What is Electric fields: Definition and 506 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. S

    Electric Fields through dielectrics

    My question is simple; yet, I can not find the answer. In the picture below, all variables are identical; the plate separations, surface area, etc. The only difference is the fact that example 1 has 2 different dielectrics. Better yet, it has a dielectric that doesn't extend the entire distance...
  2. Y

    Three charges located on a straight line

    Homework Statement Three charges, Q1, Q2 and Q3 are located on a straight line. The charge Q3 is located 0.169 m to the right of Q2. The charges Q1 = 1.56 μC and Q2 = -3.03 μC are fixed at their positions, distance 0.268 m apart, and the charge Q3 = 3.18 μC could be moved along the line. For...
  3. C

    Measuring Electric Fields w/Neon?

    Good day everyone! n00bie here. I did do a search before I posted this... found a lot of info, most of which I couldn't apply to what I am doing (because I wouldn't know how). I have something that I am working on that creates an electric field to alter certain chemical compounds. The distance...
  4. L

    Induced Electric Fields: Exploring Gauss' & Lenz's Laws

    In electrostatics, ∇ × E = 0 so E that is a conservative field and there must be sources of E from which E flows. We know that this sources are the electrical charges given by Gauss' Law. But when B changes in time, ∇ × E = - ∂ B / ∂t. Now the Gauss' Law no longer applies and if there are not...
  5. TheExibo

    Electric Fields and charged particles

    Let's say there's a question where there are two charges placed, and a point in between and above the line connecting the two charges forms a triangle like this: http://session.masteringphysics.com/problemAsset/1413940/2/p19.5.jpg What would one have to do in order to find the electric field...
  6. P

    Electrical Charge and Electric Fields

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  7. R

    Prove E field does not depend on dielectric (capacitors)

    Homework Statement "Show that the variation of the potential between the plates of a large parallel plate capacitor remains the same if the air between the plates is replaced by a conductive medium." Homework Equations E = σ/ϵ0 ; C = ϵ0A/d ' C = Q/V ; E = -dV/dx ; R = ρl/A The Attempt at a...
  8. F

    Determining angular frequency in an electric field using velocity.

    1. There are 2 negatively charged plates opposite each other. In between them, there is a vacuum tube (50 cm long), containing only 1 electron. Assume it is completely isolated. The charge value for the plates is equivalent to 10000 electrons. Initially the single electron is directly in the...
  9. S

    Do Oscillations Occur in Inductors When Modifying AM Transmitter Circuits?

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  10. Warpspeed13

    How to generate powerful electric fields in a small space

    How would you generate extreme electric fields between two small surface area parallel plates.
  11. M

    How Does Electron Shape Affect Electric Field Energy?

    Homework Statement a. Calculate the energy density of the electric field at a distance r from an electron (presumed to be a particle) at rest. b. Assume now that the electron is not a point but a sphere of radius R over whose surface the electron charge is uniformly distributed. Determine the...
  12. davidbenari

    Do electric fields really exist?

    I'm limiting my question to this field because it is the only one I know of with a certain degree of knowledge. I doubt they really exist because of the following reasoning: Coulombs law was stated because it makes mathematical sense (think of "force directly proportional to the charges and...
  13. W

    Electric Fields: Thin wire in conducting cylinder

    Hello PF, I am having a bit of difficulty understanding this question. Homework Statement "A thin wire with linear charge density λ is surrounded by a conducting cylindrical shell." (There is a hollow cylinder with a wire though it) "If the electric field must be zero inside a conductor, is...
  14. X

    Electric Fields - continuous charge distributions

    Homework Statement A plastic rod of finite length carries an uniform linear charge Q = -5 μC along the x-axis with the left edge of the rod at the origin (0,0) and its right edge at (8,0) m. All distances are measured in meters. Determine the magnitude and direction of the net electric...
  15. J

    Do stationary electric fields have a magnetic field too?

