What is Electric potential: Definition and 1000 Discussions

The electric potential (also called the electric field potential, potential drop, the electrostatic potential) is the amount of work energy needed to move a unit of electric charge from a reference point to the specific point in an electric field with negligible acceleration of the test charge to avoid producing kinetic energy or radiation by test charge. Typically, the reference point is the Earth or a point at infinity, although any point can be used. More precisely it is the energy per unit charge for a small test charge that does not disturb significantly the field and the charge distribution producing the field under consideration.
In classical electrostatics, the electrostatic field is a vector quantity which is expressed as the gradient of the electrostatic potential, which is a scalar quantity denoted by V or occasionally φ, equal to the electric potential energy of any charged particle at any location (measured in joules) divided by the charge of that particle (measured in coulombs). By dividing out the charge on the particle a quotient is obtained that is a property of the electric field itself. In short, electric potential is the electric potential energy per unit charge.
This value can be calculated in either a static (time-invariant) or a dynamic (varying with time) electric field at a specific time in units of joules per coulomb (J⋅C−1), or volts (V). The electric potential at infinity is assumed to be zero.
In electrodynamics, when time-varying fields are present, the electric field cannot be expressed only in terms of a scalar potential. Instead, the electric field can be expressed in terms of both the scalar electric potential and the magnetic vector potential. The electric potential and the magnetic vector potential together form a four vector, so that the two kinds of potential are mixed under Lorentz transformations.
Practically, electric potential is always a continuous function in space; Otherwise, the spatial derivative of it will yield a field with infinite magnitude, which is practically impossible. Even an idealized point charge has 1 ⁄ r potential, which is continuous everywhere except the origin. The electric field is not continuous across an idealized surface charge, but it is not infinite at any point. Therefore, the electric potential is continuous across an idealized surface charge. An idealized linear charge has ln(r) potential, which is continuous everywhere except on the linear charge.

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  1. E

    Ambiguity when taking the Earth as a zero for electric potential

    When you ground something in electrostatics, the potential of that body becomes the potential of the Earth once equilibrium has been reached. In this context, it is usually taken that the Earth is at 0V. There are two possibilities for this. Either the constant of integration is chosen such that...
  2. P

    Calcualtion of electric potential and radioactive decay

    This is just a representative diagram to visualize Surely a very tough one for me to solve. The number of nickel atoms are not mentioned. if the number of decays are ##3.78∗10^8## and with each decay depositing 100keV. The total energy deposited is ##100keV∗3.78∗10^8=6.048∗10^6## I have to...
  3. 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...
  4. 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...
  5. 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...
  6. 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...
  7. 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...
  8. 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
  9. 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.
  10. K

    Determine the Electrical potential at a given point

    A rod with a circular center in the middle (which causes the rod to change direction by 90 °) has an evenly distributed linear charge density 𝜆 of electrons along the entire rod. Determine the electrical potential of the red dot in the figure below which is at the center of the circular round...
  11. Tryhard314

    Why does the potential of A decrease when plate B is nearby?

    Summary:: if Plate A had a potential of 9V, This means as We approach a unit charge from +Infinity to A we have to do this precise amount of work Now we remove plate A, And replace it with plate B that has a potential of -9V Again that means to go from +Infinity To B we actually gain energy, or...
  12. Tryhard314

    Salt water and potential difference

    Imagine a container of salt water at 0V (Relative to ground),Now you've put in it 2 electrodes,one at +500V (Electrode A), The other at +250V(Electrode b), Normally positive ions should go to the negative electrode , and Negative ions should go to the positive electrode , But in our example the...
  13. J

    Finding electric potential at a point between 3 electrodes.

    Firstly, I am not a English speaker. So I apologize that I cannot use English well.. I got a), c), e) a) at 0.5cm, E = -q/(2e_0*A) - Q/(2e_0*A) + q/(2e_0*A) = -1.4*10^7 V/m c) at 1.5 cm, E = 0 (inside electrode) e) at 2.5cm, E = -q/(2e_0*A) + Q/(2e_0*A) + q/(2e_0*A) = 1.4*10^7 V/m And I am...
  14. I

    How can I get help with my technical and schoolwork questions on the PF forum?

