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.

View More On Wikipedia.org
  1. S

    Finding the charge and initial position, electric potential problem.

    The electric potential a distance r from a point charge q is 2.40×104 V. One meter farther away from the charge the potential is 6500 V. Homework Equations V=kq/r The Attempt at a Solution 6500 = 8.99x10^9 (q) / 1m q = 7.230 x 10^-7 then, r= kq/v r= 8.99x10^9 (7.230 x 10^-7)...
  2. J

    Stiffness vs. electric potential

    How is stiffness affected by potential?
  3. D

    Energy Conservation - Electric Potential Energy

    Homework Statement In proton-beam therapy, a high-energy beam of protons is fired at a tumor. The protons come to rest in the tumor, depositing their kinetic energy and breaking apart the tumor’s DNA, thus killing its cells. For one patient, it is desired that 0.10 J of proton energy be...
  4. G

    Calculating Electric Potential Differences

    Homework Statement When an electron moves from A to B along an electric field line in the figure below, the electric field does 2.00 10-19 J of work on it. What are the electric potential differences: (a) VB - VA (b) VC - VA (c) VC - VB Homework Equations Ok so I know that the...
  5. N

    Calculate the change in electric potential energy

    1. Calculate the change in electric potential energy for a -10µC charge in a uniform electric field of strength 1750 N/C, traveling in a the straight paths OA, OB, or OC as shown. The figure shown is a rectangle with OA being a base, OC being a side and OB being a diagonal (No angle is given)...
  6. K

    Find the electric potential at any point on the x axis

    Two positive point charges each have a charge of +q and are fixed on the y-axis at y = +a and y = -a. (Use k, q, a, and x as necessary.) (a) Find the electric potential at any point on the x axis. V = 2kq/[sqrt(x^2+a^2)] (b) Use your result in part (a) to find the electric field at any...
  7. A

    How Is Maximum Speed Calculated for Identical Charges Released Simultaneously?

    Homework Statement Two identical +6x10^-6 C charges, each with a mass of 10^-6, are placed as shown in the diagram below. All coordinates are in meters. ... An identical charge is brought in slowly from far away to point P. ... All three charges are released simultaneously. What is the...
  8. A

    How does electric current change electric potential?

    Suppose we have an electrically insulated box in a room, and the potential difference between the box and the room is given by V_1=V_{Box1}-V_{room}. Now suppose we inject the box with X amps of current, for t seconds. The new voltage is now given by V_2=V_{Box2}-V_{room} By how much does the...
  9. R

    Change in Electric Potential Question

    In Ernest Rutherford's scattering experiment, described in detail in an earlier homework problem in this chapter, alpha particles (with a mass of 6.68×10–27 kg and a charge of 3.20×10–19 C) come from a few milligrams of radium (to be very precise, its decay product radon). They leave with an...
  10. R

    Potential difference, electric potential energy and work

    Four charges are arranged at the corners of a rectangle as shown in the diagram. How much work needs to be done to move the charge q2 to infinity? Since change in PEe = W, am I suppose to find total potential electric energy of the four charges and then subtract the total potential electric...
  11. S

    Electric Potential Energy of a Rod

    Homework Statement There is a thin rod of length L that carries a uniform charge per unit length \lambda. Starting from the expression for the potential of a point charge, derive an expression for the electric potential V (y) at a distance y away from the centre of the rod on the axis (y) of...
  12. S

    Derive Electric Potential Energy

    [b]1. The problem statement, all variables and given/known For a a uniformly charged sphere of radius R with total charge Q, show that the potential energy of a point charge q' varies with r U(r) = Qq'/4\pi\epsilonR * (3/2 - r2/2R2 if r < R Homework Equations \DeltaU = - \intE(r)q'dr...
  13. P

    Change in electric potential energy

    1. Homework Statement A tire of radius 32.5 cm has a surface that is conducting. A charge of 4.89×10-8 C is then placed on the surface. The potential on the tire's surface is 1.35E+03 V. Later, suppose that some of the air is let out of the tire, so that the radius shrinks to 10.5 cm, the new...
  14. P

