Rules Definition and 516 Threads

I'm getting confused with the problems that ask you to find potential and when to use the rule that the sum of all the V = 0. There were a lot of questions in my physics book that ask to find a potential in each capacitors and when i was doing those, i just used V = Q/C instead of Kirchhoff's...

Problem: Two automobile batteries are connected in parallel to power a wheelchair. If each of the batteries has electromotive force 12V and internal resistance r=0.025Ohms, and the the wheelchair motor has resistance R=1Ohms, find the current provided to the motor. Attempt at solution: So I...

[b]1. Calculate the three currents indicated in the circuit diagram below. I have attached the diagram. How would I use Kirchhoff's laws to find the currents I am getting thrown off by the third loop.

Homework Statement In this video; the uploader states at 0:47 that there are three rules. 1. Can swap rows 2. Can multiply a row by a constant 3. Can add a multiple of one row to another Do these rules apply only to rows? Can they be applied to columns? The uploader has not stated...

Hi I am reading about transition in Helium, and I have come across a question. It is clear that triplet-singlet transition are not allowed, i.e. ΔS=0. But in my book (Foot's Atomic Physics) it says that Δl = ±1. This is what I don't understand. The selection rule Δl = ±1 we derived for...

There's something that doesn't make sense to me regarding these two rules. I was hoping someone could pat me on the head and tell me that everything was okay, and that both Slater's Rules and Hunds rule were actually complimentary and correct. So when beginning to explain Slater's Rules...

I really need help. I actually don't know how to do this Use Kirchoff's rules to determine I1, I2 and I3 for the following circuit: Circuit figure https://chip.physics.purdue.edu/protected/Prelab221img/e4pp2.jpg E1 = emf = 9 V r = internal resistance = 1.5 R1 = 5 R2 = 15 R3 =...

I have recently seen my Grade 7 brother's maths homework script and I was shocked to find out that he was marked down for not writing down '(Answer)' next to each of the results for his problems. Also, I found out that he was marked down for writing just 'the cost = ...' and not 'the cost of...

I understand that a(b/c) = \sqrt[c]{}(a^b) so this suggests that (-1)(2/3) \sqrt[3]{}((-1)^2) = -1 right? Wolfram alpha and my calculator disagree.

From what I've gathered, certain physical states cannot exist in superposition. When applying the Schrodinger equation to a quantum system, do we get the relevant superselection rule results, or will it produce an answer giving two physical states in superposition, when according to the...

I wanted to know if there are any rules for interpreting mathematical expressions. If we succeed in interpreting a mathematical expression as a physical reality we will make math more friendly and very interesting. What are the rules for interpreting math expressions?

I'm trying to do the following problem: ie. I'm trying to use the Feynman rules for momentum space to write down the mathematical expression that the diagram is supposed to represent. However, I don't feel very confident in what I've managed so far. Now as I understand it, these diagrams...

Question: You have 100 coins. 99 are fair and 1 is double sided. You pick a random coin and flip it 10 times and get 10 heads in a row. What is the probability that you picked the double sided coin? Response / help needed: Probablity of picking a 1 sided coin = .01 Probability of heads 10...

I am detaching this to BSM because it is already getting too much parameters in the bag. What has happened this year is that Werner Rodejohann and He Zhang, from the MPI in Heidelberg, proposed that the quark sector did not need to match triplets following weak isospin, and then empirically...

Homework Statement Calculate the current through the resistor of resistance for circuit B. Express your answer in terms of EMF, R1, and R2. http://imageshack.us/photo/my-images/163/screenshot20111112at110.png/" Homework Equations Kirchhoff's Loop and junction rules The Attempt at a...

Homework Statement A 1.0 g bullet is fired into a 0.5 kg block attached to the end of a 0.6 m nonuniform rod of mass 0.5 kg. The block-rod-bullet system then rotates in the plane of the figure about a fixed axis at A (the figure shows a vertical rod labeled A at its top. A block is attached...

Superselection rules claim that some superpositions are physically impossible. But why are they so? Consider an example from another thread: But why such a superposition makes no sense physically? Clearly, if such a state has been produced from a charge eigenstate, then such a...

