What is Potential difference: Definition and 699 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).

View More On Wikipedia.org
Recent contents Top users
  1. A

    Potential Difference Question

    Homework Statement Point charges of equal magnitudes (50 nC) and opposite signs are placed on diagonally opposite corners of a 60 cm 90 cm rectangle. Point A is the unoccupied corner nearest the positive charge, and point B is the other unoccupied corner. Determine the potential difference VB...
  2. A

    Potential difference across a solenoid

    Hi, I have just started studying EM induction and I got stuck with the derivation of potential difference across a solenoid when the current in it is changing. My textbook (Physics for Scientists and Engineers by Tipler) derives it in very mathematical way just by saying that because the...
  3. M

    Potential difference formula

    [b]1. Consider point a which is 70 cm north of a -4.2 µC point charge, and point b which is 74 cm west of the charge (Fig. 17-23). (a) Determine Vba = Vb - Va. (b) Determine Eb - Ea. Magnitude Direction (counterclockwise from east is positive) [b]2. Vb-Va=(EPEb/q)-(EPEa/q) [b]3...
  4. M

    Potential Difference: 4.2 C Charge & 4.5 MJ Energy Boil/Vaporize

    A lightning flash transfers 4.2 C of charge and 4.5 MJ of energy to the Earth. (a) Across what potential difference did it travel? (b) How much water could this boil and vaporize, starting from room temperature?
  5. M

    Solved: Potential Difference Between a & b

    [SOLVED] potential difference Consider point a which is 70 cm north of a -4.2 µC point charge, and point b which is 74 cm west of the charge (Fig. 17-23). Figure 17-23. (a) Determine Vba = Vb - Va. V (b) Determine Eb - Ea. Magnitude N/C Direction °...
  6. B

    Potential Difference: Comparing Positive & Negative Charges

    By convention, potential difference is defined as the \frac{W}{q_0}, where q_0 > 0 correct? When computing potential differences in my textbook, states in the derivation of the relationship that V_f - V_i = \[ \int_i^f E\dot ds\] by assuming a positive charge. From the relationships of...
  7. M

    Potential difference in an electron

    Homework Statement An electron acquires 3.01e-16 J of kinetic energy when it is accelerated by an electric field from plate A to plate B. What is the potential difference between the plates? _____V Homework Equations - (Wba / q ) = V The Attempt at a Solution - (3.01e-16 /...
  8. B

    How Do You Calculate the Potential Difference to Accelerate a He+ Ion?

    Electric Potential Difference...Please HELP! Homework Statement What potential difference is needed to accelerate a He+ ion (charge +e, mass 4u) from rest to a speed of 2690000 m/s? Homework Equations The Attempt at a Solution Change in V = Change in K Change in V = 1/2 mv^2...
  9. B

    What is the Potential Difference VC-VA in the Electric Field Problem?

    Potential difference please help! Homework Statement It takes 3.3 μJ of work to move a 34.26 nC charge from point A to B. It takes -3.3 μJ of work to move the charge from C to B. What is the potential difference VC-VA? Homework Equations Uel = qV The Attempt at a Solution Don't...
  10. S

    Potential Difference for X-Ray Emission

    [SOLVED] Potential Difference argh ... Homework Statement What is the minimum potential difference that must be applied across an X-ray tube to observe a line of frequency 1.61x10^16Hz Homework Equations OK well we can define potential difference as the amount of energy required to emit...
  11. P

    How Do You Calculate the Hall Potential Difference in a Copper Strip?

    Homework Statement 12. A strip of copper {150{\textcolor[rgb]{1.00,1.00,1.00}{.}}{\mu}m} thick and {4.5{\textcolor[rgb]{1.00,1.00,1.00}{.}}mm} wide is placed in a uniform magnetic field {\vec{B}} of magnitude {0.65{\textcolor[rgb]{1.00,1.00,1.00}{.}}T}, with {\vec{B}} perpendicular to the...
  12. A

    Potential difference, uniform electric field

    Homework Statement What is the potential difference between A and B? Homework Equations ΔV=Vpos-Vneg=-∫Esds The Attempt at a Solution I got the distance between the points to be about 0.0761577 m After this I multiplied it by 1000, giving about 76.1577, which is incorrect Thanks in...
  13. J

    Potential difference across capacitors, can someone check this?

