What is Electric field: Definition and 1000 Discussions

An electric field (sometimes E-field) is the physical field that surrounds electrically-charged particles and exerts force on all other charged particles in the field, either attracting or repelling them. It also refers to the physical field for a system of charged particles. Electric fields originate from electric charges, or from time-varying magnetic fields. Electric fields and magnetic fields are both manifestations of the electromagnetic force, one of the four fundamental forces (or interactions) of nature.
Electric fields are important in many areas of physics, and are exploited practically in electrical technology. In atomic physics and chemistry, for instance, the electric field is the attractive force holding the atomic nucleus and electrons together in atoms. It is also the force responsible for chemical bonding between atoms that result in molecules.
Other applications of electric fields include motion detection via electric field proximity sensing and an increasing number of diagnostic and therapeutic medical uses.
The electric field is defined mathematically as a vector field that associates to each point in space the (electrostatic or Coulomb) force per unit of charge exerted on an infinitesimal positive test charge at rest at that point. The derived SI units for the electric field are volts per meter (V/m), exactly equivalent to newtons per coulomb (N/C).

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  1. cookiemnstr510510

    Electric field above a disk that equals half the max electric field

    Homework Statement At what distance, a, along the axis of a uniformly charged disk of radius R is the axial electric field strength equal to one half its value at the surface of the disk at the center. Homework Equations electric field of disk (attached) The Attempt at a Solution First I...
  2. cookiemnstr510510

    Electric field of ring of charge/washer of charge/disk of charge

    Homework Statement Homework Equations charge density equations, electric field equations, The Attempt at a Solution My attempts are attached. The attachment labeled A, is part A. Part B took a lot of paper so there are two attachments labeled B1 and B2. It is really B and C that I am...
  3. C

    Electric Field Force Exerted Vertically

    Homework Statement A proton enters the uniform electric field produced by the two charged plates shown below. The magnitude of the electric field is 4.0 × 105 N/C, and the speed of the proton when it enters is 1.5 × 107 m/s. What distance d has the proton been deflected downward when it leaves...
  4. Physics Dad

    Finding the electric field of insulated shell

    An insulating spherical shell of inner radius r1 and outer radius r2 is charged so that its volume density is given by: ρ(r) = 0 for 0 ≤ r < r1 p(r) = A/r for r1 ≤ r ≤ r2 p(r) = 0 for r > r2 Where A is a constant and r is the radial distance from the center of the shell. Find the electric...
  5. A

    Electric field distribution in the brain

    I have a PhD in Molecular Neuroscience but am working on something that requires knowledge of electric field distribution in the brain. I understand that electric field intensity (V/cm) is E=(V1-V2)/d in a theoretical model (between 2 infinite plates, that are parallel and equidistant through a...
  6. A

    What is the Role of Electric Field Distribution in the Brain?

    Hi, I have a PhD in Molecular Neuroscience but am currently working on something that requires a deeper understanding of electric field distribution in the brain. I joined the forum hoping to be able to discuss this topic with a fellow scientist who specializes in this field.
  7. D

    Electric Field of a Non-Uniformly Charged Sphere | Homework Help

    Homework Statement A solid isolated sphere with radius R has a non uniform charge which is given by ρ= Ar², with A a constant and r<R measured from the centre of the sphereHomework Equations (a) Show that the electric field outside the sphere is equal to E = (AR5)/(5ε0r²) (b) Show that the...
  8. R

    Complete screening of an Electric field?