Homework Statement Given the following integral and value of n, approximate the integral using the methods indicated (round your answers to six decimal places): \int_0^1 e^{-3x^2} dx n = 4 (a) Trapezoidal Rule (b) Midpoint Rule This is the only one I'm having trouble...

Can someone refer me to Feynman rules for electroweak interactions in the general case of SU(2) multiplets of weak isospin n and weak hypercharge Y interacting with EW gauge bosons? I can only find the standard rules for SU(2) doublet electron - neutrino. Thanks!

If you are given part of a period of a Function, what rules would you apply to draw out the full function, so that it converges as quickly as possible as a Fourier series? thanks

Why is it that you are able to have 1 initial value problem with 2 solutions, but not 2 initial value problems with 1 solution for an ODE? Is there a theorem that states this?

For some reason I am struggling with these problems. I am lost as a goose trying to fly south for the winter! Homework Statement 9^(5-x2) and another derivative problem using chain rule r/square root of the whole term r^2+5 Homework Equations 1st equation= d/dx= a^x ln a 2nd...

I hope its not a problem if I don't have an actual problem. I have a question about partial fractions. When I spilt it into two, the numerator of the original is equal to unknown constant A times secondimerator, plus unknown constant b times first denominator. What if it is spilt into three...

Recent searching of the light from the quasars indicate lack of the quantum fluctuation of the spacetime. http://arxiv.org/PS_cache/arxiv/pdf/1108/1108.6005v1.pdf Does it mean the lack of quantum foam rules out the discretness of the spacetime too ? How to explain Casimir effect and...

There are several rules in calculus which have far reaching applications in field of mathematics, physics etc. unfortunately there is no derivation or visualisation of those rules in my maths book. SO SHAME!. one of these is that definite integral of function from x1 to x2 gives geometrical...

Homework Statement Determine the current in each branch of the circuit shown (here:) [PLAIN]http://img811.imageshack.us/img811/5084/physicschapter2817.jpg Homework Equations Kirchoff's rules, I think is (and I'm probably looking at it wrong): summation of ΔV around closed loops is 0, summation...

I recent.y received a polite warning about a 'jumbled" post. I will try and restructure it. My problem is that I do not speak the same language you do. the numbers do not mean to me what they do to you. So I have to use terms or phrases that will convey my thoughts. In simplistic...

Hi all, I'm trying to calculate the Feynman Rules for the effective electroweak chiral Lagrangian. For example, this is the first term in the Lagrangian: \begin{eqnarray} \mathcal{L}=\frac{v^2}{4}\text{Tr}(D_{\mu}U D^{\mu}U^{\dagger}) \end{eqnarray} where \begin{eqnarray}...

Homework Statement y = ln | sin x | Homework Equations - The Attempt at a Solution No attempt at a solution, because it's more of a "which part of this is incorrect" question. y = ln | sin x | Would everyone agree that this is equivalent? y = ln \sqrt{(sin x^2)} Then...

Homework Statement Let an be monotone sequences. Prove or give a counterexample: The sequence cn given by cn=k*an is monotone for any Real number k. The sequence (cn) given by cn=(an/bn) is monotone. Homework Equations The Attempt at a Solution On the first one, I don't...

The US Supreme Court ruled that http://www.supremecourt.gov/opinions/10pdf/08-1448.pdf. A few things were notable about this decision. For one thing, Scalia and Thomas were on opposite sides of the issue (they almost never disagree on decisions). Secondly, Alito should be commended on his...

I've been thinking about some of the topics where the rules change. For example, - before Plank time - in the core of black holes - at the quantum level - others Do these events/regions/horizons suddenly experience a change in the rules or is it a more gradual change? If some of...

Homework Statement Find the derivative of g(t)=\frac{1}{\sqrt{t}} I cannot use any derivative rules on this problem. Just the difference quotient. It's from the Stewart book (6E, Chapter 3, problem 26). Homework Equations Difference Quotient The Attempt at a Solution Here is where I am at...

Homework Statement Remember to show your working explicitly throughout your answer to this question. (a) (i) Use the Composite Rule to differentiate the function f(x) = (x^2− 6x + 23)^(3/2) (ii) Use the Quotient Rule and your answer to part (a)(i) to show that the function: g(x) = (x −...

