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  1. M

    High power low pass filter

    A friend of mine has a TIG welder, which uses a high frequency signal to make the start of the weld much smoother. He's noticed that the welder seems to be tripping his GFIs (works fine on non-GFI circuits). So, that got me thinking, is it possible to build a low pass filter for something like...
  2. M

    Motor for steering a laser beam

    Hi guys, I'm trying to make a rudimentary projector of sorts using a low power (class 1) laser diode. I'd like to shine the laser onto two mirrors: one would control the horizontal portion of the scan, and the other would control the vertical portion of the scan. My problem is this: what...
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    Laplace transform with time shift

    Homework Statement I need to find the Laplace transform of t*e-t*u(t-tau) 2. Homework Equations and attempt at solution I know the general form of the transform, but my problem is in the time shift of the step function. If both parts of the expression were (t-tau), then I could just...
  4. M

    Computer DIY embedded linux microcontroller

    Hi all! Does anyone know of any good sites for how to build a DIY embedded linux microcontroller? I know that I'll need a processor of some sort (was thinking maybe an ARM device), a ROM for the bootloader and kernal, RAM for the general processing, and a JTAG or programming interface of...
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    Need to drop part of dual major (how employable is EE)?

    Hi guys, I'm looking at potentially dropping my computer engineering degree from my dual degree plan (EE is my other degree). I would still maintain an emphasis in computer engineering for my degree, but do you think by doing this I will be harming my chances to be employable after...
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    Engineering Computer vs. Electrical engineering

    Hi all, I have a big decision to make, and I'm looking for advice from those in the fields. I'm trying to decide whether to be a computer or an electrical engineer. For the moment, I have been dual majoring in both, but due to family reasons, I will be transferring to a new university in the...
  7. M

    Prove two squares and a cube equal an integer

    Homework Statement Disprove or prove the statement that every positive integer is the sum of at most two squares and a cube of non-negative integers. 2. The attempt at a solution I'll call the numbers that can be squares a and b. C will be the cube. The easiest way to disprove something is...
  8. M

    Filter DC and HF gain

    Homework Statement I need to find the DC and high frequency (HF) gain of this filter: http://www.flickr.com/photos/96575810@N00/4420162040/ [Broken] [Broken] (The url is [PLAIN][PLAIN]http://www.flickr.com/photos/96575810@N00/4420162040/ [Broken] [Broken] in case that doesn't work)...
  9. M

    Parts, componets, and things that do stuff

    Parts, componets, and things that "do stuff" Hi guys! I'm actually an electrical engineering student, but I figured this might be more applicable here. I'm trying to find websites that are good for ordering parts such as bearings, shafts, gears, chains, cogs, and more. I'm planning on...
  10. M

    Discrete Math proof

    I'm completely stumped on how to begin a discrete math proof, and I'm looking for a little advice on what might be a good way to approach this. In a previous problem I did a proof by contradiction to show that at least one of the real numbers a1, a2, ... an is greater than or equal to the...
  11. M

    IR Photodiode or Phototransistor?

    Hi guys! I'm a beginning EE students, and haven't taken many courses yet (haven't even covered transistors in my circuits class yet-- we're up to diodes, woo!). For a "for fun" project, I've been messing around with the Arduino microcontroller...
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    Simple diode questions

    Homework Statement Here is a link to two figures I drew from a book I am using http://www.flickr.com/photos/96575810@N00/4339202724/sizes/o/ [Broken] These figures are assuming ideal diodes (no voltage drop, no resistance). In this example, on the left hand circuit, the voltage is...
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    Translating english to predicate logic

    Homework Statement I've been given a problem: "C(x,y) is x and y have chatted over the internet. The domain is students in a class. Express there are two students who combined have chatted with all of the students in the class". 2. The attempt at a solution I think this is the correct answer...
  14. M

    Biconditional equivalences

    Homework Statement I have to prove that !(p <-> q) = (p <-> !q) 2. The attempt at a solution I started by trying to just work out what each side of the equation was. So, starting with the left hand side !(p <-> q) = !((p->q) * (q->p)) (biconditional law) = !((!p + q) * (!q + p))...
  15. M

    Shipping problem (algebra)

