Infinite Definition and 1000 Threads

  1. A

    Considering a circle to be an infinite sided n-gon

    as a regular polygon increases in sides, it becomes rounder. As you increase the number of sides, the polygon will tend towards a perfect circle but never quite make it. you can only make the circle with an infinite number of sides - stopping at any other number but infinity you will only get a...
  2. A

    Why is a magnet not an infinite source of energy?

    Hi Guys Could someone please point out where I'm going wrong with the following problem. If I place a magnet on a vertical surface such that the magnet must resit the force of gravity in order to hold itself in place, will this magnet stay in place forever? If it does why does this not...
  3. M

    Proof of infinite primes (why is it wrong?)

    So I thought up a "proof" for infinite primes. I'm assuming I did something wrong, but I don't know what, it would be nice if someone could tell me what I did wrong. Suppose there are a finite number of primes of quantity n which are listed from smallest to largest in the list: p1, p2, ... ...
  4. Saitama

    What is the Equivalent Resistance of an Infinite Circuit with 1 kΩ Resistors?

    Homework Statement Determine the resultant resistance of the infinite circuit made up of ##1 k\Omega## resistors shown in the figure between points A and C, and between points A and B. Homework Equations The Attempt at a Solution I can find the equivalent resistance between A...
  5. M

    Infinite square well, Probability of measurement of particle's energy

    Homework Statement Homework Equations The Attempt at a Solution I have managed to do the first 3 parts of the questions. The last two 4 markers are the ones I am having difficulties with. I have tried using the expansion postulate which states the wavefunction is equal to the...
  6. U

    Use fourier series to find sum of infinite series

    Homework Statement Find the value of An and given that f(x) = 1 for 0 < x < L/2, find the sum of the infinite series. Homework Equations The Attempt at a Solution The basis is chosen to be ##c_n = \sqrt{\frac{2}{L}}cos (\frac{n\pi }{L}x)## for cosine, and ##s_n = \sqrt{\frac{2}{L}}sin...
  7. Saitama

    MHB Infinite Sum of Powers of x over 1-x^2

    Problem: If $0<x<1$ and $$A_n=\frac{x}{1-x^2}+\frac{x^2}{1-x^4}+\cdots +\frac{x^{2^n}}{1-x^{2^{n+1}}}$$ then find $\displaystyle \lim_{n\rightarrow \infty}A_n$. Attempt: I tried to see if it can be converted to a telescoping series but I had no luck. Then, I tried this: $$\lim_{n\rightarrow...
  8. U

    Is the wavefunction for this system unique?

    Homework Statement Part (a): Find wavefunction and energy levels. Part (b): Find a possible wavefunction. Is this wavefunction unique? Part (c): What is the probability of finding it in the ground state? Part (d): What's the probability of finding it in the second excited state? Homework...
  9. EternusVia

    Infinite divisibility of matter?

    Hi all. I'm rather a novice in the realm of physics, aside from a class in high-school and my own independent interest. I often wonder if matter is infinitely divisible. What if it's possible to divide quarks, gluons, etc, we just don't have the methods? Does anyone have input on this...
  10. B

    Net Force on a circular current carrying wire, from an infinite wire.

    Homework Statement -I've attached a picture of the problem- An infinitely long straight wire of steady current I1 is placed to the left of a circular wire of current I2 and radius a as shown. The center of the circular wire is distance d(≥ a) away from the straight wire. Let’s find the net...
  11. 3

    The gravitational field at a mass point produced by an infinite plane

    I'm reading: http://www.feynmanlectures.caltech.edu/I_13.html#Ch13-S4 1. In the link it says: ##2\pi\rho d\rho## is the area of the ring of the radius ##\rho## and width ##d\rho##, if ##d\rho \ll \rho##. Why is this true?? 2. A bit further down in the text it says: Since ##r^2 =...
  12. Y

    Electric field in all regions of infinite cylinder

    Homework Statement A uniform linear charge of λ is located along the z axis, and concentric circular cylinder of radius 2 [m] has a surface distribution charge of α . both distributions are infinite, the distribution of linear charge is contained in the interior of the circular cylinder as...
  13. T

    Infinite Line of Charge and Electric Potential Difference

    Homework Statement 1. Consider a line of charge (with λ charge per unit length which extends along the x-axis from x=-∞ to x=0 (a) Find all components of the electric field vector at any point along the positive x-axis (b) Find the electric potential difference between any point on the...
  14. E

