# What is Electric potential difference: Definition and 70 Discussions

Voltage, electric potential difference, electromotive force (emf), electric pressure or electric tension is the difference in electric potential between two points, which (in a static electric field) is defined as the work needed per unit of charge to move a test charge between the two points. In the International System of Units, the derived unit for voltage (potential difference) is named volt. In SI units, work per unit charge is expressed as joules per coulomb, where 1 volt = 1 joule (of work) per 1 coulomb (of charge). The old SI definition for volt used power and current; starting in 1990, the quantum Hall and Josephson effect were used, and recently (2019) fundamental physical constants have been introduced for the definition of all SI units and derived units. Voltage or electric potential difference is denoted symbolically by ∆V, simplified V, or U, for instance in the context of Ohm's or Kirchhoff's circuit laws.
Electric potential differences between points can be caused physically by electric charge build up or imbalance (eg. well known "static" and electronic capacitor) also by electric current through a magnetic field, and by time-varying magnetic fields (eg. dynamo or generator), or some combination of these three. Additionally on a macroscopic scale potential difference can be caused by electrochemical processes (cells and batteries) and pressure induced piezoelectric effect and heat induced emf across metal junctions. These latter processes at microscopic level have the physical origins previously mentioned. A voltmeter can be used to measure the voltage (or potential difference) between two points in a system; often a common reference potential such as the ground of the system is used as one of the points. A voltage may represent either a source of energy (electromotive force) or lost, used, or stored energy (potential drop).

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1. ### Potential difference between 2 points in a capacitor circuit

In the given circuit, a transient current will flow and when this current finally stops at equilibrium, the charges ##q_1## and ##q_2## are assumed to deposit at the capacitor plates as shown below. The dashed line indicates an isolated system that will have it's total charge conserved. If I...
2. ### Electric Potential Difference -- Conceptual Question

I am able to get V1 = kq/a - 4kq/b and V2 = kq/b + -4kq/b For some reason the solution says it is V1-V2 as opposed to V2-V1. Maybe has something to do with positive shell in the center and negative outer shell? I know the electric field goes from positive to negative, but I don't know how...
3. ### Potential Gradient for individual charges and parallel plates?

In my book, the potential gradient for a charge placed anywhere in space is defined as: E = -V/r HOWEVER, for parallel plate (capacitors) the potential gradient is defined as E = V/d (V being the potential difference). How come there's no negative sign for the potential gradient of the parallel...
4. ### Final electric potential difference in a circuit with two capacitors

So, each capacitor must have a different potential difference, given by its capacity and charge... this would cause charge and current accordingly to flow in the circuit. But how do I determine the final potential difference, which would of course be the same for both of them? I have tried...
5. ### Electric potential difference at the ends of a resistor

So, having two parallel resistor ##R_{1}## and ##R_{2}## , the current flowing through the equivalent one will be ##I_{eq}=I_{1}+I_{2}##. Now, it comes the point I'm not totally getting: why is ##V_{eq}=V_{1}=V_{2}##? These V's are the difference of potential measured between which points...
6. ### Determine the Electrical potential at a given point

A rod with a circular center in the middle (which causes the rod to change direction by 90 °) has an evenly distributed linear charge density 𝜆 of electrons along the entire rod. Determine the electrical potential of the red dot in the figure below which is at the center of the circular round...
7. ### Salt water and potential difference

Imagine a container of salt water at 0V (Relative to ground),Now you've put in it 2 electrodes,one at +500V (Electrode A), The other at +250V(Electrode b), Normally positive ions should go to the negative electrode , and Negative ions should go to the positive electrode , But in our example the...
8. ### The source of the electric field of a battery?

If you place a zinc / copper battery it will create an electric field pointing from the copper to the zinc and my question is this what makes this electric field , the zinc pushes electrons in the circuit and never "stays" negatively charged for an electric field to be created same for the...
9. ### Clarification of electric potential difference

I have some questions regarding the sign of potential difference. For example, given the literal definition as the difference in potential between two locations it should be possible for potential difference to be negative if the final potential is less than the initial, but while reading texts...
10. ### Electric potential difference between a battery's + terminal and the ground

Hi, I've a question about electricity in the following scenario: consider an accumulator (e.g. a 9V battery) and an analog/digital voltmeter having a probe connected to the accumulator + clamp and the other to the ground (for instance connecting it to a metal rod stuck in the ground). Do you...
11. ### Conceptual Issue RE: electric potential difference

Homework Statement My main conceptual issue here surrounds positives and negatives as they apply to electric potential difference. I will post two questions that illustrate my confusion, if that's ok. 1) The electrons in an old TV picture tube are accelerated through a potential difference of...
12. ### Solving Electric Potential Difference in a Linearly Varying Field

Homework Statement I'm trying to do a problem two ways, and things aren't consistent, finding the electric potential difference in a linearly varying field. The electric potential difference between two points is often summarized in texts as ΔV = Vf - Vi = - ∫ E⋅ds where the lower bound of...
13. ### Electric Potential Difference Problem

Homework Statement Two charges, A (-3 C) and B (+4 C), are placed 2.40 m apart. Point X is 30 cm from A, and Point Y is 30 cm from B. What is the electrical potential difference going from X to Y? Homework Equations W = △Vq The Attempt at a Solution Teacher gave answer as 6.9 x 10^4 V I am...
14. ### How Is Electric Potential Difference Measured Without Specific Distances?

