Short Definition and 505 Threads

Homework Statement i was told that the friction loss is significant in short pipe , but not so significant in long pipe . However , the friction formula is given by formula f(L/D)(V^2)/2g , as L is big , friction loss is big . so the friction loss is big , right ? Homework EquationsThe...

Homework Statement I'm trying to understand the dependence of short circuit current and open circuit voltage on illumination. Short-circuit current is due to the generation and collection of light-generated carriers -- so does that mean the short circuit current is linearly dependent on...

Hi friends , today we are just general talking with my boss. and he asked me a question . and that is, if we have equipment that is rated short circuit current is 40kA. for 1 sec. and if we must have to use that same equipment for 3 sec time. that how much short circuit current they can...

I have been looking at some of the theoretical physics programs in the UK and a lot of them seem to be very short 9 months to a year. It just seems insane to learn so much material in such a short amount of time. Is the material covered in the same depth as many U.S. universities? Can someone...

my book gives a number of short questions, one of which seems trivially simple. Is my solution correct or am I missing the point? 8. If p(x) is irreducible and has degree 2, prove that F[x]/<p(x)> contains both roots of p(x). Soln. Let the two roots be a and b. F(a) is isomorphic to...

Is there any research that was done on animal long and short term memories? And short of empirical analysis, if there is none, is there much we could conclude, based purely on what we know about their brains? For example, from knowing which brain parts deal with explicit and which with...

Just a curiosity about what happens to the flux, when you short circuit an induction machine. Say there is an initial flux and you're rotating the shaft of an IM and then you short circuit the stator, so no doubt you'll get large currents in the stator, but those large currents, will they cause...

Hello everybody, How do you like the short story "They're Made Out of Meat" by Terry Bisson? http://www.terrybisson.com/page6/page6.html Apparently, this has been circulating online for a very long time already, but I only discovered it recently. Although the story is very short and simple...

Hi folks, I would like to clarify few doubts on my mini-project as mentioned below: I am designing a small kit using a transistor (2N3904) and an OP-AMP (LM741- Voltage follower) with few resistors connected to them. My power supply voltage value is 5V. Please refer to the below picture for...

Hello all, Guys, I just pointed out that I actually lacking in somewhere in the understanding of the phenomenon of diffraction of light, of which I am aware from no less than 10 years. Recently I revised Huygens wave theory of Light and studied in what ways Newton criticize it. At one of the...

Hi, So we're doing this Lab on Transient reactance of a synch generator and I'm reading Sarma's classic: Electric Machines Steady-state theory and Dynamic performance p. 474-479 But I can't see how to get the actual exponential time constants for the sub-transient and transient reactances? Thanks

In short circuit it is said that there is no resistance. So the current produce heat and wire is burnt. But as the rise in temperature increase the resistance then in short circuit heat must rise the resistance. How can we say there is no resistance in short circuit?

Hello Guys, This is my first time posting here - just wondering if anyone has some insight on a project that I am working on. I want to be able to temperature control an insulated shoe box sized volume at ~5 degrees Celsius for about 20 minutes. The main constraints are that I would need the...

$\newcommand{\Z}{\mathbb Z}$. Question: Let $m$ and $n$ be positive integers. What are all the abelian groups $A$ such that there is a short exact sequence $0\to \mathbb Z/p^m\mathbb Z\to A\to \mathbb Z/p^n\mathbb Z\to 0$. It is clear that any such abelian group $A$ has cardinality $p^{m+n}$...

peterdonis submitted a new PF Insights post A Short Proof of Birkhoff's Theorem Continue reading the Original PF Insights Post.

Hi everyone! I'm a sixth form student currently writing an EPQ (5000 word essay) on artificial intelligence. I would appreciate it if you could spare five minutes of your time to take this short survey. I hope you find it interesting. <<link deleted>> Thank you for your time! Rob

Hello, I'd like to create a list of short, intensive physics and/or math courses offered around the world. I'm primarily focuses on the U.S. as that is where I live but for the sake of completeness, anywhere would be good. The courses I'm looking should be short, usually 1-3 weeks in length and...

