Convention Definition and 184 Threads

Hey all, The way I was taught GR, the summation convention applies on terms where an index is repeated strictly with one covariant, one contravariant. But reading through a translation of Einstein's GR foundations paper just now it looks like the index placement doesn't matter (I've seen it...

Homework Statement One mole of an ideal gas at 300K expands isothermally from a pressure of 2x10^6 Nm^-2 to a pressure of 2x10^5 Nm^-2. Calculate the work done ON the gas. Homework Equations dW = PdV The Attempt at a Solution Following through the integral, it becomes clear that work is...

Unintuituve naming convention: "para-" denotes antiparallell? I did a project a week ago that required studies of the helium atom. Depending on if the two electrons spin are parallell or anti-parallell it is referred to as orthohelium (parallell) or parahelium (antiparallell). Intuitively I...

Homework Statement Determine which of the five sources in Fig. (attached) are being charged (absorbing positive power), and show that the algebraic sum of the five absorbed power values is zero. I've labelled how I'm referring to the sources in red...

Homework Statement I solved the problem, but upon further observation, I discovered that what I did didn't make sense. (these are rounded numbers, which shouldn't make a difference in my question) do = 13 cm (do is what I solved for in the problem, and according to the online system it was...

Homework Statement Calculate the power in the voltage source for this given circuit: Homework Equations P = \frac{V^2}{R} Or P = - \frac{V^2}{R} The Attempt at a Solution If we take the bottom left corner as the Initial node then and go around the circuit, then the voltage is a...

I'm studying Lie groups using G. 't Hooft's tutorial: http://www.phys.uu.nl/~thooft/lectures/lieg.html In page 34, he introduces superscript and subscript indices starting from equation 6.27: \phi_{\alpha} \rightarrow \phi_{\alpha}' = X_{\beta}^{\alpha}\phi^{\beta} What is the...

Hello, It's my first time login. I'm not good at english. Of course, I'm not native speaker. I wonder why we call 'passve' sign convention. have a good day. :)

a positive charge, q, moves a distance d from position a to b under an electric field <------------E <------------ <---a----b---- <------------ <------------ <------------ what is the change in potential? This is more of a question of notation. Should the change in potential be...

is a turbine an example of convention? (because it is a fluid or gas) are vents an example of radiation? are heavy drapes an example of conduction? are window tints an example of radiation? because it is a reflector of heat are white tiles and paint an example of radiation?

turbine-convention? (because it is a fluid or gas) vents-radiation? heavy drapes-conduction? window tints-radiation? because it is a reflector of heat white tiles/paint-radiation?

Hey guys, was sitting through a physics class today and something bothered me. They referred to the p material of a diode as being the anode and the n material being a cathode. Being a chemistry student I am aware that the cathode is + while the anode is -ve. Why has it changed around, due to...

I'm curious about how people here view Einstein's prescription for determining simultaneity in an inertial frame, and how the extension of that approach to other inertial frames spawns the Lorentz transformation. It seems to me the competing pictures here are that this is an arbitrary way (in...

What is the rationale for the sign convention in the space-time 4-vector? How is it related to the sign convention in the energy-momentum 4-vector, if at all?

Homework Statement In a wye connected circuit with a balanced UPF load, what is the phase displacement between the line voltages and current for an ABC and ACB phase sequence Homework Equations n/aThe Attempt at a Solution My trouble is I can't find anything pertaining to the "syntax" of...

[SOLVED] Sign Convention - Physics - Optics I was just looking at some sign conventions and I was wondering if this is true: Along the principle axis, if Si > 0, then does that mean you have a real, inverted image? Also along the principle axis, if So < 0, then does that mean you have a...

Einstein Summation Convention / Lorentz "Boost" Homework Statement I'm struggling to understand the Einstein Summation Convention - it's the first time I've used it. Would someone be able to explain it in the following context? Lorentz transformations and rotations can be expressed in...