    Homework Statement What is the potential difference across C2 when C1 = 5.0 µF, C2 = 15 µF, C3 = 30 µF, and V0 = 24 V? http://img503.imageshack.us/img503/9994/capacitanceqb1.jpg Homework Equations C = Q/V The Attempt at a Solution I calculated total capacitance of C1 and C3...
  14. A

    Calculating Potential Difference in a Uniform Electric Field

    Homework Statement What is the potential difference between yi= -5cm and yf=5cm in the uniform electric field E = ( 20,000{ i } - 50,000 { j } )V/m? Homework Equations ∆V = V(sf) - V(si) = -∫ Es ds with the limits of the integral being sf and si The Attempt at a Solution I tried doing the...
  15. V

    Current and potential difference, simplifying circuit diagrams

    [SOLVED] current and potential difference, simplifying circuit diagrams Consider the circuit shown in Figure P31.69, in which RA = 25 and RB = 7 . Tabulate the current through, and the potential difference across, each resistor. Figure P31.69 resistor current (A) potential...
  16. X

    Current and Potential difference in a circuit

    For the circuit shown find the current through and the potential difference across each resistor. i was using the loop rules to make equations i could substitute into each other to solve this.. but i got stuck when i was making the last one for the currents... thus far i have I3= I4+I5 I1=...
  17. B

    Potential Difference and Potential Near a Charged Sheet

    Homework Statement Let {\rm A} = \left(x_1,y_1 \right) and {\rm B} = \left( x_2,y_2 \right) be two points near and on the same side of a charged sheet with surface charge density + \sigma . The electric field \vec{E} due to such a charged sheet has magnitude E = \frac {\sigma}{2 \epsilon_0}...
  18. M

    What's the Current of the Potential Difference?

    Homework Statement A potential difference is applied between the electrodes in a gas discharge tube. In 2.0 s, 3.3*10^16 electrons and 1.2*10^16 singly charged positive ions move in opposite directions through a surface perpendicular to the length of the tube. What is the current in the tube...
  19. M

    Potential difference between Bird's Feet?

    Homework Statement A bird sits on a high-voltage power line with its feet 2.0 cm apart. The wire is made from aluminum, is 3.0 cm in diameter, and carries a current of 160 A. What is the potential difference between the bird's feet? Homework Equations I=neAv Where I is current, n is...
  20. M

    What is the Potential difference?

    Homework Statement As a positron moves through a region of space, its speed decreases from 9.20*10^6 m/s to 2.20*10^6 m/s. The electric force is the only force acting on the positron. Homework Equations KE1 + U1 = KE2 + U2 Where KE is kinetic energy and U is potential energy. The Attempt...
  21. W

    Finding electric potential difference

    Homework Statement Two parallel plates having charges of equal magnitude but opposite sign are separated by 14.2 cm. Each plate has a surface charge density of 33.3 nC/ m2. A proton is released from rest at the positive plate. Determine the potential difference between the plates...
  22. T

    Potential difference across parallel circuits

    I am currently having some difficulty in recalling/understanding the potential difference across parallel circuits. Why is the potential difference across individual components of the parallel circuit the same? Let's for example say 2 resistors of different resistance are connected in...
  23. G

    Speed of an electron and potential difference

    I have a question here where a potential difference is applied to a stationary electron. I have calculated the energy translated to the electron already and I know the mass energy of the electron. If I want to find its final speed I assume that I use a rearrangement of the relativistic...
  24. B

    Electric potential, potential difference, and potential energy

    1. Here is a problem that I know how to solve Through what potential difference would an electron need to be accelerated for it to achieve a speed of 2.3% of the speed of light (2.99792x10^8 m/s), starting from rest? Answer in units of V. For this problem I used: deltaK + deltaU = 0...
  25. E

