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. T

    Why is electric potential energy U defined negative in this example?

    Homework Statement From Young and Freedman's book University Physics, ch 23, problem 23.54: In the Bohr model of the hydrogen atom, a single electron revolves around a single proton in a circle of radius r. Assume the proton remains at rest. ++ (the rest is irrelevant to my question)...
  2. N

    Electric Potential Homework: Answers to 1 & 2

    Homework Statement 1. A positive charge of magnitude 2 microC is at the origin. (b)How much work must be done by an outside agent to bring a 3 microC charge from infinity to r=4, assuming that the 2 microC charge is held fixed at the origin ? (c) How much work must be done by an outside...
  3. T

    Electric potential of a ring

    Homework Statement what is the electric potential a distance x above the center of a ring of charge Q with a radius R surrounded by another ring of charge -Q with a radius 2R? Homework Equations V= kQ/sqr root(a^2+x^2) The Attempt at a Solution I know the above equation would be...
  4. S

    Electric field and electric potential for point charges problem

    Homework Statement Given two 1.80 µC charges at +/- 0.800 m from the origin and a positive test charge q = 1.30x10-18 C at the origin. What is the electric field at the origin due to the two 1.80 µC charges? What is the electrical potential at the origin due to the two 1.80 µC charges? related...
  5. B

    Electric Potential with a hollow insulated sphere

    Homework Statement Consider a hollow metallic sphere of finite thickness, with the inner radius a and the outer radius b. A point charge q is placed inside the sphere at a distance a/2 from the center of the sphere (the sphere is insulated). a) What is the potential at a point r outside the...
  6. P

    Electric potential for an infinite plane charge distribution

    Hello everybody, I have to calculate the electric field and the potential for a charge q placed at distance d from an infinite plane charge distribution \sigma. For the electric field there's no problem, but how I can get the electric potential for an infinite charge distribution?
  7. M

    Electric Potential: Solving for Time w/ E, V, & X

    I'm not asking anyone to solve my homework for me but I am stuck on this problem. The problem includes finding the time is takes for an electron with a horizontal initial speed v m/s to make it through a region with an electric field X V/m pointing vertically upward. One equation I found...
  8. D

    Electric Potential From Electric Field

    Homework Statement Two particles, of charges q1 and q2 are separated by distance d. The net electric field due to the particles is zero @ x=d/4. With V=0 @ infinity, locate (in terms of d) any point on the x axis (other than infinity) at which the electric potential due to the two...
  9. T

    Electric Potential Difference b/w A & B: Solving for VA - VB

    Homework Statement Two points (A and B) are shown in a constant electric field of E = 850 N/C. The distance between A and B is L = 2 m. The line joining the two points makes an angle of 40 degrees with the electric field. Determine the electric potential difference (in Volts) between points A...
  10. C

    Finding electric potential of a sphere with a given volume charge density

    Homework Statement the volume charge density Pe= Po (1- (r^2/r0^2)) the sphere has a radius of r0 and r is measured from the center for a point P inside the sphere (r<r0), determine the electric potential V if V=0 at infinity Homework Equations E= Qencl/ eps0*A= kQ/r^2 Qencl=...
  11. L

    E-field & electric potential of a metal conductor

    A few questions about electric field here: 1. Why do charges have to be on the outer surface of the conductor? 2. Why no charge on the inner surface of a hollow conductor? 3. If charges cannot be inside the conductor, how come the electric potential is constant throughout the conductor when...
  12. F

    Again an electric potential question ?

    Again an electric potential question ? Homework Statement Question # 1 A charge of 7.034 nC is uniformly distributed along the x-axis from −4 m to 4 m. What is the electric potential (relative to zero at infinity) of the point at 5 m on the x-axis? Homework Equations...
  13. C

    Electric potential energy and point charges

    Homework Statement Two point charges , Qz= +5.00 nanoC and Q2= -3.00 nanoC, are separated by 35.00 cm. a) What is the potential energy of the pair? What is the significance of the algebraic sign? b) what is electrical potential at a point midway between the charges? (here I'm supposing i'd...
  14. O

    Electric Potential from a uniformly charged sphere

    Homework Statement A nonconducting sphere has radius R = 2.70 cm and uniformly distributed charge q = +7.00 fC. Take the electric potential at the sphere's center to be V0 = 0. (a) What is V at radial distance r = 1.45 cm? (b) What is V at radial distance r = R? Homework Equations E...
  15. K

    Electric Potential and Potential Difference

    Homework Statement Calculate the speed of a proton that is accelerated from rest through a potential difference of 135 V. 1 km/s (b) Calculate the speed of an electron that is accelerated through the same potential difference. 2 Mm/s Homework Equations V=U/q The Attempt at a...
  16. W

    Electric Potential Energy Question

    A test charge of +1.0 x 10^-6 C is 40 cm from a charged sphere of 3.2 x 10^-3 C. a) How much work was required to move it there from a point 1.0 x 10^2 m away from the sphere? b) How many electrons were gained or lost from the test object. Relevant equations: Ee = kq1q2/r N = q/E...
  17. M

    Electric Potential Normalization

    I was in my Electrodynamics lecture last week, still working the Laplacian and Poisson equations, when we discussed an infinite parallelpipid (infinite in the x direction, length a and b in the y and z direction respectively) with a potential of \Phi=\Phi_0 at x=0 plane and every other face...
  18. D

    Electric potential difference

    A solid insulating sphere has radius a = 3.2 meters and total charge Q = 3.6 Coulomb's. Calculate the potential difference between the center of the sphere and a point r = 0.64 meters from the center of the sphere. (A positive answer represents the center is at a lower potential, a negative...
  19. T

    Electric Potential, spherical shell: Multiple Choice

    A non-conducting, spherical shell centered at the origin has radius r1 and total charge -Q, where Q is a positive value. (DO NOT ASSUME THE POTENTIAL AT INFINTIY IS ZERO!) http://i662.photobucket.com/albums/uu347/TwinGemini14/ELECpotential.gif 1) The electric potential just outside the...
  20. L

    Why does the inside of a conductor have the same electric potential everywhere?