    Hi, I have difficulty understanding the term screening. Screening is reducing of the electric field, as far as I have understood until now. 1. Why does screening occurs? Is it due to collective interaction of plasmons? 2. If we have a slow electric field, will screening occur or will it not...
  9. V

    Capacitor problem with a beam balance -- balancing after changing the charge

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  10. Krushnaraj Pandya

    Potential difference in uniform electric field

    Homework Statement There is a uniform electric field=100 V/m inclined at 45 degrees with the x axis. My doubt boils to which is greater? V(0,0) or V(10√2,0) (since my answer has the wrong sign) Homework Equations All electrostatics formulas The Attempt at a Solution The work done to move a...
  11. Krushnaraj Pandya

    Electric field and potential at vertex of cube

    Homework Statement A solid non-conducting cube of side l and uniformly distributed charge q, has electric field E and potential V at one of its vertex, imagine this cube to be made of 8 smaller cubes of side l/2. if one such cube is removed, find the new field and potential at the point where...
  12. Mirza Danish Baig

    Electric field between conducting and non-conducting sheets

    Homework Statement Two infinite sheets of charges are placed parallel to each other. If the sheet on the left is non conducting and have a uniform charge density 3(sigma) and the one on the right is conducting and has a uniform charge density (sigma). If the area on both plates is 1m^2 then...
  13. Muhammad Usman

    Capacitor Electric Field in a Dielectric?

    Hi, I was reading the capacitor and its operation and it is written there that when the DC is applied to the capacitor it becomes open circuit. The main mechanism behind this phenomena is explained as below:- "When DC voltage is applied the charge started accumulating on the plates of the...
  14. shahbaznihal

    Spatial dependence of induced Electric field

    The Faraday's law and Lenz's law together give you, $$\xi = -\frac{\partial\phi_B}{\phi t}$$ or put another way,$$\vec{\nabla} \times \vec{E} = -\frac{\partial \vec{B}}{\partial t}$$. My question, I am just asking to make sure, the spatial dependence of ##\vec \nabla \times \vec E## will be the...
  15. A

    Gauss' law: find the electric field

    Homework Statement A long, thin, straight wire of length 1.3 m has a positive charge 4.1 × 10-8 C distributed uniformly along it. The electric field created by this wire at a radial distance 3.2 cm has a magnitude of ε= 8.85E-12 Homework Equations I think I need to use E= q/(4πr^2ε) but I...
  16. D

    Why electric field is always perpendicular to equipotential?

    I have some understanding, but I'm not sure about how accurate it is: Electrostatic force is given by F = qE, where F and E are both vector quantities. If the dot product of either side and the displacement vector Δs along an equipotential line is taken, the equation becomes F⋅Δs = qE⋅Δs. F...
  17. A

    Electron speed and acceleration in an electric field

    Hi everyone, I often work on a SEM, a type of microscope which is based on electron acceleration between an electron source and the sample you are working on. For this reason and since a few weeks I was wondering how an electron (in term of speed) behaves in a constant and linear electric field...
  18. A

    Changing electric field generating magnetic field

    I would very much appreciate a clarification on what is meant by a changing electric field in the context of statements such as 'a changing electric field creates a changing magnetic field'. My question is does the electric field actually need to reverse as a lot of examples show where two...
  19. I

    Electrical version of Faraday effect?

    The Faraday effect is a magneto-optical phenomenon caused by the interaction between light and a magnetic field. Is there a corresponding electrical-optical phenomenon, caused by the interaction between light and an electric field?
  20. M

    Work in a uniform electric field

    I need a little help here when calculating the work done in a uniform electric field on a positive charge to move it from point a at higher potential to point b at lower potential that means the charge is going towards the negative plate we first use V = - ED and then we have a...
  21. Z

    Electric Field Outside of a Ring of Charge in the X-Y Plane

    If I try to calculate the electric field in the x-y plane of a ring of charge resting at the origin on the x-y plane, I keep getting zero. I start with Coulomb's Law. $$ dE(r) = \frac{1}{4\pi\epsilon}\frac{dq}{r^2} = \frac{\lambda R}{4\pi\epsilon}\frac{d\theta}{r^2},$$ in which ##\vec R## is...
  22. S