    Potential difference Capacitance problem

    Homework Statement http://img509.imageshack.us/img509/8805/problem5fw8.th.png The potential difference V = 100 V is applied to the capacitor arrangement shown in the figure. Here C1 = 10 microF, C2 = 5 microF, and C3 = 4microF. If capacitor C3 undergoes electrical breakdown (i.e. becomes...
  26. S

    Physics electric generator potential difference question

    Hi all, I'm on the final question of an assignment, unforunatly its not really a calculation or anything and i can't find any information on it i thought maybe someone could help me out 13. At a coal-fired electric generating station, heat from the burning coal is used to drive a steam...
  27. S

    Potential difference question

    Potential difference question... Homework Statement A proton (mass = 1.67 10-27 kg, charge = 1.60 10-19 C) moves from point A to point B under the influence of an electrostatic force only. At point A the proton moves with a speed of 60 km/s. At point B the speed of the proton is 80 km/s...
  28. C

    Potential difference and a proton

    Homework Statement a proton (mass=1.67x10^-27kg, charge 1.6x10^-19C) moves from point A to point B under the influence of an electrostatic force only. at point A the proton moves with a speed of 50km/s and at point b it moves with a speed on 80km/s. determine the potential difference vb-va...
  29. E

    The Electric Potential Difference Created by Point Charges

    Homework Statement One particle has a mass of 3.00 10-3 kg and a charge of +7.50 µC. A second particle has a mass of 6.00 10-3 kg and the same charge. The two particles are initially held in place and then released. The particles fly apart, and when the separation between them is 0.100 m...
  30. K

    Potential difference and kinetic energy between plates

    A point charge q = −2.40 nC is initially at rest adjacent to the negative plate of a capacitor. The charge per unit area on the plates is 4.50 µC/m2 and the space between the plates is 6.50 mm. (a) What is the potential difference between the plates? kV (b) What is the kinetic energy of...
  31. A

    Proton accelerated thru potential difference - find final speed

    Homework Statement A proton is accelerated from rest through a potential difference of 107 V. Calculate the final speed of this proton. Homework Equations I'm not really sure which equations to use, but I figured I give all I tried... V=-Ed V=PE/q PE=-qEd and I think this...
  32. S

    Finding the potential difference?

    okey the question goes like this A plate capacitor with area A and distance d1 is charged to a potential difference of V1 between the plates. Now the distance between the plates increases to d2 = 2*d1. a) What is the new potential difference, V2, between the plates? b) Find the increase...
  33. K

    Potential difference of a capacitor

    A defibrillator is used to restart a person's heart after it stops beating. Energy is delivered to the heart by discharging a capacitor through the body tissues near the heart. If the capacitance of the defibrillator is 8.00 µF and the energy delivered is to be 100 J, to what potential...
  34. B

    Calculating Potential Difference Between A(0,1) & B(1,0)

    Hi, I would like to have some suggestion about how to do this problem: Given the electric field vector E=x(1-sin (phi))+ y.cos(phi) x and y are unit vectors. Calculate the potential difference between the points A(0,1) and B(1,0). along : 1- Circular arc from(0,1) to (1,0)...
  35. L

    Potential Difference between two points of a circuit

    Homework Statement Given the following circuit, what is Vab? Explain... Homework Equations Kirchoff's Law and Ohm's Law The Attempt at a Solution Here is my solution... Is this describing it correctly? Kirchoff’s Loop Law to find current: -10 Ω (I) + 30 Ω V – 100 Ω (I) –...
  36. T

    Magnetism (Charge, E-field, potential difference, mass) - A bit confused

    Homework Statement Image: http://img.photobucket.com/albums/v696/talimtails/PP23.jpg A particle with unknown mass and charge moves with a constant speed v = 1.9 x 10^6 m/s as it passes undeflected through a pair of parallel plates, as shown above. The plates are separated by a distance d...
  37. C

