What is Flux density: Definition and 144 Discussions

Flux describes any effect that appears to pass or travel (whether it actually moves or not) through a surface or substance. A flux is a concept in applied mathematics and vector calculus which has many applications to physics. For transport phenomena, flux is a vector quantity, describing the magnitude and direction of the flow of a substance or property. In vector calculus flux is a scalar quantity, defined as the surface integral of the perpendicular component of a vector field over a surface.

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  1. E

    Graphing the flux density between two line charges in matlab

    Homework Statement I am trying to graph the flux density field between two infinite line charges located at y = 1 and y = -1 Homework Equations I am trying to do it using the equation for a line charge that I got from lecture notes. The above equation is derived from this: Here is the...
  2. M

    Finding magnetic flux density from magnetization vector

    Homework Statement A long cylinder of radius a with magnetization vector M=M_0*(r/a)^2*a_φ. Find the magnetic flux density inside and outside the cylinder. Homework Equations J_m=∇×M J_ms=M×a_n[/B] A=(μ_0/4*π)*(∫(J_m/R)dv+∫(J_ms/R)ds) B=∇×A The Attempt at a Solution Basicly what I thought...
  3. S

    Total Magnetic Flux Density Law Problem

    We know Total Magnetic Flux B = B_0 + B_m Where, B_0 is the external field and B_m is the field inside a material. Now, we get, B = B_0 + μ_0*M (M is the magnetization) My question is - Do I always have to use μ_0 ? If yes then Why? The material isn't free space, is it?& also B =...
  4. B

    Magnetic flux density calculation for high permeability material

    Hi to all of you, As the Biot-Savart-Law is based on experimentations in air, i like to know how to calculate the magnetic flux density in material with much greater permeability, where the circular like shape of the field distribution troughout the vicinity does not apply. Does anyone has a...
  5. D

    Problem in Magnetic Field and magnetic effect of electric current

    I read in class 10. I am having problem understanding magnetic fields, magnetic flux,magnetic flux density,magnetic field strength,magnetic permeability and strength of magnetic field produced due to a straight and closed loop current carrying conductor at a certain point at a certain distance...
  6. bibo_dvd

    Problem with electric flux density

    hello guys :) i need your help with this problem i can understand that in (a) we will use the integral of row(v) * dv to get the charge and in (b) we will use the formule D(r)=Q/[4*PI*r^2] but in (C) should it be zero or what ?? and if it should be zero why in the solution manual it...
  7. F

    Charge density from electric flux density

    Homework Statement Determine the charge density due to the following electric flux density: \overrightarrow{D} = \hat{r}4rsin(\phi ) + \hat{\phi}2rcos(\phi)+\hat{z}2z^{2}Homework Equations \rho _{v} = \triangledown \cdot \vec{D} \rho _{v} = \frac{\partial }{\partial r} + \frac{\partial...
  8. M

    Terminology of electric flux density

    In my book is says the electric flux density D is equal to εE if the medium is linear and isotropic, where E is the electric field and permittivity ε is a scalar. I have no idea what they mean by a linear and isotropic medium.. How am I suppose to know if the medium is linear or isotropic?
  9. D

    Find the Current and Flux Density in a Feromagnetic Core

    Homework Statement A ferromagnetic core is shown the figure below. The depth of the core is 5 cm. The other dimensions of the core are as shown in the figure. Find the value of the current that will produce a flux of 0.003 Wb. With this current, what is the flux density at the top of the...
  10. L

    Flux density inside and outside a coaxial cable.

