Electric Definition and 1000 Threads

  1. S

    Frequency of pendulum in the presence of electric field

    I imagine the setup to be like this: the pendulum is moving horizontally, then it will experience electric force upwards so there is additional upwards acceleration, in addition to the acceleration from restoring force. Since the resultant of the two accelerations is not directed horizontally...
  2. L

    Electric field for a spherical shell when r=R?

    Griffith's keeps mentioning the case r<R and r>R blah blah blah. Ok. But what if r = R? My attempt at an answer: when I take the limit from outside the sphere, I get the case when r > R. When I take the limit from inside the sphere, I get the case when r < R. Left and side hand side limits do...
  3. Dev

    Gauss' Law for Non-Uniform electric fields

    The answer key shows option D is correct. But I think option C is also correct. Which option is correct here?
  4. R

    Maximum electric field from a blob

    For part a) we have $$ E = \frac{Qy}{4 \pi \epsilon_0 (x^2 + y^2)^{3/2} } = \text{constant} $$ I am stuck on part b). What should the shape of the volume?...
  5. MatinSAR

    Maxwell's Equations: How E and B Fields Interact

    In Maxwell's equations, the electric field appears in both Gauss's Law and Ampère's Law. Do these refer to the same electric field, or are they different components of the overall electric field? I think Gauss's Law gives electric field 1 and Ampère's Law gives electric field 2. So the total...
  6. Y

    TE and TM polarization parallel definition

    Homework Statement: TE and TM polarization parralel question Relevant Equations: its a photo Hello, In the photo on the left bellow E-field is not parralel not to X nor to Z direction. to what exactly is it parralel? Thanks.
  7. P

    Electric Field of a Toroid carrying a changing current I = kt on axis

    The relevant equation listed above as ##\vec{E} \left( \vec{r} \right) = \frac{1}{4 \pi} \int {\nabla’ \times \frac{\partial \vec{B}}{\partial t}}\frac{1}{\left| \vec{r} - \vec{r}’ \right|}\, d \tau’## Seems to me to be a natural consequence of the Helmholtz Theorem so I don’t see why it...
  8. Astronuc

    Permanent Magnet Motors & Koenigsegg’s ‘Dark Matter’ Electric Motor

    The thread was inspired by an article, "Here’s How Koenigsegg’s ‘Dark Matter’ Electric Motor Makes 800 HP" https://www.thedrive.com/news/heres-how-koenigseggs-dark-matter-electric-motor-makes-800-hp What is "raxial flux?" It's not a new genre of EDM...
  9. L

    Electric field of an infinitely long wire with radius R

    Hi, I don't know if I have calculated the electric field correctly in task a, because I get different values for the Poisson equation from task b The flow of the electric field only passes through the lateral surface, so ##A=2\pi \varrho L## I calculated the enclosed charge as follows...
  10. H

    A Physical interpretation of hopping between orthogonal orbitals

    Suppose two orthogonal neighbouring orbitals ##|\phi _1 \rangle## and ##|\phi _2 \rangle## so that ##\langle \phi_1|\phi _2 \rangle =0##. Applying an electric field adds a new term ##u (c_1^{\dagger}c_1-c_2^{\dagger}c_2)## to the Hamiltonian which u is a constant potential. Obviously, we still...
  11. M

    I Electric field inside & outside of a spherical shell

    Hi, I am reading Griffiths Introduction to electrodynamics. Currently I am solving problem 2.11 which asks to find an electric field inside and outside a spherical shell of radius R. Inside: $$\int{E \cdot da} = \frac{Q}{e_0} = |E|4\pi r^2 = \frac{Q}{e_0} = 0$$ The result is $$0$$ because we...
  12. kirito

    I Appropriate coordinates for a given electric field

    this is the field I was provided and this is the charge density that I have reached I tried to use this yet the output was different I also used Cartesian it gave me the same output as the spherical ones
  13. K

    Two spring-coupled masses in an electric field (one of the masses is charged)

    Here's what I've tried. First of all, I assume that q is positive. For particle A, then, I can write $$q E -k {\left( x _{A }-x _{B }\right) }=m \ddot{x }_{A }, $$ where ##x _{A } ## and ##x _{B } ## are the coordinates of the particles relative to their equilibrium positions from the point of...
  14. du_768

    How can the electric potential be constant between two points in a wire?

