What is Electric flux: Definition and 283 Discussions

In electromagnetism, electric flux is the measure of the electric field through a given surface, although an electric field in itself cannot flow. It is a way of describing the electric field strength at any distance from the charge causing the field.
The electric field E can exert a force on an electric charge at any point in space. The electric field is the gradient of the potential.

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  1. flamebane

    Electric Flux through a semi-spherical bowl from a charged particle

    I believe this does has a couple of Calculus aspects to it but I don't really know how I'd find the surface area of inside the bowl. The answer sheet says the answer is 252 with a margin of error of +/- 1
  2. M

    Alternative method of finding Electric flux from non-uniform field

    For this problem, The solution is, However, why can the differential area not be: I tried integrating and got, Can someone please tell me what I have done wrong? Thank you!
  3. A

    I Electric field, flux, and conductor questions

    1) Why is the electric field 0 at the bottom of Gaussian surface? Isn't the electric field on both sides of the surface, pointing down and outwards like a plane of charge? see image. 2) Why does a charge distribution with cylindrical symmetry have to be infinitely long? 3) My book says a...
  4. A

    I Calculation of electric flux on trapezoidal surface

    I am confused at this calculation of the electric flux through a trapezoidal surface. The flux in should equal the flux out. The flux in equals -E*A1 where A1 is the area of the bottom of the trapezoid. The flux out equals E*A2 where A2 is the area of the top of the trapezoid. But the two fluxes...
  5. Harikesh_33

    I Question regarding the use of Electric flux and Field Lines

    1)Field Lines is supposed to represent the electric field around a charge ,now we can draw infinite field lines around a charge and sinc Electric flux is No of Field Lines /area ,does it become infinite ,the whole concept of field lines is quite in the Gray Area for me ,I can in theory mark...
  6. G

    Surface charge density of a plane

    $$\phi_E=\dfrac{Q_{\textrm{enclosed}}}{\varepsilon_0}\Rightarrow Q_{\textrm{enclosed}}=9,6\cdot 10^{-7}\, \textrm{C}$$ $$Q_{\textrm{enclosed}}=\sigma S=\sigma \pi R^2\Rightarrow \sigma =\dfrac{Q_{\textrm{enclosed}}}{\pi (0,1^2)}=3,04\cdot 10^{-5}\, \textrm{C}/\textrm{m}^2$$ I have a lot of...
  7. G

    Flux of the electric field that crosses the faces of a cube

    a) $$\phi_T=\phi_F-\phi_I=10^4\cdot 4\cdot 4-10^4\cdot 4\cdot 4=0\, \textrm{Nm}^2/\textrm{C}$$ b) $$\phi_F=\underbrace{300\cdot 4}_{\vec{E}}\cdot \underbrace{4\cdot 4}_{\textrm{area}}=19200\, \textrm{Nm}^2/\textrm{C}$$ $$\phi_0 = 300\cdot 0\cdot 4\cdot 4=0\, \textrm{Nm}^2/\textrm{C}$$ Then...
  8. S

    B Electric flux density and confusion about units

    My general understanding of electric flux density is 'electric flux per unit area'. This gives the SI unit N/C. But According the formula of electric flux density, D=eplison*E, the SI unit is C/m^2. How come the dimension in both cases not matching if both are true?
  9. S

    B Electric flux -- Which of these three definitions is correct?

    I have read three definitions of electric flux in textbook which is confusing me.. 1. Electric flux is the number of electric lines passing through any area of a surface. 2. Electric flux is the number of electric lines passing through unit area per second held perpendicularly. 3. Electric flux...
  10. E

    Gauss' law and flux concept issues

    Hi guys i have some concept issues about flux. My book says flux is proportional to the number of lines passing through that area. so my question is: first i am thinking that a 2D circle which has a 2r diameter and it is enclosing a 2q charge so its flux should be 2q/Epsilon.then i am thinking a...
  11. V

    Electric Flux for a cube problem

    I have tried to understand the solution given in the book which is as pasted below. The solution uses Gauss's Law but makes no mention of which Gaussian surface is used. The diagram that I have used to understand this problem is also given at the end. From the diagram, faces OADG, OABE and OEFG...
  12. Alex Schaller