    For question 4b in the problem sheet attached below, is my working correct for B outside and inside the coaxial cable? Ans: Outside coaxial:∫B.dl = μI (the integral is between 0 and 2∏r) => B = (μI)/(2∏r) Inside the coaxial: \int_{2\pi a}^{2\pi r} B.dI = μI.\frac{a^2}{\pi...
  11. E

    Understanding Flux Density in Coils: Equations and Factors Explained

    Hello, I am looking into magnetic flux density in coils can anyone tell me if there is a general equation that equates flux density to the electric current, the coil's dimensions and number of turns? Any help would be appreciated. Thanks.
  12. J

    Calculate Displacement Current from Electric Flux Density

    Homework Statement If electric flux density (D) is given by the vector (xy,yz,xz) then calculate the displacement current density Homework Equations Jd = dD/dt The Attempt at a Solution if you differentiate D, in terms of t, then you just get 0..but that apparently isn't the answer
  13. D

    Electric Flux Density: 4.5Xe + .50MV/m

    Homework Statement Given Xe=4.5 and E=.50 MV/m find the displacement flux densityHomework Equations D=ε0εrE εr=1+XeThe Attempt at a Solution Using the equation above I get (8.85e-12)(5.5)(.50e6)=.000024338 C/m^2 which is not what the answers say they give it in nC which I can't see how they can do?
  14. D

    Engineering Flux density in magnetic circuit

    Homework Statement Consider the magnetic circuit shown in figure 3 Assuming that the core (μr=1000) has a uniform cross section of 4 cm^2, determine the flux density in the air gap the picture is very small so here are the values L=42cm, Ig=0.1cm, turns=500, and I=0.2A Homework Equations...
  15. FOIWATER

    When does the surface charge density equal the electric flux density?

    Homework Statement The electric field intensity in polystyrene (relative permittivity 2.55) filling the space between the plates of a parallel plate capacitor is 10kV/m. The distance between the plates is 1.5mm. Calculate the surface charge density of free charge on the plates, and the surface...
  16. D

    Find the dielectric flux density and the abilty to polarize

    Homework Statement In a slab of Teflon (epsilon=2.1), the electric field is E= 6Ux+12Uy-20Uz V/m. Find D and P (BTW epsilon stands for the relative dielectric constant) Homework Equations Upload The Attempt at a Solution Upload
  17. B

    Connection between coloumbs , ohms and magnetic flux density

    what is the connection between coloumbs , ohms and flux !
  18. D

    Max Flux Density for DC Generator Cores

    Hello! I would like to know what is the maximum flux density that can be used in a core for DC generator without taking the core in it's saturation point now a days?
  19. N

    Magnetic Flux Density vs Magnet Geometry

    Gentlemen, the the image shows 2 N48 neodymium magnets of the same volume 54 in2. On several website I can use magnetic flux density calculators to get the Br of the rectangular magnetic but haven't found one that calculates the value of the arc magnet. The Br value of the rectangular magnet is...
  20. G

    Units of Flux Density: Electric Field vs Displacement Vector

    While I do understand the use for the displacement vector D = (e0)E + P, I don't quite understand why they label it as "flux density". The units for the displacement vector are C/m^2. The units for electric flux are Vm, so wouldn't electric flux density become Vm/m^2 = V/m which is just equal to...
  21. J

    Estimating Neutrino Flux Density

    1. Problem "Estimate the flux of neutrinos passing through your body per second if the present energy density of neutrinos from the Big Bang is 0.2 MeV/m3. Assume that you are a standard size covering 0.01 m2". Homework Equations nv = Uv(T) / <Ev> The Attempt at a Solution I've assumed that...
  22. W

    Increasing flux density increases magnetic force?

    Hi! When calculating the attraction/repulsion force generated by a magnetic field should I consider the flux density of both and add them to the calculation? By increasing that vector would it increase the total force generated or it has no relevance at all?
  23. N

    Calculating Electric Flux Density in a Dielectric Material

    Hey. So if I have a condenser, where the electric field between the plates is equivalent to 50kV/m, the electric flux density D= ε0*50kV/m. If I insert a dielectic between the plates, the electric field will decrease to 10kV/m, and kappa (the relative permittivity) equals 5. So, will the flux...
  24. H

    Calculating Flux density in a DC-DC converter coil

    Hello Everyone. I am working on a DC-DC converter design which uses a transformer with an additional inductive element on the secondary side. The coil charges a large capacitor. Since there is an additional inductive element on the secondary side the inductive element builds up a field...
  25. heycoa

