Sources Definition and 538 Threads

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

    Finding current across a capacitor in a circuit with two AC voltage sources

    Homework Statement Homework Equations My answer: I_C=(\frac{1}{6}-\frac{1}{2j})(cos(2t)+\sqrt{2}cos(2t-0.25\pi)) THIS IS WRONG.The Attempt at a Solution The way I went about doing this was: 1. Ignored V2 and worked out the total impedance in the circuit for V1. 2. Calculated the voltage...
  2. T

    Finding the spiral sinks and spiral sources of a linear system

    Homework Statement Basically, the problem involves a linear system dx/dt = ax + by and dy/dt = -x - y, with a and b being parameters that can take on any real value. Basically, you go through this system for several values of a and b (I did -12 to 12) to find the state at various points...
  3. N

    Navigating Physics I Lab Reports: Principal Results & Sources of Uncertainty

    Hello there, it's my first semester in Physics I, so I'm not exactly sure which is which. If someone would clarify what these are, that would be wonderful. They're for our lab report. - Principal Results - Sources of Uncertainty (in order of importance) This is our first lab...
  4. S

    Engineering Thevenin Equivalent for circuits with dependent sources

    Hi! Good day! I was studying Circuit Theorems when I stumbled upon this circuit that has a dependent current source asking for a Thevenin equivalent. Up until now, I was only familiar with solving circuits with independent sources so this has me having a hard time. I tried using...
  5. N

    Read article on Pulsars, not clear how a sphere sources pole-only emission?

    The pole still has extremely strong gravity, how can a sphere suddenly concentrate the radiation at the pole to be emitted there ? As this is the only exit, should there not be a strong deformation ? How does the radiation make it to the pole, or, is the radiation we are getting only from...
  6. L

    Any good sources for starter motors (without gearbox/solinoid)?

    I'm trying to find a DC motor in the 3-3.5kW 12-24V range (Preferably 24V) for a project that will utilize the motor at maximum power for occasional short bursts of maybe 2-3 seconds in duration at most. The motor needs to be fairly small, lightweight, and CHEAP ($100 or less). Starter motors...
  7. E

    Gravity and Permanent Magnetism as energy sources

    I'm an IT person - non-scientist - but this problem has challenged me ever since high school physics: If two permanent magnets - pole to like pole - repel each other, the magnet suspended possesses potential energy. If a material can be found (that is non-magnetic and without any power...
  8. S

    Can two independent sources of light be coherent?

    Can two independent sources of light be coherent?
  9. A

    Nodal analysis with 2 voltage sources

    Can someone solve this circuit Find v and i in the circuit. I know that we have to make somethng with supernode, but where the supernode is here? How to develop this problem? Please help me :) Btw it is nice forum, today i have found that. I hope I will be able to help you in other...
  10. Holocene

    Our sources of fear/anguish; permitted by the physical universe.

    I believe in something very strongly, and that's that "right and wrong" are human fabrications, and are not tangible constituents to the nature of reality. When a young child is sexually assaulted and killed, consider what no one else ever does; what is the ultimate consequence for the universe...
  11. F

    Why Is the Source Distinction Between E and B Fields Important?

    EM field and its sources... hello forum, a simple question about EM field and its sources. In a time-varying situation, maxwell equations tell that the E field has the time-changing charge density rho as a source, while the B field has the time-changing current density J. But both...
  12. H

    Dual Power Sources: Supplementing Solar w/ Battery

    Hey! I'm trying to create something with some power cells, and I've run into the issue of inconsistent power supply. I'd like to supplement power from a solar cell with a battery, but I'm not exactly sure how to keep the input to something at a set value. Basically, when the solar cell...
  13. R

    Understanding Current Sources in Circuits

    In the following circuit what does the current source mean? Am I supposed to use 3A to determine how much voltage is running across the 10 ohm resistor? If not, how do i determine how much voltage is running across that resistor? i need to know so i can determine the final equation of my set of...
  14. R

    What Should I Major In to Research New Sources of Energy?

    I want to be involved in the research for searching for new forms of energy, to decrease our energy dependence. I am a starting senior in high school, and want to know what I should declare my major as. (As of now, I'm just going to go in as Physics most likely)
  15. A

    Kirchhoff's Laws with 3 voltage sources

    Homework Statement Find the potential differences across the 5 ohm, 4 ohm, 3 ohm, and 2 ohm resistors. Homework Equations 5I_1-4I_2+3-12=0 Left Loop 3-18+5I_3-4I_2=0 Right Loop 12-18+5I_3-5I_1=0 Whole loop The Attempt at a Solution I simplified the first diagram...
  16. M

    Most efficent Portable Energy sources

    Sorry if this is stupid question, but I am just curious. And sorry if I posted in wrong forum but it seemed to um... Fit the most. And sorry if my English isn't perfect :). Ok now, the title might be a bit confusing. What I am looking for are the most efficient energy sources, which are...
  17. N

    Interference of waves from two sources.