Hello, I'm struggling to understand how the electric potential difference is measure especially when a distance is not given. For instance in Serway, on the explanation of the Van de Graaff Generator the authora write, "Van de Graaff generators can produce potential differences as large as 20...
15. ### 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 10×〖10〗^(-11) m. Find the electric potential difference. Homework Equations ∆E_K=q∆V λ=h/mv The...
16. ### Electric Potential Difference

Homework Statement Two charged rods, each with net charge -Q0 are held in place as shown in the top view diagram below. a. A small test charge -q0 travels from point X to point Y along the circular arc shown. i. Draw an arrow on the diagram at each point to show the direction of the electric...
17. ### Speed of an electron due to a ring charge

Homework Statement A uniformly charged thin ring has radius 13.0 cm and total charge 21.5 nC . An electron is placed on the ring's axis a distance 32.5 cm from the center of the ring and is constrained to stay on the axis of the ring. The electron is then released from rest. Find the speed of...
18. ### Electrical Circuit Problem / Electric Potential Difference

Homework Statement In the following picture, the absolute value of the difference in electric potential, between points A and B is: A)5V B)4V C)3V D)1V E)0V Homework Equations E =qV V = iRThe Attempt at a Solution I have no idea where to start on this one, just started my electric circuits...
19. ### Capacitance - does a general approach really exist?

I have spent hours on the web and in libraries to obtain a general and careful approach to the notion of capacitance, without success. Please, read carefully the question: I already know the usual blabla about capacitance. Also, I appologize in advance for the length of this question. I...
20. ### Two point charges and electric potential difference

Homework Statement In an experiment modeling point charges I had to find equipotential lines. I did so using a voltmeter. The results looked like this: Not a good quality picture, but the equipotential line on the right says 1.3 mV and the one on the left says 2.3mV. From this I had to...
21. ### Diagram of electric potential difference in plate capacitor

Homework Statement Plate capacitor is filled with two dielectrics of constants 3 and 4, and with a metal as seen in the picture. If the el. field in the first dielectric is 30 kV/cm, do: a) diagram of el. potential difference with calculated characteristic values using point C as a...
22. ### Electric Potential Difference during thunder storm

Homework Statement During a thunder storm, movement of water molecules within clouds creates friction which causes the bottom of the clouds to become negatively charged. This means that the bottom of the cloud and the ground begin to act like parallel plates. Once the electric field between the...
23. ### Electric potential difference in a charge

So I have two questions relating to potential difference 1.An electron with a velocity of 5.0x10^6 m/s injected into a parallel plate apparatus through a hole in the positive plate. it moves across the vacuum between the plates, colliding with negative plate at 1.0x10^6 m/s. what is the...
24. ### Solving for Electric Potential Difference in Square diagram

Homework Statement I've attached a url with a picture of the problem setup and diagram https://instagram.com/p/7nYNXTscre/ Homework Equations I used the equation V = KΣiqi/ri to solve for potential at A and B The Attempt at a Solution For Va I used K((Q/d)+ (2Q/(d^2+d^2)^.5)) I just plugged...
25. ### Calculating Potential Difference in a Teltron Tube

Homework Statement If 3000V is applied to the teltron tube with EHT voltage, what would be the potential difference between the parallel plates in the teltron tube? Homework EquationsThe Attempt at a Solution Since one end of the plate is positive, the other end is negative, 3000V-(-3000V)=6000V
26. ### Description of electric potential difference?

Homework Statement Homework Equations V=IR W=VQ The Attempt at a Solution The answer is B, though I thought that electric potential difference is the ratio of energy to charge? Why is the answer stating the ratio of energy to current instead?
27. ### What is the relationship between electric potential and potential difference?

what is electric potential?and what is the difference between electric potential and potential difference?
28. ### Why use conservation of energy in particle velocity problems

Suppose we have an electric field, and push a proton or electron through it (from rest). We're accelerating it through an electric potential difference of some kind. Why do we apply conservation of energy to the particle-field system to find the speed of the particle? Example: Calculate the...
29. ### Finding Electric Potential Difference in a TV Tube