    Optics | Amplitude of Electric Field Given Radiant Flux Density

    Homework Statement A laser provides pulses of EM radiation in vacuum lasting 7.47* 10-12 s. If the radiant flux density is 2.65 * 1020 W/m2, determine the amplitude of the electric field (x *1011) of the beam. Units are required as listed in instructions. Homework Equations Irradiance =...
  26. S

    What Is Flux? Scalar or Vector? Difference Between Flux and Flux Density

    what is flux...?? is it a scalar or a vector and difference bet flux and flux density i have read the articles where the flux (either in case of electric flux or magnetic )is described as the no of lines passing through a surface area ( open in case of magnetic characterized by boundary and...
  27. S

    Air gap flux density in DC machine

    Why is it that the air gap flux density is flat topped at no load. What happens to it's shape when machine is loaded?
  28. A

    Flux Density (Jy) to Luminosity when wavelength is involved

    Hi, I think my problem may be a little trivial however I have been stuck on it for quite some time. I have plots of flux density (Jy) versus wavelength in order to look at a particular forbidden line. I want to find the luminosity of the line, however as I am dealing with Jy [W/(m^2 Hz)] I do...
  29. iVenky

    What exactly is Electric Flux Density?

    We define flux density as D= ε E right? or even ∇.D=ρ But I can't link the above with what is given in the wiki where they have used the symbol "phi" http://en.wikipedia.org/wiki/Electric_flux What is the difference between D and symbol "phi"? I would be really happy if you could...
  30. S

    How Does Gauss' Law Apply to Infinite Charge Slabs?

    Homework Statement An infinite slab of uniform charge density ρ occupies the region -∞<x< ∞, -∞<y<∞, -d/2<z<d/2. Homework Equations Use Gauss' Law to calculate the electric field density for -∞<z<∞ The Attempt at a Solution D=εE. Using that, I just need to find D =...
  31. D

    Lumens and photon flux density

    Is there a simple way of calculating photon flux density from the lumens produced by a fluorescent tube?
  32. T

    How to find magnetic flux density at center and ends of solenoid

    Homework Statement A solenoid has a radius of 2mm and a length of 1.2cm. If the # of turns per unit length is 200 and the current is 12A, calculate the magnetic flux density at a) the center and b) the ends of the solenoid Homework Equations The biot-savart law: \vec{B} = \frac{\mu_0}{4...
  33. I

    Trying to increase the magnetic flux density

    Hello all, long time follower, first time poster. (Also feel free to move this if it's not in the right section.) Basically I have this mechanism pictured here: You can imagine that the drawing is of a top view of a section cut of the total mechanism. This is the radius view, the full diameter...
  34. C

    How voltage amplification affects plasma flux density?

    Would a voltage amplification with the same power output increase plasma density and increase the magnetic field of the plasma, if the power output does not change? In the case of a USB plasma globe with a current flow of 300mA through 5 volt, amounts to 1,5W. CASE A: Ofcourse this...
  35. K

    Can TdS be computed using an area, time double integral of heat flux density?

    Can the TdS by a system be calculated by taking the area, time double integral of the heat flux density? If so, is it possible that this double-integral would take on an opposite sign if inside there was a dominating, growing black hole, where, I would presume, heat flows inwards, and not...
  36. K

    Relativistic aberration and locally measured electric flux density

    Does relativistic aberration apply to electric fields and magnetic fields? If a spaceship accelerated to a relativistic speed with respect to an initial inertial frame, in a constant direction with respect to a uniform electric field, do the effects of aberration affect the magnitude of electric...
  37. M

    What is magnetic flux and magnetic flux density? Please keep it simple.

    Im revising for my A levels and I could really do with a simple, straight forward definition for magnetic flux and magnetic flux density. Can anyone please help? I'd be very grateful. F=BIl ∅=BA
  38. beyondlight

    Magnetostatics. Calculate the magnetic flux density.

