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. R

    Electric potential due to two point charges near origin

    Homework Statement A charge + q is fixed at each of the two points (±a,0,0). Show that the potential V at a point (x,y,z) near to the origin may be expressed as V = [q/4∏*ε*a] [[2+(2x2-y2-z2)/a2] where x, y and z are small compared with a. Homework Equations V(x) = q/4∏i*ε*r ...
  2. H

    Electric Potential Vs. Electric Potential Energy Concepts

    Homework Statement A charge moves towards a positively charged sphere, as it does, it's electric potential (V) increases. Give an instance on when the Electric Potential Energy (Ee) will decrease. Homework Equations V= Ee/q The Attempt at a Solution Alright, This is basically a theory...
  3. Entanglement

    Can Zero Electric Potential Prove No Current Flow in a Connected Wire?

    how can I prove that no current would flow in a wire connected between two wires of equal potential. For an example a resistor of 2 ohms carrying a current of 3 Amp and a resistor of 3 ohms carrying a current of 2 Amp, and a wire "A" is connected between them. Obviously, the potential difference...
  4. S

    Electric Potential Due to Spherical Shells

    Homework Statement A spherical shell of radius R0 has a non-uniform surface charge density: η=η0*cos(2θ), where θ is the angle measured from the positive z axis and η0 is a constant. This shell is inserted into another spherical shell (this one has a volume) with its inner lip at radius R1...
  5. M

    What is the Meaning of 0 V or 0 Potential Between Two Charges?

    What does it mean by 0 V or 0 potential between two charges? If there are two point charges A and B. And if there is a point between them that has 0 V then why is: Va + Vb = 0?
  6. S

    Electric Potential on z-axis due to circular disk

    Homework Statement Hey guys, I am a little bit confused how my textbook arrived at the answer it did for this particular question. The disk is in the xy-plane with radius b and uniform charge density. They go V=\frac{\rho_S}{4πε}\int_0 ^{2π}\int_0...
  7. A

    Finding work done when you know electric potential and the charge.

    Problem: Points A and B each have an electric potential of +9 V. How much work is required to take 2 mC of charge from A to B? Equation: V = W / q 9V = W / .002 C W= .018 J. This answer I'm getting is incorrect and I'm not sure what else to try. Any help in the right direction would...
  8. Y

    Electric potential at the center of a sphere

    Homework Statement The electric field at the surface of a charged, solid, copper sphere with radius 0.19m is 2800 N/C , directed toward the center of the sphere. What is the potential at the center of the sphere, if we take the potential to be zero infinitely far from the sphere...
  9. C

    Electric potential along the x-axis

    Homework Statement The electric potential along the x-axis is V=100e^(−2x/m), where x is in meters. Find Ex at x=1.0m and Ex at x=2.1mHomework Equations V=Ed Ex = dV/dx (?) The Attempt at a Solution I took the derivative of V and got (-200/m)e^(-2x/m) I don't know what m is and I'm just not...
  10. L

    Electric Potential: Does Energy Increase/Decrease?

    Homework Statement As an electron moves from a high potential to a low potential, its electric potential energy? a) increases b) remains the same c) decreases Homework Equations we know that V=U q0 the electric potential = potential energy times the charge. The...
  11. D

    MHB How Does Electric Potential Behave Across a Circular Boundary in Electrostatics?

    The inside of a circle of radius \(R\) is held at a constant potential \(V_0\) in the xy plane. The outside is held at a constant potential \(0\). Show that that the electric static potential for \(z > 0\) is \[ T(r, z) = V_0R\int_0^{\infty}\mathcal{J}_0(kr)\mathcal{J}_1(kR)e^{-kz}dk. \] Since...
  12. D

    Ranking Electric Potential of Electrons in a E Field

    Homework Statement Note this is a PRACTICE midterm problem. Not due for homework or for a grade. My exam is on Tuesday "an electron moves from point A to point B in a uniform electric field as show below. Rank the electrons in diagrams 1 through 2 by the changes in potential from greatest...
  13. L

    Superposition of Electric Potential problem

    1. A system consists of the charges -q at (-d,0), +2q at (d,0), and +3q at (0,d). What is the total electric potential energy of the system. 2. I'm wondering, is it necessary to calculate each electric potential between charges from lower electron potential to higher electron potential...
  14. L

    Greater electric potential but less electric potential energy?

    Greater electric potential but less electric potential energy?? The picture in my book looks like this: 1. The electric potential at pt. B in the parallel-plate capacitor shown here is less than the electric potential at pt. A by 4.50V. The separation between pts. A and B is .120cm, and the...
  15. F

    Electric potential of a uniformly charged thin rod.