    Graphing Infinite Series (Mathematica)

    Homework Statement I just have to graph this function to see where the "Gibbs phenomenon" occurs in its Fourier Series representation. I am pretty sure I integrated correctly.Homework Equations Fourier Series The Attempt at a Solution...
  15. C

    Infinite square well with barrier in the middle

    Homework Statement Show that the energy levels of a double square well V_{S}(x)= \begin{cases} \infty, & \left|x\right|>b\\ 0, & a<\left|x\right|<b\\ \infty, & \left|x\right|<a \end{cases} are doubly degenerate. (Done) Now suppose that the barrier between -a and a is very high, but finite...
  16. C

    Electric field at a point due to an infinite line charge

    Homework Statement Charge is distributed uniformly along an infinite straight line with density λ. Develop the expression for E at the general point P. Homework Equations The electric field at a point P, caused by N point charges Qi, each a distance ri from P, is given by \mathbf{E}...
  17. QuantumCurt

    Determine the convergence or divergence of the infinite series

    Homework Statement This is for Calculus II. We've just started the chapter on Infinite Series. n runs from 1 to ∞. \Sigma\frac{1}{n(n+3)} The Attempt at a Solution I used partial fraction decomposition to rewrite the sum. \frac{1}{n(n+3)}=\frac{A}{n}+\frac{B}{n+3}...
  18. anemone

    MHB Evaluating an Infinite Sum of Binomial Coefficients

    Evaluate $\displaystyle\lower0.5ex{\mathop{\large \sum}_{n=2009}^{\infty}} \dfrac{1}{n \choose 2009}$.
  19. LunaFly

    Time Dependent Wave Function for Particle in Infinite Square Well

    Homework Statement A particle is in a bound state of the infinite square well. It is in a state represented by the following wavefunction, written here at t=0: ψ(x)= -√(2/3)√(2/L) * sin (3πx/L) + i*√(1/3)√(2/L) * sin (2πx/L) (a)Write the full time-dependent wavefunction for this state...
  20. S

    Wave function in infinite square well, with potential step

    Homework Statement A Particle energy A trapped in infinite square well. U(x)=0 for 0<x<L and U(x)=U0 for L<x<2L. find the wave function of the particle when A) E>U0 B) E<U0 C) E=U0. Homework Equations 1-D time independent Schrodinger equation. The Attempt at a Solution I have...
  21. D

    Conformal mapping of an infinite strip onto itself

    Homework Statement Find a conformal mapping of the strip ##D=\{z:|\Re(z)|<\frac{\pi}{2}\}## onto itself that transforms the real interval ##(-\frac{\pi}{2},\frac{\pi}{2})## to the full imaginary axis.The Attempt at a Solution I tried to map the strip to a unit circle and then map it back to the...
  22. A

    So, no matter what, if | a-b | is less than every positive ε, then a = b.

    Homework Statement Let \Lambda = N and set A_{j} = [j, \infty) for j\in N Then j=1 to \infty \bigcap A_{j} = empty set Explanation: x\in j=1 to \infty \bigcap provided that x belongs to every A_{j}. This means that x satisfies j <= x <= j+1, \forall j\inN. But clearly this...
  23. D

    Cartesian product of (possible infinite) family of sets

    Hi all. I'm having trouble understanding the cartesian product of a (possible infinite) family of sets. Lets say \mathcal{F} = \{A_i\}_{i \in I} is a family of sets. According to wikipedia, the cartesian product of this family is the set \prod_{i \in I} A_i = \{ f : I \to \bigcup_{i...
  24. N

    Why is 1+2+3+4+5+... equal to -1/12?

    I'm not sure which category this post actually belongs to, or if the title of this post is even accurate. I guessed Calculus was the closest one. I watched this video on the web after a professor told me this mathematical phenomenon (http://www.youtube.com/watch?v=w-I6XTVZXww‎). It asserts...
  25. R

    Infinite Potential Colliding with Wave Function: Is it Correct?

