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. Mason Smith

    Find the magnitude of the electric field at regions 2 and 3.

    Homework Statement The three parallel planes of charge shown in the figure have surface charge densities (-1/2)η, η, and (-1/2)η. Homework Equations I think that the electric field is equal to eta divided by epsilon naught. The Attempt at a Solution Well, I know that the electric field at...
  2. Cocoleia

    Electric field & energy in a spherical distribution of charge

    Homework Statement Homework Equations Gauss The Attempt at a Solution I am really confused with question a, I have an idea of how to answer b and c once I obtain an answer for part a... My best guess would be to use Gauss, but I am not sure. Would the field inside be 0? What will the bounds...
  3. grandpa2390

    Electric field due to a flat circular disk

    Homework Statement Find the electric field at a distance z above the center of a flat circular disk of radius R Homework EquationsThe Attempt at a Solution My attempt to solve this was take the line integral from the center of the circle to the edge. Then, knowing the circle is symmetrical...
  4. jlmccart03

    Magnitude of the work done by electric field.

    Homework Statement The membrane around a cell normally has layers of charge that create a potential difference between its outer and inner surfaces. This difference is about 72 mV . When a singly ionized potassium ion moves through a channel in the membrane passing from the outside to the...
  5. R

    Electric Fields Question, What is the speed of the electron?

    Homework Statement An electron is released from rest in a weak electric field given by -2.8 x 10^-10 N/C [PLAIN]https://www.flipitphysics.com/Content/smartPhysics/Media/Images/Tipler/Symbols/jhatbold.gif. After the electron has traveled a vertical distance of 1.9 µm, what is its speed? (Do not...
  6. J

    Magnitude and angle of an electric field vector

    Homework Statement The electric potential at points in an xy plane is given by V = (1.5 V/m2)x2 -(2.9 V/m2)y2. What are (a) the magnitude of the electric field at the point (3.9 m, 2.9 m) and (b) the angle that the field there makes with the positive x direction. Homework EquationsThe Attempt...
  7. R

    Calculating Electron Speed in an Electric Field - Homework Question

    Homework Statement An electron is released from rest in a weak electric field given by -2.8 x 10-10 N/C [PLAIN]https://www.flipitphysics.com/Content/smartPhysics/Media/Images/Tipler/Symbols/jhatbold.gif. After the electron has traveled a vertical distance of 1.9 µm, what is its speed? (Do not...
  8. tarkin

    Electric Field due to multiple point charges

    Homework Statement [/B] Derive expressions for the magnitude and direction of the electric field at point P and the potential at R. Charges Q1 and Q2 are both positive. Distance from Q1 to P is h, distance from Q2 to P is √2 h Homework Equations E = k q/r^2 The Attempt at a Solution I...
  9. P

    Electric field at a point affected by two charges

    Homework Statement (a) What is the strength of the electric field at the position indicated by the dot? (b) What is the direction of the electric field at the position indicated by the dot? Specify direction as an angle measured ccw from the positive x-axis. ##Q_{1} = 4.0 C## ##Q_{2} = 9.0...
  10. doktorwho

    Calculating Bound Surface Charge Density at Dielectric Discontinuity

    Homework Statement ##e_{r1}=2## ##e_{r2}=10## ##α_1=\pi /4## ##D_1=100 nC/m^2## ##ρ_s=0## On the borderline of two dielectrics there is no free charge. Calculate the surface bond charge density of both dielectrics. ##ρ_{bs1}=?## ##ρ_{bd2}=?## Homework Equations 3. The Attempt at a Solution...
  11. ThunderLight

    What composes the E Field of the Electromagnetic Wave?

    What composes the E Field of the Electromagnetic Wave where "disturbances" for propagation occurs? If electromagnetic waves cause disturbances in the Electric Field… what “is” in this E Field which photons Interact with? I ask because in Vacuum, there are no electrons to excite. So what is...
  12. J

    Gaussian shell and electric field

    Homework Statement Homework EquationsThe Attempt at a Solution Okay, parts a-c are zero as they are within both shells. Lets begin with d because i fear I am just repeating the same error in all of the following parts. Part d qenclosed=ρ(4πr^3/3-4πa^3/3) =...
  13. Iftekhar Uddin

    I Probably a Dumb Question: How are E and (delta)V correlated?