    I am a undergrad student dying slowly to solve few questions that came into my mind lately. Some help might be helpful.
  15. adamaero

    Electric energy density in the dielectric of a coaxial cable

    V(ρ) = V_o*ln(ρ/0.0018)/ln(45/180) (Attached picture is where the unit vector of r is really ρ.) In cylindrical coordinates ∇V = ρ*dV/dρ + 0 + 0 ∇V =derivative[V_o*ln(ρ/0.0018)/1.386]dρ ∇V = V_o*0.0018/(1.386*ρ) E = V_o*0.0012987/ρ Work = 0.5∫∫∫εE•E dv Bounds: 0.0018 to 0.00045 m D = εE =...
  16. kmm

    Potential of a grounded conductor in the presence of an external charge

    If we set the potential at infinity to be zero, we find that the potential of a grounded conductor is V=0. The conductor being grounded has no net charge and produces no external field, so I understand why in that situation we would say the potential of the conductor is zero. However, in...
  17. Haorong Wu

    How to calculate electric potential, given some other potential?

    The problem can be simplified to a configuration in ##x-y## plane where two point at ##y## axis with ##y=\pm R## have potential of ##0##, and two point at ##x## axis with ##x=\pm R## have potential of ##U=V_0 \cos \Omega_T t##. The expression of ##U## is not important, the problem is now to...
  18. E

    Does electric potential exist without a test charge?

    Usually for a charge Q we state that for each point in space there exists a potential, and we can calculate this, draw graphs of potential etc. However, if electric potential energy is a property of a system of two charges, and potential is PE for a 1C test charge, then how can we even define a...
  19. AndresPB

    Electric Field from its Potential of a Half Circle along its Z axis

    So I figured out the potential is: dV = (1/(4*Pi*Epsilon_0))*[λ dl/sqrt(z^2+a^2)] . From that expression: We can figure out that since its half a ring we have to integrate from 0 to pi*a, so we would get: V = (1/(4*Pi*Epsilon_0))*[λ {pi*a]/sqrt(z^2+a^2)] In that expression: a = sqrt(x^2+y^2)...
  20. dRic2

    Simple electric potential and Laplace equation

    Imagine to be in 2 dimensions and you have to find the potential generated by 4 point-charges of equal charge located at the four corners of a square. To do that I think we simply add all the contributions of each single charge: $$V_i(x, y) = - \frac k {| \mathbf r - \mathbf r_i|}$$ $$ V(x, y)...
  21. K

    Clarification of electric potential difference

    I have some questions regarding the sign of potential difference. For example, given the literal definition as the difference in potential between two locations it should be possible for potential difference to be negative if the final potential is less than the initial, but while reading texts...
  22. S

    Potential at the origin due to an infinite set of point charges

    Summary: Potential at origin of an infinite set of point charges with charge (4^n)q and distance (3^n)a along x-axis where n starts at 1. From V=q/r, we find Vtotal=sum from 1 to infinity of (4/3)^n(q/a), which diverges. There cannot be infinite potential because there is a finite electric...
  23. cianfa72

    Galvanic cell - open circuit voltage and EMF

    Hi, having not a deep knowledge of electrochemistry I've some doubts about processes involved in a galvanic cell. Take for instance a Zn/Cu Daniell cell for which E0cell is 1,10V. That means emf for it is 1,10V. Starting to read from how battery works I had a first understanding of how...
  24. T

    Capacitance and induced charge of a spherical Capacitor + dielectric

    I) For the first part I used: ##V = - \int E ds = \int_a^c \frac{1}{4\pi\epsilon_0} Q /r^2 dr+ \int_c^{c+d} \frac{1}{k} \frac{1}{4\pi\epsilon_0} Q /r^2 dr + \int_{c+d}^b \frac{1}{4\pi\epsilon_0} Q /r^2 dr ## And by using ##C = Q/V## We get an answer which is somehow large for writing here...
  25. Aryamaan Thakur

