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. C

    Electric field strength between charged plates help

    Homework Statement Homework EquationsThe Attempt at a Solution E=kq/d2 how do I involve the kinetic energy K in the equation?
  2. C

    Electric field strength between charged plates

    Homework Statement Homework EquationsThe Attempt at a Solution E=kq/r2 so when the distance increase E should decrease? I know this is wrong, but can someone explain why? Thanks
  3. A

    Understanding Electric Field Lines: An Introduction to E Bar and Tangent Vectors

    Hi, I'm reading the textbook and there is my image. http://imgur.com/a/9BqHm It says "The field vector E bar is tangent to the electric field line at each point". I might want to ask what "tangent" means in this sentence? Sorry to ask that stupid question.
  4. A

    How Do You Calculate the Electric Field of an AC Source in MATLAB?

    Hello everybody I got really confused. I want to calculate the Electric-Field of an alternating current source( Sine(wt)). I do not know what is its equation. I need to run it in Matlab to get a result. Can you please give me some hints? I need to write the equation to calculate the E-field in...
  5. S

    Electric field above the centre of a rectangle

    Homework Statement Exercise in integration: Using the Electric Field E of a straight line segment of charge, find the electric field at height 10 cm above the centre of a rectangle of sides 10cm and 20 cm carrying charge density 4 μC/m2. Homework Equations µ=Q/L µ = charge density Q = total...
  6. P

    Charged sphere and charged conducting shell

    Homework Statement A + q = 5 pC charge is uniformly distributed on a non-conducting sphere of radius a= 5 cm , which is placed in the center of a spherical conducting shell of inner radius b = 10 cm and outer radius c = 12 cm. The outer conducting shell is charged with a -q charge. Determine...
  7. R

    Electric Field of a Charged Sphere?

    Homework Statement A sphere of radius R has total charge Q. The volume charge density (C/m^3) within the sphere is ρ = ρ_0 (1 - r/R). This charge density decreases linearly from ρ_0 at the center to zero at the edge of sphere. a. Show that ρ_0 = 3Q/πR^3. b. Show that the electric field inside...
  8. SetepenSeth

    Electric field in the center of an arc

    Homework Statement Consider a conductor wire with a charge Q uniformly distributed, shaped in the form of an arc of radius R and amplitude 2A (were A is a given number between 0 and π). Find the value of the electric field in the center of the arc. Homework Equations ##E(P)= \int K_e...
  9. C

    Which point has the strongest electric field strength in this scenario?

    Homework Statement Homework EquationsThe Attempt at a Solution I tried to use the formula: F=kq1q2/r2 So at point B, the electric field strength is( 2kQ/r2) - (-kQ/r2)= 3kQ/r2 At A: (2kQ/r2)+(-kQ/r2)=kQ/r2 At C: -(2kQ/r2)-(-kQ/r2)=-kQ/r2 So B is the strongest? Is there an easier way to do it?
  10. Arup Biswas

    Electric Field Behavior Between Charged Parallel Plates

    One side of a plate has a uniform positive charge density. Two of those plates are placed parallel to each other in a distance away, with their charged side facing each other! The electric field between is zero then! If we put a charge there it will feel no force? I think if the charge is put...
  11. R

    Explanation on the Electric Field in Griffiths' Textbook

    Hi. I'm going over the discontinuity aspects of the electric field as we cross the surface charge. A pillbox Gaussian surface was drawn and the electric field for "below" is throwing me off. Can someone explain why the electric field is pointing in the same direction from both sides of the...
  12. Arup Biswas

    Why is the electric field inside a conductor zero?

