think that I'll leave the financial issues aside). I'm not...

As a condition for a topological phase transition it seems that there must be an energy gap that closes and reopens. I have seen this many places, but never an intuitive, easy explanation. Can someone give that?

All, My brother is a final year student at one of the top engineering colleges in India (IIT). He is pursuing mechanical engineering with a minor in physics. He is interested in doing a PhD in theoretical physics. This year his admission was declined by most major universities, so we are...

Greetings! Having finished my A-Levels, some unforeseen circumstances had forced me to take 2 gap years before starting my undergraduate studies in Physics, and I hope to make these 2 years count by doing something meaningful. The first thing that comes to mind is work experience/internship...

The proposed orbit of Planet Nine looks like it falls in a gap between the heliopause and the Oort cloud; could planet Nine have caused the gap? Would Planet Nine get most of it's energy (electro-magnetic) from extra solar sources, since it is outside the heliopause?

Hi I am applying to the universities but I think I am bit confused with something. Actually I am applying to the universities after taking a year gap. But some universities are asking me to make my decision between these two option: Mature student or high school student or gap year student...

I am doing an experiment where we have to use the threshold voltage of LEDs to determine Planck's constant given the following relation $$ eV_0 = E_g = \frac{hc}{\lambda} $$ where ## V_0 ## is the threshold voltage, ## \lambda ## is the wavelength of emitted light and ## E_g ## is the band...

Hi. I am sometimes asked to find the energy gap at a point k in the reciprocal space of a lattice with a periodic potential. From what I've read I understand that I have to 1) use Schrödinger's equation in k-space, from which I 2) get a system of infinitely many equations, and then 3)...

Hi there people! So my question is why you can see localized surface states within the band gap of the material with an STM. How is a tunneling circuit being established?

Hello guys I have a question about semiconductor, suppose I have a semiconductor say silicon at room temperature. The forbidden energy gap in case of Silicon is 1.1eV. Suppose I give I introduced an electric field(or by any other way give energy) which could give each electron an energy more...

I have a thin gap between a disk shaped component (7.5"OD, 0.5" thick, let's call it the "mount") and a long pipe serving as a vacuum chamber. I'd like to fill this gap with something to reduce the conduction between the two volumes on either side of the mount. The mount already has a sizeable...

The article on undecidability of presence of spectral gap by describing its microscopic structure seems to contradict the fact that we can decide whether a CNT is metallic or semi -conducting by checking its diameter and its twist.

So there is a new paper. Presented here: http://arxiv.org/pdf/1502.04135.pdf Published here: http://www.nature.com/nature/journal/v528/n7581/full/nature16059.html And broadly described here: http://phys.org/news/2015-12-quantum-physics-problem-unsolvable-godel.html Here is an excerpt from the...

in induction motor there is air gap between stator and rotor. the air gap needs to be as small as possible. but some air gap is needed for mechancial reasons. i understand that a big air gap would reduce power factor as you'd need more magnetizing current. but are there any advantages of big...

Hi, How can I prove direct band gap property of a Transition Metal Dichalcogenide electrically and optically through experimentation? I can use PL measurements to prove this for optical band gap. Is there any other equipment or technique to prove this? I can not use ARPES because channel length...

Is there any method for how to choose k-points in band structure calculations for aluminium slab 5*5*4 can somebody help in this question? Thanks

I'm an intern currently and doing some analytic project in a company. So i am required to determine the gap between 2 contact surface (2 O-rings). I've obtain some result by using "node to node" contact with some commands and also probe "gap". There's some difference between the results and the...

Homework Statement Nobel prize for physics for blue laser diode using Gallium Nitride with band gap of 3.4 eV and a refractive index of 2.429. Explain how these parameters determine at what wavelength a Gallium Nitride semiconductor will laser at. Homework Equations E=\frac{hc}{\lambda}...

Homework Statement Is diffraction at a maximum when the width of the gap is similar in length to the wavelength of the light? (ie. W ≈ λ, where w=width) Or is it a maximum when the width is smaller than the wavelength? (i.e W < λ)Thanks for the help!Homework Equations n/a (this is a homework...

