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. 2

    Deriving the formula for electric potential?

    Homework Statement I'm getting really confused when it comes to electric potential. The definition I am using is 'the work done per unit charge on a small positive test charge when it is moved from infinity away to a point'. My first problem is that I'm not sure whether 'the work done' refers...
  2. A

    Electric potential energy and its applications

    Hi guys I just want to make sure that my understanding of potential difference is right or wrong I just want someone to tell me whether my understanding is right or wrong. I know that when we move a charge if it's attracted to another charge it gain potential energy and when we leave it it lose...
  3. P

    Trivial question about electric potential

    Hi! I'm having an hard time with a trivial question that suddenly I can't figure out: Computing the potential between the plates of a spherical capacitor. The problem is taken from this url (first page and a half)...
  4. H

    Change in Electric potential, potential energy, and work problem.

    Homework Statement Imagine a lithium atom where the two electrons in the first orbital are at exact opposite sides of the nucleus and the electron in the second orbital is in line with the other electrons so that the three electrons and the nucleus all lie on a straight line. How much work...
  5. N

    Regarding electric potential with respect to a negative charge

    Homework Statement If I have a electric source charge, does that mean that electric potential increases as r increases (because it gets increasingly less negative as you go farther from the source charge) as opposed to a positive charge in which potential energy would increase as r...
  6. N

    Regarding the Electric Potential Formula

    Homework Statement The formula for Electric Potential as I have it is: "Let Q be a point source charge. At any point P that's a distance r from Q, we say that the electric potential at P is the scalar given by this formula: electric potential = k * (Q/r) My question is what if at...
  7. B

    Zero electric potential related to electric field.

    Homework Statement Which one of the following statements concerning electrostatic situations is false? a) No work is required to move a charge along an equipotential surface. b) If the electric potential with a region of space is zero volts, the electric field within that region must also be...
  8. M

    Is Electric Potential the Key to Understanding Earnshaw's Theorem?

    I was working on a problem out of Griffiths, and have become a bit confused. The problem is regarding to Earnshaw's theorem, which states that a particle cannot be held in stable equilibrium by electrostatic forces. (3.2 for anyone with the text). He suggests a cube with a positive charge on...
  9. M

    What is the electric potential of Earth?

    What is the potential of Earth with respect to (wrt) infinity (C=710uF)? I am assuming that infinity is the correct reference here. Suppose a capacitor that's normally used in an electric/electronic circuit is a) discharged by connecting its two (2) terminals. b) then they are...
  10. STEMucator

    How Should Electric Potential Energy Be Ranked at Point P?

    Homework Statement Rank the electric potential energy at point ##P## for the following four cases: http://gyazo.com/c7d9df3d3d64cda909ddc0d2ab7686bc Homework Equations ##\Delta U_e = - W_∞## The Attempt at a Solution I believe it should be ##U_2 > U_1 > U_3 > U_4##, but I am not certain.
  11. Greg Bernhardt

    Exploring Voltage: Electric Potential & Power

    Definition/Summary Voltage is electric potential difference, which is potential energy difference per charge: V\ =\ U/q Energy per charge equals energy per time divided by charge per time, which is power divided by current (watts per amp): V\ =\ U/q\ =\ P/I Since potential energy is...
  12. M

    Negative in a Electric Potential Energy/Kinetic Energy Question

    Homework Statement My questions reads: An electron is pulled away from a fixed charge of 1.3μC. The electron is moved from the positive charge to 4.0 cm away from the charge. If the electron is released from the 4.0 c mark, what is the max velocity of the electron? Homework...
  13. P

    Green's First Identity involving Electric Potential

    I am attempting to work through a paper that involves some slightly unfamiliar vector calculus, as well as many omitted steps. It begins with the potential energy due to an electric field, familiarly expressed as: U_{el} = \frac{\epsilon_r\epsilon_0}{2} \iiint_VE^2dV =...
  14. Satvik Pandey

    Electric Potential due to conducting sphere and conducting shell

    Homework Statement A solid conducting sphere having a charge Q is surrounded by an uncharged concentric conducting hollow spherical shell. Let the potential difference between the surface of the solid sphere and that of the outer surface of the hollow shell be V. If the shell is now given a...
  15. A

    Can the electric potential be negative ?

    I have just solved a problem about electric potential and it is: " A positive point charge of 1.0 nC is located at position x=0.00 . A second point charge q=-1.0 nC is located at x=0.10 m. (a) What is the value of the electric potential on the x-axis at x=0.3 m ? (b) What is the value of the...
  16. A

    A Problem in " Electric Potential "

    Please I want to check my answers of this problem:- Two charges 4 µc , -6 µc are placed on the x-axis 10 cm apart. where is the electric potential be zero ? My Answer is:- "4 cm apart from the charge of 4 µc" Is that right ?!
  17. Hardik Batra

    Electric potential energy definition doubt?