    I know that a magnetic field will have an electric field bc there is charges, and they are moving. Thanks physicsforums!
  16. almarpa

    Ohm's law and emf for non static electric fields

    Hello all. I am currently studying electromagnetism with Griffiths' books, and I have already donde electrostatic and magnetostatics. Now I am reviewing Ohm's law en emf concepts, but I have a doubt: In griffths book, when explaining ohm's law and emf, it seems to me that he assumes...
  17. J

    Why are magnetic and electric fields not considered the same?

    Why are magnetic fields and electric fields still considered different phenomena? Doesn't relativity and QFT explain that they are the same thing. A photon is a photon, isn't it? I mean, what is happening when two magnets repel? They exchange photons. What happens when two electrons repel? They...
  18. O

    Electric Fields: Magnitude and Direction.

    Homework Statement Calculate the magnitude and direction of the electric field at point Z in Figure 13, due to the charged spheres at points X and Y. Homework Equations E = kq1/r^2 The Attempt at a Solution Determine each vector component: Ex = (9.0x10^9 Nm^2/C^2)(50.0 x...
  19. M

    Electric Fields -- Charges at corners of equilateral triangle

    Consider an equilateral triangle of side 15.6 cm. A charge of +2.0uc is placed at one vertex and charges of -4.0C uc each are placed at the other two, as shown in the diagram to the right. Determine the electric field at the centre of the triangle ANgle= 60 sides--> d1= d2=d3=0.156m...
  20. B

    How Does a Changing B Field Induce Electric Fields Inside Layers of Dielectric?

    Hi all, I am looking into induced electric fields by changing B fields inside layers of dielectric. For example, if a block of several layers of a dielectric material is placed inside a capacitor plate, the E fields inside each layer is shielded depending on the relative permitivitty...
  21. tristanm

    Electric Fields of Cylinders and Cylindrical Shells

    Homework Statement 1. Use Gauss' Law to calculate the electric field at a radius of 5.0cm from the z-axis 2. Use Gauss' Law to calculate the electric field at a radius of 8.0cm from the z-axis 3. What is the surface charge density σmetal on the outer surface of the metal cylinder...
  22. patrickmoloney

    How Do Electric Fields Affect Electron Motion Between Charged Plates?

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  23. Ascendant78

    Electric fields vs magnetic fields?

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  24. F

    Potential and Electric Fields: Understanding Charges and Fields on a Line

    Homework Statement Consider a line of length L=0.950 m and uniform positive charge per unit length λ=2.9 μC. Point A is a distance x=0.23 m from the center of the line, while B is the same distance from the line but a distance y=0.28 m farther along the line; point C is a distance z=0.050 m...
  25. M

    Electric fields of a spherical shell

    My class hasn't delved into Gauss's Law much besides describing conductors at electrostatic equilibrium to have no net electric field or force within itself. For the picture, the question is: What are the magnitudes of the electric fields at: 1) r = a 2) r = 3/2 a 3) r = b...
  26. A

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  27. J

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  28. C

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  29. C

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  30. T

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    Greetings PFers, Can someone help explain to me the difficulties of designing a device which utilizes static electric fields to map an objects’ internals and externals? My understanding is that as a electric field propagates through matter, it encounters absorption. I envision a device...
  31. R

    Electric fields and a spherical surface

    If there's a point charge Q at the center of a spherical surface(of radius a) made of conducting material that is connected to earth, why is the electric field past r>a zero ? Doesn't it imply that the spherical surface becomes charged with -Q ? And why is that? What would be the...
  32. H

    Electric fields and mean free path?

    Just need someone to tell me if I'm doing this right. If I have accelerated a particle in which the mean free path is 50nm and I need the collision to be 5eV would this be correct in determining the required electric field strength? 5/.00000005 = 100MV/m
  33. B

    Parallelepiped with two electric fields. Find the charge inside.

