What is Electric field lines: Definition and 85 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. LarryS

    I Coulomb’s Law in a Moving Reference Frame

    In classical electromagnetism, Coulomb’s Law gives the force between two stationary charged particles, a certain distance apart. It is an inverse square law – the density of the electric field lines is spherically symmetric. What if the same two charged particles are moving in parallel, say to...
  2. G

    I Do Electric field lines propagate by themselves away from a charge?

    I'm trying to understand how kink would be formed for only electric field for now. Let me share my pictorial understanding. Here is the Link. Moderator's note: The use of external image servers is not allowed. Please upload all images to PhysicsForums. Note that I'm not looking for...
  3. V

    Discontinuity in an Electric line of force

    This is a tricky and difficult question for me. I know from reading various textbooks that electric lines of force are always continuous without breaks, but cannot pinpoint a reason for this. The only reason I can come up is that an electric line of force must always begin and end on charges...
  4. guyvsdcsniper

    Electric field lines of H2O molecule

    I wanted to post my work so far to see if I am on the right path toward the correct answer so far. I have attached a ss of the actual problem and my work in the attachments
  5. patric44

    A problem in graphing electric field lines

    hi guys our instructor asked us to try to graph the projection of the electric field intensity at a certain point p(x,y) , for two charges q+-q located at (-a,0) , (a,0), Now starting with the equation $$\frac{dy}{dx} = \frac{E_{y}}{E_{x}}$$ after transforming this equation I got...
  6. Costweist

    Changes in electric field lines as a result of an oscillating charge

    The last couple of days I’ve been troubled with a specific part of electromagnetism. How will electric field lines be affected by an oscillating charge? More specific, what will happen with the “amplitude” of a wave in an electrical field line as the wave propagate away from the charge? 1. Will...
  7. huszarerik

    Electric field lines between a point-charge and a conducting sheet

    figure 1: → I don't understand how to approach this problem. Basically it asks for the distance r.I think I should use Gauss's law, but I've been thinking about the shape of the gaussian surface and I'm not sure about how it should look or where I should place it. Any help would be useful...
  8. J

    Finding equations for electric field lines

    Hi, I am interested in finding the equation for electric field equipotential lines. Ideally, it would be nice to have one equation that worked to find it for different geometries. Unfortunately, I don't think that exists. Assuming it does not exist, I think I would probably have to either solve...
  9. B

    Not necessarily homework help but I do not understand Field lines

    Homework Statement: This is not for homework but I have an AP physics exam on field lines and am confused about the proportionality between the charges of objects and the number of field lines. Homework Equations: E=(k*q)/r^2 I am struggling with the number of field lines to put based on the...
  10. P

    Electric Field Lines: Should Earthed Plate Have No Charge?

    Shouldn't the plate that is earthed be with no charge? making B correct. but the accepted answer was A.
  11. J

    Electric Field Lines for Two Objects on a Frictionless Table

    Homework Statement In the diagram, two small objects, each with a charge of -4.0nC, are held together by a 0.020 m length of insulating string. The objects are initially at rest on a horizontal, non conducting frictionless table & the effects of gravity on each other are negligible. (b)...
  12. 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?
  13. 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...
  14. 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...
  15. 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...
  16. sergiokapone

    Electric field lines of a sphere in a uniform electric field

    I need to draw electric field lines of sphere in uniform electric field with LaTeX/TikZ. Can anyone show me equation of field lines in polar coordinates?
  17. K

    Electric Field Lines: Charge Movement and Conductor/Insulator Interactions

    1. The problem statement "If charges are free to move, the field lines will straighten and shorten as the charges move together" 2. Questions in relation to statement Are there any cases in which charges aren't free to move between two charged objects such as between conductors or insulators...
  18. 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.
  19. Mausam

    Electric Field Lines: Does Positive Test Charge Follow?

    Does a positive test charge follows along the path of electric field lines if it is free to do so? I mean the trajectory of the charge is along the electric field lines and the field lines are not necessarily straight.
  20. G

    What do electric field lines look like for two metal plates?