I'm asking because I'm slow when it comes to mathematics in Physics exams , and I was wondering if Universities cater for people who are slow thinkers by making Physics exams longer than high school exams?

Hi everyone, just wondered if anyone knew about presencial open programs/courses/events/certifications available to engineering students in general, preferably in the areas of mechatronics (controls, electronics) or aerospace engineering. I'm an engineering (undergrad) student from Mexicali...

The way that my undergraduate career went, I had the opportunity to finish a MS at the same time as my BS within 4 years and now believe I will now have an opportunity to continue my MS to a PhD. I've heard that this typically isn't very good for employment opportunities, but would this be the...

suppose a side of an equation : 26q+1 , and i want the least positive integer value for q that makes this side of equation divisible by 7, is there any short method to do this ?

http://en.wikipedia.org/wiki/Exact_sequence Let's look at the following short exact sequence: 0-->A-->B-->C-->0. Since the sequence is exact, the mapping from A-->B will be invective and the mapping B-->C will be subjective. The wikipedia article says that we can think of the mapping A-->B as a...

i know that short circuit is when current is max while resistance is zero and open circuit is when resistance is infinite and current is zero, but in terms of voltage, if i have a part of circuit and i want to know whether it is short or open circuit and i only know : the voltage and if the...

Consider a Lagrangian: ##L(x,x',t)## Define now: ##L'(x,x',t) = L + x ## We have seen that Lagrangians can differ up to a total time derivative of some function ##F(x,t)## in such cases and give the same equation. When checking explicitly these two give different equations. Why would it be...

I'm reading about short circuit current in a solar PV cell and I am a little confused. The short circuit current is defined as the current across the solar cell when there is zero potential difference across the cell. At this point the short circuit current is equal to the light current. What...

The equations are incredibly difficult, so I'm just after a general idea of how the force on a magnet bellow a coil changes with the distance to the coil. Shown bellow: Axial symmetry: o x o x cross section of coil o x o...

I had a small question, which one contributes more to evolution: 1)short term adaptation and heritable 2)long term adaptation and heritable ?

Hi everyone, Basic question here. Residential pole mounted transformers and many other transformers that produce a neutral have that neutral "center taped" from a current carrying coil in the transformer and bonded to ground. My question is why doesn't the current in the coil short threw that...

Homework Statement A short circuit test is performed on a small single phase transformer. The results are: Primary Voltage 5V, 60Hz Primary Current 2A Secondary Current 10A Primary Power 8W a) Making suitable approximations deduce the primary/secondary turns ratio (single number)? b) Making...

So I noticed a mistake in the mathematical analysis in a paper and I want to propose the revised version. What should I do? I think it doesn't worth a journal since the revision probably only takes a page. Is there other ways of doing such revision? I have heard there is this short...

Hi All, New to the forum. I am a lineman by trade so I have an understanding of physics as it applies to not getting yourself killed when setting telephone poles and line tension. I am also a short track inline roller speed skater and they just announced that they will be allowing 125 mm...

Hi, It's been a while but from what I remember when you short circuit a transformer, electrically it's like you've series'd up the coils and shorted the magnetisation branch. And when you open circuit a side of the TX it is like the current flows through a side then through the magnetisation...

Homework Statement Which of the following are self-contradictory combinations of circuit elements? - A 2 Amp current source in parallel with a short circuit. Homework Equations KVL- "the sum of voltages around a closed loop amounts to 0. KCL- "the current into a node equals the current out...

I am reading Adhikari and Adhikari's (A&A) book, "Basic Modern Algebra with Applications". I am currently focussed on Section 9.7 Exact Sequences. On page 391 A&A state and prove the Short Five Lemma. I need help with some of the details of the 'diagram chasing' in the proof. The Short Five...