    Electric potential energy of a charge q at a point in an electric field due to any charge configuration as the work done by the external force in bringing the charge q from infinity to that point without any acceleration.. In this definition, why charge is moved without any acceleration?
  18. Hardik Batra

    Find the points where electric potential is zero?

    There are two charges 2 C and 3 C and 100 cm apart from each other. Find a point where electric potential is zero? Consider 2 C charge on the origin.I have tried out but don't get it solution... 1) If you take point between two charges then 2 C----------100 cm------------------3 C...
  19. Hardik Batra

    Electric potential and conducting wire

    There are two sphere of radius a and b and they are connected by conducting wire. Then why the electric potential becomes same of both the sphere?
  20. M

    Increase in electric potential energy

    If a positive charge A moves towards another stationary positive charge B then the A's electric potential energy increases. But shouldn't the electric potential energy of B also increase as it is also in a way moving towards the A inside the A's electric field? So shouldn't the total...
  21. M

    What is the relationship between electric potential and work?

    Hello, my questions are not really about an exercise or something "given". Instead, I'm having trouble understanding the concepts behind electric potential and work formulae/meaning. Maybe (probably) I missed the basics. Assume that I'm working with a puntiform charge. 1 - I've seen...
  22. S

    Electric Potential & Electric Field

    Homework Statement Three positive charges lie on the x-axis; q1 = 15 μC is at the origin, q2 = -30 μC is at x = 2 m, and q3 = 15 μC is a x = 3 m. ( please also refer to the attachment.) Find the electric potential and electric field at point “P” aroused from q1, q2 and q3. The Attempt at...
  23. H

    Electric potential due to multiple charges

    Hello! For Single Charge: I studied the formula for electric potential for a point charge (V=kq/r). It was derived when the test charge approached the source charge from infinity "head-on". In this case the electric field due to source charge and displacement of test charge were vectors in...
  24. F

    Biophysics: Concentration and Electric potential

    Homework Statement Consider a membrane which is permeable to a singly charged ionic species. If the concentration on one side is 25 times that of the other, what is the electric potential required to maintain a net flux of zero at 37C? Homework Equations I'm not sure: U = KQq/r flux...
  25. D

    Formula for electric potential energy

    In a velocity selector apparatus, i had an electric potential set across two points, and a proton at rest at one end. The potential was 350 V. My instructor used : qV = 1/2 mv^2 to find the velocity at the end of the apparatus. Where did the left hand side of the eqn come from??
  26. T

    Infinite Line of Charge and Electric Potential Difference

    Homework Statement 1. Consider a line of charge (with λ charge per unit length which extends along the x-axis from x=-∞ to x=0 (a) Find all components of the electric field vector at any point along the positive x-axis (b) Find the electric potential difference between any point on the...
  27. A

    Electric Potential of a Spherical Shell

    Homework Statement A conducting spherical shell has inner radius a, outer radius b, and has a +Q point charge at the center. A charge of -Q is put on the conductor. a) What is the charge on the inner and outer surface of the shell? b) What is the electric field everywhere? c) What...
  28. B

    What is the electric potential of a metal cylinder?

    As the title says, what is the electric potential of a metal cylinder? If I am missing any variables, which variables do I need? My little brother asked me this but I don't want to turn up short-handed. I'm not really a physics guy
  29. M

    Electric Potential Energy in Different parts of Circuit

    When a positive charge leaves the positive part if the battery it has maximum electric potential energy then as it moves through a wire with a zero resistance the charge is closer to the negative side of the battery. So, while traveling in a wire in a circuit does it lose electric potential...
  30. W

    Electric Potential between two charges of equal magnitude

    Homework Statement Two charges of equal magnitude Q are held a distance d apart. Consider only points on the line passing through both charges. If the two charges have the same sign, find the location of all points (if there are any) at which the potential (relative to infinity) is zero. a)...
  31. K

    What does 0 electric potential difference mean?

    This isn't a homework question, but while working on some questions in Physics AP C, I've come across several questions involving 0 PD (potential difference). My question is simple; what does 0 PD mean? so far i know that 0 potential difference of any kind is arbitrary, since it represents the...
  32. L

    Electric potential halfway between two equal but opposite charges

    I'm having a hard time understanding why the electric potential halfway between two equal but opposite charges is 0. If I put a positive charge halfway between a 5 mC charge and a -5 mC charge, it will accelerate toward the negative charge, but how can it do this if it starts with no potential...
  33. D

    Electric field and electric potential

    Homework Statement hi, all, can anyone explain why the ans is C for this question? http://i.imgur.com/yGyu5G3.jpg for the second question? shoudnt the ans is D ? http://i.imgur.com/R4Gvjoz.jpg Homework Equations The Attempt at a Solution
  34. S

    Why Does an Electron Move from High to Low Electric Potential Energy?