    Change in electric potential energy

    Homework Statement A tire of radius 32.5 cm has a surface that is conducting. A charge of 4.89×10-8 C is then placed on the surface. The potential on the balloon's surface is 1.35E+03 V. Later, suppose that some of the air is let out of the tire, so that the radius shrinks to 10.5 cm, the...
  15. O

    Find the change in electric potential energy

    Homework Statement A uniform electric field with a magnitude of 6890 N/C points in the positive x-direction. Find the change in electric potential energy when a +12.5 µC charge is moved 5.87 cm in the following directions. In the positive x-direction In the negative x-direction...
  16. A

    How Is Electric Potential Calculated for a Charged Wire Bent into a Circle?

    Homework Statement A wire that has a uniform linear charge density of 2.2 μC/m is bent into the shape as shown below, with radius 3.7 m. The Coulomb constant is 8.98755 × 109 N · m2/C2. Find the electrical potential at point p. Here is the image...
  17. R

    Position Varying Electric Potential

    http://img168.imageshack.us/img168/3786/66134795.png Part one was simple enough, just insert the variables in the equation given V = (5)(92)(7) - (9)(9)(6) - (9)(72) = 1908 V Part two, three and four is where I am getting confused. Usually I would use triangles to figure out...
  18. M

    Electric Potential Homework: Find Q (microC) from 0.4J KE at x=0.5m

    Homework Statement A point charge Q resides at the origin. A particle of mass 0.001kg carries a charge of 6 microC. The particle is released from rest at x = 3m. Its kinetic energy as it passes x = 0.5m is 0.4J. The coulomb constant is 8.99x10^9Nm^2/C^2. Find the charge Q. Answer in microC...
  19. fluidistic

    Electric potential, hard problem

    Homework Statement There's a cylindrical conductor of radius d, whose linear charge density is \lambda which is situated at a distance D from a infinite conductor plane. 1)Calculate the potential in the region that starts from the plane and ends at infinity (hence the cylindrical conductor...
  20. D

    Electric Potential and Coulomb's Law Questions

    Any answers would be great, thanks! Homework Statement 1. A charge Q is uniformly spread along the x-axis from x=0 to x=l. Find the electric potential function at points on the x-axis for x>l. 2. An electron moves from one point to another where the second point has a larger value of the...
  21. D

    Electric potential with regards to an insulating spherical shell

    An insulating spherical shell with inner radius 25.0 \rm cm and outer radius 60.0 \rm cm carries a charge of + 150.0 \mu {\rm C} uniformly distributed over its outer surface. Point a is at the center of the shell, point b is on the inner surface and point c is on the outer surface. What will...
  22. C

    Electric Potential: Solving for Center of Sphere

    Homework Statement What is the electric potential at the center of a uniformly charged sphere? Homework EquationsEd=-VThe Attempt at a Solution Integrate from infinity to the center of the sphere and be sure to account for the changing electric potential. I was told that the answer might be...
  23. C

    Electric Potential: V=-ED for Capacitors?

    Homework Statement Why is the change in the electric potential between two capacitors V=ED ? Homework Equations V=-ED The Attempt at a Solution Isn't the change in electric potential equal to the negative of the product of the electric field and displacement? So, why is it that...
  24. R

    Electric Potential Homework - Alpha Particle & Electron Impact Speeds

    Homework Statement A 2mm diameter plastic bead is charged to -1nC (*note - the bead is not hollow) a) An alpha particle is fired at the bead from far away with a speed of 1x106 m/s and it collides head-on. What is the impact speed? b) An electron is fired at the bead from far away. It...
  25. fluidistic

    Electric potential of a hollow sphere

    Homework Statement Consider a radial charge distribution of the form \rho = \rho _0 \frac{b}{r}, for a \leq r \leq b. Find the potential for all r. Homework Equations Not sure. The Attempt at a Solution From my memory (and I didn't find it in wikipedia), the potential at a point...
  26. K

    Electric Potential of 3 point charges

    [b] 1. The arrangement of charges shown in the figure is called a linear electric quadrupole. The positive charges are located at +-s. Notice that the net charge is zero. Find an expression for the electric potential on the x-axis at distances y>>s. Homework Equations V= \sum1/4pi...
  27. C

    Charge on Ion After 10V Potential Difference: Calculate?