    Homework Statement The electric field E1 is constant over the whole of one surface of parallelepiped and directed out of the surface. On the opposite surface is field E2 constant over the surface and is directed into the surface. the two surfaces forming an angle of 30 ° with the...
  34. S

    I don't understand electric fields.

    According to my textbook, the electrical field is defined as E = F/q where q --> 0, because we want the test charge to affect the other charges around it in the least possible way. It then goes on to say that qE = F is true for charges not strong enough to move the other charges. Why is that, if...
  35. J

    Finding Electric Fields and Electrostatic Potential

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  36. J

    What Causes Maximum Voltage Inside a Conducting Sphere?

    reading this page : http://hyperphysics.phy-astr.gsu.edu/hbase/electric/potsph.html it says "The electric field inside a conducting sphere is zero, so the potential remains constant at the value it reaches at the surface:" if the electric field inside the sphere is 0, then wouldn't that...
  37. B

    Can Circulating Electric Fields Be Considered Valid Electrostatic Fields?

    Homework Statement Consider two “circulating” electric field configurations. Expressed in polar coordinates (s,φ,z) they are: (these expressions are not dimensionally correct) 1. E = (0,s,0) 2. E = (0,1/s,0) a. Calculate ∇×E for both configurations. b. Note that ∫E⋅dl≠ 0 in either...
  38. G

    Electric Field Calculation for Infinitely Long Charged Line and Rod

    Homework Statement An infinitely long, uniformly charged straight line has linear charge density λ1 coul/m. A straight rod of length 'b' lies in the plane of the straight line and perpendicular to it, with its enared end at distance 'a' from the line. The charge density on the rod varies...
  39. B

    Do electric fields in a conductor go to zero in all instances?

    In the absence of external forces, the electric field inside a conductor is supposed to go to zero. This is because if any field were to exist, then the charges in the conductor would experience force and continue moving until they canceled the field. However, is it true that for any system a...
  40. T

    Electric fields change in the spacing between the plates?

    Homework Statement A,B,C,D are four 'thin',similar metallic parallel plates,equally separated by distance d,and connected to a cell of potential difference(V) as shown in the attachement. Write the potentials of A,B,C,D. If B and C be connected by a wire,then what will be the potentials...
  41. C

    Stopping Ice Formation on Surfaces: The Power of Electric Fields

    Hi guys, brand-new simpleton here. Quick question: would it be possible to stop ice formation on a cold surface with an electromagnetic field? How strong should it be (if possible)? Thank you!
  42. Crazymechanic

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    hello , could someone please remind me I have forgotten a few things. So the electric field is perpendicular to the conductor and the flow of charge. So if i have a pipe and in the pipe flows a conducting gas or a plasma , now around the pipe I have a simple copper wire wound in many many...
  43. N

    Electric Field Distribution of a Charged Disk: The Role of Symmetry

    Hey. Let's say you have an infinitely wide and long disk with a thickness h. Inside the disk, there is a constant charge density ρ0. Why would the electric field lines be perpendicular to the disk? Can somebody explain how symmetry and such generally affect electric field distribution of a...
  44. B

    Coulomb's Law Electric Fields

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  45. N

    Question about electric fields

    Hey guys, just got a question at school and the last part makes no sense. I replicated it almost exactly, except for the diagram. Just imagine the dotted line is a solid line indicating the electric field lines. Ignore the 4 dots around X, it was just to keep the field lines in line.Question 4...
  46. P

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  47. V

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  48. R

    Determine electric field at point P, Electric fields question

    Homework Statement Heres the probelm: http://imgur.com/TbzJxVa Homework Equations e = kq/r^2 The Attempt at a Solution q-p Ex = (9*10^9)(4)/(0.80)^2 = 5.625*10^10 Q-p E1 = (9*10^9)(6)/(1)^2 = 5.4*10^10 Ex = E1sin45 = -3.82*10^10 Ey = E1cos45 = 3.82*10^10 P p =...
  49. A

    Calculating electric fields due to continuous charge distributions

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  50. T

    Levitation using directed electric fields

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