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1. Unclear Transformer Specifications

Can someone help me better understand the specs for this old transformer I found? I'm confused why the input and output power see to differ greatly (115V*1.2A ~140W while 40,000V*2mA~ 80W). Also, the fuse rating is unclear to me. Does that mean 1 and 2/10 amp?
2. Virtual Ground Voltage Reference

I'm building an Arduino voltage logger that includes an op-amp (OP27G) as a buffer on the input. Since I'd like to be able to measure voltages all the way down to zero, I want to power the amp with a bipolar supply. My initial thought was to build the rail-splitter below so I wouldn't have to...
3. MATLAB User Specifying a Fit Function in a Separate File

I have five data points (x,y,z), with two independent variables (x,y), and have written a function in a separate file z = f(x,y,A,B,C), with three undetermined constants (A,B,C). How can I use a Matlab fitting program to try and determine the constants? I've written a fit function before where...
4. I Nuclear g-factor

Looking at the Wikipedia page for the Lande g-factor, I'm a bit confused. I thought that g_I\approx5.585, that of the proton, but then there is the line saying that https://en.wikipedia.org/wiki/Land%C3%A9_g-factor It makes sense that the nuclear and Bohr magnetons would differ by the mass...
5. LaTeX Prevent Latex from Including the Location of Every Citation

I'm using Zotero to export my Bibtex file (references.bib), and including it with: \addcontentsline{toc}{chapter}{\bibsecname} \renewcommand{\bibname}{\bibsecname} \bibliographystyle{plain} \bibliography{references} For some reason, in the final References section, it is including a chapter...
6. Concerting 0.1" pitch header pins to 0.150"

I made a mistake on a PCB I designed, and have a set of through holes that are spaced 0.150" apart, when the component I want to put into it has a pin-pin spacing of 0.1". Does anyone know of a simple adapter that could go between these two sizes? I'm looking to avoid the time consuming task of...
7. Reference Pin on Differential Amplifier

I want to use a differential amplifier to separate the digital and analog ground portions of a circuit, but am not confident in my understanding of the datasheet of the amps I have on hand (amp03). http://www.analog.com/media/en/technical-documentation/data-sheets/AMP03.pdf I think that...
8. HeNe Laser Power Supply Components

I recently salvaged a Melles-Griot HeNe laser from an FTIR system. I neglected to save any of the electronics except for what I think is the step-up transformer attached to the laser tube. The laser is "05-LSC-708-540" and the transformer is "05-LPM-850-045". I have a 12V power supply, but was...
9. Breit-Rabi Formula Derivation for j=1/2

1. Homework Statement Derive the Breit-Rabi equation in the case that the quantum number j is equal to 1/2, specifically the 1S_1/2 state of Hydrogen. This is the equation describing hyper-fine and Zeeman splitting of the energy levels in an applied magnetic field. 2. Homework Equations We...
10. Approximating H Wavefunction Circular State for Large n

1. Homework Statement We are studying circular states of the hydrogen atom (states where the l quantum number is = n-1). We are asked to evaluate \langle \Psi_{n,n-1,n-1}| r_{n,l=n-1}|\Psi_{n,n-1,n-1}\rangle . The wave function is that of the hydrogen atom, and the thing we are taking the...
11. Starting Motor Without it's Starter Capacitor

I found a motor I think is from an old AC unit in the recycle. It is a 1/4 HP, 265V, 1.20A AC motor. I've been looking to make a low-torque sander and was thinking about using this as a a drive motor. I know the starter capacitor is there to provide an initial burst of current to get it up to...
12. Force Computer ATX Power Supply to turn on Without Motherboard

I'm trying to re-purpose an old Compaq (and another HP) ATX computer power supply to use as a lab PS. I've seen tons of articles on line about how to do this, for example. I can't get it to even start up though. I have the power-on pin from the ATX connector that goes to the motherboard shorted...
13. Four Tensor Derivatives -- EM Field Lagrangian Density

1. Homework Statement Given the Lagrangian density \Lambda = -\frac{1}{c}j^lA_l - \frac{1}{16 \pi} F^{lm}F_{lm} and the Euler-Lagrange equation for it \frac{\partial }{\partial x^k}\left ( \frac{\partial \Lambda}{\partial A_{i,k}} \right )- \frac{\partial \Lambda}{\partial A_{i}} =0...
14. Graduate Internship Decision

Hi All, While applying to fellowships last semester as a first year grad student, I also applied on a whim to the AFRL Scholars internship program. I got an offer from them this summer to work on Rb and Ca Vapor Cell Clocks. It's a paid 12-week summer internship, and there are no associated...
15. Creation/Anhilation Operator Commutation Relation

1. Homework Statement Simplify the following commutator involving the creation and annihilation operators. [a^{\dagger}a,a \sqrt{a^\dagger a} ] 2. Homework Equations I know that [a,a^\dagger] = 1. 3. The Attempt at a Solution I think I should be trying to put the creation operators to the...
16. Creation/Anhilation Operator Exponential Commutator Relation