    It can be mathematically shown by Gauss's law that it is true but physically how? In case of a symmetrical conductor(Eg Sphere,Cyllinder) there are charges uniformly distributed and field of one charge cancels out the opposite charge's field! But which are not symmetrical, for them what makes...
  13. A

    How can two equal and opposite forces produce motion? [EM]

    I am having hard time understanding the definition of work done to move a charge in an electrostatic field book says that if charge A and B sitting at some position and now if I move the charge say A towards B from arbitrary direction that force required is exactly equal and opposite to the the...
  14. R

    Magnitude of the electric field

    Homework Statement http://imgur.com/a/g5acE # 34 A plastic rod of length L = .24 cm is uniformly charged with a total charge of 12 x 10^-6 C. The rod is formed into a semi circle with its center at the origin of the xy plane. What are the magnitude and direction of the electric field at the...
  15. R

    Find the electric field at the origin

    Homework Statement Given two charged particles: 1) 5x10^-9 C, (-.03 m, 0 m) 2) -20x10^-9 C (.04 m, .02 m) find the electric field at the origin.Homework Equations F = (kQq)/r^2 E = (kQ)/r^2 The Attempt at a Solution So I know since 1)'s charge is plus, its field vector is ( (8.99x10^{-9})...
  16. amjad-sh

    Discontinuity in electric field

    I was recently reading jackson's book of electrodynamics regarding surface charge distributions and discontinuity in electric field. I reached that part and almost didn't understand anything. I will write the whole text: One of the common problems in electrostatics is the determination of...
  17. chopnhack

    Calculating Potential Difference in an Electric Field with Given Field Equation

    Homework Statement An electric field is given by Ex = 2.2x + 5x2kNC-1. Find the potential difference between two points on the x-axis at x = -2.0 m and x = 2.0 m Homework Equations ∫5x2+2.2x from -2 to 2 The Attempt at a Solution I got the answer of 27V. Solution said - negative 27V Can...
  18. jlmccart03

    What is the Electric Field at Two Points?

    Homework Statement A 90 μC point charge is at the origin. Find the electric field at the point x3 = -35 cm , y3 = 80 cm . Express your answers using two significant figures. Enter the x and y components of the electric field separated by a comma. Homework Equations E = kQ/r^2...
  19. jlmccart03

    Finding the magnitude of electric field

    Homework Statement A uniform electric field exists in the region between two oppositely charged parallel plates 1.59 cmapart. A proton is released from rest at the surface of the positively charged plate and strikes the surface of the opposite plate in a time interval 1.50×10−6 s . Find the...
  20. B

    Electric Potential and Electric fields

    Homework Statement Can there be a point in space where there is an electric potential but not electric field? Can there be a point in space where there is an electric field but no electric potential? Explain you answer. What would the electric field lines look like if the electric field was...
  21. chopnhack

    Electric field strength on particles of various distances

    There is no math in this one! I just wanted to know if I had the idea correct. Homework Statement If I have two positively charged particles at a distance between them that a field is produced between and around them, will test particles that repel away be solely a function of their distance...
  22. G

    Electric field of a thick infinite non-conducting plate

    Homework Statement An infinite non-conducting plate of thickness ##d## lies in the ##xy## plane. The bottom surface of the plate lies in the plane ##z=0##. The charge density of the plate is ##\rho=\rho_0 z /d~,~\rho_0>0##. Find the electric field in the regions ##z<0~~,~~0<z<d~~,~~z>d## and...
  23. T

    Electric field in different frames of reference

    I study electromagnetism and I got to the chapter about special relativity, in this chapter my professor (since we are not using the electromagnetic tensor in this course) used a specific case to show that the electric field parallel to the velocity of a frame of reference stay the same in both...
  24. joerylee palmerola

    Electric field due to a point charges

    Suppose a charge q is placed at point x=0, y=0. A second charge q is placed at point x=8.0m, y=0. What charge must be placed at the point x=4.0m, y=0 in order that the field at the point x=4.0m, y=3.0m be zero?
  25. GAURAV DADWAL

    Energy, charge and electric field

    Hi there, Im familiar with the concept that electric field has associated energy with it Now if in space an electron apppeared at some instant t=0 then electric field will not be established instantaneously but will propagate at speed of light through space As electric field is bieng...
  26. C

    Question about uniform charge distribution

    1. The problem statement, all variables, and given/known data Suppose you have a wire of length l and a uniform line charge density λ. Find the electric field at the midpoint that is height r above the x-axis Homework Equations (see attached) The Attempt at a Solution To solve, I used the...
  27. A

    Why is the electric field inside the dielectric cancelling?