    B Different formulas for electric flux

    I noticed that in some textbooks (Physics - Tipler) the electric flux formula is different than in other textbooks (Engineering Electromagnetics -W. Hayt) Which one should we use?
  13. rudransh verma

    B Understanding Flux: The Measure of Field Lines Passing Through a Surface

    Phi= int(E.da) through a surface S is a measure of “number of field lines” passing through S. I put this in quotes because of course we can only draw a representative sample of field lines. The total number would be infinite. But for a given sampling rate the flux is proportional to the number...
  14. rudransh verma

    I Confusion with the direction of E-fields near conductors

    In this page you can see it’s written: E must be perpendicular to the surface. If it were not then the charges would move due to a component along the surface. I am assuming the field is generated due to the charges on the surface. I have a doubt. Is the author saying if it were not...
  15. bboo123

    I Exploring the Impact of Dielectrics on Electric Flux Density

    In the 7th edition of the book "Elements of Electromagnetics by Matthew N. O. Sadiku" On page 190 the author goes on to say: "We now consider the case in which the dielectric region contains free charge. If ##\rho_v## is the volume density of free charge, the total volume charge density...
  16. V

    Electric flux through ends of an imaginary cylinder

    When I look at this question, I can see two possible values of electric flux depending on how I take the normal area vector for either ends ##A \text{ and } A^{'}##. What is wrong with my logic below where I am ending up with two possible answers? The book mentions that only ##2E\Delta{S}## is...
  17. rudransh verma

    I What is Electric Flux and How is it Calculated?

    Gauss law relates between E at some point on guassian surface with the net charge enclosed by that surface. Using gauss law is like being able to tell what (ie charge)is inside a gift box by just looking at the wrapper(electric field). There are two types of problem. Sometimes we know the charge...
  18. Hamiltonian

    Electric flux through a square lamina

    taking origin at the centre of the square. ##d\phi = \vec E.\vec{da}## $$d\phi = \frac {kqa}{(x^2 + y^2 + a^2)^{3/2}} da$$ $$\phi = \int_{-a/2}^{a/2}\int_{-a/2}^{a/2}\frac{kqa}{(x^2+y^2+a^2)^{3/2}}(dx)(dy)$$ on evaluating this double integral i get $$\phi = (q/\pi{\varepsilon}_0...
  19. preachingpirate24

    Electric Field inside the material of a hollow conducting sphere

    Let's say I place a positive point charge inside a hollow conducting sphere. If we take a Gaussian surface through the material of the conductor, we know the field inside the material of the conductor is 0, which implies that there is a -ve charge on the inner wall to make the net enclosed...
  20. D

    What Does a Flat Disc Bounded by a Circle Mean in Electric Flux Calculations?

    Hi! My main problem is that I don't understand what the problem is telling me. What does it mean that the surface is a flast disc bounded by the circle? Is the Gauss surface the disc? Does that mean that inside the circle in the figure, there is a disc? Can you give me some guidance on how to...
  21. cookiemnstr510510

    How Is Electric Flux Calculated for a Rectangle in an Electric Field?

    Homework Statement A 2cm x 3cm rectangle lies in the xy plane. What is the electric flux through the rectangle if Electric field= (100i +50k) N/C Homework Equations Φe=E⋅Acosθ (Electric Flux Equation) The Attempt at a Solution My question is to find the magnitude of the electric field we...
  22. CDL

    Electric Flux through the Face of a Cube

    Homework Statement Griffiths' Introduction to Electrodynamics problem 2.10, Homework Equations Gauss' Law, ##\int_{S} \textbf{E}\cdot \textbf{dS} = \frac{Q_{\text{enc}}}{\epsilon_0}##[/B]The Attempt at a Solution It seems reasonable that the flux through the shaded surface and the front...
  23. Wrichik Basu

    Finding electric flux using Gauss' Law

    Say you have a hollow cylinder, whose one side is open. Now, you pace a positive charge ##Q## at the centre of this open end (such that it is just inside the cylinder). How much should be the flux coming out from the closed end? I just thought of this problem. In order to use Gauss' Law, we...
  24. R