    What I Think I Understand: ΔV = Ed (d being dstance) and that V = kq/r please correct me if I'm misunderstanding those. What I need to know: When E = 0, what happens to the electric potential? and vice versa. Me Working it out: So if i use the first equation up here, If E = 0, then electric...
  14. Mason Smith

    How do I find the points where the electric field is zero?

    Homework Statement Two pairs of charges are shown in Figure 1. Homework EquationsThe Attempt at a Solution I originally thought that the electric field past point 7 (i.e. points 8,9, 10) was the solution. However, this is wrong. I then considered point 1, yet that was wrong too. I even...
  15. A

    Electric field of a washer (hollow disk)

    Homework Statement A washer made of nonconducting material lies in the x − y plane, with the center at the coordinate origin. The washer has an inner radius a and an outer radius b (so it looks like a disk of radius b with a concentric circular cut-out of radius a). The surface of the washer is...
  16. jlmccart03

    Find electric field strength expression for a specfic region

    Homework Statement A thick, spherical shell of inner radius a and outer radius b carries a uniform volume charge density ρ. Find an expression for the electric field strength in the region a<r<b. Homework Equations Gauss's Law ∫E⋅dA Area of a sphere The Attempt at a Solution I know I am...
  17. jlmccart03

    Electric field strength near a metal plate

    Homework Statement A total charge of 21 μC is applied to a thin, 1μm square metal plate 72 cm on a side. Find the electric field strength near the plate's surface, far from the edges. Homework Equations I think E = kq/r^2, but I really don't know. The Attempt at a Solution I am...
  18. jlmccart03

    Magnitude of electric field near spherical shell

    Homework Statement A 10-nC point charge is located at the center of a thin spherical shell of radius 8.0 cm carrying -20 nC distributed uniformly over its surface. What is the magnitude of the electric field 2.0 cm from the point charge? Homework Equations E = kq1q2/r^2 The Attempt at a...
  19. J

    Gaussian Shell and net electric field

    Homework Statement Homework Equations σ=q/(4πr^2)→q=σ(4πr^2) E=q/(4πEod^2) E=(4πr^2σ)/(4πEod^2)The Attempt at a Solution So the first thing that i could include was that the point p was inside Shell 1 and therefor would not be affected by Shell 1. So it should be a fairly simple plug in the...
  20. J

    Finding the Electric Field given the potential in spherical

    Homework Statement The problem statement is in the attachment Homework Equations E[/B] = -∇φ ∇ = (∂φ/∂r)er The Attempt at a Solution I am confused about how to do the derivative apparently because the way I do it gives E = - (∂[p*r/4πε0r3]/∂r)er = 3*(p*r)/4πε0r4er
  21. J

    Net Electric Field Homework: Find Ea, Eb, and Enetx

    Homework Statement Homework Equations Enetx=((kq1)/r^2 +^2) with the pos/neg of the coefficients being dependent on the position of the charges around the point The Attempt at a Solution As everything is one dimensional we can assume the j an k compnents of the electric field are 0 Part a...
  22. L

    Coulomb's Law problem: Charged particles and the net electric field and force

    Homework Statement Figure (a) shows charged particles 1 and 2 that are fixed in place on an x axis. Particle 1 has a charge with a magnitude of |q1| = 19e. Particle 3 of charge q3 = +16e is initially on the x axis near particle 2.Then particle 3 is gradually moved in the positive direction of...
  23. S

    Electric Field diagram question

    http://imgur.com/a/Hg23p 1. Homework Statement In each of the figures below some electric field lines are drawn. But in most cases, there are mistakes. For each drawing, select which of the above rules are broken or if the diagram is essentially correct. http://imgur.com/a/Hg23p Homework...
  24. Ryan Sandoval

    Calculating Two Unknown Charges from a Tripole

    Homework Statement Written Problem: Summing the Electric Field Three point charges q1, q2, and q3 are placed along a straight vertical line to create a “tripole”. At point P, which is directly to the right of q1, the net electric field is exactly zero. We also know that q1 = 1 μC. b) Write a...
  25. J

