Electric Definition and 1000 Threads

  1. G

    Find the Electric potential from surfaces with uniform charge density

    I do not have the solutions to this problem so I'm wondering if my attempt is correct. My attempt at solution: We have two surfaces which we can calculate the area of. I think we can use gauss law to find the electric field and then integrate the E-field to find the electric potential. So for...
  2. B

    Electric Force and Field homework problem

    This is my homework. And we don't have online lessons. But my teacher gave this for homework. I couldn't solve this problem. Can you help me?
  3. T

    Why will 240 volt condenser kill me but not 7,000 volt electric fence?

    I used to attend an HVAC program at a trade school. One time my instructor and i were working on either the outdoor unit of a split-system heat pump or the condenser of a split-system straight air-conditioner. Even though the unit we were working on was either an "outdoor unit" of a heat pump or...
  4. P

    Electric field in the Spherical Cavity

    a. For the question a the solution is If the uniform charge density is ρ then the charge of the sphere up to radius r is q = ρ * (4/3)*π * r3; Hence the electric field is E = (ρ *4π*r^3)/(3*εο*r^2); E = (ρ*r)/(3εο); b. I don't understand what is superposition? How to proceed? Please advise.
  5. EsinDerin

    Electric Field's Force on a Suspended Plastic Ball

    Hi,I couldn't do this problem.I hope someone could help meths is my first time in this forum
  6. Bilbo B

    Electric potential of a spherical conductor with a cavity

    Summary:: If the conductor is having a cavity and is provided with some charge, with the cavity too having some charge then how the potential will be affected on the outer surface of the conductor. The center of cavity and the center of hollow sphere does not coincide. As if their centers do...
  7. M

    The vector sum of the electric forces exerted on a particle

    r_{13}=r_{23}=\sqrt{(30*10^{-3})^2+(90*10^{-3})^2}=\sqrt{9*10^{-3}}\\ F^E_{13}=F^E_{23}=9E9\cdot\frac{5*10^{-9}\cdot3*10^{-9}}{9*10^{-3}}=1.5*10^{-5}\\ \theta=tan^{-1}(\frac{90*10^{-3}}{30*10^{-3}})=71.565\,degrees\\ \vec{F}^E_{13}=<F^E_{13}cos\theta, F^E_{13}sin\theta> = <4.743*10^{-6}...
  8. D

    Torque calculations for a small electric vehicle

    Hello guys, I'm trying to calculate the torque for a 3 wheeler electric (small vehicle). 2 driving wheels and one driven wheel. At the driving wheels we have a BLDC motor for each wheel. We want to calculate the torque for resting( not going down hill) on inclined plane (angle={5,10,15...
  9. D

    How Do Magnetic and Electric Fields Interact in a Changing Environment?

    Hello, If you have an appropriately oriented conductive ring in a constantly changing magnetic field, current will flow in the ring. There will also be a magnetic field associated with the current in the ring. I understand (maybe ... ) that the current is due to the electric field which is...
  10. G

    Electric field around a sphere with an internal charge distribution

    I'm just going to skip some of the step since I only need help with understanding the last part. After rearranging the equation stated at "Relevant equation" (and skipping some steps) we will get: E * 4*pi*e0*R^2 = integral pv * 4*pi*R^2 dR E = 1/(4*pi*e0*R^2) * 4*pi * integral pv*R^2 dR E =...
  11. Bell

    What's the direction of electric field in Laguerre-Gaussian beams?

    As for Laguerre-Gaussian beams, the direction of wave vector is helical, and how about the direction of electric field? I found that there was little literature mentioned this.
  12. Jackoyo

    Solving Electric Field & Potential: Jack Needs Help!

