What is Sources: Definition and 537 Discussions

A tertiary source is an index or textual consolidation of primary and secondary sources. Some tertiary sources can be used as an aid to find other sources. The exact definition of tertiary varies by academic field.
Academic research standards generally do not accept tertiary sources as citations.

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  1. J

    Engineering Thevenin Resistance complex circuit with dependent sources

    I am attempting to find Rth in the circuit attached however, I am totally lost. My work gets so messy and i seem to run around in circles. Can someone please explain to me how they would do this problem. Any help would be greatly appreciated
  2. L

    Dependent sources - can the gain (g) be negative?

    So the goal in this case is to find k, the gain of the dependent source shown as a diamond. Formula for dependent voltage sources: V=g*V0 In this case V=k*Va I would get a negative value for k, because k=V/Va=-10V/(0.2A*10Ω)=-5 But can you have a negative value for k? Is that possible? Or...
  3. K

    Doppler effect and multiple independant sound sources.

    If I am stationary and a sound source moves towards me at a constant velocity, I will hear it (the sound) increase in frequency until it is adjacent to me and then as it moves away from me, I will hear a decreasing frequency. Fundamental stuff right? It works with radio waves and light which is...
  4. cocopops12

    Two different voltage sources in parallel....

    What would happen if this circuit was implemented practically with batteries? This circuit makes no logic to me because how can the same node be at two different electric potentials?. But i tried thinking about it and here's my 'naive' explanation: The 12V battery will start supplying a...
  5. dexterdev

    Solving Audio Sources Doubt - Devanand T

    Audio sources doubt... hi all, I don't know where to post this. sorry for that. My doubt is that if there are 2 audio sources like one mp3 music file playing from a cd player and another speech signal coming from a radio. If I can hear both signals, what is the resultant audio...
  6. K

    Finding the Current in a circuit, with series opposing voltage sources.

    Homework Statement V1-12V V2-9V R1-4 Ohms R2-7 Ohms R3-8 Ohms Each current has to be found when the switch (k) is both open and closed. Homework Equations The Attempt at a Solution I can find each current when the switch is open, however I'm confused at what would happen when it becomes closed.
  7. S

    Physics help please - Sources of error in lab experiments

    Physics help please -- Sources of error in lab experiments Ok so i need some help with a few labs.. some I've tried out and a few i just can't get.. what i want to know is whether the limitations and sources of errors that i wrote down for each of these labs are correct or not and what i could...
  8. C

    What are the uses of current sources?

    Hi everyone, In our undergraduate electrical course,we came across current sources as theoretical concepts. Are current sources used in real life(such as in electronics)?How important are they? Thanks in advance. Chander
  9. M

    How can I find reliable sources of information on the LHC and its experiments?

    I'm sorry that this is probably in the wrong place, but I couldn't find a place to post where I am allowed to start threads which was relevant. I'm hopefully starting a degree in particle physics next year, I'm currently in my last year of high school. Myself and one other student at my...
  10. JJBladester

    Finding resistor's voltage with current and voltage sources present

    What is the voltage across R2? You should convert the 4 V source and resistor into a current source as your first step. The first thing I did is create a second current source out of the 4 V voltage source and the series resistor R2. I called it I_2. I_2 = E/R_2 = 4V/100Ω = 40 mA...
  11. F

    Funding sources outside of the department (Graduate)

    Greetings, this is my first post here. I just graduated with a B.S in Physics and will be attending a university for a M.Sc program (Terminal degree there). I will be receiving a state university grant, additionally there are TA/GA positions that I am applying for. I will also...
  12. T

    Sources on explicitly time-dependent Hamiltonian formalism

    Not sure I am posting this in the right subforum, if this is not the case, please feel free to move it. Anyway, the title about sums it up - I need to find a good source which offers a thourough treatment of Hamiltonian formalism for the explicitly time-dependent case - could someone possibly...
  13. M

    Sources for Crystal Models (FCC, BCC, etc)?

    I have been acquiring some nice molecular models of graphene, buckyballs, and things like the model below. http://www.indigo.com/images/product/172.jpg One thing I have not been able to find are crystal models with the different orientations like face-centered cubic, body-centered cubic...
  14. A

    What websites/magazines/news sources do you check daily?

    Just looking for some good science/engineering related reading
  15. M

    The inverse square law for point light sources inside an opaque medium

    Hello all, I already know that the radiant intensity of a point light source falls off with the inverse square of the distance to the source. This, however, only happens in a vacuum. My question is, what is the more general law for a point source inside an opaque medium with a known...
  16. R

    Having trouble understanding sources of hetroscedasticity

    Hey. Iam trying to understand how specification of the equation can lead to hetroscedasticity. This is stright out of my notes. Yt=B1+B2x2t+B3x3t+...+BkXkt+\gamma\varpi+ε^{}_{t} Yt=B1+B2x2t+B3x3t+...+Bkxkt+ε^{*}_{t} where ε^{*}_{t} = εt + \gamma\varpit Since Var(εt) =...
  17. B

    Calculating beta for two moving light sources

    Question Two monochromatic light sources approach each other head-on with equal speeds, v=\beta c relative to the laboratory. When they pass each other, the frequency of the light each receives from the other is halved. Show that \beta =3-\sqrt{8} Attempt at solution I have tried to...
  18. M

    Voltage and Current Behavior in Parallel Circuits

    Hello Everybody, My question is: Why when a resistor is in parallel with a "short circuit" the voltage across the resistor is zero, & so will the current passing through it? But when instead of a resistor we have a voltage source, this is not the case? "I was informed that the voltage source...
  19. L

    How are sources of AC power matched in a common grid?