    Calculating Net Electric Field for a Charged Arc

    Homework Statement Homework Equations L=pi*r/2 λ=q/L Enet=∑λ(2sinθ)*kThe Attempt at a Solution So first to calculate L for each arc L1=pi(.107m)/2 L2=pi(.214m)/2 L3=pi(.321m)/2 and lambda: λ1=3.3E-6/L1=2E-5 λ2=-12E-6/L2=-3.9E-5 λ3=29.7E-6/L3=5.9E-5 So using θ=pi/2 and rearranging the...
  26. F

    An electric charge feels its own self electric field

    Hello, In classical electromagnetism, we learn that an electric charge generates and electric field which other charges can feel through a force. But the source charge does not feel its own generated electric field. In reality, a charge feels its own field. Why are we able to ignore this...
  27. J

    Calculating Electric Field Using Coulomb's Law

    Homework Statement Homework Equations Ex=1/k*1/(a^2/2)*1/(sqrt2)*cos(theta)*(sum of charges) Ey=1/k*1/(a^2/2)*1/(sqrt2)*sin(theta)*(sum of charges) The Attempt at a Solution So first off I can see that I don't need to calculate the force in the x direction as each q cancels out when...
  28. jlmccart03

    Find the electric field on a proton by an electron

    Homework Statement A proton is at the origin and an electron is at the point x = 0.36 nm , y = 0.34 nm. Find the x- and y-components of the electric force on the proton. Homework Equations E = kQ/r2 The Attempt at a Solution So I found that E = 9.38 * 10-28, but my problem is that I do not...
  29. jlmccart03

    Find the electric field at x and y coordinates?

    Homework Statement A 60 μC point charge is at the origin. Find the electric field at the point x1 = 50 cm , y1 = 0. Homework Equations Coulombs Law: F = (kQ1Q2)/r2 Electric Field: E = kQ/r2 k = 8.99*109 C The Attempt at a Solution So taking Coulombs Law and deriving the Electric Field...
  30. Cocoleia

    Electric field at centre of hollow half sphere

    Homework Statement Homework EquationsThe Attempt at a Solution I figured you could consider it as infinitely many rings? Here is what I did so far: I feel like 0 is the wrong answer. Can anyone help me? Thanks.
  31. E

    Electric field on the x-axis of a semicircle

    Homework Statement There's a charged semicircle, the ends of which are on the x-axis and it extends into the positive y-axis. It has uniform line charge density. I need to find the electric field at an arbitrary point on the x-axis that's not the origin. Homework Equations I don't know. The...
  32. DoubleE7

    Electric field at the center of a hemisphere

    Homework Statement What is the electric field at the center of a hemisphere bounded by r=a, 0<θ<pi/2 / and 0<∅< 2pi with a uniform surface charge density? Homework Equations (1/4piε0) ∫ p(r') ((r-r')/[r-r']^3) dr' The Attempt at a Solution Forgive my formatting ds= (r^2)sinθdθd∅ (In direction...
  33. U

    Electric field at centre of a hollow hemisphere shell.

    Homework Statement Homework Equations ' The Attempt at a Solution Please excuse the poor writing. I believe it should be legible enough, but if you have any questions, i'll clarify or rewrite it. Please excuse the poor writing. I believe it should be legible enough, but if you have any...
  34. P

    Electron/proton released from charged parallel plates

    Homework Statement Two parallel plates 1.40 cm apart are equally and oppositely charged. An electron is released from rest at the surface of the negative plate and simultaneously a proton is released from rest at the surface of the positive plate. How far from the negative plate is the point at...
  35. B

    Electric Field at the End of a Line of Charge

    Field at End of Line of Charge 2 A charged rod of length L=7.10 m lies centered on the x axis as shown. The rod has a charge density which varies according to λ=ax^2 where a=−20.2 μC/m^3 . What is the x component of the electric field at a point on the x-axis a distance of D=3.70 m from the...
  36. RoboNerd

