Confused Definition and 1000 Threads

Hi, I'm trying to teach myself a bit about spinors, mainly from reading about geometric algebra. There is something that I can't figure out though. According to GA, spinors are elements of the even graded subalgebra, so scalars, bivectors and so on. But the electromagnetic field is a bivector...

See link: http://www3.interscience.wiley.com:8100/legacy/college/cutnell/0471713988/ste/ste.pdf. When defining surface tension, the article makes reference to a C-shaped apparatus. Why is γ = F/2l and not F/l? It says something about there being two surfaces, but it seems to me that because...

Hi I'm confused about voltage and it would seem every student before me has also been confused abotu voltage if you read all the internet forums :) From I = V/R if you increase the voltage you increase the current, so you get a greater amount of charge passing a point at a particular...

So I've been confused about transformers lately. In searching for some information regarding the basic transformer, I came across this: http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/transf.html#c1. While this page was informative, I am still left confused in regards to one point in...

Hi I'm doing some work on finding the derivative of an inverse function and getting a bit lost, probably because I am confusing myself with the inverses. So i think i need to clear up the inverse part before I move on to the calculus bit. You have the function f(x) = 1/3x3 - x2 + 5x -11...

The question might be simple for you guys but the problem is that it is not for ME ! I have a circuit and I have to determine the node voltages by Nodal Analysis method. And the one which I learned was in cases when we had a current source, I could simply write the equations using KCL...

Okay so today i sat a AS level physics paper and after finishing the exam i looked threw the equation booklet and decided to do some manipulation and i came up with this and was wondering what you guys think of it. I am confused! :) E=hc/λ AND λ=h/mv subbing in gives E=hcmv/h which is E=cmv...

Hello everyone, Ok I'm no longer worried about why Newton's third law is occurring. Doc Al advised me in the last thread to look at some action reaction pairs instead, and I think that is what I needed to do. Ok I'm having difficulty understanding Newton's third law when two objects are...

okay. i recently had a forum asking about gear ratio that has me so confused on the concept of ratio that it hurts. if you have a 40 spline gear and a 20spine gear. and ur power input is on the 40 spline gear. doesn't that mean the 20 spline gear will rotate twice every time the 40 spline...

hi there, now I've been googling around for ages now trying to find this answer but i cant i have read time and time again that a nucleus always has less mass than the sum of the masses of the nucleons in it. This is put down to the binding energy, this is where i get confused surely if it...

I understand the general aspects of how a hard disk drives works. I have gone deeper and have learned about the various types of magnetoresistance, both AMR and GMR. I understand the fundamentals of how these systems work compared to older units. But people keep telling me that the data...

Normally this is a very easy task, but i just can't get this one right. the data set is 14 14 14 15 15 15 15 15 15 16 16 16 16 16 16 17 17 17 18 25 And i get Q1 and Q2 right at 15 and 16, but i keep getting the upper quartile as 17, when it is meant to be 16.5. Can...

Hello there, I am so confused about the term battery specific energy (in Wh/kg) and specific power (in W/kg) Actually, I know what it means by power and energy, of course P = E/t But looking at the text, which quotes like "Ni-Cd batteries have high specific energy (than Ld-acid) but...

i was told the binomial theorem is as follows: (1-x)^n = 1-nx+ (n(n-1)/2!)x^2 - (n(n-2)/2!)x^3 ... not sure if this is right could some one clear this doubt for me any help is appreciated was told this in a physics class

Hey, This is kinda a thick question but never mind. A car travels 30KM and that for 30mins. What is the average speed of the car?Formula is Average speed= Distance Travelled DIVIDED BY Time taken. But its not 30 DIVIDED by 30 is it? Is it 30 DIVIDED by 0.5 as 30mins is half of an hour? And how...

Ok it says I am to computer using a series accurate to within 0.001. I'm really not sure where to start. Do I integrate this first by parts? Or am I thinking about this too much? Could someone point me in the right direction please! Help would be much appreciated!

