What is Electrostatic potential: Definition and 137 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. J

    Do Electrons gain mass in an electrostatic potential?

    Hi, I have been looking into the phenomenon of Zitterbewegung which is a high frequency oscillatory motion of the electron that is predicted by the Dirac Equation for a free electron. One way of looking at this motion is that it is the interference of plane waves with positive and negative...
  2. C

    Electrostatic Potential from a uniform line of charge?

    Homework Statement a) What is the value of an electrostatic potential V, a distance r from a point charge Q? b) A uniform line of charge, of linear charge density (\lambda), extends along the x-axis from x = 0, to x = a. i) By considering the contributions from the infitisimal elements...
  3. R

    Electrostatic potential and velocity

    Homework Statement Point A is at an electrostatic potential of +1V relative to point B in a vacuum. An electron initially at rest at B moves to A. What is its velocity in m/s? Homework Equations E = PE + KE PE= J/q * q KE = 0.5 mv^2 (where v = velocity) The Attempt at a Solution...
  4. Q

    Electrostatic Potential Energy

    Homework Statement How much work is required to exchange the positions of q2 and q3? q2 q3 q1 q1 and q2 are separated by a distance of 4.00 cm and q2 and q3 are separated by a distance of 2.00cm The charge on q1 is 5.00nC, q2 is -5.00nC and q3 is 10.0nC Homework...
  5. T

    Electrostatic potential in Legendre polynomials

    Homework Statement Two spherical shells of radius ‘a’ and ‘b’ (b>a) are centered about the origin of the axes, and are grounded. A point charge ‘q’ is placed between them at distance R from the origin (a<R<b). Expand the electrostatic potential in Legendre polynomials and find the Green...
  6. U

    Electrostatic potential energy in a circuit with and without a battery

    I have two plate capacitors serially connected in a circuit with a battey and a switch between the battery and one of the plate capacitors. I have two situaions: a) I charge the capacitors, cut the switch, and double the internal distance in one of the capacitors. b) I charge the...
  7. J

    What is electrostatic potential

    I can't understand what actually is the electrostatic potential.The definition given in my textbook is as follows : "Electrostatic potential at any point in a region of electrostatic field is the minimum work done in carrying a unit positive charge from infinity to that point without...
  8. Z

    Electrostatic Potential Question - Basic physics

    Hi Everyone! I'm new to this forum, and English isn't my first language - I would really appreciate your help with this question :) Homework Statement http://img225.imageshack.us/img225/3807/1milliontotheground.jpg there are given 2 thin shells with radiuses b and c, and a full sphere...
  9. S

    How Does Changing Voltage Affect Particle Descent Time?

    Homework Statement Two parallel plates are positioned horizontally and when the potential te?difference between the plates is 400 V, a charged particle is suspended freely 10 cm above the lower plate. If the potential difference is suddenly changed to 200 V, how long will it take the particle...
  10. V

    Electrostatic potential of a split sphere, using the laplacian for spherical coord

    Homework Statement Two concentric spherical shells. The outer shell is split into two hemispheres at potentials +Vo for the upper half and -Vo for the lower half. The inner shell is at zero potential (see attachment). " what is the potential in the region; r > R' " (the potential in the...
  11. G

    Electrostatic Potential Energy of a Conducting Sphere

    Homework Statement Determine the total electrostatic potential energy of a conducting sphere of radius r_0 that carries a total charge Q distributed uniformly on its surface. Give your answer in terms of Q, r_0, epsilon_0 and appropriate constants. Homework Equations The Attempt at...
  12. K

    What is the potential of the bigger sphere when the smaller sphere touches it?