Homework Statement In a TV tube, an electric potential difference accelerates electrons from a rest positive towards a screen. Just before striking the screen, the electrons have a wavelength of 1.0⋅10-10. Find the electric potential difference.Homework Equations [/B] Should I use these...
30. ### Understand pH Meter Functioning: An Electric Potential Difference

Hello! I have a question concerning the functioning of a pH meter. All the sources online that I can find either omit, I think, important information, or describe it in "technical terms" with equations. I would like to know what is happening at the level of the distribution and movement of...
31. ### Electric Potential Difference diagram

Homework Statement Point charges q and Q are positioned as shown. If q= +1.0 nC, Q = -2.0 nC, a = 3.0m, and b = 4.0m, what is the electric potential difference, Va - Vb? **The question with the diagram is also attached ** Homework Equations V = ke (q/r) The Attempt at a Solution V =...
32. ### Electric Potential Energy Conversion

Hello everyone, Imagine two points that have a Electric Potential Difference of 10V and they are connected through a conductor wire. Let's call these points A and B: Now imagine we have a charge on A of 1C. To move the charge to B, we need to make a work of 10J, right? So, now, imagine the...
33. ### 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...
34. ### 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...
35. ### Electric potential difference vs. voltage drop

Are these the same thing? Or does the electrical potential difference refer to the voltage source only?
36. ### 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...
37. ### 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...
38. ### 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...
39. ### Electric Potential Difference and electric field

Homework Statement A uniform electric field points in the –y direction with magnitude 325 V/m. Find the electric potential difference VB-VA between the points A at (-0.200, -0.300) m and B at (0.400, 0.500) m. Homework Equations ∆V=-int(E . dl) (Dot Product) The Attempt at a...
40. ### Electric Potential and Energy on a Circular Arc?

Homework Statement three point charges are located on a circular arc as shown: a) find the electric potential at the centre of the arc (point P) b) find the electric potential energy of a 25 pC point charge placed at P Diagram: [ r= 4 cm = 0.04 m]...
41. ### Electric potential difference across capacitor and resistor

Homework Statement In the circuit shown a resistor of 200k ohm is in series with a capacitor of 500uF and a 9v battery. Switch closed at t=0. What is the electric potential difference across the capacitor and the resistor at t=100? Homework Equations Q=cv Tau=rc Q=q(1-e^t/rc)...
42. ### Finding the electric potential difference?

Homework Statement Please don't do the problem for me, but explain to me in detail each steps I should take and why in my calculations (so I didn't include any numbers). There's an insulating infinite cylinder of equal charge distribution at origin (density given- rho). Let's say it's radius...
43. ### Electric Potential Difference and COE

Homework Statement 10. If an electron is released from infinity, how fast will it be traveling after falling to within 10-8m of a charge q of 4.8*10-19? a. 1.32*104m/sec b. 8.7*104m/sec *c. 2.76*105m/sec d. 4.01*105m/sec Homework Equations ΔU=ΔVq V=kq/r conservation...
44. ### Are Capacitors Connected to a Voltage Source in a Circuit?

Ignore this. How does one delete a post?
45. ### Electric potential difference to accelerate electron

Homework Statement What electric potential difference is required to accelerate and electron, initially at rest, to the speed at which it will move in a circular path with radius 1cm when the electron enters a region of uniform magnetic field of 1.0T, if the field is perpendicular to the...
46. ### Electric Potential Difference involving Alpha Decay question

Homework Statement A plutonium-239 nucleus, initially at rest, undergoes alpha decay to produce a uranium-235 nucleus. The uranium-235 nucleus has a mass of 3.90x10^-25 kg, & moves away from the location of the decay with a speed of 2.62x10^5 m/s. Determine the minum electric potential...
47. ### Electric Potential Difference on a Cone

Homework Statement I'm working out of Griffith's "Intro to Electrodynamics" and the problem states: "A conical surface (an empty ice-cream cone) carries a surface charge \sigma. The height of the cone is h as is the radius of the top. Find the potential difference between points a (the...
48. ### Rust Prevention by Electric Potential Difference.

I hope I'm posting this in the right spot, but I've been wondering this for a while now and figured this would be the best place to ask... I know that rust is an process involving electricity and rust forms on the negatively charged anode right? If that's the case, since a car is on rubber...
49. ### Electric Potential at a Distance

Homework Statement Find the electric potential difference at a point 4.0x10-2m away from an alpha particle. Homework Equations V= kq/r The Attempt at a Solution k= 9x109 r= 4.0x10-2 I'm not quite sure how to get this answer considering I don't have any charge and there's nothing...
50. ### Determin the Electric Potential Difference

Homework Statement The drawing shows a uniform electric field that points in the negative y direction; the magnitude of the field is 3000 N/C. Determine the electric potential difference (a) VB - VA between points A and B, (b) VC - VB between points B and C, and (c) VA - VC between points C...