    Electric Flux Through Spherical Surface Centered at Origin

    1. A uniform linear charge density of 4.0 nC/m is distributed along the entire x axis. Consider a spherical (radius = 5.0 cm) surface centered on the origin. Determine the electric flux through this surface. Homework Equations L=2rπ φ=Q/ε λ=Q/L The Attempt at a Solution I found the charge by...
  25. Pratik007789

    Homework Help: Find the Electric Flux Through a Hole In a Sphere

    Homework Statement [/B] An uncharged nonconductive hollow sphere of radius 10.0 cm surrounds a 20.0 µC charge located at the origin of a cartesian coordinate system. A drill with a radius of 1.00 mm is aligned along the z axis, and a hole is drilled in the sphere. Calculate the electric flux...
  26. T

    Electric flux of a cube due to a point charge

    Homework Statement Homework Equations Gauss's Law The Attempt at a Solution I simply used logic and observed the symmetry of the cube. If the charge is placed on the middle of the cube, the flux would simply be Q/∈0. The face of the cube itself can be split into 4 squares, with the charge at...
  27. F

    Net electric flux through a cylinder's surface

    Homework Statement Homework Equations ΦE = ∑Q enclosed / ε ∑Q enclosed = λh The Attempt at a Solution ΦE = ∑Q enclosed / ε ∑Q enclosed = λh ΦE = λh / ε
  28. F

    Electric flux through a wedge shaped block

    Homework Statement Homework Equations - The Attempt at a Solution Flux on opposite sides = 0 The answer is (E) , right ?
  29. F

    Electric Flux in a Closed Space: Volume, Area & Benefits

    I believe the electric flux within a closed space can be found with the equation phi = Q/ε0. Can this be used for volume and area, or just volume? Also what good does this do. Why would I want to know the electric flux of something?
  30. Const@ntine

    Gauss' Law: Charged Rod & Sphere (Electric Flux)

    Homework Statement A charged, straight line/rod of infinite length has a Discrete uniform distribution of charge, has a linear density of λ and is at a distance d from a sphere with a radius of R. Find the entirety of the Electrical Flux that is caused by this charged rod, which passes...
  31. D

    Electric Flux through Cubical Surface Enclosing Sphere

    Homework Statement A uniform charge density of 700 nC/m3 is distributed throughout a spherical volume of radius 6.00 cm. Consider a cubical Gaussian surface with its center at the center of the sphere. [reference picture] What is the electric flux through this cubical surface if its edge...
  32. R

    Electric Flux Equation for Rotating Loop?

    Homework Statement A circular loop with radius r is rotating with constant angular velocity w in a uniform electric field with magnitude E. The axis of rotation is perpendicular to the electric field direction and is along the diameter of the loop.Initially, the electric flux through the loop...
  33. W

    Calculating electric flux when given a charge (Gauss)

    Homework Statement A charge Q=5.14 nC is located at the center is located at the center of a Gaussian sphere of radius R=10.0 cm . The sphere lies within a uniform upward electric field E=2100 NC The net outward electric flux through the sphere is What? Second problem (bonus round!) A...
  34. Sunbodi

    What is the Electric Flux through a Net in a Uniform Electric Field?

    Homework Statement [/B] A butterfly net hangs from a circular loop of diameter 400 mm . You hold the loop horizontally in a region where the electric field is 150 N/C downward, as shown in (Figure 1) . What is the electric flux through the net? Homework Equations k = 9E9 N E = kq/r2 Flux = Q...
  35. AlphaLearner

    Electric Flux Questions (about the definition)

    I can say that Electric Flux is Electric field passing per unit area perpendicular to electric field lines. But the formula came up as Φ = ∫ E⋅dA. Well, take the case of pressure! That is force acting per unit area perpendicular to direction of force. But it's formula came up as P = F/A. Now my...
  36. J

    Elementary question on Electric flux units

    The net flux over a closed surface is: Flux = The surface integral of the field E = charge / permitivity in space (Gauss law) The permitivity in space is: 8.85 10-12 Coulombs2/N m 2 So I understand the units of Flux are: Newton meter2/Coulombs Is this correct? I don't understand why in a...
  37. C

