Electric field Definition and 1000 Threads

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. 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]...
  2. 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...
  3. 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...
  4. 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...
  5. 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...
  6. 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 ?
  7. 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...
  8. F

    The work done by the electric field between two plates

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  9. 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 ?
  10. W

    Understanding Electric Potential and Field in a Ring of Charge

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  11. F

    Electric Field from Charged Cylinder | Radial Distance

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  12. S

    Jump conditions for electric field across an interface

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  13. D

    Calculating the magnitude of the total electric field at P

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  14. A

    Electric field vector due to very long thread

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  15. 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...
  16. S

    Electric Field induced by a Magnetic Field inside a Solenoid

  17. 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...
  18. 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...
  19. A

    Determining the direction of electric field lines

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  20. G

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

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  21. Manolisjam

    Non-conductve sphere with cavity -- find Electric field

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  22. N

    Electric field inside a uniformly polarised cylinder

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  23. radiant_june

    Electric field strength at a point between charges

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  24. 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...
  25. PumpkinCougar95

    Direction of induced electric field?

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  26. C

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

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  27. NoahCygnus

    Electric field on Gaussian surface due to external charge

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  28. L

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  29. F

    Electric field inside a conductor

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  30. David John

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

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  31. Muhammad Usman

    What is the Significance of the Electric field in a closed circuit

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  32. C

    How Much Voltage Is Needed to Suspend Charged Water Droplets?

    Homework Statement You intend to suspend water droplets in mid-air to understand rainfall. You give the droplets a small positive charge, and keep them suspended by an electric field upwards. The experiment consists of two horizontal metal plates, separated by 9.3m. The water droplets have a...
  33. Helmy

    Question about Electric Field lines (MCQ)

    *This is a question in an assignment that i have to submit. 1. Homework Statement Two imaginary spherical surfaces of radius (R) and (2R) respectively surround a positive point charge (Q) located at the center of the concentric spheres. What is the number of electric field lines (N2) going...
  34. P

    When is an Electric Field eqn set as - or + ?

    Homework Statement Two point charges are placed on the x axis.(Figure 1)The first charge, q1 = 8.00 nC , is placed a distance 16.0 m from the origin along the positive x axis; the second charge, q2 = 6.00 nC , is placed a distance 9.00 m from the origin along the negative x axis. Find the...
  35. P

    Electric field due to current carrying conductor

    Does static charge near to a constant current carrying conductor experience force on it? I am asking this question because i have learned that electric field and mangnetic field are same thing but viewing differently with respect to the frame of reference...when a positive test charge moves (...
  36. S

    Apparent disagreement between Coulomb's Law and Gauss' Law

    This is probably my misunderstanding, so please clarify. In a region of empty space, there are two point charges with the charges+Q and -Q. Exactly in the middle of the two charges (distance r from both charges) is point P, colinear with the centers of both charges. A Gaussian surface that...
  37. SirChris93

    How to find vectors and bisectors of an electric field

    <Moderator's note: User has been warned not to remove the template, and upload images instead of linking to an external site.> I'm very lost here, I don't know where to begin. My instructor is little help, the notes he gives are not even useful, and I cannot find anything in the book.We were...
  38. A

    Why isn't a capacitor an open circuit?

    I understand the basics of how capacitors work. If you hook one up to a power source, negative charge will build up on one plate, and positive charge will build up on the other plate. As the charges build up, an electric field forms between the plates and a potential difference is established...
  39. A

    When Electric Field is 0 is potential also 0?

    So here is how my book defined electric potential. If you take a charge, it will have a corresponding electric field associated with it. If you put another charge in that electric field, an electrostatic force will act on it and give it kinetic energy. This kinetic energy can't come from thin...
  40. F

    Understanding the Relationship between Electric Field Line Distance and Strength

    Supposedly the strength of the electric field is is related to the distance between electric field lines. I have two questions about what exactly this means. 1.) What is the distance between electric field lines? Is it just the distance between two points on adjacent electric field lines that...
  41. PKM

    What should be the electric field intensity inside a sphere

    If the force acting between two point charges were proportional to \frac{1}{r^ 3}, instead of \frac{1}{r^ 2}, what would be the electric field intensity and charge density inside a charged solid metallic sphere?
  42. L

    Three parallel plates -- find the electric field

    Homework Statement Find the field at A. Homework Equations ##\oint E\cdot dA = Q_{enclosed}/\epsilon_0## The Attempt at a Solution My first intuition was to do a Gaussian cylinder from A to the middle of the bottom plate. My logic is that the field inside the bottom plate is 0, so I'd have...
  43. F

    Flux with a non-uniform electric field

    If the electric field is uniform, the electric flux passing through a surface of vector area S is , where E is the electric field (having units of V/m), E is its magnitude, S is the area of the surface, and θ is the angle between the electric field lines and the normal (perpendicular) to S...
  44. 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...
  45. 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...
  46. 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...
  47. 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...
  48. 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...
  49. 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...
  50. 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...
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