Doubts Definition and 192 Threads

Hello, everybody First some context: I live in Argentina and I'm a few months away from starting my first year of college. In here they make the distinction between Electrical Engineering and Electronics Engineering (and then there's also Informatics Engineering which I think is the equivalent...

Hi, I have a couple of questions on photoelectrons. When a photoelectron of about 3-eV (varies) interacts within 0.2-um depletion region of silicon, what happens? I know, it will generate an electron-hole pair with an efficiency of 1 for 3.6-eV photoelectron. But what happens if the...

First doubt: The impedance Z is defined how Z = R + j X and the reactance X can be wrote how: Source: https://en.wikipedia.org/wiki/Electrical_reactance So, by analogy, the admitance Y is defined how Y = G + j B and the susceptance B can be wrote how what? So: B = \left( \frac{\omega C}{1}...

About Electric field due to an infinitely long straight uniformly charged wire my book says the assumption that the wire is infinitely long is very important because without this we can not take vector E to be perpendicular to the curved part of the cylindrical gaussian surface.I think it should...

In my book following points have been given 1-due to conservative nature of electric field ,the electrostatic field lines will not form any closed loop.I want to ask how forming a loop makes if non conservative? 2-Field lines have tendency to contract in length (longitudinal contraction )like a...

Two hollow spheres, both the mass and radius R M , which are rotating around a center of mass ( CM ) , with an initial period To, are kept distant from each other by an ideal wire with a distance of 8R. At a given instant a motor is driven by wrapping the wire and making the two spheres meet...

It's not clear to me how I can balance the following equation, most of all because of K which I don't know how to deal with: \mathrm{SO_2 + K_2Cr_2O_7 \to Cr_2(SO_4)_3 + SO_3} [this is the text of the exercise] It's acidic solution for sulfuric acid, so the equation can be better written so...

Homework Statement [C2O4]-2 ------> CO2 Find if the reaction is oxidation or reduction and determine the no. of electrons lost or gained by carbon. Homework EquationsThe Attempt at a Solution I started with finding the oxidation states of both elements. It's 3+ and 2- for carbon and...

Hello everyone,Has anybody already did the computations to reach equations 10.41, 10.44 and 10.45 in Peskin's book? It would be very much appreciated and useful.

I read that nebulae are formed by stars exploding and they are also thought to be the birth place of stars. Stars explode when all the hydrogen atoms are fused into heavier elements and they are no longer able to fuse heavier atoms right ? If that's the case then the nebulae should contain...

Well, recently I have started to deal with electronics and I've seen several new concepts such as ohm's law, parallel and series circuits, what's AC and DC and many other topics. Ok, I have no doubt on what's direct and alternate current or what a series and parallel circuits are; rather than...

What are the rules for choosing main branch ? Wikipedia states - "Identification of the parent hydrocarbon chain. This chain must obey the following rules, in order of precedence: 1 It should have the maximum number of substituents of the suffix functional group. By suffix, it is meant that...

Hey Everyone, So I was set. I studied and re-took the pgre. I thought long and hard about what I wanted to do in graduate school. I thought about career goals. I talked to professors and graduate students. I even submitted two apps! Two schools that I would be extremely happy to attend...

Could somebody explain the logical reasoning behind lorentz contraction when an object travels faster and faster ?

Homework Statement Homework EquationsThe Attempt at a Solution I did a source conversion on the right-most 1A current source to get a voltage source to work with for this question. However, when I tried to work out the solution, my values seem wrong, but I don't understand why, especially...

Hi there! After giving a thought about this phenomena I came with some doubts and I thought that maybe it was a good idea to put them all together in one thread so I don’t star many discussions simultaneously and also because maybe their answers are related. So here I go: a) As they...

Hello. I'm Bruno, a Brazilian High School graduate that loves high school (and everything I had the capacity to learn) Physics. I plan to pursue a career in Physics, and found some troubles. I did a post on this troubles first (as I didn't read my inbox :P), so if there is anyone out there who...