Hello, I am currently on a gap year after having finished my A-levels here in the UK. I hold offers from Imperial College and Manchester for their "Physics with Theoretical Physics" courses. I have the option, if I go to Manchester, to switch to the "Mathematics and Physics" course, which is...

In the process of deriving .\nabla^2u(x,y). in polar coordinates I am confuse how to work through the steps. The first step from the book is to find \frac{\partial u}{\partial x} Standard partial differentiation is at follow: \frac{\partial u}{\partial x} = \frac{\partial u}{\partial r}...

Make matrix defective if possible and identify the values of alpha. \begin{bmatrix} 3\alpha & 1 & 0\\ 0 & \alpha & 0\\ 0 & 0 & \alpha \end{bmatrix} Skipping the boring stuff we obtain (\alpha-\lambda)^2(3\alpha-\lambda)=0 as the characteristic polynomial. \lambda_1=\lambda_2=\alpha and...

Homework Statement I'm so confused about how to use the right hand rule..there are so many different sources telling me different things...like i need to use the RHR to like find the direction of the magnetic field using the current (and nothing else)..like i followed my book, and they said to...

Confused about light! Hello everyone, I'm confused about light. I know when a photon with certain matching energy comes, it excites the electrons to a higher orbital, and releases a photon when it comes back. 1. What happens to the orginal photon that lost energy? 2. I then read about...

My notes give the variational principle for a geodesic in GR: c\tau_{AB} = c\int_A^B d\tau = c\int_A^B \frac{d\tau}{dp}dp = \int_A^B Ldp and then apply the Euler-Lagrange equations. By choosing p to be an "affine parameter" where \frac{d^2 p}{d\tau^2} the Euler-Lagrange equations are...

Homework Statement Consider a force field F = c(iy - jx). From the force field calculate the work required to move a particle from the origin to the point 2i + 4j without acceleration along the two different paths: From the origin to 2i then to 2i + 4j From the origin to 4j then to 2i + 4j...

hi, we all know when we derive the time dialtion formula we choose a vertical light clock, and basically since the light take a longer zig-zag path to the stationary observer, the time is dilated. That's ok but when deriving length contraction, firstly we accept time dilation for horizontal...

Homework Statement I'm dealing with densities of liquids. When using the formula P = Patm + ϱgh, where ϱ is the density of the liquid, what should the units of ϱ be? Homework Equations The Attempt at a Solution I have P in kPa, so just looking at the units gives: kPa = kPa +...

In the section shown here http://sites.google.com/site/juliansrealativity/_/rsrc/1271044270997/home/time-from-stationary.bmp" is the right hand side of the equation intended to refer to light in the moving frame, or to light in the stationary frame ?

Homework Statement I just finished solving about 10 different DEs, but this one has me totally confused. It says: (R)dQ/dt + (Q/C) = 0, with initial condition Q(0) = Q_0? Most of the problems I've done thus far have looked like: y' + (2/t)y = (cost)/(t^2), with initial cond y(pi) = 0 and t>0...

I have to plot the period t² vs the length but now i am confused which goes on the x-axis and which goes to the y axis, i was wondering if someone could help me out with this issue

Hello, We know that to calculate the orbital velocity we use the relation : Vo=2* pi* r /time of one cycle but if we want to calculate the orbital velocity when a body moves from the point a to the point b on a circular path we use the relation : Vo = The line segment ab / time...

Hi, I've been a bit confused with how the equation Vp/Vs = Np/Ns came about. From reading a physics textbook, I understand that the voltages came from the emfs ε (primary) and ε (secondary). The primary voltage through the primary coils causes a change in magnetic flux which induces an emf...

Background: Math & Physics undergrad Reason for asking: So I was trying to understand semiconductor diodes and realized it all hinged on the PN junction which in turn is worthy of attention because of the effect created by the depletion zone. As I continued on studying up on this I began...

Homework Statement Basically, i was told to describe the physics involved with a person who just happens to be falling out the sky...However, I'm a bit overwhelmed as to where i should start off Human mass: 54kg Earth's gravity: 9.8m/s^2 Air resistance:?perhaps negligible or would that...

