Recent content by *FaerieLight*

  1. F

    Magnetic and Electric Field outside Solenoid

    Hi, I've seen a couple of posts in the Homework section of Physics Forums about the fields of solenoids, but neither of them seem to address the problem that I have about it. The set-up is a long solenoid that has a sinusoidally varying current going through it. We can establish that the...
  2. F

    How can I solve a first-order non-linear ODE?

    Hi! Thanks for your help! What I meant by rearranging is that I just put dx/dt on the LHS and A-B*sin(x) on the RHS, and then integrated both sides with respect to t, so that I got an integral of sin(x) with respect to t. I then rewrote dt as dt/dx * dx, and got an expression in terms of sin(x)...
  3. F

    How can I solve a first-order non-linear ODE?

    Hi! I'm having a lot of trouble solving the following ODE: dx/dt = A - B*sin(x) where A and B are constants. My ODE skills are a bit rusty, and I wasn't able to find anything on the Internet that could help me, so could someone please show me how to solve for x in terms of t? I've...
  4. F

    Total Charge on Conducting Hollow Sphere

    I've just worked out using the method of images that the total induced charge on a grounded hollow conducting sphere in the presence of a dipole outside the sphere pointing in the radial direction is non-zero. I can't think of an intuitive explanation as to why a dipole outside would induce a...
  5. F

    How can the Universe be flat and accelerating in its expansion?

    I've heard that a flat Universe is one where there is enough density in the Universe to prevent a big crunch or ever-accelerating expansion, and that the fate of such a Universe is that the expansion slows down to zero as time goes to infinity. I have also heard that the Universe is accelerating...
  6. F

    What Causes the Plateaus and Zeros in the Quantum Hall Effect?

    Hi! I'm having trouble understanding the quantum hall effect, that is, the fact that the Hall resistance versus magnetic field curve has regions where it drops to zero, and the longitudinal resistance versus magnetic field curve features plateaus. When the filling factor is an integer, this...
  7. F

    Uncertainty Relation between Lx and Ly

    Oh, I see! Thanks!
  8. F

    Uncertainty Relation between Lx and Ly

    There is an uncertainty relation between the x component and the y component of the angular momentum L of a particle, because [Lx, Ly] = i\hbarLz which is not 0. But what happens when Lz does equal 0? Would we in principle be able to measure both the x and y components of the angular...
  9. F

    Asymptotic Expansion of an Integral

    Thanks for your help! I've succeeded in deriving the power series approximation. I don't know about Hilbert Transforms yet, but it looks really nice, like Fourier Transforms or Laplace Transforms. Thanks for introducing it!
  10. F

    Asymptotic Expansion of an Integral

    Yes, I think it is. It's expansion is supposed to be \sqrt{\pi}(1+\frac{1}{2s^{2}}+\frac{3}{4s^{4}}+ higher order terms) I'm not really familiar with the Cauchy Principle Value. Thanks!
  11. F

    Asymptotic Expansion of an Integral

    I'm not exactly sure that what I want to do is an asymptotic expansion, but basically I would like to find a power series approximation in s of -s \int \frac{e^{-x^{2}}}{x-s} dx for large values of s. The integral is meant to be from -∞ to +∞. I can see that for large s, the...
  12. F

    MATLAB How Can I Generate a Poisson Distributed Vector Without Zeros in MATLAB?

    I want to generate a Poisson distributed vector of random numbers, without any of the numbers being 0. The code I have is k = poissrnd(kmean,1,N); % where kmean is the mean of the distribution, and has been defined previously %The above generates a N by 1 vector of Poisson distributed...
  13. F

    Energy and Momentum in Particle Decay

    If a particle decays via A →B + C, and A had some initial non-zero momentum, is it possible for either B or C to be stationary? I can't seem to find a restriction on this from energy conservation or momentum conservation. From energy conservation, the stationary particle B still contributes...
  14. F

    Is the Inductance of an Ideal Transformer Infinite?

    So...in an inductor of infinite inductance, no energy is transferred to the inductor, while in an inductor of finite inductance, energy is transferred back and forth between the inductor and the power source?
  15. F

    Is the Inductance of an Ideal Transformer Infinite?

    @phyzguy: No, I've never used SPICE, but I just looked it up and it looks like a really fun program to use! I will try it out when I get a spare moment. @jim hardy, phyzguy and kmarinas86: Thank you for your answers! So if a transfomer with no secondary load acts like an inductor with infinite...
Back
Top