    Electric potential at the edge of a thin charged circular plate

    My question might sound stupid to you but please clear my confusions. I'm taking an circular arc like element on the plate. That arc has a radius of 'r' (AB) and the radius is inclined at an angle 'θ' with OA (∠OAB). The area between arc of radius r and r+dr is dA. dA = 2θr.dr The charge on...
  26. cianfa72

    Electric potential difference between a battery's + terminal and the ground

    Hi, I've a question about electricity in the following scenario: consider an accumulator (e.g. a 9V battery) and an analog/digital voltmeter having a probe connected to the accumulator + clamp and the other to the ground (for instance connecting it to a metal rod stuck in the ground). Do you...
  27. archaic

    Is the 'test charge' in electric potential energy defined as immobile?

    Hello, quick question, when EPE was defined, did we decide that the "test charge" is immobile in the field? Otherwise a force equal and opposite to that of the electric field would just stop the charge from accelerating.
  28. A

    Electric Potential across charging battery.

    Homework Statement [/B] A car battery with a 12v emf and an internal resistance of .040 ohms is being charged with a current of 50A. A.) What is the potential difference across the terminals? B.) The rate of energy dissipation in the battery Pr. C.) the rate of energy conversion to chemical...
  29. fight_club_alum

    Uniform charge density and electric potential

    Homework Statement A charge Q is uniformly distributed along the x-axis from x = a to x = b. If Q = 45 nC, a = –3.0 m, and b = 2.0 m, what is the electric potential (relative to zero at infinity) at the point, x = 8.0 m, on the x axis? a . 71 V b. 60 V c. 49 V <-- correct answer d. 82 V...
  30. Miles123K

    Calculating the charge of two concentric conductive spheres

    Homework Statement The solution to this problem is B, and I was able to get the answer by calculating the total potential at ##r = 2a##, however, what I don't seem to understand is why must the voltage be calculated at ##r=2a## but not ##r=3a##. Homework Equations ##V(r) = - \int_a^b E(r)...
  31. fight_club_alum

    Electric Potential slowing a charged particle to a stop

    Homework Statement A particle (mass 6.7 × 10–27 kg, charge 3.2 × 10–19 μC) moves along the positive x-axis with a speed of 4.8 × 105 m/s. It enters a region of uniform electric field parallel to its motion and comes to rest after moving 2.0 m into the field. What is the magnitude of the...
  32. L

    Potential Energy and Potential -- Systems versus Particles

    When I first learned about these subjects, I did what was intuitive to me and treated particles as if they carried potential energy. I would do this similarly for rigid bodies where I would also treat them as a particles with their body's mass at the center of mass. This wasn't helped by...
  33. D

    Calculate Electric Potential from Non-uniform Linear Charge

    Homework Statement "A rod of length L lies along the x-axis with its left end at the origin. It has a non-uniform charge density λ=αx where α is a positive constant. a) What are the units of α? b) Calculate the electric potential at A. Homework Equations Linear charge density: λ = Q/L where Q...
  34. CharlieCW

    Finding electric potential using Green's function

    Homework Statement We have two semi-infinite coplanar planes defined by z=0, one corresponding to x<0 set at potential zero, and one corresponding to x> set to potential ##V_0##. a) Find the Green function for the potential in this region b) Find the potential ##\Phi(r)## for all points in...
  35. J

    Electric Potential and Field Diagram - True/False

    Homework Statement Four charges are arranged at the corners of a square as shown in the figure. Q1 is at (-L/2,L/2), Q2 is at (L/2,L/2), point a is at the origin and Q1=Q2=-Q3=-Q4. Which of the following statements correctly describe the electric field E and the potential at points a,b and c...
  36. R

    Electric Potential on the axis of a truncated cone

    1.Data: We have an truncated cone with a volumentric charge density ρ, and it's uniform. The image show the truncated cone and show some info of the radios. 2. Question. We need to calculate the potential on the vertical axis. note: adding an image of the problem but it's in spanish, hope...
  37. K