    Homework Statement A spherical conductor of radius 2 m is charged to 120V. It is now placed inside another hollow spherical conductor of radius 6m. Calculate the potential to which the bigger sphere would be raised if the smaller sphere were made to touch the bigger sphere. Homework...
  13. L

    Electrostatic Potential homework

    Homework Statement A test charge +q is brought to a point A a distance r from the center of a sphere having a net charge +Q. Next, a test charge +2q is brought to a point B a distance 2r from the center of the sphere. Compared with the electrostatic potential at A, the electrostatic potential...
  14. S

    Electrostatic Potential of 4 charged spheres on corners of a square

    Homework Statement Four idential charged spheres are located at the corners of a square with side length 2a. The spheres are much smaller than the size of the square (r<<a) and each sphere has a mass m and carries the same charge -Q. a) What is the total electrostatic potential energy of...
  15. S

    Electrostatic Potential for Two Concentric Cylindrical Shells

    Homework Statement Two very long hollow conducting cylindrical shells are situated along the x-axis. The shells are concentric and have negligible thickness. The inner shell has a radius a and a linear charge density +lambda, while the outer shell has a radius b and a linear charge density...
  16. A

    Electrostatic potential independent of distance?

    Say I have a packet of electrons just sitting there, before they repel each other, what is their potential energy? I have no idea of how to calculate their potential energy since at r = 0 , U = infinity, which is not helpful since my problem requires U to be finite but the only way I know of...
  17. V

    Minimum distance & electrostatic potential energy

    An alpha particle (made of 2 protons and 2 neutrons) with initial kinetic energy of 1.20 × 10^-12 J travels directly towards the nucleus of the stationary zinc atom The nucleus of a zinc atom contains 30 protons and 35 neutrons, and has a diameter of 4.00 × 10^-13 cm. The alpha particle slows...
  18. D

    Electrostatic potential of unit charge in vacuum

    Homework Statement I'm having hard time seeing that from this picture: Follows that: \phi(\vect{r})=\frac{q}{4\pi\varepsilon_0}\cdot\frac{1}{|\vec{x}|} The thing that puzzles me isn't the equation but this...
  19. J

    Electrostatic Potential inside sphere of uniform charge.

    1. Given a sphere of uniform charge Q, radius R: Find an expression for the electrostatic potential V as a function of r for r ≤ R. Prior proof: E= Q(r)/(4πϵ0)r^2 ,for r≤R where Q(r) is the excess charge in the spherical volume of radius r 2. Relevant equation: V = Q/(4πϵ0)r 3. I tried...
  20. L

    What Causes the Negative Sign in Electrostatic Potential Energy Calculations?

    another pretty simple question that i can't see: a 1d harmonic oscillator of mass m carries an electric charge q. a weak uniform, static electric field of magnitude E is applied in the x direction. what is the classical electrostatic potential energy for a point particle at position x...
  21. H

    Electrostatic potential problem (got 1/3) correct

    Point charges q1, q2, and q3 are fixed at the vertices of an equilateral triangle whose sides are 2.50 m long. Find the electrostatic potential energy of this system of charges for the following charge values. a.)q1=q2=q3=3.90uC I got the right answer for this one 164mJ...
  22. A

    Change of variable in electrostatic potential energy.

    Homework Statement Hello everyone i have a problem in visualizing why a a change of variable happens. To evaluate a volume integral. I hope that someone could give me a hint of the reasoning that makes you think in that specific change of variable. Homework Equations See the attachment for...
  23. L

    Does Electrostatic Potential Obey Superposition?

    why does electrostatic potential obey superposition? it's a solution of poisson's equation and solutions of poisson's equation definitely do not obey superposition!
  24. L

    Light in electrostatic potential

    Is electromagnetic radiation affected, in any way, by a strong electrostatic field (or gradient of field)? Specifically, is it possible to reflect light with such a field or to confine an EM wave inside an electrostatic potential well?
  25. C

    Electrostatic Potential Energy

    Homework Statement What is the electrostatic potential energy of an isolated spherical conductor of radius 24 cm that is charged to 3.9 kV? Homework Equations Electric potential U = (kQ)/r The Attempt at a Solution U = ((8.99 * 109 ) * (3.9 * 103)/(0.24) Could...
  26. S