    Why is Electric Field Below an Infinite Plane 0? Exploring Griffiths' Result

    Hello! I am reading about image charges for an infinite plane and a charge above the plane. In the book I am reading (Griffiths) the author says (and uses this results several times) that the field below the plane is 0. How do we know this? The method of the mirror charges gives the V above the...
  23. A

    Electricity and Magnetism Electric Field Problem

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  24. P

    Magnitude of the electric field at equator (measured in kV)

    Hi there Only known variables include the solar flux on the Earths atmosphere at the equator is 1.5 kWm^ -2. I've calculated the total energy from the Sun as 4 x 10^26 W, but can't seem to get to a calc of the mag of electric field at equator (measured in kVm^-2).
  25. H

    Find the scalar value and direction of the electric field

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  26. C

    Work done per unit charge by electric field on charge

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  27. T

    What is the direction of the electric field inside a battery?

    Outside the battery, in the conductor it is in the direction of conventional current. But what about inside? Since magnetism and electricity are related, and magnetic field inside a magnet is from South to North (outside it is North to South), i doubted for any correspondence.
  28. HastiM

    Electric field from voltage drop

    Homework Statement Calculate the electric field given by a voltage drop of 1 V across an insulator with thickness 20 nm. 2. The attempt at a solution I am not sure which formula to use in order to obtain the electric field. I think one should use the formula E=U/d, where E denotes the...
  29. R

    Do photons carry the electric field?

    In basic electrostatics any charged particle will produce an electric field at every point in space, and will have electric filed lines spreading out radially. E = kQ/r^2 The Standard model of particle physics says that the Photon is the force carrier for the Electromagnetic force, just like...
  30. Suyash Singh

    Electricity and Electric field

    Homework Statement Homework Equations gauss law q=charge on sphere Q=total charge enclosed by gaussian surface Q=alpha/r x (4/3 pi r^3-4/3 pi R^3) + q The Attempt at a Solution EA=Q/ε[/B] E=Q/(Aε) now for E to be independent of r, alpha/r x 4/3 pi r^3 + q = 1/(4)(pi)(r^2) alpha x 4/3...
  31. J

    Electric Field Lines for Two Objects on a Frictionless Table

    Homework Statement In the diagram, two small objects, each with a charge of -4.0nC, are held together by a 0.020 m length of insulating string. The objects are initially at rest on a horizontal, non conducting frictionless table & the effects of gravity on each other are negligible. (b)...
  32. A

    Electric field inside a conductor

    The electric field inside a conductor is zero. Or: the internal electric field is equal in magnitude but opposite in direction to the external electric field, so that the net electric field inside the conductor is zero. Why is this? The part where I am confused is why the magnitude is equal...
  33. N

    Velocity of a charged particle as it approaches infinity

    Homework Statement Homework Equations F = k(q1q1/r^2) K = (mv^2)/2 The Attempt at a Solution I got number 18 easy enough, number 19 seems simple but I'm not getting the right answer. I'm calculating Force exerted by each charge on the new charge using F = k(q1q1/r^2) for the three charges...
  34. M

    Camera Lens works as a Polarizer or not?

    I read maxwell says electric field polarizes the dielectrics. Does it mean above effect used at photographic camera lens design to make that lens sometimes works like polarizer filter ? Mustafa Umut Sarac Istanbul
  35. S

    Electric Field of a Line of Charge

    If the electric field of a line charge at a distance 'a' is µ/2Π ε0a (µ is linear charge density), then the potential at that point should be µ/2Π ε0 (since potential = electric field x distance). This means that the potential is constant at every point around the line of charge. Hence, this...
  36. E

    Where are these directions coming from? (Electric Field)

    Homework Statement Two uniform infinite sheets of electric charge, one with charge density +o and the other with -o, intersect at right angles. Find and sketch the electric field \vec{E} Homework Equations \vec{E} = \frac{\sigma}{2e_0} The Attempt at a Solution Given solution: [/B]...
  37. E

    Finding the electric field at point - Can someone check my work?