    Homework Statement Having a real tough time with this problem was wondering if anybody could help Two identical loudspeakers 2 m apart are emitting 1800hz sound waves into a room where the speed of sound is 340m/s. Is the point 4m directly in front of one of the speakers, perpendicular to...
  18. S

    Monte Carlo and Inverse Monte Carlo - Good Sources for Self Study?

    Hello there, Does anyone know some good sources (preferably on the Internet) for Monte Carlo and Inverse Monte Caro methods (especially the latter)? There is plenty of stuff to find on Monte Carlo, I am particulary pleased with Stefan Weinzierl's 'Introduction to Monte Carlo methods'...
  19. A

    Solve Homework Questions on Point Sources & Mirrors

    Homework Statement 1) A 24 cd point source lamp and a 73 cd point source lamp cast equal illuminances on a wall. If the 24 cd lamp is 6.3m from the wall, how far from the wall is the 73 cd lamp? Answer in units of m. 2) Two lamps illuminate a screen equally. The first lamp has an intensity...
  20. L

    FWHM of radioactive sources confusion

    I am not sure if I should be using this board or the nuclear board but I chose this board because it is for class work. Anyways over the past few months I have been collecting data from radioactive sources (Th-230, Am-241, Po-210, Pu-238). Now I understand that the number of events divided by...
  21. L

    Spectroscopy Light Sources: Books & Web Links

    Can someone point me to good books or good web links that deal with standard light sources (standard lamps to be precise) used in spectroscopy?
  22. C

    Probabilistic complexity classes and acceptable sources of entropy

    (This may be a little bit outside the normal scope of this particular forum. I realized after writing this I didn't really know where to go with questions about computational complexity. Does anyone have any recommendations as to places where this question might be more appropriate? Anyway:)...
  23. I

    Exploring Alternative Energy Sources: What Research is Being Done?

    As we know, nearly all energy we utilized is transformed from matter, such as chem reaction, biochem process, nuclear reaction,... and the most efficient way that could transform all matter to energy now we know is the reaction produced by matter with its anti-matter. But the cost is much...
  24. A

    Frequency changes in respect to moving sources and observers

    I am a little confused about the change in frequencies. I am working on a problem involving a train. The train is moving at a constant velocity and blows its horn at a certain frequency. I know that the frequency heard by those on the train station will be f1= f/(1-(Vs/Vsound)) when the...
  25. J

    What are the main sources of gamma ray bursts both short and long duration

    Hey guys having a bit of problem with my year 1 essay. Would really appreciate any help :) What are the main sources of gamma ray bursts both short and long duration? I know some are from supernovae but where do others come from?
  26. J

    Circular Orbits: Sources of Error & Relationship between T and L

    Hi i am doing a lab on circular orbits similar to this one: http://www.batesville.k12.in.us/physics/phynet/mechanics/Circular%20Motion/labs/cf_and_speed.htm I was wondering if someone can tell me what the main sources of error are, as well as the most significant source of error. Also, i...
  27. S

    Measuring Intensity of Sources of Light

    how do i measure the intensities of different sources of light? eg. candle light, tungsten filament etc.
  28. H

    IC Biasing with Current Sources

    I understand current sources are used to bias IC circuits, but how does the Ro (Dynamic Output Resistance) of the current source (Either simple, Widlar, or Wilson) effect the amplifier? Why is a higher Ro better than a lower Ro?
  29. G

    How Does Current Change with Resistance in Constant Voltage Sources?

    Hey guys I am new to Electrical Eng, i got a question to answer, it says that a variable resistor is connected to a " Constant Voltage Source", how does the current through the resistor changes as its resistance varies from zero to infinity? I also need with the same question, but with a...
  30. F

    Why does the sum of incoherent light sources result in non-zero intensity?

    I was thinking about a collection of monochromatic light sources with a randomly oriented phase - for example in a sodium lamp the atoms will radiate almost independently, so they should act as such a collection of incoherent light sources. Assume for simplicity each light source is classical...
  31. T

    Electricity and Magnetism- Energy sources and power stations

    1. wHAT ARE ENERGY SOURCES AND POWER STATIONS? 2.WHO WAS THE FIRST PERSON TO DISCOVER THE ENERGY SOURCE? 3.WHO BUILT THE FIRST POWER STATION AND WHO DISIGNED IT? 4.WHY DID HE/SHE DECIDED TO BUILD THAT POWER STATION THERE? 5.WHAT DO SOUTH AFRICANS GAIN FROM THAT POWER STATION? 6.IS THERE...
  32. S

    Looking for bulk sources of chemically pure sulfur

    For the last several months I've been trying to locate sulfur in bulk so I can try out something called sulfur casting (lost-wax casting using liquid sulfur instead of molten metal). All I've been able to find is five pound bags of something called soil or garden sulfur at nurseries and home...
  33. Loren Booda

    What are the main heat sources for Earth's equilibrium surface temperature?

    What would Earth's equilibrium surface temperature range be from 1. Internal fission alone 2. Gravitational tidal forces alone 3. Solar radiation alone
  34. F

    Greetings, asking for sources.