    Homework Statement A friend of mine passed along this problem he's having trouble with in a business class, and I have to admit, I'm a bit stumped coming up with the proper mathematical framework for it. Here's the problem: A company manufactures loudspeakers in plants I and II. Output at...
  16. M

    Computer aided design programs

    Hi all! I'm a second year student at a university, and I'm wondering, what programs do "real" EE or computer engineers use to design their circuits or register-transfer-level systems? I'm currently in a computer organization course, where I've designed a (limited) MIPS processor, and...
  17. M

    Engineering Thevenin's Eq. Circuit

    Homework Statement I have to find the power delivered by the 2v source (see "Thevenin1.jpg" -- attached) The attempt at a solution (See "Thevenin2.jpg") I started by placing my equivalent nodes at X and Y. Since this circuit has both dependent and independent sources, I used nodal analysis...
  18. M

    Second order homogeneous DE

    Homework Statement 4xy'' + 2y' + y = 0 2. The attempt at a solution In class, we were given that y1 = c1Cos(\sqrt{}x). We then used reduction of order to figure out the other solution Yet, I've been trying to figure out, is how do you get y1 in the first place? To me, it doesn't...
  19. M

    Seperable Differential Equation

    Homework Statement I have dP/dt = (b - kP)P - hP (population problem with harvesting) I'm told this is separable into a 1st order DE.... so this is what I've tried: dP/dt = bP - kP^2 - hP dP/dt + (h-b)P = -kP^2 At this point, I get stuck... It doesn't appear to be a separable DE to me...
  20. M

    Integrate Sqrt[ e^x + 1 ]

    Homework Statement Integrate Sqrt[ ex+1] 2. The attempt at a solution I first multiplied the equation by e^x / e^x, then tried substitution, with u = e^x + 1 du = e^x dx This gave me: Integral 1/(u-1) * (u)^1/2 du However, I'm stumped at this part. Substitution here doesn't...
  21. M

    Simple sample variance problem

    The length of time, in minutes, for an airplane to obtain clearance for takeoff is a random variable Y = 4X + 2, where X has the density function: f(x) = 1/3 e^(-x/3) for x > 0 Find the variance of Y. ----- I found the expected value of X to be 14 minutes, which was correct. This...
  22. M

    EM plane wave question

    This isn't a homework question so much as a general question about the equation I see used in the textbook: The E field of an EM wave is defined as E(x, y, z, t) = E0sin(kx - wt)y_hat and the B field of an EM wave is defined as B(x, y, z, t) = B0sin(kx - wt)z_hat. Why is there a minus sign...
  23. M

    Faraday's law and distance

    This is just a general question, no calculations or homework-like wording involved! It's just a little something that has been bugging me. Faraday's law states emf = change in flux with respect to time. Let's say I'm generating this change in flux with an inductor somewhere in space. (I want...
  24. M

    One more torque problem

    First off, thanks to alphysicist for helping with my last problem :) I'm not trying to flood the board, but I have given a good attempt to this problem and can't see where I'm going wrong. Thanks to the community for having this board in the first place-- you guys are great! :) Homework...
  25. M

    Torque from a magnetic field

    Homework Statement A rectangular loop of wire of 150 turns, 34 by 23 cm, carries a current of 2.5 A and is hinged at one side. What is the magnitude of the torque that acts on the loop, if it is mounted with its plane at an angle of 28 degrees to the direction of a 1 T uniform magnetic field...
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    Current in a loop (Kirchhoff's Laws)

    Homework Statement Given the following circuit: Calculate the currents I1, I2, and I3 The given resistances are: r: 1.05 ohm R1: 11.7 Ohm R2: 10.5 Ohm R3: 7.20 Ohm R4: 14.3 Ohm R5: 18.8 Ohm The given emf's are: E1 = E2: 9.0 V E3: 3.0 V Homework Equations We know...
  27. M

    Electric field at a point on a contour line

    Hi guys! In this question I am asked to "Calculate the size of the electric field at k". See image at: http://capa-new.colorado.edu/msuphysicslib/Graphics/Gtype54/prob04a_threeqcontour.gif Note: although the picture states "Volts", everything is actually measured in kV. Homework...
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