    Homework Statement Four equivalent charges are placed at (0,0), (a,0), (0,a), and (a,a). What is the electric field at point B (a, a/2)? Homework EquationsThe Attempt at a Solution My attempt: Charges at (a,a) and (a,0) cancel each other out. E_{(0,a)}= \frac{Q(\hat{x}a...
  38. S

    Maximum electric field from magnetic field

    Homework Statement In the central region of a solenoid that is connected to a radio frequency power source, the magnetic field oscillates at 2.5·10^6 cycles per second with an amplitude of 4 gauss. What is the amplitude of the oscillating electric field at a point 3 cm from the axis? (This...
  39. J

    Equipotential surface and electric field

    Homework Statement Homework EquationsThe Attempt at a Solution I know the relation between electric field and electric potential . I can also find Electric field if expression for potential is given and vica versa . But I do not know how to work with electric field and equipotential...
  40. B

    Electric field inside/outside (uniformly charged sphere)

    A sphere of radius a carries a total charge q which is uniformly distributed over the volume of the sphere. I'm trying to find the electric field distribution both inside and outside the sphere using Gauss Law. We know that on the closed gaussian surface with spherically symmetric charge...
  41. F

    Find the electric field at a point away from the charged cylinder's axis

    Homework Statement Homework Equations ##E=\frac{kQ}{r^2}## 3. The Attempt at a Solution ##Q_{enclosed} = 0 ## , because there is no charge inside the conducting cylinder. E = 0 Can anyone check my answer please ?
  42. A

    Calculating permittivity in a constant field

    Homework Statement Having a conducting sphere with radius ##R## and charge ##Q##, dielectric is put on it so that a spherical shell with inner radius ##R## and outer radius ##3R## is formed. Calculate: 1. Electric permitivitty ##\epsilon## such that ##E(r), R<r<3R## is constant and there's...
  43. F

    The work done by the electric field between two plates

    Homework Statement Homework Equations ##V=Ed## ##ΔU=ΔV Q## The Attempt at a Solution Since the electric field is constant between charged plate conductors , d and the potential difference (ΔV) don't change.So, the potential energy (ΔU) remain the same . The answer is (C). Right ?
  44. F

    Find the electric field of a point P at a distance r

    Homework Statement Homework Equations The Attempt at a Solution Can anyone check my answer please ?
  45. W

    Understanding Electric Potential and Field in a Ring of Charge

    Homework Statement A potentially silly question that I have put off too long to ask, any assistance is greatly appreciated! The electric field evaluated along the Z axis of a ring of charge centered on the origin and lying on the XY plane is only a function of ##z## and points only along...
  46. F

    Electric Field from Charged Cylinder | Radial Distance

    Homework Statement Homework Equations The Attempt at a Solution Can someone tell me where is my mistake ?
  47. S

    Jump conditions for electric field across an interface

    Hi, I have some confusion about the jump conditions for an electric field across an interface between two materials with different properties. In general, we have the two jump conditions across an interface: n.(ɛE)+ - n.(ɛE)- = σ...
  48. D

    Calculating the magnitude of the total electric field at P

    Homework Statement Two electric charges each produce electric fields. At a certain point in space P, the electric field due to the first charge has a magnitude of 8 N/C, and points directly to the right. The electric field at that point due to the second charge has a magnitude of 3 N/C, and...
  49. A

    Electric field vector due to very long thread

    Homework Statement Two parallel very long threads are uniformly charged with linear charge density of 10-8 C/cm . Distance between them is 15 cm. Find electric field vector at a distance of 15 cm from both threads. Homework Equations E*dA=Qenclosed/permittivity of free space The Attempt at a...
  50. B

    Polarizibility, Electric Field & Force

    Homework Statement A neutral atom with known polarizability α is located at the origin. A point charge Q is situated on the y-axis a large distance d from the atom. (The atom therefore becomes polarized due to the electric field of the point charge.) (a) Find the electric field due to the atom...
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