    Potential and wave function If a particle comes from +infinite and collides with a potential of the form : V = ∞ , x < 0 (I) -V0 , 0<x<a (II) 0 , x≥a (III) Is the wave function for region (I) = 0? And for region (II) = A sin(kx) with k constant? Really need to...
  26. Saitama

    MHB Find Infinite Product: $\sqrt{\frac{1}{2}}$

    Find : $$ \sqrt{ \frac{1}{2}}\sqrt{ \frac{1}{2} + \frac{1}{2} \sqrt{\frac{1}{2}}} \sqrt{ \frac{1}{2} + \frac{1}{2} \sqrt{ \frac{1}{2} + \frac{1}{2} \sqrt{\frac{1}{2}}}}\sqrt{ \frac{1}{2} + \frac{1}{2} \sqrt{ \frac{1}{2} + \frac{1}{2} \sqrt{\frac{1}{2} +\frac{1}{2}\sqrt{\frac{1}{2}}}}} \cdots...
  27. gfd43tg

    Navier Stokes two infinite parallel plates

    Homework Statement Compare the COMSOL results to the analytical solution for laminar flow between flat plates. Assume no effect of gravity on the flow (g = 0). The comparison will involve obtaining the velocity at a point in the flow field and the ΔP/L term. For example, you can compare the...
  28. gfd43tg

    Navier Stokes thin film on infinite wall

    Homework Statement Consider steady, incompressible, parallel, laminar flow of a film of oil falling down an infinite vertical wall (Figure P-1). The oil film thickness is “h” and gravity acts in the negative Z-direction (downward on the figure). There is no applied pressure driving the flow –...
  29. L

    EMF in a square loop due to magnetic field from an infinite wire

    Homework Statement Determine the emf induced in the square loop in the figure if the loop stays at rest and the current in the straight wire is given by I(t)=(15.0A)sin(2500t) where t is in seconds. The distance a is 12.0 cm, and b is 15.0 cm. Homework Equations emf = Δmagneticflux/Δt...
  30. M

    Finding order of an infinite series

    Homework Statement I have been working on a truncated Fourier series. I have come up with a truncated series for cos (αx) and it matches my book, where in this case I'm letting x=π, and then I have shown as the book asks, Truncated series = F_{N}(π) = cos (απ) + \frac{2α}{π}...
  31. D

    What Is the Potential of a Charge Above an Infinite Conducting Slab?

    Hello everyone! Homework Statement A charge, +q, is placed above an infinite conducting slab located at z<=0, at (0,0,d). Find the potential everywhere in space, without using the image-charge method. Homework Equations Laplace's equation(and its solution in spherical coordinates). (CGS units...
  32. kmm

    Should the Normalization Constant be Positive or Complex?

    In finding solutions to the time independent Schrodinger equation we have to normalize \psi to find the constant A. So we get \int_{0}^{a} |A|^{2} sin^{2}(kx) dx = |A|^2 \frac{a}{2}=1 For A we then get |A|^2 = \frac{2}{a} . Griffiths says that this only determines the magnitude of A but...
  33. A

    Suppose you have an object with infinite mass

    Now you put the object right above the Earth's surface, like just a few meters above the ground. Let's just assume the object will have no gravitational affect against the Earth, or any object for that matter. It's defying logic, I know, but let's just roll with that. Assuming the object would...
  34. M

    MHB Closed infinite orthonormal system

    Hey! :o I am lokking at the proof of the following sentence. An infinite orthonormal system $\{e_1, e_2, ... \} \subset H$, where $H$ an euclidean space, is closed at $H$ iff $ \forall x \in H$ $$||x||^2=\sum_{i=1}^n{|(x,e_i)|^2}$$ We suppose a subspace of $H$, that is produced by the basis...
  35. E

    MHB How to Expand the Quantity (t + P)^(1/2) in Terms of t/P?

    Expand the quantity (t + P)^(1/2) about 0 in terms of t/P. Give four non-zero terms. (t + P)^(1/2) ~ =
  36. M

    Divergence Test for an Infinite Series (General question)

    This might seem like a rudimentary question but when trying to prove divergence (or even convergence) of an infinite series does the series always have to start at n = 1? For example would doing a test for \sum^{∞}_{n=1}\frac{1}{n} be any different from \sum^{∞}_{n=0}\frac{1}{n}
  37. caters

    MHB Discovering Intersections of Infinite Primes Sets

    We have this set of primes which is infinite. This has lots of different subsets. Here is the list of subsets: Real Eisenstein primes: 3x + 2 Pythagorean primes: 4x + 1 Real Gaussian primes: 4x + 3 Landau primes: x^2 + 1 Central polygonal primes: x^2 - x + 1 Centered triangular primes: 1/2(3x^2...
  38. craigi