    Problem description: A wery long, than and flat metal plate of width 2a carries the total current I in the z-direction. The current density is uniformely distributed over the metal plate. A point P of particular interest is also shown in the figure, where the point has the position r=ax+ay...
  39. O

    Determine the radial flux density (jr) of chlorine ions

    Homework Statement A cell 20 microns long and 2 microns in diameter enclosed in a membrane 80 nonometers thick with a dielectric constant of 8 (neglet the ends). The cell has a potential difference between outside and inside of -70 millivolts, calculate the extra chlorine ions that must...
  40. T

    Electric Flux Density for Coaxial Cable

    Homework Statement I am given the following problem: http://forum.allaboutcircuits.com/attachment.php?attachmentid=35938&d=1320027350 Homework Equations The Attempt at a Solution My known equations and attempt to the problem...
  41. F

    Calculate the value of magnetic flux density in air

    Homework Statement Calculate the value of magnetic flux density in air in the middle of two straight parallel wires carrying currents of 10A and 20A in the opposite directions. The distance between wires is 10cm. The Attempt at a Solution \oint \vec{B}\cdot d\vec{A} = \Phi \oint \frac{\mu_0...
  42. S

    Magnetic flux density in the centre of a current carrying loop

    Homework Statement A current carrying loop of wire is being monitored using a Hall-effect magnetic field probe placed at its centre. The loop is in air and has a radius of 0.5 m. It is required to monitor the magnetic flux in order to trip the circuit breaker if the current exceeds 100 A...
  43. S

    Vector potential and constant magnetic flux density

    Hi, I would like to verify analytically that a vector potential of the form A=1/2(-yB0,xB0,0) produces a constant magnetic flux density of magnitude B0 in the z direction. (I guess I'd have to use the relation B=\forall\wedgeA...)
  44. Vyse007

    Gauss's Law with electric flux density

    I am taking a course in Electromagnetic Wave Theory, and the prescribed book for us is Engineering Electromagnetics by William Hayt. The book if excellent, till I reached the part about Gauss's Law. I will be describing my queries here, kindly help me out with them. 1) The book first states...
  45. M

    Measuring Magnetic Field Intensity (H) and Magnetic Flux Density (B).

    Now here is a real world practical application. Australia Post has a warning for shipping magnetic material in the post. Section D2.9.2 states... Any material that, when packed, has a magnetic flux density of 0.159 A/m or more at a distance of 2.1 meters from any point on the surface on the...
  46. M

    Proving Electric Flux Density: eE Determination

    How to prove that D = eE. Use a general proof. I know how to prove it assuming a point charge.
  47. R

    Calculating Magnetic Flux Density in a Solenoid

    The magnetic flux density B( in tesla ) inside the solenoid and parallel to its axis is given by the expression B= permeability of free space x n x I, where n is the number of turns per metre length of the solenoid my question is so for example, if n = 100turns in 1m and I = 2Ampere...
  48. K

    Flux Density of Salt in Horizontal Tube: How Does Advection Affect Transfer?

    Homework Statement What is the flux density of salt in a horizontal tube, 10cm in length, connecting seawater (salinity 30g/L) to a tank of freshwater (salinity ~0) assuming no advection occurs? Homework Equations J (g/m2s) = C (g/m3) x V (m/s) The Attempt at a Solution C = 30g/L *...
  49. J

    Energy flux density and and energy fluence question work shown

    energy flux density and and energy fluence question! work shown please help! A point source of Co-60 gamma rays emits equal numbers of photons of 1.17 and 1.33 MeV, giving a flux density of 5.7 x 10^9 photons/cm^2-sec at a specified location. a.)What is the energy flux density there...
  50. B

    Electric flux (Φe) vs electric flux density (D)

    As the title states i would like to know the definitions of the above two terms. Also i would like to know the differences and a relation (if there is one) between them. I would be really grateful to anyone who takes the time to answer my probably silly questions.
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