    Homework Statement An ion accelerated through a potential difference of 10V experiences an increase in kinetic energy of 7 J. Calculate the charge on the ion.Homework Equations U=qV -qV=WThe Attempt at a Solution My book says the charge is positive, but I think that the charge is suppose to be...
  28. M

    Find the electric potential energy of this system of charges

    Homework Statement A point charge q_1 = 86.5 uC is held fixed at the origin. A second point charge, with mass m = 5.90×10−2 kg and charge q2 = -2.95 uC, is placed at the location (0.323 m, 0) 1) Find the electric potential energy of this system of charges. 2)If the second charge is released...
  29. fluidistic

    Electric potential of a configuration of charges

    Homework Statement The configuration is as follows: there's a charge q separated by another charge q (the distance is a) which is separated by a charge -q. And it continues to infinity. The distance of separation is always "a" and all the charges are linearly situated. I must show that...
  30. K

    Find an expression for the electric potential at P

    The thin, uniformly charged rod shown in the figure below has a linear charge density λ. Find an expression for the electric potential at P. (Use k_e for ke, lambda for λ, a, b, and L as necessary.) Homework Equations dV=k*dq/r lambda*dx=dq The Attempt at a Solution I integrated...
  31. L

    Finding the relationship between electric potential and the electric field

    Homework Statement Consider if these things are scalars or vectors. Which is easier to work with, scalar or vector quantities? What is the relationship between electric potential and the electric field? Homework Equations The electric field equation: E = 4*pi*k*sigma / (- (base zero)...
  32. L

    Relating Electric Feild and Electric Potential

    Looking at the equations for electric field and for electric potential: The electric field equation: E = 4*pi*k*sigma / (- (base zero) The electric potential equation: /\U (base E) = -W(base E) = -q*E*d /\ - delta Could someone help me figure out their relationship? I am...
  33. D

    Help figuring out Electric Potential

    Homework Statement Three charges are laid out in a Cartesian Plane: +q: (0,a) -q: (0,0) +q: (0,-a) There is some point p located on the x-axis in the positive x direction Show that the points where the Electric potential is 0 is x= +/- a/sqrt(3)Homework Equations I believe I am to use...
  34. L

    What is the relationship between electric potential and the electric field?

    I know of the equations can be found here: http://hyperphysics.phy-astr.gsu.edu/hbase/electric/engfie.html And the equations are similar both involving permittivity, but I don't know their fudemental relationship. Could someone help? Thanks in advance.
  35. F

    The electric potential of 2 hollow concentric spherical shells

    Homework Statement Consider two concentric conductive hollow spherical shells. The inner shell has radius R1 and holds the charge +q. The outer shell has charge R2 and holds charge -q. Determine an expression for the potential difference between the shells.Homework Equations V = q / (4 pi ε0...
  36. E

    Electric potential energy in a lightnight bolt

    1. During a particular thunderstorm, the electric potential difference between the clouds and the ground is Vcloud-Vground = 10^9 Volts with the cloud being at the higher potential. Now, there is a lightning flash in which a charge of -25C is transferred from the groud to the cloud. 2. a)...
  37. A

    How does current affect electric potential?

    Suppose you have an two objects A and B having different potentials \phi_A, \phi_B and voltage V=\phi_A- \phi_B. Suppose you allow current to flow from one object to another for some period of time according to Ohm's Law (V=IR) Now what is the new value of the voltage? thanks
  38. B

    Electric Potential problem, 4 equal charges, different signs, weird shape.