    So, I was studying force between the plates of a capacitor when a dielectric is inserted. Here is my question https://ibb.co/cenvXk Shouldn't it be like this picture below https://ibb.co/kOUsCk So, why is my teacher saying that the electric field inside the dielectric cancelling. So, what...
  28. F

    Find electric Field at a point A

    Hi Guys, I've been learning electric field, and i want to ask about this question.EF net = EF1 + EF2 my EF1 = 9 x 109 * 4 x 10-8 / (0.6)2 = 1 x 103 (From Q1) EF2 = 9 x 109 * 2 x 10-8 / (0.3)2 = 2 x 103 (From Q2) then EFnet = (2+1) x 103 = 3 x 103 and what i get from key answer is 2.2 x 103...
  29. Decimal

    Electric field of two plates separated by a spacial charge.

    Hello, I think I solved the question, but I am confused by the elaboration on the exercise given by my professor. 1. Homework Statement A very large plate charged with charge Q is placed between x = -d and x=0. A similar plate charged with charge 3*Q/2 is placed between x = 3*s and x = 3*s +...
  30. P

    Electric Field of Linear Charge along a Line Segment

    Homework Statement Consider a straight line segment of 3L and with a linear charge density λ. Determine the electric field, E, of at point P, which is a point within the segment and along the axis. (figure attached) Homework Equations dE=kdQ/r^2 The Attempt at a Solution I attempted solving...
  31. weezy

    E field of a conductor with an arbitrary shape enclosing charge

    In this image charge q is enclosed within an arbitrary shaped conductor. I'm asked to find what if the Electric field in regions 1,2,3,4 are uniform and if the surface charge densities on the interior wall of the arbitrary shaped conductor and the hollow sphere conductor are uniform. My...
  32. psy

    Calculating work done by an Electric field on a positive charge

    Hey How can i calculate the work done by a homogeneous electric field on a positive charge q = 7 × 10^-8 C when the charge moves from point 1 to point 2 . I have two cases: a) the charge is parallel to the Electric field; b) the displacement of the charge takes place at the angle α = 60 ° to...
  33. F

    Electric Field Produced by a Finite Charged Wire

    Homework Statement A charged wire of negligible thickness has length 2L units and has a linear charge density λ. Consider the electric field E⃗ at the point P, a distance d above the midpoint of the wire. What is the magnitude E of the electric field at point P? Throughout this part, express...
  34. psy

    Calculation of the electric field strength

    Hey, First I want to find the electric field strength from the middle between two point charges q1 = 8nC and q2 = -6nC. The distance between the two charges is 10 cm. Then i want to find out at which point of a straight line, which runs through the two charges is the electric field strength...
  35. D

    Electric potential related to electric field question

    Homework Statement (i) Consider a non-conducting sphere of radius R with non-homogeneous charge density ρ = ρ(r) = r, where r is the radial co-ordinate. (a) Find the electric field inside and outside of the sphere(b) Find and plot the electric potential inside and outside of the sphere...
  36. AdrianMachin

    Calculating work on an electron on an equipotential surface

    This is not a homework, but a question formed in my mind after reading my textbook. Homework Statement Consider an electron (a charged particle) on a metallic equipotential surface. We know that all the points on the surface are equipotential, thus there will be no force on charged particles...
  37. AdrianMachin

    A problem regarding the electric potential of an electron

    Homework Statement There is a sample problem in my physics textbook (Fundamentals of Physics, 10th Edition by David Halliday and others) which has some confusion in it for me. Please take a look at the snapshot I took, in the attachments. Homework Equations 3. The Attempt at a Solution [/B]...
  38. P