Hey guys, I need some help clearing up voltage signs, its always confusing me and I have my final this Friday. First off I'm not talking about voltage in a circuit, but rather if there is an electric field caused by a charge distribution. First off, I understand potential energy for gravity...

Hello: I need help determining if I and V assignments follow the passive sign convention. Here is the image of the circuit: http://img178.imageshack.us/img178/9572/pic1xu2.gif I know that in order for it to follow PSC the current I needs to flow towards +V. I'm not sure if that is...

This is my (error full?) understanding from my readings: 1. positive current flowing into a positive terminal of let's say a rechargeable battery is power being absorbed by the battery...so positive watts 2. negative current flowing into a positive terminal encounters the higher electrical...

Homework Statement http://online.physics.uiuc.edu/cgi/courses/shell/phys102/fall06/prep2a.pl?practice/exam1/fa06 Homework Equations W =F*D The Attempt at a Solution I have it solved, now i thought - would be if i put work into the thing to move it but looking at it since both of...

I'm having a lot of difficulty understanding a really simple concept in my first year physics text. See the diagram below... http://www.avhq.com.au/~metrosexuality/ele_pass_conv.JPG "First, consider Figure 1.5-1a. When the current enters the circuit element at the + terminal of the...

In terms of the thermodynamic identity: dU = {\tau}d{\sigma} - pdV the term for the work done on the system (-pdV) must be positive if there is a compression, in which case dV would be negative, correct? If one wanted to write the identity in terms of the work done *by* the system, you...

This bothers me every time I study circuits, currently introductory level. I can solve problems just fine, but something is just not "clicking" here. Mostly conventions for things like current, power absorption, etc... Is there some where an explanation of what actually happens in a...

Why not make a gun that shoots bullets that have a rather large core of Rubidium or Cesium with say a thine copper jacket that blows off inflight thusly exposing the Rubidium or Cesium and causing big troubles for the poor guy who it hits. As it would virtually be melting in the air and burning...

I was reading the electronic notes for my class on finite automata and the professor defines something as the smallest set having certain properties. The thing is that all sets having those properties are countable infinite. But there is a potential ordering, because all sets having those...

Just a friendly reminder, the first postulate of the special theory of relativity, namely that the speed of light c is the same in all inertial frames, only holds true in view of Einstein's clock synchronization convention. There is no experimental basis whatsoever for preferring this convention...

"There is evidence that suggests the 311th MI personnel and/or translators engaged in physical torture of the detainees," a memo from the investigator said. The January 2004 report said the prisoners' rights under the Geneva Conventions were violated. ... According to the report, the abuse...

Hi Could someone point me to websites with tutorials on the real-virtual sign convention for geometric optics (and possibly other known conventions too)? I've been googling for some time but the results aren't too satisfying. PS--Tutorials with mathematics are preferred... Thanks and...

Watched a disturbing report on bbc of a us soldier killing a seriously wounded person (through a window) in a room with no escape thought to be an insurgent in Fallujah, it was very cold hearted/cowardly and sickening . Surley this must violate the geneva convention. This must have been...

God Damnit, The ****ing Republicans Closed Their Convention With An Evangelit Prayer! OH MY ****ING GOD! The Republican National Convention just ended with a congressman from Georgia/Evangelist leading a large group prayer about the glory of god and all that crap, GOD DAMNIT, THEY HAVE NO...

Is the closed interval [a,a] considered a legitimate notation for the set {a}? Would (a,a) denote the empty set?

Hi! I'm new to this forum. The index of refraction of a medium can be expressed as n'-jn" or n'+jn" as per the convention chosen for the phase advance in time(n" stands for absorption). Am I right in saying that the complex reflection/transmission coefficient calculated as a function of...

I just saw Donald Rumsfeld on TV, complaining about the way Iraq treats the American soldiers it has captured, sating it is against the Geneva Convention on POWs to put them on TV. Personally I think his real problem is the demoralisation of US troops from such things. But the important point...