Homework Statement A transformer has 500 turns in its primary coil and 4000 turns in its secondary. (a) What will be the voltage in the secondary if the primary voltage is 110? (b) If 5 amperes flow through the secondary circuit of the transformer, what will the current in the primary be...

Rocket flies from Earth to a star, 4.5 light years away, at 8.66C (the actual numbers are irrelavent, so they might be wrong). When the rocket gets up to speed, instantly, the distance between Earth and the star contracts to about 2.3 light years. So the journey only takes about 3 years...

Quite confused. I've read the book/online definitions yet I suppose I may need a simpler explanation. Lets say I have a table of x y values. x 1 2 3 4 5 y 6 7 8 9 10 how would I carry out the linear least squares fit of the data to determine the slope and y-intercept?

Hello, When you read, you see that there are different opinions on the question, does a photon have mass? From what I think, I know that a black hole's mass increases when it consumes photons, and everybody knows that a photon has energy and momentum. Since energy can be trasformed to...

I confused how memetics works.. Could you share your knowledge?

Homework Statement Calculation of the number of moles of IO3- used in the titration(i.e. in the Erlenmeyer flask): KIO3(s) → K+(aq) + IO3-(aq): balanced eqn of dissolving KIO3 in water 1. Calculate the moles of KIO3 used: Molecular weight of KIO3 = 214.0011 g/mol...

Hi, I have a pretty elementary question, but I'm having trouble finding an adequate explanation on the web. I'm trying to figure out how a carburetor works, and am having difficulty figuring out how a venturi tube works. On the one hand, as air flows through a narrow section of a pipe, it...

Hi, first off - Go easy on me, I'm only learning :redface: My book is talking about linear independence. As I understand the concept it means that a vector has to be in a different direction, i.e. non-collinear, with the vector in comparison. Mathematically, my book has defined...

I am confused about something, this isn't homework I was just fooling around with complex numbers, and found this: e^{2\pi i}=1 so ln e^{2\pi i}=ln 1=0= 2\pi i Can someone explain this? the 2\pi i=0 part...I must have done something illegal...

Hello; What is the relationship between the two? Are they proportional or inversely proportional to each other? I ask this because my physics teacher said that they were proportional on one day, then inversely proportional on another day. I thought that more current = more voltage... am I...

Hi, I am incredibly confused about second derivatives of the metric. I know that in general, the covariant derivative of a vector is given by \nabla_a v^b = \partial_a v^b + \Gamma^b_{ac}v^c and I think I understand how to generalize to higher rank tensors (just decompose into an...

What is the smallest switching time of a transistor ? ! :confused:

I'm teaching myself QM and have a question about a problem in my text. (If this makes it homework, sorry to post in the wrong forum). Basically the question is about three observables A,B,C. They obey the following rules: [A,B]=0, [A,C]=0, but [B,C] not equal to 0. So this is like the...

hi there, I'm trying to plot r against \phi by solving the following ODEs using runge-kutta. The problem I'm having is with the square root. How do I know when it will be positive and when it will be negative? If this is a simple question I apologise I'm not that great with the maths :). E and...

Very confused...need a not so urgent help! Hello everyone, Im new to physics forums...well to anything other than online gaming forums...So if this topic has been already posted please tell me so i can redirect this topic and merge it with them. I am a space loving (space travel and...

Hi everyone, I'm a final year student majoring in physics in china, but I feel very confusing about my future. since I have not applied for any master or PhD program this year, I plan to work for a year before I make any decision regarding my study next year. Personally I am interested in the...

Homework Statement I understand the maths... I'm here to ask WHY we have to do it this way. The question states: "The power dissipated in a resistor is given by P= E^2/R. If E=200 and R=8 , find the change in P resulting in a drop of 5 Volts in E and an increase of 0.2 Ohms in...

Hi everyone, i really don't understand the philosophy of BC/AD notations.. but i only know the order goes like this: ..., 3 BC, 2 BC, 1 BC, 1 AD, 2 AD, 3AD, ... Now in which year we are now... when we say 2010, will it mean 2010 AD?? Why historians always prefer to say in BC AD notations...