    Work done by electric field

    1. Homework Statement Hi everyone, I am having trouble solving this question. I know that the right answer is d. Homework Equations No equations here, only conceptual stuff. The Attempt at a Solution Say I have the following points: A and B A...
  37. A

    Electric field acting on a negative test charge due to semicircular rod

    Homework Statement A thin semicircular rod is broken into two halves. The top half has a total charge +Q uniformly distributed along it, and the bottom half has a total charge -Q uniformly distributed along it. A negative test charge is placed at points A, B, and C. *Image attached* Consider...
  38. A

    Electric field at a point (point charge and semi-circle rod)

    Homework Statement A thin semicircular rod has a total charge +Q uniformly distributed along it. A negative point charge -Q is placed as shown. (Point C is equidistant from -Q and from all points on the rod.) *Image Attached* Let Ep and Er represent the electric fields at point C due to the...
  39. RoboNerd

    Resistor made from two materials

    Hi everyone, I am having problems figuring out how to solve a particular problem. Because I was not able to access PhysicsForums recently, I typed everything about my issues into a pdf file that I have attached below. I am grateful for your help in advance, and make it a great day...
  40. ORF

    A How the emission spectra can be affected by E/M field?

    Hello A friend of mine asked me if he could improve the (amateur) characterization of minerals by studying the absorption spectra during the application of a magnetic field. I thought that maybe the electron cyclotron resonance could work, but then I noticed that very low temperatures are...
  41. S

    Is the direction of electric field the direction of current?

    Is the direction of electric field save as the direction of (conventional) current?
  42. T

    2008 us physics olympiad pendulum in electric field

    1. Homework Statement i was solving the 2008 semi final us physics olympiad paper when i got stuck on question B2 in part 2 http://www.aapt.org/Programs/contests/upload/olympiad_2008_semi-final_soln.pdf the link takes you a pdf with questions and solution however i don't understand the soution...
  43. Tanmay Gupta

    Electric field question -- Charges....

    When a charge placed at anywhere,then it produces a powerful field around itself,is called electric field. It is exist whenever charge exist.And charge takes very very small time in propagate electric field.
  44. J

    Electric field inside a cavity

    It is a simple arrangement. Imagine that we have an empty cubic box. Outside the box the electric potential is infinite. Imagine that you put an electric charge at the geomectric center of the box. What is the field around this charge? In other words, the tool I have to calculate the field...
  45. D

    Angle of electron in an electric field

    Homework Statement https://imgur.com/zEoCpc0 I am trying to figure put the angle and my attempt is tanx=sy/sx (I have calculated a value for the distances) But my book is saying: tanx =vy/vx I don't understand why my way of solving it is wrong... I don't get the same answer for x :/
  46. L

    Net electric force and Net electric field

    Homework Statement a) Find the net force on charge 1. b) What is the net electric field acting on charge 1? Please see the attached files to view the image that goes with the questions above. Homework Equations I'm having trouble with this unit in general and I'm not to confident in these...
  47. J

    How Does Melting Affect the Polarizability and Dielectric Constant of a Medium?

    I understand that as a solid melts, it increases can increase in polarizability of the medium, and increase the Dielectric constant (K). -ex. like dissolving NaCl and having ions in solution. Why does Thermal motion reduce the polarizability of the medium, thus decreasing the dielectric...
  48. Schaus

    Electric fields - Finding Net force acting on Q2

    Homework Statement What is the Net force (include direction) acting on charge Q2 due to Q1 and q? (ans: Fnet = 174N right) Homework Equations F=kQ1Q2/r2 E=F/QThe Attempt at a Solution I've figured out a) and b). It's just c) that's giving me trouble. I tried using the first equation - (9.0 x...
  49. Schaus

    Electric potential at a point due to two charges

    Homework Statement What is the electric potential at P due to charges Q1 and Q2...
  50. B

    Ionization energy of an electric field

    Hi, If I had a charged parallel plate capacitor which was not connected to a circuit (so the charges stay on the plates) creating an electric field strong enough to cause ionization, and I then fired a neutral atom between the charged plates (the charge starts outside of the electric field)...
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