    Hi everyone, I have abit of trouble with this question. Please help! Given charges +q, +2q, −5q and +2q are placed at the four corners ABCD of a square of side a, taken in cylic order from the bottom left corner. Find the electric field E and the potential V at the centre and verify that they...
  13. P

    MATLAB Creating the Electric Octupole Tensor of a cubic electric octupole

    I created an array, where the first three entries of each column are the x,y, and z coordinates. The last entry in each column is the charge. I called this array PCQ. l/2 l/2 -l/2 -l/2 -l/2 l/2 l/2 -l/2 -l/2 l/2 l/2 -l/2 -l/2 -l/2 l/2 l/2 l/2 l/2 l/2 l/2 -l/2 -l/2 -l/2 -l/2 q -q q -q q...
  14. V

    Motion of a Proton in Electric and Magnetic Fields

    a) 248*10^3 eV for 248kV Calculate the energy in J K=248*10^3*1.6*10^-19 =396.8*10^-19 J b) K=(1/2)mv^2 v=sqrt(2k/m) =sqrt((2*396.8*10^-19)/1.67*10^-27) =218^10^3 m/s c) r=mv/qB =1.67*10^-27*218*10^3/1.6*10^-19*1.5*10^-4 =15.17 mr=mv/qB...
  15. Z

    Electric field direction on a grounded conducting sphere

    I am required to find the direction of the electric field on the surface of a grounded conducting sphere in the proximity of a point charge ##+q##. The distance between the center of the sphere and the point charge is ##d## and using the method of images we find that the charge of the sphere is...
  16. Leo Liu

    Understanding the Electric Field of a Charged Sphere

    This page claims that "[t]he electric field outside the sphere is given by: ##{E} = {{kQ} \over {r^2}}##, just like a point charge". I would like to know the reason we should treat the sphere as a point charge, even if the charges are uniformly distributed throughout the surface of the...
  17. jisbon

    How is the Electric Field in Energy Bands Calculated?

    This is my attempt at this question, and I'm probably wrong, will need some help/guidance from the experts here :/ i) (ii) Since energy band given by ##6.67x^2##, can I assume that electric field is simply the energy difference from 0-3m divided by 3m? In this case, would the answer simply be...
  18. S

    Does ECO mode in electric cars make sense?

    I just saw a video about an electric car which has an ECO mode. In ECO mode the car has less power. So let's say in normal mode the car has 100 kW and in ECO mode 60 kW. But why should the range of the car be greater if it has less power? Because as far as I know to reach a speed of v it...
  19. A

    How can we deduce the kink effect in the electric field?

    Hi. In videos online the kink is explained as a delay in the electric field when charges accelerate. Does this mean we can deduce the existence of kinks from coloumb law. Does the simple form of plane electromagnetic waves which is well treated in most books really exist. What is the...
  20. T

    Is There an Electric Field Within the Cavity of a Polarized Hollow Conductor?

    Suppose we have a hollow metallic conductor, just a thin metallic shell forming a large hollow cavity. It is then polarized by electric charges placed nearby externally. The equilibrium electric field must be parallel to the surface normals of the shell, there must be no tangential component...
  21. G

    Engineering Calculating the total electric field from two charges

    a) Should be pretty straight forward, from the equation E = kQ/R , we see that scaling is simply 1/R. b) Here is gets a bit trickier. We know that q acts as a source (E-field points outwards) and -q acts as a sink (E-field points inwards). If the distance is far away do we consider the Q1 and...
  22. B

    Deflection distance for an electron beam in an electric field

    Have tried doing this question but I'm a bit confused on where I'm going wrong This is what I have done but get a value that doesn't match to any of the options given above? Any help would be really appreciated, Thanks!
  23. K

    Calculate the current in all parts of this electric circuit

    In the circuit below, the output is 23 W across the resistor with the resistance 6 Ohm. Calculate the amount of current in all parts of the circuit as well as the polarity and EMF ε of the unknown battery. Circuit: My attempt: I get 6 unknowns with 5 equations. I don't know how to find the...
  24. Stephenk53