    Homework Statement: circuits - terms Relevant Equations: - How exactly can the electric potential be constant between two points in a wire; (assuming that it is electron current); if the electron is moving from a region of high electric potential to a low electric potential because of the...
  15. Irvin Atkins

    B Move in Space without mass exchange

    I did a thought experiment and I can't figure out what the mistake is. There is a system of 2 electric motors weighing 1 kg each with batteries in the Earth's orbit. The motors are rigidly connected by a 1-meter-long bar. If one motor starts rotating in one direction on a signal, the entire...
  16. jack action

    Is Electric Mining Equipment the Future of the Industry?

    It seems that electric mining equipment is all the craze right now: Liebherr electric excavator Caterpillar 240-ton electric haul truck Liebherr and Fortescue partner on world’s first autonomous electric haul truck EPCA plans to convert 50-70 mining trucks to electric power annually Liebherr -...
  17. damarkk

    Electric sinusoidal field on a hydrogen atom - Quantum Mechanics

    Hello to everyone. I have some doubts about one problem of quantum mechanics. My attempt. I need to calculate the coefficient ##W_{ij}=<\psi_i | H' |\psi_j>## where ##H' = -eE(t)z## is a perturbation term in the hamiltonian and ##|\psi_i> = |\psi_{nlm}>##. We have four states and sixteen...
  18. yashraj

    I Does a time varying magnetic field in vacuum produce electric field or not?

    Suppose there is very long current carrying wire. A charged particle is present somewhere around it. The current in the wire varies with time, thus by biot-savart's law there should be time varying magnetic field. I want to know that will this time varying magnetic field produce electric field...
  19. C

    Possible feedback problems of a uni-directional torque

    Hi, I wonder if someone can help with the following problem? We have a sealed box in space and inside the box is an electric motor with the stator attached to the box. The rotor arm is attached to the inner race of a bearing and the outer race of the bearing is also attached to the box. There...
  20. BuggyWungos

    Why does electric potential energy increase if you move against the field?

    My understanding of this question is that, if you have a proton standing against a positive electric field, and move it in the opposite direction of the field, you're putting in work and therefore should have greater electric potential energy. But that idea breaks down when you consider a...
  21. Heisenberg7

    How to Apply Derivatives in Physics Problems?

    I would like to discuss a few ways to apply derivatives in physics (I don't understand it fully). I don't need a full solution, I only need to understand how to successfully apply the derivatives First example, Thin insulating ring of mass M, uniformly charged by charge ##+q## has a small cut...
  22. BuggyWungos

    Solving for potential using surface charge density of a sphere

    surfafce area = 0.502 E = -q/A2(en) = 3800 -q = 3800*(A2(en)) -q = 1.68*10^(-8) -q = 3.37*10^(-8) V = kq/r V = (9.0*10^9)(-3.37*10^(-8))/0.2 V = -1519 V
  23. kirito

    Find the electric field between 2 finite discs

    I did make the problem simpler by looking at the the part from d/2 down the upper plate here are my initial parameters I am making my size step be h since lowering it may make calculating harder I am especially getting weird results for the field and capacitance R = 0.1; % Radius of the...
  24. Heisenberg7

    B Electric Field Inside a Hollow Sphere

    Let's assume that we have a hollow sphere with holes at opposite ends of the diameter. What would be the field inside the hollow sphere? I know that we can look at this as the superposition of the hollow sphere without holes and 2 patches with opposite surface charge density. For some reason, in...
  25. S

    Electric field of point along the central vertical axis of a triangle

    here is my attempted solution. ## d^2 = z^2 + \frac {L^2} {3} ## ## C ## is coulomb constant since the point is symmetric, only the vertical component of the electric field remains. So, $$ E = 3 E_y =3 \frac {C Q cos \theta} {d^2} $$ $$ E= 3 \frac {C Q z} {d^3} $$ thus part (a) is done ( i...
  26. Heisenberg7

    B Electric Field Created by 2 Infinite Plates

    Today, I watched a video about electric field created by an infinite plate by Khan Academy. They were talking about the clever application of the Gauss's law in this case (the cylinder method), so I wondered if I could apply the same thing but to 2 plates. For example, let's say that the plates...
  27. tellmesomething

    What is taken as datum level for the following absolute potentials?

    We take out "formulas" for electric potential from the relation $$V=\int E.dx$$ Some general formulas are : For a hollow sphere : ##\frac{Q} {4π\epsilon_0 x}## when x>R, x =distance of that point from the center And the problem is we just input the distance in sums to calculate absolute...
  28. kirito

    Why are the electrostatic field lines normal to a charged conductor?