I just uploaded a post on the class SE of short exact sequences in Mod_R ... and tried to use Latex Code to achieve the same fancy script for S and E as Paul E Bland used in his text "Rings and Their Modules" ... but seemingly did not achieve the right script for S (E seems OK, or at least...

I am reading Paul E. Bland's book, "Rings and Their Modules". I am trying to understand Section 3.2 on exact sequences in Mod_R and need help with the proof of Proposition 3.2.7. Proposition 3.2.7 and its proof read as follows:I am having trouble in understanding the proof that condition (2)...

I am reading Paul E. Bland's book, "Rings and Their Modules". I am trying to understand Section 3.2 on exact sequences in Mod_R and need help with the proof of Proposition 3.2.6. Proposition 3.2.6 and its proof read as follows:The part of the proof that perplexes me is the section of the proof...

[FONT=Arial]In a Google image search image search for "Ricci Flat manifolds" I came up with Calabi-Yau manifolds for dummies at, http://universe-review.ca/R15-26-CalabiYau01.htm Lots of pictures and important terms. Other good stuff there as well, click on home button.

Homework Statement Consider a Rossby wave propagating in a homogeneous ocean with a water depth of 4,000m at 35o N latitude. If the wave length of this wave is 500km, is this a long or short Rossby wave? Homework Equations shortwaves: |kx-1| <<RD longwaves: |kx-1| >> RD kx is the x-component...

Homework Statement So this is a small part of a much larger problem that I'm working on that I don't want to post here. Basically, I want to find the contribution to the torque about the hinge of a ladder BY the mass of the ladder itself. A ladder is propped open at an angle α. What is the...

I seek to build a vacuum chamber for shipping radon contamination sensitive samples. The cylinder will have a height of approximately 2 inches, and needs an inner diameter of 10 inches. The plan is to weld stainless steel pipe to a plate on the bottom, and to have a lid bolt on to the pipe with...

Greetz all I am trying to find a short story which I recall as being in a Heinlein collection but that may be wrong. The story revolves around 2 main characters - a scientist and an investigator- in some fictional future in which all scientific explorations and study is rigidly controlled by a...

The day after the contest ended, we had nice weather... here's a few that were a day late and a dollar short:

What does it mean when I have to find the second derivative of a circle at a given point? (Implicit diffing) In specifics, the equation is 9x2 +y2 =9 At the point (0,3) You don't really need the rest at all, but it was just my process. This seems to make no sense. first D'v 18x+2yy'=0 Second...

Homework Statement Find the equivalent resistance of the circuit shown below. Homework Equations R=\Sigma_{i}R_{i} 1/R=\Sigma_{i}1/R_{i} The Attempt at a Solution I'm having a lot of trouble understanding how this circuit can be simplified. All I see is a big short circuit where the...

The at rest distance between Betty the astronaut and a flag in open space is 1 unit. If Betty approaches the flag at constant speed while laying out metre rulers, will she have laid out 1 unit of at rest rulers when she reaches the flag? Or will the number of rulers laid out exceed 1 due to...

Dear All: I like to write and I’m a physicist myself. Right now, I’m currently outlining a short sci-fi story called “Borrowed Time”. It goes as follows: In the near future, science has conquered the technology that allows the manipulation of the flow of time. Space and time limitations, as...

Hello! I want to induce a (weak) signal in a wire across the room from me. I was just wondering, how would I go about doing this if I couldn't touch the wire and couldn't modify the equipment to accept these signals BUT was close and in line of site of the wire?

Hi,let: 0->A-> B -> 0 ; A,B Z-modules, be a short exact sequence. It follows A is isomorphic with B. . We have that tensor product is right-exact , so that, for a ring R: 0-> A(x)R-> B(x)R ->0 is also exact. STILL: are A(x)R , B(x)R isomorphic? I suspect no, if R has torsion. Anyone...

Hi everyone, I am working with a solar cell realized with a metal-semiconductor junction. I need to find an expression for the short circuit current of this solar cell, but in the literature I have only found models for the standard case of a pn junction solar cell. Does anyone know a...