What is Field lines: Definition and 210 Discussions

A field line is a graphical visual aid for visualizing vector fields. It consists of a directed line which is tangent to the field vector at each point along its length. A diagram showing a representative set of neighboring field lines is a common way of depicting a vector field in scientific and mathematical literature; this is called a field line diagram. They are used to show electric fields, magnetic fields, and gravitational fields among many other types. In fluid mechanics field lines showing the velocity field of a fluid flow are called streamlines.

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  1. S

    Electric potential and Field Lines

    Sorry for any errors in posting, this is my first thread. Any help would be greatly appreciated! Homework Statement a.)On the contour map that is attached, find the magnitude of the electric field at each point A, B, and C. b.)Calculate the work done in moving a 1C positive charge from point A...
  2. M

    Field lines on parallel plates with same charge

    Homework Statement Draw the field lines between two parallel plates with +3V on one plate and +1V on the therHomework Equations The Attempt at a Solution The answer is (D) for a uniform field between the plates, however when two positive charges are drawn the field lines diverge as in (B)...
  3. 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...
  4. K

    A Plot of Magnetic Field Lines

    Hi, I was wondering - In the plots that we see of magnetic lines of force (like this one) what exactly are they plotting against what? Meaning is it Bx vs x vs y, or is it Bx vs By vs Bz?
  5. S

    How Do Magnetic Field Lines Break?

    When people talk about sunspots and the solar cycle and stuff like that, they often mention magnetic field lines poking through the surface of the sun. I'm pretty sure I get why the magnetic field lines would be twisted up by the non-uniform rotation of the sun, and why they would poke out of...
  6. P

    Electric field lines from a solid charged sphere.?

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

    Why do two field lines never intersect?

    Why can't two field lines intersect? The answer that i have often heard is that if they were to intersect, then there would be two different directions for force. But then two field lines can interesct in such a way that their tangetes at the point of intersection point in the same direction. (...
  8. B

    Prove Electric Field Lines Go from High to Low Voltage Sources

    Homework Statement In my electromagnetism lab, we had one electrode connected from the negative end of a power supply to one end of a conductive sheet, and the other electrode connected from the positive end of the supply to the other end of the conductive sheet. The potential difference of...
  9. M

    Visualizing field lines with moving current

    Let's say I have a circle filled with positive charges. Some distance away I have an identical circle filled with negative charges. Since the distribution is uniform in the circles, I can just use the center of the circles as points and calculate the field lines between the two. So far so good...
  10. 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
  11. A

    Magnetic field lines direction.

    It might seem trivial for most of you but i am confused by the definition of direction of magnetic lines. It's well known the magnetic field is directed from S to N but if one looks from outside and follows the magnetic line then one come from N to S. I am aware of that magnetic lines are closed...
  12. 5

    Magnetic field lines in a current carrying circular loop

    I wanted to ask that do each point of the current-carrying circular loop would create a magnetic field and hence the magnetic field lines? And if yes wouldn't the field lines produced by each point of the loop would intersect each other? I read somewhere that magnetic field lines never...
  13. 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...
  14. K

    Easy Electrodynamics Question on Field Lines

    Homework Statement Explain why the electric field is perpendicular to any conducting surfaces in static situations. Is this true in general (i.e. even for changing electric or magnetic fields)? Are there similar conditions on the direction of a magnetic field at the surface of a...
  15. K

    Determining Field Lines of a Vector Field in R^3

    Homework Statement Determine the field lines of the vector field f: R^3 --> R^3 defined by f(x,y,z) = (x/(1+z2) , y/(x2+y2) , 0) Homework Equations The Attempt at a Solution I know that my vector field is: F(x,y,z) = (x/((1+z^2)*(x^2+y^2))*i + (y/((1+z^2)*(x^2+y^2))*j + 0k I choose...
  16. 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...
  17. 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...
  18. 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!
  19. A

    Given an electric field, how to find its field lines?