Homework Statement f(t) = t^2- \sqrt{t} Find f'(t) Homework Equations Difference Quotient The Attempt at a Solution f(t) = t^2-\sqrt{t} \lim_{h\to0} \frac{(t+h)^2-\sqrt{t+h}-t^2+\sqrt{t}}{h} \lim_{h\to0} \frac{t^2+2th+h^2-\sqrt{t+h}-t^2+\sqrt{t}}{h} \lim_{h\to0}...

Consider question 1 in this paper: http://www.maths.cam.ac.uk/postgrad/mathiii/pastpapers/2002/Paper65.pdf How do we "read off" the Feynman rules? I can see that the interaction terms give contributions \lambda_3 , \lambda_4 , \lambda_6 to the relevant 3,4 and 6 point vertices respectively...

Consider equation 5.46 in these notes: damtp.cam.ac.uk/user/tong/qft/qft.pdf (i) why does only one term have the i \epsilon in it? I thought this was because the (p-p')^2-\mu^2 term can never vanish but this doesn't make sense since the \phi particle will have momentum p-p' and since momentum...

I'm not always on the same computer, often times I'm using my phone to look for answers when doing physics on the go. Does anyone know a good, correct resource for ALL of the tree level feynman rules for QED+EW+QCD? Feynman gauge would be preferred, or ungauged. I can find most for the...

Hi All! I am trying to get used to Mathematica and rules and all things syntax. What I am trying t do is this: If I define a variable as such m = Solve[x^4 - 4 == 0, x] The output is: {{x -> -Sqrt[2]}, {x -> -I Sqrt[2]}, {x -> I Sqrt[2]}, {x -> Sqrt[2]}} So I believe what this means...

It seems like there has been a couple of times in the history of physics when we have observed something that seemed to break the rules of accepted theory. What do think were some of the most surprising discoveries in the last 50 years or so that broke the rules of what what we thought was possible?

triple product is given by A.(B x C) = B. (C x A) = C. (A x B) so why is ∇.(F x G) = [∇ x F].G - F.[∇ x G] ? if i let A = ∇, B = F , C = G, then ∇.(F x G) = - F .( ∇ x G) = G.(∇ x F) its as though they carried the 3rd term over to add to the 2nd term ?

Homework Statement If each capacitor is filled with a dielectric material (with constant K, kappa), what is the new equivalent RC circuit? All resistors have equal value, and capacitors have equal value (without a dielectric), C. Homework Equations C = (Epsilon * Area) / Distance C with a...

Can someone please explain the basic rules that must be adhered to when using Gauss-Jordan Elimination? I've been having some difficulty with it because apparently I keep doing things that you aren't allowed to do. So far, I know only the following: -You CAN multiply an entire row by a...

I have come across in the solution to a question. -(y^2-1)^(1/2)= (1-y^2)^(1/2). However I do not know why this has to be the case, and would appreciate anyone showing me, presumably using rules of exponentials, how this could be shown to be true. Similarly if the power is not fractional but...

http://www.damtp.cam.ac.uk/user/tong/qft/qft.pdf Consider the Feynman rules for Green's Functions given at the top of p79 in these notes. Now let us consider the diagram given in the example on p78. Take for example the 2nd diagram in the sum i.e. the cross one where x1 is joined to x4...

Please note the following from the posting guidelines https://www.physicsforums.com/showthread.php?t=5929 Let me make this clear. If you accuse another member of lying, you will receive an infraction. This rule applies as do all other rules regardless of any personal opinions that one...

To quote Gokul: "Name your favorite politicians at the national level, and tell us why you like them - this thread is relevant to members from all countries." Why am I doing this?... I'm curious as to whether the presence of restrictions beyond the PF norm is conducive to a different kind of...

Hey guys, does any of you know where I could find the Feynman rules for scalar QCD? If they where colour ordered, even better! Cheers, earth2

I was wondering where i could find a source for the rules to find Kc from a chemical formula? My professor tonight was changeing the formula like this: H2+Br2+2HBr then showed that 2H2+2Br2=4HBr...and getting different Kc values for each. I think that this is straight out wrong but she's the...

Homework Statement f(x) = (x-1) 2/3 We were asked to find the derivative using the alternate limit form when c = 1 and then I was then I was trying to find the derivative using the multiplication rule (u dv + v du). Homework Equations f'(u*v) = u dv + v du f'(xn) = nxn-1 The...