    Not being an electrical engineer, I have always wondered how sources of AC power are matched when joining a common grid. I assume the power is generated at 60 hertz from each source but how is the match made so sources are in phase with one another? For instance, suppose an individual could...
  20. M

    Thevenin Equivalent with dependent sources

    Homework Statement See attached image Homework Equations Thevenin's theorem Node voltage method? The Attempt at a Solution So if I want the current Io, I believe I need to treat the 1K resistor as an open circuit in finding the Thevenin equivalent. I think setting ground to be the bottom...
  21. M

    Gradient Flow - Definition and Sources

    Hi all, I am struggling to find any elementary material on the "gradient flow of a functional" concept. From introductions in advanced papers I seem to have understood that, assigned a functional F (u), the gradient flow is charactwerized by an equation of the type Du / Dt = P u , where P...
  22. P

    Thought experiment with two point sources of light

    You are in a dark room with no other sources of light The walls are painted black, so no light is scattered from walls You have two point sources of light of equal power + same height about ground They are 10 feet apart You stand a thick rod vertically in middle of two, and 4 feet in...
  23. D

    Power from one or both of 2 sources

    Hi all, Apologies if this is the wrong place to post this but I can see lots of similar questions on this forum which aren't a 100% match for my question. I want to add a new interior light to my car. I want it to be on either when the headlights are on (power from the illumination circuit of...
  24. E

    Are there any peer reviewed sources of a theory which calls for a smaller

    Are there any peer reviewed sources of a theory which calls for a smaller... Are there any supported theories that call for a smaller, more accessible cosmos? Is anyone important suggesting that our fundamental understanding might be so wrong that we have an incorrect idea on the size and...
  25. S

    Using source transformation for dependent sources

    Hi all , is it possible to use the source transformation for dependent source ..? i guess yes because i came across a problem which asks to use source transformation to find Vx as shown : http://img571.imageshack.us/img571/2389/50111057.jpg and my solution was ...
  26. M

    Maximizing Efficiency: Applying the Chain Rule in Differentiating AC Sources

    Homework Statement Chain/product or quotient Homework Equations v=4sin^3 (4t) The Attempt at a Solution NB:@ Means teta(spelling might be wrong) 4sin^3 (4t) = 4sin (4t).sin (4t).sin (4t) using sin^2@=1-cos 2@ /2 v= 4sin (4t). (1-cos 2@ /2) = 4sin (4t)/2 . 4sin...
  27. M

    Loking for Gear Motor Sources

    I am looking for somewhere to get a gear motor for a very low budget project, specs as follow: Voltage = prefer 110v, could be 12 if the price is right RPM = 15-20 Torque = 100 inlb Quiet as possible Reversible Something else that would be a bonus: Soft start and stop, gradual start...
  28. xpell

    Why are there so few detected extrasolar neutrino sources?

    Hi, I've just registered in the forum because I have a couple of Physics questions. I'm not a specialist, and furthermore English is not my mother tongue, so please be indulgent with me. As far as i know (please correct if not), only two sources of natural 'extraterrestrial' neutrinos have been...
  29. T

    Where to find sources on Full Adders

    Where to find sources on "Full Adders" Ok. So I have been reading and watching this stuff on 4 bit computers. I understand how to read binary code however I am having trouble with the concept of the "full adder" This is what I have been reading first off Does anyone know of a better...
  30. J

    Asking for your sources of images of the whole earth.

    Hello there, I am a Norwegian image maker. Unfortunately, I find discrepancies between photographs of the Earth from the Apollo missions (such as the blue marble) and images from the space shuttle and orbiters, which I cannot explain. They vary from the appearance of the atmospheric scattering...
  31. N

    Help! Can't Find Primary Sources for Lab Report

    Hi. I've been having problems finding some primary sources for my lab report for days. I've used my school's search engines, but I can't find anything appropriate to use. My report will sum up my experiment on how pH affects an enzyme's activity (catecholase catalyzing catechol and oxygen to...
  32. S

    Combining two audio sources, digitally

    I was playing around with some computer code to process some audio. As part of it, I needed to combine the audio from two different sources. Everything is in raw, uncompressed, 16-bit signed samples, at 48kHz sample rate. So now I'm thinking, do I add voltage, or add power? The sample values...
  33. T

    What is the charge on a circular disc with a varying charge density?