    Electric Flux and Electric Flux Density

    Homework Statement Hi, So I'm doing a electromagnetics course and we've been given equations for electric flux and electric flux density but I can't seem to find any sort of intuitive explanation for these. In my lecture notes, the electric flux density is introduced first as vector D and...
  38. J

    Net electric flux through a Gaussian cube

    Homework Statement An electric field given by https://edugen.wileyplus.com/edugen/shared/assignment/test/session.quest2560893entrance1_N10030.mml?size=14&ver=1486488694211 =...
  39. jlmccart03

    Electric Flux through half a cylinder

    Homework Statement In (Figure 1) take the half-cylinder's radius and length to be 3.4 cm and 15 cm, respectively. If the electric field has magnitude 5.3 kN/C, find the flux through the open half-cylinder. The surface here is the right half of the surface of a full cylinder. The surface does...
  40. jlmccart03

    Electric Flux confusion and help

    Homework Statement I have three questions spanning three different situations, but each deal with the single concept of electric flux. Problem 1: Write an expression for the net electric flux through the entire surface in terms of the area vectors and the electric field E. Problem 2...
  41. jlmccart03

    Magnitude of electric flux through a sphere?

    ****EDIT****: I had improper significant figures. It was the correct number. 1. Homework Statement The electric field on the surface of a 6.0 cm -diameter sphere is perpendicular to the surface of the sphere and has magnitude 52 kN/C . What is the magnitude of the electric flux through the...
  42. mikemartinlfs

    Four Electric Dipoles = What level of electric flux?

    Homework Statement A circle, centered on the origin, has a radius of 1 mm. At each "pole" (1,0), (0,-1), (-1,0), (0,1) is an electric dipole. The positive charge of +10 microCoulombs is inside the circle, the negative charge of -10 microCoulombs is just outside the circle. What is the...
  43. Blockade

    What are the different kinds of charge density?

    At this point I was given rho, sigma and landa to hold value of these three different kinds of density ρ = Charge/Volume -------------- Volume Density σ = Charge/Area ----------------- Area Density λ = Charge/Length ---------------- Length Density How do I know which type of density to use over...
  44. Blockade

    Need help in Electric Flux within a cube with Gauss' Law

    Homework Statement I need help in figuring out if I have done this problem correctly. From what I understand ∫E * dA = E*A, where E is the electric field and A is the area of a side. My biggest concern is if I can plug in the length "L" for the "x" and "z" variables within "E = -5x * E0/L i +...
  45. A

    Calculating Electric Flux Through a Rectangle with Given Electric Field

    Homework Statement Hello, A 3.60cm x 4.50cm rectangle lies in the xy-plane. What is the electric flux through the rectangle if E=(80.0i + 50k) N/C ?Homework Equations Φ = E * A =EAcos(θ) The Attempt at a Solution My attempt: First convert the rectangle units from cm to m. 4.50cm = 0.045m...
  46. A

    How Do You Calculate Electric Flux Through a Rectangle?

    Hello, The problem: A 3.60cm x 4.50cm rectangle lies in the xy-plane. What is the electric flux through the rectangle if E=(80.0i + 50k) N/C ? My attempt: First convert the rectangle units from cm to m. 4.50cm = 0.045m 3.60cm = 0.036m Find the area of the rectangle. A = 0.036m x 0.045m =...
  47. I

    Electric Flux of Two Hemispheres with different radii

    Homework Statement Two hemispherical surfaces, 1 and 2, of respective radii r1 and r2, are centered at a point charge and are facing each other so that their edges define an annular ring (surface 3), as shown. Homework Equations The field at position r⃗ due to the point charge is: E⃗ (r⃗...
  48. gsmtiger18

    Displacement current and magnetic flux through a wire loop

    Homework Statement A long straight wire has a line charge, λ that varies in time according to: λ = λ0e(-βt). A square loop of dimension, a, is adjacent to the wire (at a distance a away from the wire). Calculate expressions for the displacement current at the center of the wire loop and the...
  49. Idyia

    B Why doesn't the flux through a Gaussian surface change with a change in shape?

    Why doesn't the flux through a Gaussian surface change, when the shape is changed? (while keeping the net charge inside it the same) Flux is the dot product of electric field and surface area, so wouldn't it change if surface area is changed?
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