    Finding charge given the electric field at origin is zero

    Homework Statement Given that we have q1 = -4nC on the y-axis at y=0.60m. q2 on the y-axis at y= -1.20m. What must be the sign and magnitude of q2 be for the net electric field at the origin to be: a. Zero b. 50 N/C Homework Equations E=KQ/R2 The Attempt at a Solution I used: ET = E1 + E2...
  39. N

    Clarification between electric field and potential energy

    From my understand, electric field is the force emitting from a charge. This means that if a charge was placed in the vicinity of the charge that was emitting the field of force, that charge placed would experience a force from it. How does potential energy differ from this? I understand that...
  40. B

    Electric field of a point charge above a plane conductor

    Some things I did not get are, 1): In the third para, it is said that potential approaches ##\infty## at ##Q##, why ? 2): In last para, The z component of field by ##Q## is said to be ##-Qh/(r^2 + h^2)^{3/2}##, Why ? should not it be ##+Q## not ##-Q## has the charge itself is positive. 3): I...
  41. curiosity colour

    About uniform electric field between parallel plates

    I have learned that the electric field between parallel plates are independent of distance since E=V/d so if I increase the distance between parallel plates, the E will decrease, right? if I am right on the previous statement, then why does the electric field are independent of distance?
  42. R

    Electric field in a cavity in a spherical charge density

    Homework Statement A uniform spherical charge density of radius R is centred at origin O. A spherical cavity of radius r and centre P is made. OP = D = R-r. If the electric field inside the cavity at position r is E(r), the correct statement is: 1)E is uniform, its magnitude is independent of r...
  43. D

    Why Do Certain Answers Apply in Basic Electric Field Questions?

    Homework Statement I'm confused about [question 16](http://image.prntscr.com/image/41a5c611927c44a7ac30104be3dd10ee.png) and [question 30](http://image.prntscr.com/image/a6aea3b9a8f04df9aca0dfe14054d4ce.png). The correct answers are e and a respectively. Homework EquationsThe Attempt at a...
  44. R

    The strength of induced electric field

    Homework Statement A thin and straight metallic rod of length L is rotating about its middle point with angular velocity ##\omega## in a uniform magnetic field B. The axis of rotation is perpendicular to the length of the rod and parallel to the magnetic field. The strength of the induced...
  45. J

    Why is the electric field within a conducting sphere 0?

    Given a charged sphere, the electric field within it is zero at every point. Why is this? Why is not merely zero only at the center? If a sphere is conducting, then its charge is all across the surface. If electric field is inversely proportional to distance from charge squared, won't the field...
  46. B

    Electric field through an aperture

    Homework Statement Solve by integration method :- From a spherical shell of radius ##a##, a circular disk of radius ##b## has been removed. The shell has a surface charge density ##\sigma##. Find the Electric field through that aperture. Homework EquationsThe Attempt at a Solution We put the...
  47. R

    What Is Incorrect About Grounding in Electromagnetic Theory?

    Homework Statement A point charge +q is placed outside a grounded conducting sphere of radius a. which of the following is ##not## true. a) There is an attractive force between the sphere and the charge b) The induced surface charge density on the sphere is not same everywhere c) The electric...
  48. B

    Electric field by continuous charge distributions.

    While reading the book, Electricity and magnetism, the author says that electric field just outside a spherical shell is ##4\pi \sigma##, on it ##4\pi\sigma r_0^2## ,inside is ##0## and outside is ##Q/R^2##. My derivations :- For inside, ##E\Delta S = 4\pi Q = 0## since ##Q = 0##. For...
  49. Arman777

    Calculating Induced Electric field

    In class we were trying to calculate the induced electric field created by changing the magnetic field stregth. Imagine there's a circular surface which magnetic field out of the screen.Since we are changing the magnetic field from Faraday's Law there should be a induced current or charge flow...
  50. Anindya Mondal

    Does there exist any electric field inside a charged conductor?

    We know that there exists no electric field inside a conductor. But while calculating drift velocity of electrons inside an electric conductor, why do we consider the electrons are present inside the charged conductor?
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