    Homework Statement Find the total charge on a circular disc of radius ρ = a if the charge density is given by ρs = ρs0 (e^−ρ) sin2 φ C/m2 where ρs0 is a constant. Are the two limits of integration from 0 -> a for ρ and 0->2∏ for φ? In the example given in the notes, ρ varies, instead of...
  34. Z

    Sources for resistivity of W depending on temperature

    Hello everyone I am trying to do an experiment involving a W bulb, in which I am completely dependent of knowing the temperature-resistivity relation of Tungsten in the temperature range 300 - 2500 K. The CRC handbook has some tables, but they have few data points and correlate poorly with...
  35. E

    Current Sources in Parallel when Simplifying Circuits

    When simplifying a circuit, can a parallel branch with a current source and a resistor in series be considered as just the current source? Also, if two parallel current sources 'point upwards' i.e. toward the positive rail, can I add them together as one source even if there are other...
  36. E

    Solving Dependent Sources in Admittance Matrix

    Homework Statement Hi, i need to find the Admintace matrix and the current voltage vector. i know how to do it if i have only non dependent sources. but how should i work with the dependednt source? s should i take the dependent voltage source and turn it to current source with parallel...
  37. B

    A bit of trouble with Thevenin equivalence with dependent sources

    This really isn't one specific problem per se as it is more of a conceptual issue, so I apologize for breaking away from the given format. I've worked through three problems involving a circuit where a thevenin equivalence circuit is required between two points, and all sources are dependent...
  38. E

    Thevenin equivalent with dependet sources

    Homework Statement Hello, i was studying diodes for my exam on monday, but i had some struggle finding the Thevenin equivalent. Here is the circuit: http://img411.imageshack.us/img411/5336/schakeling.png Homework Equations I have no clue what to put here? The Attempt at a...
  39. P

    Adding more than two coherent sound sources of different phases

    Does anyone know how to add more than two coherent sources that have different phases? An example might be a sound source and a receiver with sound reaching the receiver directly and by two reflections via different paths - maybe off a hard floor and hard ceiling. There's a good document...
  40. S

    Impedance of Parallel Dependent Sources.

    Homework Statement I have this circuit: 0----------C----------0 U1___R C I1 I2 R C ___U2 0---------------------0 That's supposed to be two sets of Resistor, Capacitor, and dependent current sources all in parallel except with a capacitor separating the dependent current sources...
  41. G

    Resolution of distant light sources

    Homework Statement How far away can a human eye distinguish two car headlights 2.1 m apart? Consider only diffraction effects and assume an eye pupil diameter of 5.0 mm and a wavelength of 550 nm. What is the minimum angular separation an eye could resolve when viewing two stars, considering...
  42. S

    Let's Talk About Energy Sources

    I'm curious to know what you all think of the future of energy. What type of energy do you think has the most promise for the future? What role do you think the various engineering disciplines will play? I'm really looking forward to the future of this whole antimatter factor haha.
  43. D

    Thevenin's Theorem : Reason behind 'nullifying' or 'suppressing' sources?

    WHY aren't voltage sources open circuited and current sources short circuited? Thevenin's theorem (and even Superposition Theorem) states that we need to 'suppress' or 'nullify' the effect of all sources. We do this by short circuiting voltage sources and open circuiting current sources. WHY...
  44. S

    Superposition with Dependent Sources

    Almost every EE I've talked to claims that you need to leave dependent sources in when using superposition to solve a circuit. I had a professor in undergrad who used to claim that statement is invalid. I've used his method since I learned it without any concern. I never saw any problem with...
  45. A

    How air molecules still carry acoustic messages when multiple sources present?

    We know that air molecules are subjected to random motion in different directions. A sound wave is a push toward these molecules to make a wave front to make them expand or contract in groups so that we can hear a voice message in our ears. The question is that what happens when different...
  46. M

    Possible energy sources that a lunar base might have as an option

    So I am doing research for the different energy sources that might be available for a space base in about fifty years from now. Some of these energy sources would likely be solar, fusion, fission, Nuclear, and I heard of radio - nuclide as well. What else could be used? In addition, does...
  47. B

    Calculating Magnetic Field from Two Perpendicular Currents

    Homework Statement Wire #1 carries a current of 8.0A along the +x-axis. Wire #2 has a current of 6.1A along the +y-axis. What is the magnitude of the magnetic field at the point (1.4,1.3)m Homework Equations I'm not sure if Long straight conductor will be the right formula to solve for...
  48. M

    Thevenin and Notron Equivalen sources, external to load

    Homework Statement Solve power dissipated by RL Find a new values for RL that will receive maximum power solve for the maximum power that can be delivered Homework Equations Nodal analysis mesh analysis superpostion etc.. The Attempt at a Solution Hello guys, I've beein...
  49. E

    Good sources for the 2007 Australian Federal Election

    I'm doing some research on the 2007 Australian Federal Election. I seriously can't seem to find a lot of the things. I would appreciate it if anyone was to provide me any information and/or references. Or even anything else you have in mind.
  50. J

    C/C++ Are there any good sources for learning Java as an experienced C++ programmer?

    I'm an experienced C++ programmer looking to learn Java SE 7. Because of the similarities of the language, you'd think there would be a tutorial out there suited for such people but I'm having trouble finding one. I've looked at a couple of Java tutorials that are tailored to C++ programmers...
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