1. Homework Statement Given that the function f can be expanded in a power series of a and a^\dagger, show that: [a,f(a,a^{\dagger})]=\frac{\partial f }{\partial a^\dagger} and that [a,e^{-\alpha a^\dagger a}] = (e^{-\alpha}-1)e^{-\alpha a^{\dagger} a}a 3. The Attempt at a Solution I've...
17. Kindle Paperwhite For Science Documents

Hi all. I'm considering buying a Kindle paperwhite (E-ink) for reading publications, textbooks, and some fun reading. Does anyone own one, and have an opinion on how readable the text, equations, and figures are? If so, do you feel the screen size is adequate? ~\$100 is about the most I have to...
18. Mathematica Mathematica: Getting part of a list, lithin a loop.

When I use the code directly below, it works (indicated by the "Out:..."). tmp2 = Flatten[{33, {1, 2 + j, 6}, 55}];(*Out:{33,1,2+j,6,55} *) tmp2[]; (*Out: 6 *) But when I use it inside a loop, it acts like the tmp2 list is not the correct size: For[j = 0, j <= 5, j++, tmp2 = Flatten[{33...
19. Commutator of a Cross Product

1. Homework Statement Given that \vec{V} and \vec{W} are vector operators, show that \vec{V}\times \vec{W} is also a vector operator. 2. The attempt at a solution The only way I know how to do this is by showing that the commutator with the angular momentum vector operator ( \vec{J}) is...
20. Mathematica Mathematica Globally Define Variable as Real

I want to write a line of code at the top of my .nb and have Mathematica treat the specified variables as real only. I've tried using "Assumptions" and "Assuming", but it just won't work. I still get back answers where the entire expression is returned inside the Re[ ] command, like it is...
21. Harmonic Osclillator Purturbation Matrix Elements

1. Homework Statement I am trying to follow Sakurai's use of perturbation theory on a harmonic oscillator, 2. Homework Equations Perturbation: v=\epsilon x^2 , \epsilon << 1 Matrix elements: V_{km}=<k|v|m> 3. The Attempt at a Solution The book says that all other matrix elements besides...
22. Series solution to nonlinear differential equation

1. Homework Statement By truncating the differential equation below at n=12, derive the form of the solution, obtaining expressions for all the ancoefficients in terms of the parameter \lambda . 2. Homework Equations The ODE is: \frac{\mathrm{d^2}\phi }{\mathrm{d} x^2} =...
23. Mathmatica Bisection Root Finding

1. Homework Statement Write code in Mathematica to find the root of f(x) = \int_0^x \frac{\sin (t)}{t} \, dt-\frac{\pi }{2} using the bisection method. I have attempted to do this using: f[x_] := N[-(Pi/2) + Integrate[Sin[t]/t, {t, 0, x}]] (*Plot[f[x],{x,0,2*Pi}]*) fg =...
24. Schools Engineering Graduate School Competitiveness

Hello, I'm a recent physics graduate (BS) who is having second thoughts about spending the next 5-6 years of my life in a physics PhD. program. I thought I wanted to do applied physics, but to keep options open I would like to include some engineering schools in my mix (will be applying...
25. Spring 2014 Internships?

Hi all, Does anyone know of any research opportunities for out-of-state students during the spring 2014 term? I am a senior physics major, graduating this semester (early). I have applied to many NASA programs through it's OSSI application, and the DOE SULI programs, but did not get in. I...
26. Good (not elite) School in Boston

Hello, I have someone who has a decent chance at gettign into MIT/Harvard that I want to be close (same city preferably) to.I am most interested in experimental condensed matter, AMO, and applied physics. Could anyone give me an idea of the best schools for these in the area that are not...
27. Grad School Resume - Include Poster Sessions?

Hello, I am applying to graduate schools in physics, applied physics, and engineering. On my resume, I would like to know if people feel I should include summer research (REU,SULI) presentations, and poster sessions I have attended. The most important poster session would be one for the...
28. Schools General GRE Math Score Importance to Engineering Schools

Hello, I am a physics major who is going to graduate soon, and am taking the general and physics GREs. I am looking at both physics and engineering graduate schools. I believe that the physics GRE is pretty much irrelevant to engineering schools, but I have had difficulty with the...
29. Calculate new boiling point with change post-pressure change

1. Homework Statement Liquid X boils at 127C, at a pressure of 10.6*10^5 Pa. Its enthalpy of vaporization is 5000 J/mol. At what temperature will it boil if the pressure is raised to 1.08*10^5 Pa? 2. Homework Equations \frac{dT}{dP}=\frac{l}{T(v_{B}-v_{A})} 3. The Attempt at a Solution It...
30. Poynting Vector Direction Confusion

1. Homework Statement I am trying to understand why, in an example in Griffiths E&M (3rd ed, 8.1) says that the Poynting vector of a current carrying wire that is being heated via resistance (Joule heating), has a Poynting vector pointing radially inward. The E field is parallel to the wire...