    Greetings everyone, I am new to these forums but just by looking around a little I see that it is a community I would love to be a part of. I am a 20 year old students of Informatics technology from Greece. I do realize that what I do is not connected directly with physics or engineering...
  35. P

    English Translations of Original QM Sources: Find Textbook & Papers

    Agree with DeepQ on the use of original sources to clarify basic concepts. (See spin thread.) It is hard, though, to find some of them in English. Any suggestions for such an older textbook? Any suggestions (journals OK) for English translations of de Broglie's thesis, and for Schrodinger's...
  36. E

    Minimum Distance Between Two Sound Sources

    [SOLVED] Minimum Distance Between Two Sound Sources Homework Statement Two sources of sound face each other and emit sounds of equal amplitude and equal frequency but are 180 degrees out of phase. For what minimum separation of the two speakers will there be some point at which (a) complete...
  37. E

    Amplitude of Sound Waves from Two Sources at a Point

    [SOLVED] Amplitude of Sound Waves from Two Sources at a Point Problem. Two sources, A and B, emit sound waves, in phase, each of wavelength \lambda and amplitude D_M. Consider a point P that is a distance r_A from A and r_B from B. Show that if r_A and r_B are nearly equal (r_A - r_B \ll r_A)...
  38. J

    Where Can I Find Affordable Bulk Magnet Wire?

    Hello All, In my projects, I am constantly winding coils and more coils, which all use magnet wire of various lengts and gauges. Most of the stuff, I buy from RadioShack or eBay in50' and 100' rolls. But since I go through a lot of it, I figured it would be worth the money to just buy a couple...
  39. Q

    Interference Pattern: Non-Laser Light Sources

    Is there any way to perform the double slit experiment and see the interference pattern without using a laser? If so, what type of light do you need?
  40. D

    Alternative energy sources to generate electricity?

    Hi there, I have a group project where we are to create (theoretically) a reliable power supply system for rural under developed areas in certain parts of the world. Now our task is under electrical engineering so it must be related to the power and ways to generate power, minimise the cost...
  41. J

    What is the behavior of ideal voltage/current sources in small signal analysis?

    Can someone please explain why ideal voltage/current sources are short circuit for voltage source and open circuit for open circuit in small signal analysis? Any mathematical proof to this?
  42. K

    Non Carbon Renewable energy sources

    Non carbon based Alternative renewable fuel sources..Ideas out side of the Box. #1. WIND POWER using a gigantic wind sock. A Wind Drome. Let's imagine a high tensil lightweight material 1000 feet across and 1000 feet high funneling down to an opening only 10 feet by 10 feet at the small end. (...
  43. A

    Introductory Physics Learning Sources. Reliable?

    I'm currently a Physics B student and I was wondering how you determine whether an online "Physics Tutorial/classroom" source is reliable and trustable based on the information it provides. For example the Physics Classroom. So far it has worked to my advantage but I'm not totally sure whether...
  44. N

    Engineering Determining Thevenin's Equivalent and Vc for Circuit with DC & AC Sources

    Homework Statement Find thevenin's equivalent for the capacitor between node a and b and determine Vc (image attached) Homework Equations I know I can use superposition to get Voc, but when I add the two answers together, can I combine them into a single source or keep them seperated...
  45. Ivan Seeking

    Where Can We Find Reliable News in Today's Media?

    Well, last night Katie Couric may have lost me for good with her ten minute interview with Karen James - wife of the climber found dead on Mt. Hood. I think it was Turbo1 who predicted that she would turn the news into the Today show, and it looks like he may have been correct. When I saw that...
  46. A

    Using Series Resistors for Audio Sources: Is Jumpering Channels Safe?

    My understanding of a passive summing mixer is to use series resistors to limit the voltage from multiple sources so as to not over drive the destination? If you are combining two audio channels say from a VCR and jumper the left and right channel will this have serious reprocutions for the...
  47. C

    Studying Learning Sources: Internet or Books?

    How do you learn new material (internet or books) for courses? Would you think that an individual would learn more efficiently using the internet instead of using books?
  48. V

    CIRCUITS: Three resistors, two Indep. Voltage sources, one Indep. Current source

    Find I in the circuit using the superposition principle: My work so far: I\,=\,I_1\,+\,I_2\,+\,I_3 This reduces down to: 16\,V\,=\,I_1\,(8\Omega) I_1\,=\,\frac{16\,V}{8\Omega}\,=\,2\,A This reduces down to: I_2\,=\,-\frac{12\,V}{8\Omega}\,=\,-\frac{3}{2}...
  49. A

    Finding Magnetic Field Solutions for a Current-Carrying Cylinder?

    the question is that: A long, straight, solid cylinder, oriented with its axis in the z-direction, carries a current whose current density is \vec J. The current density, although symmetrical about the cylinder axis, is not constant but varies according to the relation (the relation is in...
  50. T

    Do Spherical Waves from Point Sources Transform into Plane Waves?

    Hi guys, Let's assume I have a point source in a free field. Now, correct me if I'm wrong on any of the following points: As the spherical waves spread out from the point source, they will tend towards plane waves. Since planes waves lose less intensity with distance than spherical waves...
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