    Hello. I'm now taking accelerator physics class and the lectures said in the thermionic electron gun, anode metal mesh should be grounded in order to prevent electrons which traveled beyond the mesh from coming back due to the electric field lines. Without grounding of the anode, I believe...
  21. nishant mudgal

    Electric Field Lines: Can Charges Move on Conductors?

    sir, we know that the electric field lines are perpendicular to the surface of the conductor ,it means charges are rest on the surface of the conductor ,there is no work done. if we create an electric field such that the electric field lines are at a different angle to the surface of the...
  22. S

    Electric field lines from a metal shell and sphere

    Homework Statement A metal sphere of charge +6μC is surrounded by a metal shell of net charge +6μC. Which of the following diagrams represents the electric field lines of the system? Homework EquationsThe Attempt at a Solution The correct answer provided by my teacher is a figure with 12...
  23. nomadreid

    Electric field lines from a moving charged particle

    The electric field emanating from charged particle travels at the speed of light; fine. To pose an unrealistic thought experiment (a more realistic, if more complicated, thought experiment could replace this one, but the unrealistic one gives the idea), if a proton were to suddenly pop into...
  24. gracy

    How electric field lines going out from surface is zero?

    in the video above the instructor explains from time 8:22 to 8:55 that how and why electric field lines going out from the surface which do not enclose charge is zero but I don't understand then why not electric field lines going out from the spherical surface ( enclosing charge) is...
  25. gracy

    Electric field lines of positive source charge end on ....?

    I have read that electric field lines of positive source charge end on negative charge and Today I came to know that electric field lines of positive source charge end on infinity,which one is correct?I think electric field lines of positive source charge end on infinity if the positive source...
  26. gracy

    Doubts on properties of electric field lines

    In my book following points have been given 1-due to conservative nature of electric field ,the electrostatic field lines will not form any closed loop.I want to ask how forming a loop makes if non conservative? 2-Field lines have tendency to contract in length (longitudinal contraction )like a...
  27. SquidgyGuff

    Electric field lines extending to infinity?

    Given a system of two charges (+7q and -q) some of the field lines will terminate at -q while others go on towards infinity. I've read that the portion of the field lines that terminate is given by (1/7), but I have no idea why that is. I am supposed to find the maxium angle of a field line...
  28. A

    Non Uniform Electric Field Lines Problem

    Ok we know that the electric field(uniform or non uniform) is a conservative field. Imagine three horizontal electric field lines in '+X' direction separated by unequal distances let's say line 1 and 2 is separated by distance 'a' and line 2 and 3 is separted by some distance 'b' such that...
  29. schrodingerscat11

    Electric field lines from very long cylinders and thin disks

    Homework Statement Good day everyone. I am studying Gaussian cylindrical surfaces. I have three questions: (1) Books would say that the electric field lines would emanate from the lateral side of the cylinder and that the ends will not contribute anything. I cannot understand this because...
  30. H

    Electric Field Direction & Drawing Electric Field Lines

    The electric field in some region is found to have a constant direction . What you coclude about the charge in the region...?? How can I draw the electric field lines..?? :/
  31. J

    Are electric field lines and electric flux the same thing?

    I don't believe they are because the field lines don't have a representation such as flux but I want to be sure. Also are flux lines a vector quantity?
  32. R

    Electric field lines produced by two eccentric charged cylinders

    Homework Statement This is the theory for a laboratory session. If we have two hollow cylinders, one with radius r1 and the other with radius r7, the center of the first one being placed at a distance d from the center of the second one, what are the surfaces having the same electric...
  33. J

    Regarding electric field lines

    So if you have one positive charge and one negative charge (both with the same arbitrary number of field lines) close to each other, could you theoretically move a 2nd positive charge as close as desired to the first positive charge without them repelling? Or am i misunderstanding the concept of...
  34. M

    Electric field lines between 20/30 V point charges vs. 10/0 V

    Homework Statement What would the electric field lines / equipotential lines look like between point charges that are set up with potentials of 20 volts and 30 volts versus point charges that are set up with potentials of 0 volts and 10 volts? The Attempt at a Solution At first I thought the...
  35. A

    Intersection of electric field lines.