    Given the mathematical expression of an electric field, how to find its field lines?
  20. 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...
  21. 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...
  22. J

    What happens to field lines from a charge inside a hollow conductor?

    If I put a charge inside a hollow conducting body is it true that the field lines from the charge don't penetrate through the conductor but instead terminate at induced charges on its inside wall?
  23. 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...
  24. 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...
  25. S

    Which, if any, of the following statements about electric field lines is/are true?

    Which, if any, of the following statements about electric field lines is/are true? The electric field is always perpendicular to the surface outside of a conductor. - TRUE It is not possible for the electric field to ever be zero. - FALSE It is possible for two electric field lines to...
  26. P

    Why field lines must begin or end on electric charges?

    Homework Statement Use Gauss' law to explain why field lines must begin or end on electric charges. Homework Equations Gauss' law: \epsilon_0 \phi_E=q The Attempt at a Solution I'm not sure whether this solution is incomplete or inconsistent. First, I take a gaussian surface...
  27. Drakkith

    Interaction Between Magnetic and Electric Field Lines

    Hey all. I was wondering what the interaction between Electric and Magnetic field lines are. For example, when you hold up a magnet against a charged electrode. I tried searching in google, but everything just turned up one or the other or how a moving charge makes a magnetic field and etc.
  28. S

    Exploring Magnetic Flux and Field Lines

    Homework Statement <\body> <with|mode|math|\<b-phi\><rsub|B> = <big|oint>><with|mode|math|\<b-B\> \<cdot\> \<b-d\>\<b-A\>>\ \; magnetic flux is proportional to the number of field lines passing though the surface \; </body> <\initial> <\collection>...
  29. M

    Drawing field lines with MATLAB

    Homework Statement Consider a uniformly charged half spherical shell. The total charge is Q and the radius is R. a) Calculate the electric field as a function of z for – 5R < z < 5R. b) Draw equipotential curves in the xz-plane for – 5R < x, z < 5R with at least 8 equallyspaced curves...
  30. F

    Concept of Field Lines, how Electricity vs Gravity

    Homework Statement Take the Earth for instance, if I were to draw field lines, would it be field lines coming out of the mass or into the mass? I initially thought it would be going out because we could look at it as a "positive charge", but then I thought that was silly because gravity is...
  31. I

    Calculating constant field lines

    Hi, I a question related to an equation for a magnetic field vector, B, from a dipole in cylindrical coordinates. This is the equation I found for the B field (thought I'm not 100% certain this is correct). B = (u0*m/4*Pi*r^2)* {2 Cos[theta] , Sin[theta]} where the first index is the...
  32. T

    Drawing equipotential lines and field lines

    Homework Statement Draw the electric field lines and equipotential lines for the electrode configure. Assume one of the parallel plate is at a positive potential and the other one is grounded. Homework Equations The Attempt at a Solution I know the electric field lines and...
  33. Feeble Wonk

    Field Lines in Expanding Space Explained

    Can anyone explain to an ignorant layperson, with as little mathematics/geometry as possible, whether field lines in expanding space become "farther apart". I view this question as being closely related to the concept of quantum foam distribution in expanding space... do virtual point particles...
  34. J

    Electric Field Lines and Equipotential Contours

    Homework Statement The adjacent figure shows the E-field lines (with arrows) and equipotential contours for a certain charge configuration. Determine for each of the following statements whether it is true or false. Assuming that these contours are those of a point charge at the origin...
  35. T

    Why are electric field lines also referred to as "lines of force"?

    Homework Statement Why are electric field lines also referred to as "lines of force"?
  36. S

    Why are electric field lines straight around electrons moving at relativistic speed?

    Imagine an electron in uniform motion moving at a speed near the speed of light. Pictures I've seen of the electric field around such a charge look like this one from wikipedia: The field lines are straight, but clustering around the plane perpendicular to the direction of motion...
  37. C

    B field lines of an infinte solenoid?