    Conceptual Issue RE: electric potential difference

    Homework Statement My main conceptual issue here surrounds positives and negatives as they apply to electric potential difference. I will post two questions that illustrate my confusion, if that's ok. 1) The electrons in an old TV picture tube are accelerated through a potential difference of...
  38. rpthomps

    Comparing 100J and -100J of Electric Potential Energy

    Is the 100 J of electric potential energy actually greater than -100 J of electric potential energy?
  39. physics girl phd

    Solving Electric Potential Difference in a Linearly Varying Field

    Homework Statement I'm trying to do a problem two ways, and things aren't consistent, finding the electric potential difference in a linearly varying field. The electric potential difference between two points is often summarized in texts as ΔV = Vf - Vi = - ∫ E⋅ds where the lower bound of...
  40. L

    At what point is Electric Potential zero

    1. The problem statement Two charges of 3μC and -2μC are placed 2cm apart. At what point along their connecting line is electric potential zero? Homework Equations Electric potential superposition Φ=Φ1-Φ2 since q2 is negative Φ=kq/r^2 The Attempt at a Solution Let’s say the charges are on the...
  41. P

    Wire surrounded by a linear dielectric in a uniform E field

    Homework Statement We have an uncharged, conducting wire with radius a. We surround it by a linear dielectric material, εr, which goes out to radius b. We place this in an external electric field, Eo. Homework Equations We have electric potential inside (a < s < b) Vinbetween=Acosφ +...
  42. K

    Is Electric Potential value classical?

    There is no absolute electric potential. Is it due to classical ignorance (because we don't know the static fields, capacitive coupling, etc. of the surrounding environment) or is it due to quantum ignorance (the potential can fluctuate to any value due to HUP)? My question is valid because...
  43. P

    Calculating the electric potential

    Homework Statement We have the cross section of a metal pipe that has been split into four sections. Three of the sections have a constant electric potential, Vo. The fourth section is grounded so electric potential is zero. We are looking for electric potential inside and outside of the pipe...
  44. E

    The sign of F (dot) dl when finding electric potential

    The electric potential can be defined as V = - ∫C E⋅dl where we are taking the line integral along C from some convenient reference point O, where we have set V = 0, to the point r we are trying to find the potential at. Of course, C can be any curve, but it's usually the most convenient to...
  45. B

    Electric Field and Potential in a conductor

    So in my textbook (Introduction to Electrodynamics by Griffiths) it said that inside a conductor, the electric field E would have to zero, since if it wasn't the free charges would move accordingly and create a electric field that cancels the original field. But in a question that soon followed...
  46. HotFurnace

    Electric Potential Distribution in a Vacuum Diode

    Homework Statement This problem is belonging to a book, which is material for Vietnamese students who will take part in IPhO (International Physics Olympiad). Since this problem is written in Vietnamese, I will try my best to translate it to English: A vacuum diode consists of two parallel...
  47. P

    Electric potential energy between charge and moving magnet

    The setup for one magnet Introduce a magnet: Inertial Frame 1 (or lab frame) A frame where a magnet is seen to move with uniform velocity v and carries a uniform polarization P while a point charge Q is seen to be stationary at time t=0. Inertial Frame 2 (or material frame) A frame where a...
  48. L

    Electric Potential Integral Question Confused

    Homework Statement Homework Equations E=KQ/R^2 The Attempt at a Solution I'm kinda confused at what the question is asked. It is in terms of x, but I thought the integral for potential is V=int(Edr)? Also, should it be integration starting from infinity? Why is the integration from -2 to 3...
  49. L

    Electric Potential at Radius R of Concentric Spheres

    Homework Statement Homework Equations V=kQ/R The Attempt at a Solution The answer is B)kQ/R. It is because V= k(2Q)/R. I don't understand why Q=2Q in this case. Isn't the point on the inside of the outer shell, so the Q for the equation is just Q?
  50. cookiemnstr510510

    Derivation of electric potential charged disk from ring

    Homework Statement a)recall that electric potential is a scalar quantity. For a circular ring of radius, R', carrying charge, Q, what is the electric potential at a height,y, above the center of the ring? b)Use your above answer to determine the electric potential at a height,y, above the...
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