I hope I do not extend myself here. I am a Brazilian High School student, graduating this year, that plans to pursue a Physics undergraduate in the United States. Since I started High School I decided on my degree; I love physics and my ultimate dream is to research the depths of the field...

Dear All, Please see the attachment for the text i will be referring to. what does "I = τ1 · · · τm, where each τj is a transposition acting on {1, . . . , n}. Clearly, m != 1, thus m ≥ 2. Suppose, for the moment, that τm does not fix n". what does fixing n mean in a...

why should Proca eqn be like ∂γ Fγμ + m2 Aμ = 0 but not ∂γ Fμγ + m2 Aμ = 0 ? another doubt is (λ-1 ω λ)μγ = λ-1 ρμ ωρσ λσγ ? why in λ-1 transformation got upper index in the second place but not in the first place? if someone clear my doubts...I would be thanful... regards.. Kau

Homework Statement I just have some conceptional doubts and it would really be appreciated if some one would answer! Q1. What is net contact force? Q2. Does it have friction as one of its components? Q3. Is it any way similar to normal force? Homework Equations The Attempt at a...

Homework Statement I need some help regarding the gradient operator. I recently came across this statement while reading Griffith's Electrodynamics "The gradient ∇T points in the direction of maximum increase of the function T." Wolfram Alpha also states that "The direction of ∇f is the...

Hi. According to this page and other sources I found the z-component of the electronic magnetic moment is greater than the classically calculated value due to relativistic effects. Which makes me wonder: 1) What about the x and y components? I am completely lost as to why only the z axis...

(1)If the limit of f(x), as x approaches a point a doesn't exist, and the limit of g(x), as x approaches a point a doesn't exist either, the limit of (f+g)(x) and (fxg)(x), as x approaches a point a can possibly exist? (2)If the limit of f(x) as x approaches a and the limit of (f+g)(x), as x...

I understand the basic concept. A small change in the base current will lead to large change in the collector current and will lead to amplification. But the question is, the small change in base current is brought by input signal or the biasing? Also the coupling capacitors allow only the ac...

Apologies if this has been discussed in other threads already. I did a quick search on 'chain fountain' and got no hits. If you coil a length of chain into a container and let it slip out over the lip under its own weight, it will start to form an arc through the air, without touching the lip...

Hello! This is my first time starting my own thread and I have spent a lot of time reading other threads and posts about Physics grad admission. My post is not really about "WILL I GET ACCEPTED?" per say, but I just need a place to write about how I feel and for some reason I feel like doing it...

1) While plotting input characteristics of a transistor, we choose to keep output voltage constant and plot the variation of input voltage and current. Why do we choose to keep output voltage constant and not current? 2) While plotting output characteristics of a transistor, we choose to keep...

Homework Statement Well actually we were doing a beam experiment in class. It consisted of varying the position of a load and measuring the reactions to eventually analyse the relationship between the distance of load from 1 support with the 2 reactions. The reactions were provided by two...

in a classroom teacher are asked doubts on the topic taught by students . they are critical in helping their understanding of concept. what can be the extra information that may be useful for the teacher that can be asked along with the doubts in an doubts query form?

Hi everyone, this year i'll get my Bachelor Degree in Computer Engineering, i have some doubts about the master course to get; actually my university offers these courses in accordance with my Bachelor Degree: (i'll write only those who catched my interest) - Computer Engineering ...

I actually have solved the problem and received the answers that the book provided. However I am second guessing what I did, This is the problem: let rho v be 10/r^2 mC/m^3 between 1<r<4 let rho v be zero elsewhere a)find the net flux crossing the surface at r=2 m, r= 6m b)determine...

Hi all, Say I am solving a PDE as \frac{\partial y^2}{\partial^2 x}+\frac{\partial y}{\partial x}=f, with the boundary condition y(\pm L)=A. I can understand for the second order differential term, there two boundary conditions are well suited. But what about the first order differential term...