Hi every one, I face with a question on my works, As you know there in many articles Physicist introduce a material that has zero gap without spin-orbit coupling (SOC). By applying the SOC, a relatively small gap (0.1 eV) is opened and it becomes topological insulator. My question, Is that...

Hi guys, There is a software package called GAP for "Groups, Algorithms, and Programming" with emphasis on Group Theory. You can download it for free. I did. However I'm finding it so intractable to use. I would like to find the "missing group" in the Symmetric groups. That is, the group...

What exactly is the relation between these 3 quantities? As far as I can tell the work function is the energy needed to bring an electron from the fermi level out into vacuum, while affinity is from the bottom of the conduction band. Does this then mean that they can be used to calculate the...

I recently graduated with a dual BS/MS degree that my school offers. I am considering going to grad school for a PhD in the future, and I am considering applying sometime this fall after taking the GRE/PGRE and getting recommendation letters set up. My question is that if I am looking to get a...

Can anybody explain my what is the origin of this forbidden gap? I mean how it was created and what is the physics behind this issue?

Hi all, I am currently writing a report about superconductors, and am currently reading about how the band gap shows that single electrons are not the charge carriers responsible for superconductivity. However, I was confused when I read that electrons are fermions and as such there are no band...

Homework Statement Consider a monovalent 2D crystal with a rectangular lattice constants ##a## and ##b##. Find expressions for the fermi energy and fermi wavevector in 2D. Show that the fermi surface extends beyond first zone if ## 2a > b\pi##. If the crystal is now divalent, estimate the...

Homework Statement The following coil-wound core (core length = L , Gap length = lg, cross- sectional area = A , core permeability = only hysteresis graph is given, N = N turns) is driven by a Voltage source, is known that the current in the coil is 60hz AC. Determine...

Homework Statement Homework Equations See below. The Attempt at a Solution This is only a 1 mark question so I'm probably missing something really simple but I just can't figure it. Below is the slide we have been given: Does anyone have any ideas?

Hello, Here is a quote from the Wikipedia article 'Principle of relativity': http://en.wikipedia.org/wiki/Principle_of_relativity i'v added a string of asterisks around the word 'A consequence'. i feel that there is not enough elaboration about this 'consequence' thing. Was the consequence...

I recently read about the early spark gap transmitter..But I don't understand how the EM waves are generated and transmitted..Induction coil creates sparks in the gap but what produces the waves and how are they transmitted?? Need I study electromagnetic waves in detail??

For a wavefunction at the Brillouin boundary we have: \langle k|H|k\rangle = \epsilon_0 (\vec k) \langle k'|H|k'\rangle = \epsilon_0 (\vec k+\vec G) \langle k'|H|k\rangle = V_G = \frac{1}{L^3} \int e^{i(\vec k - \vec k') \cdot \vec r} V(r) d\vec r \langle k|H|k'\rangle = V_G^* Using...

Hi guys, So in my current situation it is pretty rare to come across people who are mathsy/physicsy, which is why I'm venting here for the advice of some like-minded people. I took a gap year pre-university to work, travel and generally get my head straight but am starting to worry about the...

I am struggling in understanding what the band structure (E vs. k) diagram tells me. Let's say I have the following material: http://www2.warwick.ac.uk/fac/sci/physics/current/postgraduate/regs/mpags/ex5/phonons/indirect_absorption/indirect_absorption.bmp...

Homework Statement Take a steel core (K_m = 2500) electromagnet, bend it into a loop with a small air gap, and determine the B field in the gap. The cross-sectional area of the toroid is 4cm^2, and the air gap is 2.5mm. The current through the coil's 120 turns is 15 amps. The radius of the...

Hi everyone, I am currently a senior majoring in physics and I am scheduled to graduate in May 2015. I am pretty set on going on to graduate school and getting a PhD in theoretical Astrophysics, however, I missed the deadline for the physics GRE and I was consequently not...

Hi Guys, i need your help, where can i download free articles about the band gap of semiconductor materials (like copper (II) oxide). don't mention sciencedirect and arxiv, because i already explore that, and they provide limited research articles. thank you.