    Electrostatic potential and electric fields

    Homework Statement 3. Four charged particles are held fixed at the corners of a square of side s. All the charges have the same magnitude Q, but two are positive and two are negative. In Arrangement 1, shown , charges of the same sign are at opposite corners. Express...
  27. W

    Find the electrostatic potential due to a hoop of charge

    Homework Statement (Part 1) A hoop of charge of radius k lies in the y, z plane, centred on the x axis, so that it occupies the points (0, y, z) with y^2 + z^2 = k^2. If the (linear) charge density in the hoop is j, calculate the electrostatic potential Fi at all points on the x axis, and...
  28. L

    Solving Possion's equation: electrostatic potential

    I have the problem and my work uploaded to this webpage. I believe I have the general idea down, but I'm just afraid that I've done a careless calculation and missed a minus sign somewhere. I feel that my results have a lot of negative signs, making the potential constantly negative. I'm not...
  29. E

    Photoelectric Effect and electrostatic potential

    Homework Statement A silver ball is suspended by an insulating string in a vacuum chamber and light of wavelength 200nm is directed at it. The ball and the chamber are both initially at zero electrostatic potential. Electrons ejected from the ball causes the electrostatic potential to change...
  30. K

    Electrostatic Potential in Electric Fields

    Homework Statement 1. Four charged particles are held fixed at the corners of a square of side s. All the charges have the same magnitude Q, but two are positive and two are negative. In Arrangement 1, shown below, charges of the same sign are at opposite corners. Express your answers to...
  31. Reshma

    What is the Proportionality of Electrostatic Potential at a Distance?

    Homework Statement (Objective type question) Consider a square ABCD of side a, with charges +q, -q, +q, -q placed at the vertices, A, B, C, D in a clockwise manner. The electrostatic potential at some point located at distances r(r>>a) is proportional to? Homework Equations V...
  32. W

    Electrostatic potential energy for concentric spheres

    Two concentric metal spheres have radii r_1 = 10 cm and r_2 = 10.5 cm. The inner sphere has a charge of Q = 5 nC spread uniformly on its surface, and the outer sphere has charge -Q on its surface. (a) calculate the total energy stored in the electric field inside the spheres Hint: You can treat...
  33. E

    Negative electrostatic potential energy

    I have an example in my book showing 3 point charges each at the vertices of an equilateral triangle. q1 = +2 microC, q2 = -2 microC, and q3 = +1 microCoulombs. the distance between each is 0.30m. The example calculates the electrostatic potential energy of the charge configuration, obtaining...
  34. T

    Comparing Electrostatic Potentials of Positive and Negative Charges

    This is more of a general question and not a homework question, just to make it clear. Say two test charges are brought separately, one after the other, into the vicinity of a charge +Q. First test charge +q is brought to point B a distance r from +Q. This charge is removed and a test charge -q...
  35. maverick280857

    What is the Electrostatic Potential at Any Point on a Spherical Shell Due to an External Point Charge?

    Potential at ANY point on a spherical shell due to external point charge Hi everyone Here is another problem: A point charge q is placed at a distance of r from the center of an uncharged conducting sphere of radius R (< r). Find the potential at any point on the sphere. I know the...
  36. H

    Mean Value Theorem and electrostatic potential

    Prove that for charge-free two-dimensional space the value of the electrostatic potential at any point is equal to the average of the potential over the surface of any circle centered on that point. Do this by considering the electrostatic potential as the real part of an analytic function...
  37. B

    Is Electrostatic Potential Zero When Electric Field Is Zero?

    1}If the electric field is zero in some region, must the potential also be zero?An example? 2}Give an example of a conductor that is not an equipotential.Is this conductor in electrostatic equilibrium? 3)If a high voltage cable falls on top of your automobile, will you probably be safest...
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