    Electric Potential Difference homework help

    Homework Statement Two charged rods, each with net charge -Qo, are held in place as shown in the diagram below a) A small test charge -qo travels from point X toi point Y along the circular arc shown. i. Draw an arrow at each point (X and Y) to show the direction of the electric force on...
  38. A

    Potential Difference of Capacitors

    Homework Statement A parallel-plate capacitor has an area of 5 cm^2, and the plates are separated by 1mm with air between them. The capacitor stores a charge of 400pC. a) What is the potential difference across the plates of the capacitor? b) What is the magnitude of the uniform electric field...
  39. K

    Capacitors and Potential Difference

    Homework Statement (Note: This is the fourth part of a single question, but it's the only part I'm having trouble with. Don't worry, it's not as simple as Q/V. :rofl:) "What is the potential difference between a point midway between the [circular, parallel] plates [which are 1.43 x 10-4 m...
  40. M

    Potential difference and current

    Homework Statement A typical cell membrane is 8.0 nm thick and has an electrical resistivity of 1.3 10^7 m. If the potential difference between the inner and outer surfaces of a cell membrane is 75 mV, how much current flows through a square area of membrane 1.3 µm on a side? Homework...
  41. S

    Potential Difference, current, and resistance

    How do I find the Potential Difference, current, and resistance in series and parrel circuits. arent all circuits parallel.
  42. F

    Capacitors and potential difference

    My physics textbook kinda offhandly says capacitors can be charged to higher potential differences than the battery used to charge them and uses a camera flash as an example, however it doesn't say how this is done. What it does say is attaching a capacitor to a batter in a simple circuit will...
  43. A

    What will be the potential difference?

    This is my first time on Physics Forum, so if I post this question at the wrong place please don't be annoyed. I am a Grade 9 student and I came upon this question and don't know how to solve it: An ammeter gives a reading of 5A when a switch was closed for 20 seconds. If this battery has...
  44. Z

    E&M Physics. Potential Difference

    Hello, I am in electricity and magnetism. I have a question about a homework problem. A 1000-turn loop (radius = 0.034 m) of wire is connected to a (20 ohm) resistor as shown in the figure. A magnetic field is directed perpendicular to the plane of the loop. The field points into the paper...
  45. D

    EMF, Voltage, Current, Potential Difference etc.

    Hey. At school, we are currently studying electricity, and i am having some trouble understanding some of the concepts. From what i understand, EMF is the energy given to each unit of charge, which allows it to flow around a circuit. Why do the charges need energy? Is the energy they receive...
  46. M

    Potential Difference between two points in battery

    more so help with the concept than anything else. A battery has an EMP of 12v and an internal resistance of 2 ohms. Is the terminal-to-terminal potential difference greater than, less than, or equal to 12v if the current in the battery is from a) from the neg to pos. terminal b) from pos to...
  47. M

    Finding speed from acceleration through a potential difference

    I need help finding the speed of a proton in terms of c (speed of light) when all I have is an acceleration through a potential difference of 77 MV. I started by saying this was 77,000,000 Volts, and then using PE = qV to solve for energy. I used E = mc^2 to find mass and used this and rest...
  48. quasar987

    How does it know the potential difference between the two objects?

    Suppose you have two charged conductors. Then you "use" a voltmeter on them. How does it know the potential difference between the two objects? There's no current, so it cannot use V=RI. thx
  49. R

    Potential Difference b/t 2 points

    Ok, I've got a problem: The electric field in a region of space has the components Ey = Ez = 0 and Ex = (3.91 N/C)x. Point A is on the y-axis at y = 2.83 m, and point B is on the x-axis at x = 3.97 m. What is the potential difference VB - VA? I have tried integrating E (wrt x) * x from...
  50. B

    Electric potential and potential difference

    hiya 1) Some quotes from physics tutorial site: The above all makes sense. But this is where I get lost: Wouldn't it be more correct if instead we said: *The kinetic energy charge has was transformed from charge's potential energy, and this kinetic energy gets lost as charge goes...
Back
Top