    Electronics Sites/companies used for electric parts

    Hello, I am building a battery pack to charge my laptop cooling pad and I am looking at batteries for it. I decided on LiPo because it is thin and thus should fit better on the cooling pad. I do not need help with the design since I am planning on using pre-made parts (although if you are...
  25. CrosisBH

    Trouble with Electric Potential Boundaries (Computational Physics)

    This is in python: #ELECTRIC POTENTIAL from mpl_toolkits.mplot3d import Axes3D from matplotlib import cm import numpy as np import matplotlib.pyplot as plt dx = 0.1 dy = 0.1 xrange=np.arange(-1,1,dx) yrange=np.arange(-1,1,dy) X,Y = np.meshgrid(xrange, yrange) max_dV = 10e-5 blockRadius = 3...
  26. Adesh

    Will the induced electric field be circumferential?

    Let’s say we have a right handed Cartesian system and magnetic field goes in positive z direction, and let’s assume that the magnitude of magnetic field varies with time. Now, if I draw a circle with radius ##r## in the ##x-y## plane and let the magnetic field pass through it and vary with...
  27. H

    Electric field from a charge q1

    Hi, I have a charge q1 = -10 * 10^9. The the coordinatesare (3,4)m. I found the electric field vector that is (-2160i -2880j) n/c. My questions is if I add a charge q2 to the the coordinates(0,0) is the electric field stay the same?
  28. jim mcnamara

    Protein nanowires + Geobacter + humidty = electric potential

    https://phys.org/news/2020-02-green-technology-electricity-thin-air.html I am not competent to judge this (what seems very edgy to me) article. Basically it says: a ten micron thick protein layer with Geobacter on the surface and protein nanowires arranged in a mesh, when exposed to...
  29. S

    Why is the Answer C? Electric Field in Conductors

    The answer according to the key is C. I thought the answer would be E since the electric field inside a conductor is always zero. Can someone explain why the answer is C?
  30. threeonefouronethree

    Poisson's equation: Calculating the Laplacian of an electric potential

    First I calculated the electric fields outside of the sphere in terms of the total charge Q. total charge Q: Q = aπR^4 electric field outside: (r>R) E(r) = (1/4πε) Q/r^2 (ε is the vacuum permittivity) electric potential...
  31. P

    Plotting the Poynting vector of a radiating electric dipole [matlab]

    I've attached a .txt file of my script for those who want to take a look at it Here's a picture of my vector field at time t = 0 I'm very concerned about this picture because from my understanding the Poynting vector is supposed to point outwards and not loop back around, this looks nothing...
  32. S

    Location where the electric potential is zero between charges

    a) I take "a point where it is neutral" as the electric potential at that point is zero. Is this correct? And because the two charges are both negative, there can not be any point where V = 0? Am I wrong or maybe one of the charge should be positive? Thanks
  33. Quentief

    How Could the Poulcen Arc Operate on Just 50 Volts?

    Hi everyone 🙂 I have read this article about the arc converter, also known as the Poulcen arc. https://en.m.wikipedia.org/wiki/Arc_converter It was apparently one of the first electric oscillators. Apparently, an electric arc was produced between two electrodes to put in resonance a RLC...
  34. Quentief

    Drawing Electric Arcs at 230 Volts

    Hi everyone :) I open this discussion because I would like to know how electric arcs are able to be drawn. Indeed, I have been told that it is perfectly possible to draw electric arcs at very low voltage, by simply putting in contact two electrodes and then drawing them apart. I wanted to try...
  35. F

    Electric field Difference between Electrostatics and Electrodynamics

    Hello everyone, I have been pondering on the behavior of the E field in conductors. In electrostatics (where the charges are not moving): a) Electric fields are time- independent but position-dependent b) Electric fields are always zero inside a charged or uncharged conductor. At the...
  36. moeug1999

    Electric Potential at A and B: Find the Answer

    I found the potential at A, however I tried doing it with B but it says I have the wrong answer.
  37. M

    Inducing electric current in a wire (a comparison)