    When I have an infinite solenoid , The b field lines point straight up the solenoid and the field is zero outside. But i thought that the field lines have to wrap back around on themselves. Does this not apply in this example . Or am i crazy?
  38. A

    Induced Electric Field Lines When a Magnetic Field Crosses a Plane

    If a time varying magnetic field of infinite dimensions crosses a plane at right angles what can we expect induced electric field lines to look like? Straight lines with direction determined by the right hand rule?
  39. F

    Magnetic Field Lines Formula (3D)

    Curious as to whether there's a formula for calculating the shape of the magnetic field lines, including electro magnets (solenoids). I want to create a 3D graphical display for the magnetic field lines of magnets.
  40. M

    Magnetic field lines What do they exactly mean?

    Now this might seem like a really stupid question but I'm just a high school student so please bear with me. I've been studying about magnetic fields and my teacher says (everyone does in fact) that in a magnetic field, the magnetic field lines start from the north pole and end in the south...
  41. R

    Imaginary Field Lines vs True Iron Filings

    My (high school, gah!) textbook gives an experiment: I take a straight current carrying conductor, a cardboard sheet is placed perpendicular to the conductor, so that the conductor passes straight through the sheet, remains perpendicular. Then I use a salt sprinkler to sprinkle iron filings on...
  42. P

    Calculate R from Electric field lines.

    1. The problem statement The electric field E (arrows) is produced by a point charge. Find R in meters Homework Equations E(due to pt charge) = kq/R^2 # of field lines/unit area represents relative field strength (only statement in my notes that seems to apply to problem) The...
  43. B

    EM field lines in non-isotropic media

    Electromagnetic field lines in non-isotropic media Hello, We are using time domain reflectometry (TDR) in soils to measure soil moisture. I want to know how the electromagnetic fields are oriented when the soil is not isotropic, i.e some parts of the soil consist of moist or wetter parts...
  44. J

    Magnetic Field Lines: Proving c(T)=c(0) with T≠0

    Suppose that a function B:\mathbb{R}^n\to\mathbb{R}^n and c:\mathbb{R}\to\mathbb{R}^n are defined such that c is differentiable, and \dot{c}(t) = B(c(t)) for all t. The question is that what must be assumed of B, so that it would become possible to prove that c(T)=c(0) with some T\neq 0?
  45. Q

    Magnetic Field: Are Lines an Illusion?

    I have seen people write that there are no such things as "field lines", but that the magnetic field is a continuum. But iron filings on a paper over a magnet will arrange on lines of the magnet's field...Is this an illusion, or are there "lines" that make up the field?...thank you
  46. M

    What's the causal model for direction of curl of magnetic field lines?

    untruncated version of question: As electrons move through a wire, is the direction of the curl of the magnetic field lines observed derivable from an underlying property? =========================== more detail (only to further clarify my question as useful): > looking for a mechanistic...
  47. M

    Propgating Electric Field Lines

    Hi, I am trying to get a better idea of how E-field line diagrams are drawn. The following link appears to be a nice example of field lines associated with a single charge moving linearly with constant velocity [v=0.5c]. By default, after pressing go, the animation displays the field lines for...
  48. P

    Why field lines are tangent to direction of electric forces

    can anybody tell me why electric field of lines are tangent to direction of electric force please be fast need it urgently...
  49. D

    Electric Field Lines, Misconception

    Homework Statement This is a question I read in an article that discusses about misconception of physics among students. they only provided the question and some of the wrong principles students suggested. Three Points , located on the vertices(vertexes) of an equilateral triangle and have...
  50. E

    Direction of electric field lines

    I have an intuitive understanding of electric fields but when it comes to defining it on a test I wouldn't know what to say. Is the electric field defined as the force produced by a charged object on a positive test charge or any other charged object? Also if you were told to draw the electric...
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