A body with mass 'm' moves with velocity 'v' possesses momentum and the magnitude of momentum of the particle is given by product of its mass and its velocity Who came up with this idea? On what observation leads to think him like this? I know that Newton's 2nd law states that force is nothing...

i am using textbook in classical mechanics by douglas gregory. It is known that rate of change of displacement with time is velocity , but it is given that the velocity at any instant is the equal to the product of speed and its unit tangent vector at that instant in vector form i.e, V=vT (this...

Considering d=2 or d=3, the Ising model exhibits a second order phase transition at the critical temperature T_c, where the system goes from an ordered phase (spins preferably aligned in a certain direction) to a disordered one. This is reflected by the behaviour of the susceptibility, similar...

Hello, I've been studying mech engineering for the past 2 years but over the past month I've been reading about other people's ME program and I'm not sure if mine is good enough. Would anyone be kind enough to tell me what subjects you took or are taught commonly during ME? Also, sorry for...

Hello! I have a few doubts in circular motion and I'd really appreciate your help :) 1) There is a statement in my book ( I have attached images - the first one) according to which the only horizontal force towards the center on the vehicle is friction. I know that some centripetal force is...

Hope someone can help me clarify a couple of issues about Ehresmann connections and vertical spaces. My main issue is how to define the tangent space at a point in a _general_ fiber F in a fiber bundle (and not just when F is either a vector or a manifold If I understood correctly)...

I have a few questions pertaining to some concepts in electrostatics, I'd be grateful if someone would help me out. 1) When we place a positive point charge inside a hollow conducting sphere, at its center, field lines emerge uniformly from the sphere. Okay, easy enough. Now, if we place the...

Stokes' Theorem says the curve integral of any surface S simply equals the counter-clockwise circulation around its boundary-curve C.How can this be right? Let's say you have a hemisphere surface S with centre in origo, and its shadow on the xy plane. Both surfaces will have C as their boundary...

I am just introduced to basics of superconductivity in Engineering Physics. My lecturer asked a question: Is the resistance of a superconductor zero or close to zero? And my answer was close to zero. I have read that the resistance of a superconductor is exactly zero, but then when I put some...

according to equvalence principle,acceleration can be equvalent to rest in which gravitational field exists. Earth revolves around the sun as sun produces curvature in space-time. What kind of acceleration is the curvature of space-time produced by sun equavalent too?

Hello friends, From special theory of relativity,it is understood that if two events are simultaneous to a stationary reference frame,it is not simultaneous to a reference frame that is moving uniformly in straight direction. Is opposite possible? That is are two events are simultaneous to a...

Hello everybody, First, sorry for the bad english, it is not my language. I have a few theoretical problems and I would be very thankful if you helped me. 1º: I see the graphic about covalent bonds and potential energy a lot of times and they always say that potential energy...

I have some doubts on topics related to rotation, so I thought I'd make a single thread rather than multiple ones. 1. Why are the Coriolis and Centrifugal forces "fictitious"? I think I might be getting confused by the terminology, but do they represent physical forces? My lecture notes say...

Doubts in "Epitaph of Stevinus". I have attached the link for the image- http://1.bp.blogspot.com/_YthztMsYjr4/TMB3Wmis2fI/AAAAAAAABR4/xBmLusI58AU/s400/epitaphofstevinus.png I can understand that the weight of the body should be proportional to the length of the line. What I can't...

I'm having a lot of "simple" conceptual doubts when I try to study eletrodynamics in a qualitative way. Look at the circuit below http://img802.imageshack.us/img802/5349/suidbfhksdbgsdfg.png First we have a capacitor and a generator of voltage V (A). We wait until the capacitor is fully...

I have some conceptual questions regarding capacitors and dipole antennas. Consider a parallel plate capacitor made with two conducting plates, initially uncharged. If I connect each plate to a different terminal of the battery, charge will start to flow from one plate to another. Consider...

Doubts regarding 3 question form motion of a particle! :) Homework Statement Doubts related to 3 problems..I have uploaded the question up in the attachment. Homework Equations The Attempt at a Solution for question one,the body doesn't come to rest,s is the total dist at any...