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. 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 ?
  2. 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...
  3. 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...
  4. 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...
  5. 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...
  6. S

    Electric Field induced by a Magnetic Field inside a Solenoid

  7. M

    Elementary Charge: Explaining the Integer Multiple of e

    My textbook states: "The magnitude of charge of the electron or proton is a natural unit of charge." and then has an explanation that follows. It states, "...The charge on any macroscopic body is always either zero or an integer multiple (negative or positive) of the electron charge." Here is...
  8. A

    Point where the electric field is zero

    Homework Statement Charges q1= +3 nC and q2=+8 nC have a separation distance of d= 12 cm. Find the point where the electric field is zero. Homework Equations E=kq/r2 The Attempt at a Solution I approached this problem as follows: 1) I assume the point where it happens is between charges, on...
  9. A

    Determining the direction of electric field lines

    In general, the field lines points away from the positive charge and toward the negative charge. The answer is letter E, but the second part of the answer says, "the magnitude of q1 is less than the magnitude of q2". Is that because q1 is negative and q2 is positive?
  10. G

    Using Gauss's Law to Calculate Electric Field of a Charged Thread

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  11. Manolisjam

    Non-conductve sphere with cavity -- find Electric field

    I have a non conducting sphere with a charge ρ=A/r per uni vollume A is constant. suppose there is a cavity in the centre and within a particle of charge q. i want to find the E inside the sphere in respect with r. Homework EquationsThe Attempt at a Solution for radius equal of the cavity i get...
  12. N

    Electric field inside a uniformly polarised cylinder

    This is problem 4.13 from Griffiths (edition 3). The question asks: A very long cylinder, of radius a, carries a uniform polarization P perpendicular to its axis. Find the electric field inside the cylinder. [Careful: I said "uniform," not "radial"!] I decided to try and find the bound charges...
  13. radiant_june

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    Find the electric field strength at point B between two charges shown below: Given/Known Values q1 = 4.0×10-6 C r1 = 40 cm = 0.4 m (Distance from q1 to point B) q2 = -1.0×10-6 C r2 = 30 cm = 0.3 m (Distance from q2 to point B) k = 9.0×109 Nm2/C2 Equations Electric Force: FE = (k⋅q1⋅q2)/r2...
  14. P

    Electric field inside a uniformly polarized cylinder

    Homework Statement This is problem 4.13 from Griffiths. A long cylinder of radius a carries a uniform polarization P perpendicular to its axis. Find the electric field inside the cylinder. Homework Equations ##\int \vec{E}\cdot dA = q_{encl}/\varepsilon_0## The Attempt at a Solution [/B] We...
  15. PumpkinCougar95

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    If there is a very very big(infinitely big) region of space where ## \frac {dB} {dt} = constant ## what would be the E field at any point? Obviously ## \nabla x E = constant ## but what after that ?
  16. C

    The net electric field at point A is 6.7x10^4Nm.

    Homework Statement Calculate the net electric field at point A. [/SIZE] Homework Equations Enet(total) The Attempt at a Solution [/B] The electric field at point A will due to charge 2 will point towards charge 2 because charge 2 is negative. The electric field at point A will due to charge...
  17. NoahCygnus

    Electric field on Gaussian surface due to external charge

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  18. L

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  19. F

    Electric field inside a conductor

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  20. David John

    Coulomb's Law Grade 12 Question -- Net Electric Field affecting a Charge

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  21. Muhammad Usman

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  22. C

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  23. Helmy

    Question about Electric Field lines (MCQ)

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  24. P

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  25. P

    Electric field due to current carrying conductor

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  26. S

    Apparent disagreement between Coulomb's Law and Gauss' Law

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  27. SirChris93

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  28. A

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  29. A

    When Electric Field is 0 is potential also 0?

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  30. F

    Understanding the Relationship between Electric Field Line Distance and Strength

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  31. PKM

    What should be the electric field intensity inside a sphere

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  32. L

    Three parallel plates -- find the electric field

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  33. F

    Flux with a non-uniform electric field

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  34. F

    Electric Field from Long Hollow Cylinder

    Homework Statement Consider the hollow cylinder from Exercise 1.59. Use Gauss’s law to show that the field inside the pipe is zero. Also show that the field outside is the same as if the charge were all on the axis. Is either statement true for a pipe of square cross section on which the...
  35. M

    Question about charged particle in an electric field

    Question: A) A small charged sphere is attached to a thread and placed in an electric field. The other end of the thread is anchored so that the sphere is in a static situation when placed in the field. If the thread is horizontal, find the magnitude and direction of the electric field. The...
  36. F

    How to Calculate Electric Field from Rods?