    I understand the following .a conductor is made of atoms and atoms always strive to be at equilibrium and that's why the electric field inside a conductor is zero because the electros distribute themselves in such a way so that they are in equilibrium , yet they do produce an electric field...
  29. kirito

    Electric field of a sphere and a shell

    q encolsed =0 Second case q enclosed q by gauss law At 2r
  30. P

    I Help understanding Maxwell's Equations please

    I have having trouble understanding Maxwell's Equations. Can anyone recommend some good book or website that can help me to understand these Equations? How can electric and magnetic fields travel perpendicular to each other? What causes electromagnetic waves to first radiate from its source? I...
  31. arivero

    A Why do the proton and electron have equal and opposite electric charge?

    The most common explanation I know is that anomaly cancelation implies the sum of electric charges of each particle must cancel generation-wise, so 3 Q(Up) + 3 Q(Down) + Q(electron) = 0, and electroweak doublets imply Q(Up) - Q(Down) = Q(neutrino) - Q(electron), so with Q(neutrino) = 0 it solves...
  32. tellmesomething

    Find the electric field at a point in 3 dimensional space

    I tried resolving the semi infinite rods into arcs of 90 degree each placed on the three axes but that doesnt take me anywhere.... Alternatively I tried finding out the field at the point due to each rod but im unable to find the perpendicular distance from the point to the rod...I dont think...
  33. tellmesomething

    Prove that the field due to a circular arc is same as its bounded tangent at the centre of curvature

    Lambda = charge density I tried first taking out the field due to the circular arc and I got $$ (lambda / 4π (epsilon knot) ) (2 sin (theta)) $$ For reference this is the arc that was provided in the question of angle 2(theta) and the tangent What I dont understand is how can the fields be...
  34. tellmesomething

    Electric field vector equation: Finding the neutral point for two charges

    This is the general suggested approach given in a textbook. My question is why can I not directly write it in vector form? E1 vector + E2 vector =0 should be valid no? Why are they choosing to write E1 mag + E2 mag=0 Then find a vector form Then convert the magnitude equation into a vector...
  35. B

    Physics about electric circuits: Changing the resistors changes the currents

    Please help me with this homework! I haven't had any solutions since it is all unclear.
  36. srnixo

    Gauss' law and the potential V (plane layer case)

    Here is the exercise: And these are my attempts: This is for the first question about the electric field. (I know I'm missing the drawing, which is a drawing of the plane layer of thickness 2e with a cylinder on it as a GAUSS SURFACE ). As for the second question, I'm not sure about it, so I...
  37. P

    Calculate electric force using Coulomb's law (vector components are the struggle)

    So for this problem I think I am doing something weird with the trig and/or vector components. I calculated the problem like this: First drew a picture, q1 and q2 on the x axis. q3 located equidistant between them but negative .300m in the y direction. First finding magnitude of Electric...
  38. Ben2

    Field due to an electric dipole (Halliday & Resnick, Ch. 27 problem 23)

    Using either H&R's Chapter 27 Example 3 or Problem 590 of the ##\mathbf{Physics Problem Solver}##, I've been unable to get the component ##E_x## or ##E_y##. There are now different angles at the charges. My thanks to berkeman for LaTeX advice, but any errors are of course my own. Thanks in...
  39. L

    Gauss' Law for a conducting / non-conducting sheet

    The first image is for a conducting sheet (part of it anyway), the second is for a nonconducting sheet. Gauss' law seems to tell me that the electric field strength are different - they differ by a factor of two. Is this true? The charge enclosed in both of them are the same, and my intuition...
  40. L

    Direction of electric field vector on the surface of charged conductor

    Consider a negatively charged spherical conductor. On the surface of it, what is the direction of its electric field? Well, the definition of the direction of an electric field is the direction a positive test charge would go if placed at that point. But... it wouldn't move anywhere! So is the...
  41. J

    Solar panel conundrum -- Not enough power?

    I have a student trying to build a simple solar powered vehicle for a high school design thinking class. He solar panel produces about 3.1 V as measured on a multimeter, but will not power the electric motor she had chosen. She tested the motor with a pair of AA batteries (2.9 V on multimeter)...
  42. Krazen017

    How can I find the sustain time of an electric guitar?

    How can I find the sustaining time of an electric guitar? The influence of other components besides the strings can be neglected. I need it for my term paper.
  43. A

    I Electrical breakdown in air in the presence of a single charge

    Suppose there is an electric charge of 350 micro coulombs in space. The electric field at a distance of less than one meter will be more than 3,000,000 volts/meter considering that this field is greater than the electric breakdown of air and the charge has no place to discharge, what happens...
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