    Homework Statement The drawing shows four point charges. The value of q is 1.96 µC, and the distance d is 0.93 m. Find the total potential at the location P. Assume that the potential of a point charge is zero at infinity. Image of problem is attached. Homework Equations V=kq/r The...
  39. K

    Earth as a reference for electric potential

    If we apply the formula for the capacitance of a sphere (C= 4PEr, where P=pi, E= permittivity of free space, and R= radius of the earth), and apply the values we get a value of around 700 microfarad. If we now work out the potential on the surface of the Earth (V=q/c) we get a fairly high value...
  40. H

    What Does Ground Really Mean in Electrical Terms?

    The electric potential of the ground is taken to be zero. We will get electric shock if we complete the circuit by touching the wire and standing on the ground simutaneously.(I know the shoes cannot protect us as the resistance is too small) But what does this "ground" really mean? Does it...
  41. R

    Electric potential along the centre line between 2 charged plates

    Homework Statement Explain why in the absence of any other charged bodies, the potential will be zero along the centre line between plates Homework Equations - The Attempt at a Solution not sure how to explain it. is this because that the electric field in that region is zero?
  42. D

    Electric Potential of Uniformly Charged Cone

    [SOLVED] Electric Potential of Uniformly Charged Cone I'm actually a senior in physics graduating this year, but wanted to review some E&M before grad school in the fall. I was apparently never assigned this problem during my sophomore year, but it's from Griffiths. I'm also aware that this has...
  43. J

    Potential Difference and Electric Potential

    Homework Statement A uniform electric field of magnitude 375 N/C pointing in the positive x-direction acts on an electron, which is initially at rest. After the electron has moved 3.2 cm, what is a. the work done by the field on the electron b. change in potential energy associated with the...
  44. S

    Concept of Potential Energy -vs Electric Potential in an EField

    Homework Statement 6. A positive charge is initially at rest in an electric field and is free to move. Which of the following statements is true about the movement of the positive charge? a. Start to move to a position with higher potential and higher potential energy b. Start to move to...
  45. J

    How Is Electric Potential Calculated Above a Charged Ring?

    Homework Statement What is the electric potential a distance x above the center of a ring of charge Q with a radius R? Derive the electric field from this relationship.Homework Equations ΔVab=-∫E·ds The Attempt at a Solution
  46. T

    Electric Potential of Ring of Charge: Q, R, x

    Homework Statement What is the electric potential a distance x above the center of a ring of charge Q with a radius R? Derive the electric field from this relationship. Homework Equations V=k_e\intdq/r = k_e\intdq/(\sqrt{}a^2+x^2) The Attempt at a Solution V=...
  47. C

    How to locate Two spots where electric potential is zero

    Homework Statement A positive charge of +q1 is located 3.00m to the left of a negative charge -q2. the charges have different magnitudes. a) on the line through the center of the charges, the net electric field is zero at a spot 1.00m to the right of the negative charge. Determine the relative...
  48. U

    Electric potential at a point between 3 point charges

    Homework Statement Three pointcharges are located at the following points on an x-y coordinate system, Q1 = -3 uC at (0,0) q2 = 10.0 uc at (0,0.5m), and q3 = -3 uC at (x,0) . What is the total electric potential at the point (x/2,0) where x is in units of m. At what value does x have to be...
  49. L

    Nonuniform line of charge, find the electric potential

    A nonuniform linear charge distribution given by λ = bx, where b is a constant, is located along an x-axis from x = 0 to x = 0.50 m. Suppose that b = 25 nC/m2 and V = 0 at infinity. (b) What is the electric potential at the point y = 0.30 m on the y axis? E = kq/r^2 V = -EdSince there's no...
  50. N

    Electric Potential @ center of an equilateral triangle

    Homework Statement What is the electric potential at point P, the center of an equilateral triangle with side length of 2a and total charge of Q? Use infinity as the reference point. Homework Equations ∆v = -∫E∙ds v(r)= kq/r The Attempt at a Solution I already have the...
Back
Top