    Homework Statement (a) Two long, thin parallel rods, a distance 2b apart, are joined by a semicircular piece of radius b, as shown in Fig. 1.44. Charge of uniform linear density λ is deposited along the whole filament. Show that the field E of this charge distribution vanishes at the point C...
  37. Roverse

    An equilateral triangle's electric field at its center

    Homework Statement Three 18-cm long rods form an equilateral triangle. Two of the rods are charged to +10 nC, and the third to - 10 nC. What is the electric field strength at the center of the triangle? Homework Equations $$ \vec{E} = \frac{k*q}{r^2} $$ The Attempt at a Solution 1. Draw...
  38. Likith D

    Electric field experienced by a uniformly charged spherical shell due to itself

    The electric field experienced by the points on the surface of the shell is put out as KQ/R^2 where Q is charge on shell and R is radius of shell... But the gaussian surface corresponding to the case intersects the sphere, which means there are non-infinitesimal charge quantity sitting on the...
  39. S

    How an electric field is absorbed by a dielectric

    when a em waves strikes a dielectric the atoms vibrate in response to the electric field and if the frequency matches the resonant frequency the Lorentz oscillator the electric field is absorbed how a field can be absorbed we know the em field contain energy how is the em field destroyed is some...
  40. V

    Electric Field of a solid sphere of non-uniform surface density

    A solid sphere has surface charge density, Rho (r) Rho(r) = k 1 ( 0 < r < a) k2 x ( a < r < R) 2) Find the electric field in all region i.e 1) r < a and 2) a < r < R and 3 ) R < The attempted solution and the question with the diagram is attached below Could the answer be verified...
  41. D

    I Charged black hole - static electric field lines

    Where do the static electric field lines appear to originate from a charged black hole, non rotating, Reissner–Nordström metric? I've had a number of qualified physicists say they appear to come from the center of the black hole, but people on these forums have said that doesn't make sense...
  42. Benjamin

    Calculating Electric Field from Force on a Point Charge

    Homework Statement What is the electric field at a point when the force on a 1.20 µC charge placed at that point is = (3.0 î -5.0 ĵ) × 10-3 N? Homework Equations E = KQ/d^2 The Attempt at a Solution I'm having trouble visualizing the question. I attempted to draw it out, but its not making...
  43. G

    What is the Simplified Equation for a Uniform Electric Field?

    Homework Statement [/IMG] Homework Equations See Below The Attempt at a Solution Maybe my answer is right but not simplified enough. But if it is I am having trouble seeing the mathematical equivalency. Please help. Thanks in advance!
  44. Matt Chu

    Angle of escaping electric field lines

    Homework Statement Two charges 2q and -q are located at x = 0 and x = a respectively. There are field lines extending from the positive charge and lines going inwards to the negative charge. Some of these lines go from the positive charge to the negative, but some go off to infinity from the...
  45. Brystephor

    Electric field magnitude between two charged disks problem

    Homework Statement Consider two thin disks, of negligible thickness, of radius R oriented perpendicular to the x axis such that the x axis runs through the center of each disk. (Figure 1) The disk centered at x=0 has positive charge density η, and the disk centered at x=a has negative charge...
  46. Likith D

    Gauss' law for uniformly charged space

    the problem: Say we have the entire space uniformly charged. Then, the E field experienced by any point is zero, from symmetry.* But, it means that for any Gaussian surface, the flux though it is zero even though the charge enclosed is clearly not. Gauss' law seems to disagree with symmetry, but...
  47. M

    How Do You Calculate Electric Field Strength and Direction?

    Homework Statement The diagram is attached. What is the strength of the electric field at the position indicated by the dot in Figure 1? What is the direction of the electric field at the position? Specify the direction as an angle measured clockwise from the positive x axis. Homework...
  48. M

    Electric field vector in component form

    Homework Statement A -12nC charge is located at (x,y) = (1.0cm, 0cm). What are the electric fields at the positions (x,y) = (5.0cm, 0cm), (-5.0cm, 0cm), and (0cm, 5.0cm)? Write each electric field vector in component form. Homework Equations E=k(q/r2) The Attempt at a Solution I was able to...
  49. starstruck_

    Calculating voltage within and outside of a solid sphere

    Homework Statement A solid sphere with radius R=12 m has charge Q=3 nC distributed uniformly throughout its volume. (a) Calculate the potential difference between a location at infinity and a location on the sphere’s surface. (b) Calculate the potential difference between a location on the...
  50. L

    Finding the electric field between two parallel plates

    Homework Statement Hi everyone! This is the homework problem I'm struggling with! Initial velocity = 107 meters per second The particle is an electron, so: Charge = -1.6 x 10-19 coulombs Mass = 9.11 x 10-31 kilograms Homework Equations Kinematic formula x = vot + 1/2 at2 Newton's law...
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