    1. Problem statement A thin rod of length 2L has charge Q uniformly distributed along its length. 1. Draw a graph of the charge density as a function of x from -L to L 2. Find the electric potential at point P a distance y away 3. Use the result in part 2 of the electric field at point...
  16. K

    Monster E&M Question (Coulomb's Law, Electric Potential, Kinematics)

    Homework Statement A proton (charge +1e and mass 1.67e-27kg) and an alpha particle (charge +2e and mass 6.64e-27kg) are placed 3 fm (1 fm=10e-15m) apart. a)what is the force on each particle B)what is the potential energy of the system? c)what is the acceleration of each particle at the...
  17. F

    Electric potential graph analysis

    Homework Statement Homework Equations ΔU = -q∫E * ds The Attempt at a Solution Just by looking at the graph I am thinking, if I solve for E using the equation above, the number would be always negative therefore I can conclude that the electric field at any x position would be negative and...
  18. B

    Electric potential of cylinder

    Homework Statement An insulating solid cylinder of radius R, length L carries a uniformly distributed electric charge with density \rho . Chose the z-axis along the axis of the cylinder, z=0 in the middle of the cylinder. the cylinder can be boken down into curcular tabs (disks) of thickness...
  19. F

    Can Zero Potential be Defined at Any Point in Electric Potential?

    Homework Statement My question is one of clarification about electric potential. Homework Equations See Below The Attempt at a Solution I understand that when electric potential is defined at infinity to be zero for a series of point charges, the potential is simply kq/r. My...
  20. I

    Electric Potential due to multiple charges

    Homework Statement Homework Equations E = kq1q2/r2 The Attempt at a Solution Please correct me if I am wrong but I think it is A. Since doubling the charge, doubles the potential as well, while doubling the radius between the charges would just exponentially decrease the...
  21. B

    Electric Potential, and Potential Difference

    In my physics class we are learning about electric potential right now. I know electric potential is electric potential energy with the charge divided out. I am curious if the potential difference is just the difference between the two points. My thinking is we have point A, and B. The path...
  22. J

    Places electric potential is zero when 2 charges

    Homework Statement i'm having a bit of trouble understanding/visualising why the electric potential is zero in the red cross within region III and the green dot within region II from my current understanding, the green dot is where the potentials from both charges are equal and...
  23. N

    Need help with the order of electric potential

    Homework Statement In the diagram below, there are two charges of ##+q## and ##−q## and six points (a through f) at various distances from the two charges.(See attachment) You will be asked to rank changes in the electric potential along paths between pairs of points. Homework Equations ##V...
  24. B

    What is the Relationship Between Electrostatic Force and Potential Energy?

    hi, please can anyone analyze the following sentence in terms of the formulas of electrostatic forces or Potential energy (assuming electrostatic force is directly proportional to potential energy) statement: "When the force between two objects is attractive and decreases with distance, the...
  25. M

    Electricity (Electric potential)

    Hi,can you please help to understand why is the potential difference the same across the gap between the plates of both capacitors connected in parallel?
  26. B

    What is the potential ratio at the center and corner of a charged cube?

    This is question 2.30 from the 2nd edition of the Purcell book on Electricity and Magnetism. It's an interesting puzzle, and I've been thinking about it for a while, but I can't make any headway, so maybe you guys can do better. Suppose you have a uniformly charged cube (charge density ρ) of...
  27. P

    Broglie wavelength - calculate electric potential difference

    Homework Statement In a TV tube, an electric potential difference accelerates electrons from a rest position towards a screen. Just before striking the screen, the electrons have a wavelength of 1.0 x 10^{-11} m . Find the electric potential difference.Homework Equations λ = h/mv ΔE_k = qΔV...
  28. F

    Radius of a Raindrop given Charge and Electric Potential

    Homework Statement A spherical rain drop carries a charge of 5×10-6 C and has a potential of 8.800×10-8 V at the surface. Find the radius of the drop. Homework Equations V = (kQ)/r The Attempt at a Solution I simply moved V and r to their respective spots and plugged in my...
  29. R

    Electric Potential and Field Calculations for Point Charges on the x-Axis

    Homework Statement A -11.5nC point charge and a +24.6nC point charge are 14.0cm apart on the x-axis. a) What is the electric potential at the point on the x-axis where the electric field is zero? - The answer is 1.58E2 V b) What is the magnitude of the electric field at the two points...
  30. W

    Electric field and electric potential

    hi, electric filed is a vector and electric potential is scalar. Gradient of electric potential give us electric filed - please explain by which space we can describe both quantities. thanks
  31. P

    Is electric potential always continuous in an electrostatic field?

    Is electric potential always continuous in an electrostatic field? I mean, does it suffer from discontinuity at any point?
  32. A

    Electric potential difference?

    Homework Statement An X-ray tube is similar to a cathode-ray tube. Electrons are accelerated to high speeds at one end of the tube. If they are moving fast enough when they hit the screen at the other end, they give up their energy as X-rays (a form of nonvisible light). (a.) Through what...
  33. T

    Electric potential of water droplets

    Homework Statement Twenty seven charged water droplets each with a diameter of 2 mm and a charge of 10-12 C coalesce to form a single drop .Calculate the potential of the bigger drop. Homework Equations V(potential)=\frac{q}{4∏εr} The Attempt at a Solution i don't really have an...
  34. K

    Electric Potential Problem Involving Uranium Atom

    Hi Everybody, I am currently battling with the fourth and final question of my A Level physics work for this week. The problem has been driving me crazy, as I seemed to have completed all of the relevant steps, and I find the right answer only with negative exponents, which isn’t much help at...
  35. C

    What is the radius of the equipotential surfaces for a charged cylinder?