    Field lines do not intersect because at their point of intersection,we would get two tangents indicating two directions of electric field at that point. Suppose the two filed lines JUST touch at a single point. wouldnt there be only a single tangent at the point??
  36. jaumzaum

    Electric field lines in a cylinder

    In the figure below we have 2 hollow cylinder conductors. The red conductor has radius R1 and negative charge (Q1). We then introduce the blue conductor (radius R2), first connected to the Earth by a conductor thread. Then we disconnect the thread making the blue conductor charge be positive...
  37. E

    How do we draw electric field lines for a negative charge in a vacuum?

    Suppose we have two charges in vacuum. They are positive and negative. If we want to draw the electric field lines around the negative charge. Do we draw the lines inward (negative) or outward (field lines produced by the +ve on -ve). I remember that free body diagram on a bidy does not include...
  38. A

    Understanding Electric Flux and Field Lines in a Uniform Electric Field

    Homework Statement A uniform electric field of magnitude 6.5 \frac{N}{C} passes through a circle of radius 12 cm. What is the electric flux through the circle when its face is perpendicular to the field lines. The Attempt at a Solution The only problem with this question is picturing the...
  39. B

    Electric Field Lines Can't Cross Each Other?

    Hello, This query isn't concerned with solving a problem, but only with details appendant to the problem. The question is as follows: A uniformly charged ring of radius 10.0 cm has a total charge of 64.0 µC. Find the electric field on the axis of the ring at the following distances from...
  40. M

    Electric field lines next to conductor

    Dear Physics Forums readers Let a two dimensional rectangle R1 carry a surface charge \sigma and be placed next to another rectangle R2 of the same shape made from metal (i.e. a conductor). What does the electric field look like close to the second rectangle? My intuition would tell me, the...
  41. P

    Electric field lines from a solid charged sphere.?

    What would be the pattern of electric field lines 'inside' a solid charged sphere..?
  42. C

    Can electric field lines intersect in free space?

    Can electric field lines intersect in free space? I found the answer on the internet, but I will like to understand why not? Graphics will be appreciate it a lot! Thanks
  43. N

    Radial vs tangential electric field lines in a solenoid

    I was reading through an example question calculating the electric field in a solenoid and it made an assumption that the radial electric field must be equal to zero because there is no excess charge in the system. I don't understand when this is true or even why it is true, any suggestions...
  44. K

    Equipotential lines and electric field lines

    Homework Statement I am given the equation for the potential of an arbitrary dipole. I need to draw the electric field lines for this dipole in a plane, and also show that these lines are perpendicular to the equipotential lines. I have already derived the equation for the electric field using...
  45. K

    Equipotential lines and electric field lines

    Homework Statement I am given the equation for the potential of an arbitrary dipole. I need to draw the electric field lines for this dipole in a plane, and also show that these lines are perpendicular to the equipotential lines. I have already derived the equation for the electric field using...
  46. Spinnor

    With Kaluza Klein theory can electric field lines thought of differently?

    Does Kaluza Klein theory allow one to think of the electric field lines of a point charge or a dipole differently. Is there any insight as to the nature of those field lines? Thanks for any help!
  47. C

    Electric Field Lines: Intersection & Equilibrium

    Can we have E and B field lines from 2 different sources cross. I don't think we can because then a charged particle traveling through the field would have 2 possible paths after reaching the intersection point. But then what if we have induced E fields and other sources. But IM guessing that...
  48. S

    Plotting electric field lines of a dipole

    I was given this equation as the lines of electric fields of a dipole(two opposite charges separated by a finite distance) e=(1/r^3)*((3cos^2(theta)-1)^2 +sin^2(2theta))^0.5 and I was asked to plot it. I guess it must be something like this: but when I try to plot it in wolframalpha.com in...
  49. M

    Electric Field lines running high to low voltage

    Homework Statement Show from the given equation Vb -Va=-intergral a to b (E x ds) that the electric field lines run from higher voltages to lower voltages. Also show from this equation that the electric field lines are perpendicular to equipotential lines. The voltage in our experiment ran...
  50. A

    The properties of Electric Field lines

    Homework Statement List the 4 properties and characteristics of electric field lines. Homework Equations I was not able to get them all and the ones that I did get I am confused that if it is really a characteristic or a property The Attempt at a Solution 1. Characteristic...
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