    Consider the following experiment: from a lacquered copper wire we cut off twenty to thirty pieces of about 10 cm. From them we form a bundle of parallel wires and connect the two ends with one more wire each. The other ends of these two wires are connected to a sensitive analog ammeter. We hold...
  38. S

    I Electric Field Directly Ahead of or Behind a Moving Charge

    Since it is stated that ##E'_x = E_x##, I am going to set a special case where ##z' = z = 0##, ##E_x## in (5.10) reduces to, ##E_x = \frac{1}{4 \pi \epsilon_0}\frac{Q}{x^2}## However, ##E'_x## in (5.13) reduces to, ##E'_x = \frac{1}{4 \pi \epsilon_0}\frac{Q}{\gamma^2 x'^2}## There is an...
  39. jisbon

    How Do Symmetrical Charges Affect Net Electric Field in a Circle?

    In this case, I know there won't be any net efield in the x direction because it cancels out with each other. The problem is dealing with the y axis. Am I supposed to presume an angle for each of them or what should I do instead? Thanks
  40. P

    Charged proton enters an electric field

    I tried to do Net force with electric field = E x q minus the gravitational force= mg. However, this gives me a negative net force suggesting the proton is moving downwards. I'm not sure this is correct as the initial velocity was horizontal. Was there no gravitational force before? Am I missing...
  41. jisbon

    Energy band gap when there is an electric field

    So I have just been taught this topic but this question seems to be one of a kind and I can't seem to figure it out. What I've learnt: When there is a positive electric field applied to the right, for example, the electrons that are free moving in a crystal (aka conducting band) will oppose...
  42. SianRR

    Motion in Electric and Magnetic Fields -- (Uni Level Dynamics)

    I've attached my attempt at a solution below, I thought integrating it would be the best way to go but I'm just getting so confused and could use some help. This isn't my first attempt at a solution either I've been working on this for just under two hours now.
  43. Decimal

    Spectral density of radiative electric field

    So I have to find an expression for ##\vec{A}(\omega)##, $$\vec{A}(\omega) = \frac{1}{\sqrt{2\pi}}\int_{-\infty}^{\infty} \vec{A}(t)e^{i\omega t} dt.$$ This point is where my confusion comes up. In the answer sheet they integrate over the retarded time ##t_r##, so the integral is...
  44. D

    Electric field involving 4 point charges in a rectangle

    I am stuck on the following question (Image attached of my work) appears to make sense until i try to take a limit as c--->0 because the result should be 0. Am i missing something, if so can't you point me in the right direction. Thank you
  45. B

    Electric Fields: calculate the resultant force

    Summary:: I try to find the resultant force on "q". I think I have to find the value of Q, but I'm not sure. I Know F1 = k|q * 2Q| / 3² and F2 = k|q * Q| / 2² Hi, this is my first post on this forum I hope I posted in the right section. I try to find the resultant force on "q". I think I...
  46. G

    Gauss-Theorem on a solid dielectric sphere

    The load system formed by the point load and the load distribution generates two regions in space corresponding to r<1m and r>1m, i.e. inside and outside the sphere. Given the symmetry of the distribution, by means of the Gaussian theorem we can find the modulus of the field at a distance r from...
  47. Z

    Find the electric field on the surface of a sphere using Coulomb's law

    Note that the solution is 5625 V/m in z direction which is found easier using Gauss' law, but I want to find the same result using Coulombs law for confirmation. Lets give the radius 0.04 the variable a = 0.04m. ##\rho## is the charge distribution distributed evenly on the surface of the...
  48. Saptarshi Sarkar

    Electric field inside a polarized dielectric sphere

    My attempt: I know from Gauss' law in dielectric ##\nabla .D = ρ_f## where ##D = ε_0E + P##, so as ##ρ_f = 0## (as there is no free charge in the sphere) => ##\nabla .D = 0## => ##ε_0\nabla .E = \nabla .P## from this I get ##E = \frac {-kr^2 \hat r} {ε_0}## But, I know that for a uniformly...
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