    Infinite Distribution: Generating Unbounded Real Numbers

    It seems to me that if we consider different methods of generating a distribution of an infinite number of samples of and unbounded real number then we get some distinct results. 1) If we randomly sample a value, then its probability must be non-zero, which is also true of any other value...
  39. C

    Normalizing a State Function for an Infinite Square Well

    Homework Statement Normalize: \Psi_1 (x,t) = N_1 \cos(\frac{\pi x}{L}) e^{-\frac{iE_1t}{\hbar}} Where N_1 and E_1 are the normalization constant and energy for the ground state of a particle in an infinite square well. Homework Equations Normalization Condition: \int_\infty^\infty P(x,t)...
  40. 4

    Should the Infinite Potential Well Proposal Be Approved?

    Infinite potential well "proposal" Homework Statement An experimental physicist submits a proposal to a granting agency requesting support to construct an infinite potential well analogous to the one shown in Figure 3.5. Specifically, the proposal is to build a well with L = 1mm, inject some...
  41. M

    Equivalent expressions for infinite series

    Question: I was just wondering if there was any error in what I've done in the following steps to find the series representation of ##lnx##. I know ## \frac {1}{x}## is given in the following link by doing having the a function centred at 0, you can let ##f(x) = ∑^∞_{n=0} \frac...
  42. T

    Electrostatics problem involving infinite sheet

    Homework Statement An infinite dielectric sheet having charge density σ has a hole of radius R in it. An electron is released on the axis of the hole at a distance R√3 from the centre. What will be the velocity which it crosses the plane of sheet? (e = charge on electron and m = mass of...
  43. N

    Physics 2, Three Infinite Straight Wires

    Homework Statement https://www.smartphysics.com/Content/smartPhysics/Media/Images/EM/14/h14_threewires.png Three infinite straight wires are fixed in place and aligned parallel to the z-axis as shown. The wire at (x,y) = (-10 cm, 0) carries current I1 = 2.9 A in the negative z-direction...
  44. kq6up

    Estimating Error for an Infinite Series (Mclaurin)

    Homework Statement Problem # 30 in Ch1 Section 16 in Mary L. Boas' Math Methods in the Physical Sciences It is clear that you (or your computer) can’t find the sum of an infinite series just by adding up the terms one by one. For example, to get \zeta (1.1)=\sum _{ n=1 }^{ \infty }{...
  45. A

    Diffusion: Concentration profile for point sink in infinite plane

    Hello, I have a certain diffusion problem I am trying to solve. Admittedly, I'm further behind on my math than I'd like, and have trouble setting it up properly, and no luck finding an exact analogue in the literature. I would like to solve for the time-dependent concentration profile...
  46. Saitama

    How Do You Calculate the Equivalent Resistance in an Infinite Resistor Network?

    Homework Statement Calculate the equivalent resistance of the resistor chain shown in the figure between the points a) A and B; b) A and C the resistor chain is infinite in both directions and each resistor has a resistance of R. Homework Equations The Attempt at a Solution I have solved the b)...
  47. L

    Acceleration. Infinite potential well.

    Why we don't have acceleration in quantum mechanics. For example why particle in infinite potential well can not accelerate. For example dimension of well is ##L## and ##L=\frac{at^2}{2}##, where ##a## is acceleration.
  48. U

    Delta wall and infinite square well potentials ,and 2 other questions

    Consider the following potential function: V=αδ(x) for x=0 and V=∞ for x>a and x<-a , solve the shroedinger equation for the odd and even solutions. solving the shroedinger equation I get ψ(x)=Asin(kx) +Bcos(kx) for -a<x<0 and ψ(x)=Asin(kx) +Bcos(kx) for 0<x<a is it...
  49. J

    Can Infinite Sums Be Manipulated by Shifting Terms?

    I was reading the Wikipedia article about the sum 1+2+3+4+..., and I saw this explanation: c = 1+2+3+4+5+6+... 4c = _4__+8__+12+... -3c = 1-2+3-4+5-6+... link: http://en.wikipedia.org/wiki/1_+_2_+_3_+_4_+_%E2%8B%AF My question, as one who hasn't worked with infinite sums: Why are you...
  50. H

    Using Gauss's Law to find E for an infinite volume charge density

    My E&M professor brought up this problem of considering a uniform charge density, rho, that is infinite in volume and then using Gauss's Law to find the electric field at a point. It's resulted in a lot of head scratching and I'd appreciate some help/discussion to guide me towards a resolution...
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