    My teacher said so, but I just don't understand why. Is it because of the free movement of electrons inside the conductor?
  21. S

    Electric Potential energy for geometric objects

    I recently found out how to calculate the potential energy of a charged insulated sphere of radius R and charge density rho. I would like to know how to calculate the potential energy for other geometric objects, such as a line of charges, a sheet of charges, or a pyramid of charges. I don't...
  22. fluidistic

    Electric potential energy question

    I've done an exercise that made me think a bit. Here's it is : https://www.physicsforums.com/showthread.php?t=333608. So the electric potential energy of a 1 dimensional crystal (lattice?) formed by alternating ions is about \frac{-ke^2 \ln 2}{a}. So as it is a negative number, I would have...
  23. E

    Electric potential for cylindercal

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  24. R

    Electric Potential and Potential Energy in a Circuit

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  25. F

    Calculating Electric Potential of a Proton in Hydrogen Atom

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  26. C

    Electric potential energy to kinetic energy

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  27. C

    Electric potential energy and electric potential.

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  28. N

    What is the effect of charge and distance on electric potential energy?

    Homework Statement A, B, C and D are corners of a square in empty space, sides 12 micrometres, charges +5nC and -5nC are placed at corners A and B respectively. What is the change in the electric potential from D to C? (take care with sign) A third charge of -2nC is initially at D then...
  29. E

    Electric Potential Energy of More Than Two Charges

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  30. M

    Electric Potential Energy of a sphere

    Homework Statement A test charge of +1.0x10^-6 C is 40cm from a charged sphere of 3.2x10^-3 C. How much work was required to move it there from a point 1.0x10^2 m away from the sphere? Homework Equations W = \DeltaE W = Ee2 - Ee1 The Attempt at a Solution Ee2 =...
  31. U

    Explanation regarding electric potential energy

    I just read this article (http://physics.bu.edu/~duffy/PY106/Potential.html). I am stuck on just one line where it says that potential energy is in negative...please read this and explain... """""An example : Ionization energy of the electron in a hydrogen atom In the Bohr model of a...
  32. B

    Electric potential configuration problem

    Homework Statement Hello: I was wondering if someone can help with the following: The xy, xz, yz plane are all at equipotential. A charge Q is placed equidistant from all these planes. So I think the coordinate of this Q would be (d, d, d) given some d. If I wanted to find a...
  33. E

    Where Electric Potential is Zero

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  34. B

    Optimizing Energy Storage in a Uniformly Charged Sphere

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  35. X

    The electric potential difference created by point charges.

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  36. P

    Electric potential for a sphere of charge

    Homework Statement A sphere with radius 65 cm has its center at the origin. Equal charges of 2 µC are placed at 72 degree intervals along the equator of the sphere. The Coulomb constant is 8.99×10 N·m^2 / C^2. (a) What is the electric potential at the origin? Answer in units of kV. (b) What is...
  37. P

    Electric potential at the origin

    Homework Statement A sphere with radius 65 cm has its center at the origin. Equal charges of 4 μC are placed at 60◦ intervals along the equator of the sphere. What is the electric potential at the origin? Homework Equations V=KQ/R The Attempt at a Solution I just plug the...
  38. U

    Still confused about electric potential difference *read first*

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  39. P

    Electric Potential: Solving Proton Displacement & Energy Conservation

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  40. P

    Calculating Point Charge from Kinetic Energy and Electric Potential

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  41. N

    Electric Potential Earth and Sun?

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  42. A

    Electric potential and electric field

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  43. B

    Electric Potential: Solve for Energy to Move -5uC Charge to Infinity

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  44. C

    Stuck integral (electric potential)

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  45. P

    I think i did this electric potential problem correctly but

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  46. C

    Help compute integral (electric potential)

    Homework Statement How to calculate the following integral: Integral( 1/ |x-y| dS) where x and y are vectors in R^2, || represents norm. So say x= (x1,x2), y=(y1,y2). Then the integral is [ dS/ sqrt ((y1-x1)^2 + (y2-x2)^2)]. The problem is: I need to integrate this over any plane in...
  47. C

    Help compute integral (electric potential)

    Homework Statement How to calculate the following integral: Integral( 1/ |x-y| dS) where x and y are vectors in R^2, || represents norm. So say x= (x1,x2), y=(y1,y2). Then the integral is [ dS/ sqrt ((y1-x1)^2 + (y2-x2)^2)]. The problem is: I need to integrate this over any plane in...
  48. R

    Why is the change in electric potential leading to a negative work value?

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  49. G

    Electric Potential: Calculating the Final Ball Potential

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  50. A

    Electric Potential: Find x for Zero Net Electric Potential

    Homework Statement Particles of the charges q1=+5e (at origin) and q2=-15e are fixed in place with a separation of d=0.24m. With V=0 at infinity, what are the finite (a) positive and (b) negative values of x at which the net electric potential on the x-axis is zero? Homework Equations...
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