    1. Explain why the electron moves in the above way (from left to right between two parallel plates that is positively charged on the left, negatively charged on the right) in terms of electric potential energy Homework Equations 3. I know the electron moves from left to right when...
  35. E

    Why Is Electrostatic Potential Independent of Path in a Field?

    Homework Statement Which one of the following statements best explains why it is possible to define an electrostatic potential in a region of space that contains an electrostatic field? A) Work must be done to bring two positive charges closer together. B) Like charges repel one another...
  36. D

    Find electric potential and field from Electric Quadrupole

    Homework Statement So the problem revolves around a Linear Electric Quadrupole, with two positive charges on z-axis (in positions s and -s from origo) and two negative charges in origo. 1. Show that potential from a position R can be written as 2. The quadrupole moment can be...
  37. A

    Calculating electric potential from constant E-Field

    Hey, folks. I've typed out the question here. I hope you don't mind my just linking this (if that's against the rules or something, I'll type it out). I'm still pretty confused about what to do. I assume, as usual, it's probably something... well... stupid—but I can't figure out what. Thanks...
  38. K

    Electric potential difference vs. voltage drop

    Are these the same thing? Or does the electrical potential difference refer to the voltage source only?
  39. M

    When is electric potential negative and when is it positive?

    Homework Statement When is electric potential negative and when is it positive? Homework Equations V=Es The Attempt at a Solution I first thought that when you are moving in the same direction as the electric field the electric potential will be a positive value. However I...
  40. applestrudle

    Electric potential when there is a negative test charge?

    For when there is a negative test charge: The work done to get from infinity to r would be negative, corresponding to a decrease in potential energy so since dr must be a path element and therefore in the negative direction (towards the source of the E field) does that mean the...
  41. L

    Charged ring, integrate for electric potential

    Homework Statement A flat ring of inner radius R1 and outer radius R2 carries a uniform surface charge density σ. Determine the electric potential at points along the axis (the x axis). [Hint: Try substituting variables.] Homework Equations V = (kQ)/r The Attempt at a Solution...
  42. J

    Electric Potential: Understanding the Difference

    Hello I'm very confused on what the difference is between electric potential and Potential Energy. I though they were the same but I realized they're not after I got a 30% on a physics quiz. I tried googling it but it keeps telling me that potential energy is equal to mgh which is from...
  43. P

    Finding the Zero Point of Electric Potential Between Two Point Charges

    Homework Statement Two point charges are placed on the x axis. The charge + 5 q is at x =1.50m , and the charge −q is at x= -1.50m . There is a point on the x-axis between the two charges where the electric potential is zero. Where is this point? The electric potential also vanishes...
  44. L

    Electric Potential Intuition Needed

    I'm trying to understand why the voltage across parallel circuit elements is the same. I keep finding the answer "because they are both connected to the same voltage source." Why is it the case, in a physical sense, that voltage MUST be the same across, say, capacitors that are connected in...
  45. M

    Electric potential and negative potential gradient

    is electric field strength always equal to negative potential gradient or can it be equal to positive potential gradient sometimes?
  46. G

    Electric Potential inbetween Conducting Metal Ball and Thick Shell

    Homework Statement A conducting metal ball of radius 2m with a charge of 3μC is surrounded by a concentric spherical shell of inner radius 4m and outer radius of 5m with a total charge of 4μC. Determine the electric potential in volts between the ball and shell at a radius of 3m...
  47. D

    Electric potential is separation of charge?

    I am having some troubles wrapping my head around the electric potential concept. From what I gather it is a separation of charge? Is this true? On a more formal level electric potential energy is the amount of energy in joules it takes to move a charge against an electric field or the amount...
  48. P

    Ring of charge electric potential

    Homework Statement The ring is in the z,y plane. D = 2m R = 4m Q = 8 * 10^-6 C X = distance to the edge λ = dQ/dX dX = rdθ dQ = infinitely small charge dX = infinitely small arc of ring What is the potential difference at the point D perpendicular to the centre of the ring? Homework Equations...
  49. Q

    MHB Deriving Y-Component of Uniform Electric Rod | E=-▽V

    This is essentially the problem. And this is what I did. Realizing the following: E = -▽V I simply took the derivative in regards to the vertical component, in this case "a". So: -dV/da [the above formulae] And I got the following: Κλl/(a sqrt(l^2+a^2)) Does that seem about right...
  50. M

    Electric potential outside of a parallel-plate capacitor

    My book says it is zero, but I don't know where to start , why is it zero ? I have to take an exam in few hours :cry: so a simple explanation would be appreciated ( I'm not studying pure physics:smile: Here are the electric fields of the three regions . Thanks in advance :smile:
Back
Top