    Homework Statement A very long cylinder of radius 2.00 cm has a uniform charge density of 1.50 nC/m. Taking the reference level for the zero of potential to be the surface of the cylinder, find the radius of equipotential surfaces having potentials of 10.0 V, 20.0 V, and 30.0 V. Homework...
  36. A

    Calculating Electric Potential Difference for Machinery Operation

    Homework Statement A generator has an output of 240V. It is intended to operate machinery some distance away. If the machinery has to operate on 25A and the cables carrying the current have a total resistance of 5.0Ω. find the PD across the ends of the cables. Will the machinery operate...
  37. P

    Electric Potential in Coiled Blood Vessels?

    The basis behind electric energy is the movement of electrons or ions through a wire or medium. That is simple. I know that blood vessels carry ions such as K+, Cl-, and Na+ through them in varying concentrations. What I want to know is if it would be viable to create a biological solenoid by...
  38. S

    Calculate the electric potential of a charged bar

    Consider that the bar has a linear density λ and is in the x axis. Also consider that V=0 in infinite. Determine the potential in point P. I can calculate it, but I don't understand how the bounds of the integral are supposed to be determined: dq =\lambda dx'\\ r = x + x'\\dV =...
  39. totallyclone

    Electric Potential and Electric Energy

    Homework Statement Consider point a which is 65 cm noth of a -2.8μC point charge, and point b which is 80 cm west of the charge. Determine (a) Vba=Vb-Va, and (b) Eb-Ea (magnitude and direction)Homework Equations k=9x10-9 V=kQ/r V=kQ(1/rb-1/ra) E=kQ/r2 E=kQ(1/rb2-1/ra2)The Attempt at a Solution...
  40. S

    Electric potential and velocity

    Hello all. I had written a test today on ELECTRIC POTENTIAL and I got this particular question wrong:Homework Statement If an electron would travel from a region of low potential to a region of high potential , would there be a change in velocity? 2. My take at the problem : electric...
  41. E

    Electric Potential in circuits

    Hi, I'm just starting to study circuits, and there's a thing I don't understand about electric potential. I was under the impression that as a charge moves through the circuit from the high potential end of the battery to the low potential end, it lost electric potential energy which...
  42. U

    What is the Electric Potential at a Point on the Surface of a Charged Sphere?

    Homework Statement A point charge q is placed at a distance 2r from the centre O of a conducting charged sphere of radius r. Due to the induced charges on the sphere, find the electric potential at point P on the surface of sphere(it is at a distance 3r from q) (if Kq/r = 18 volt) Homework...
  43. J

    Electric potential at the center of two concentric shells

    Homework Statement If the electric potential of the inner shell is 10 volts and that of outer shell is 5 volts, then the potential at the center will be? Homework Equations The radius of inner shell = a (given) The radius of outer shell = 2a (given) The Attempt at a Solution Having read...
  44. P

    Electric Potential in electric fields true/false

    Homework Statement 1. If the electric field is zero at a point, the potential must also be zero at that point 2. If the electric potential is zero in some region of space, then the electric field must also be zero in that region. 3. If the electric field is zero in some region of...
  45. X

    Why is there a contradiction in the signs for electrical potential equations?

    We have two equations delta EP = -W V = -Ed Now, to my understanding for the second equation (E = -V/d) since its a vector quantity, we need to make it have direction Therefore, if we substitute values E = -50V / 5 m = -10 N/C We add in the negative sign to the equation because...
  46. T

    Shape of an Electric Potential?

    Homework Statement Hi. I'm doing some practice problems to prepare for an upcoming exam, and I encountered this question: What is the shape of the electric potential around an isolated electric charge? a. Circular b. Square c. Oval d. No specific shape e. Triangle This is an odd...
  47. U

    Electric Field Strength of Cylinder Capacitor at Inner Radius

    capacitance cylinder Homework Statement Hey guys! :) I have an exam tomorrow i am a stuck with this question while reviewing :S.. Can anyone help me please? consider a cylinder capacitor of length 1m , inner radius 0.1cm and outter radius 0.2cm. You connect the capacitor to a 10V...
  48. S

    Finding electric potential with non-uniform charge density?

    We have a spherical shell. We want to find the electric potential everywhere. Given charge density σ=k*sinθ, k is constant. Also it is wanted from direct integration. V=1/4piε ∫σ/r da. How can we do this, please help? I thought because it is sphere da is in the direction of r so da=r^2sinθ dθ...
  49. T

    How is the alternating electric potential produced in cyclotrons?

    If the cyclotron frequency is f = (q B)/(2 pi m) this gives a very large frequency for a relatively large magnetic field and for an alpha particle say. If the acceleration of the charged particle across the "dees" is cause by an alternating electric potential (usually in the form of a square...
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