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. C

    I Iron core barely boosting field strength

    Hello, I am a chemistry intern currently running a project that involves both chemistry and electromagnetism. Bottom line, I'm a little out of my depth and have much to learn, and I'm having a bit of trouble with the coils I constructed. My setup will consist of four coils positioned...
  2. O

    Flux density help please (seawater flowing in a tube)

    What is the flux density of salt in a horizontal tube 10 cm in length connecting seawater (salinity = 30 g/l) to a tank of freshwater (salinity ~ 0) assuming no advection occurs?
  3. J

    Engineering Calculating maximum flux density

    Hi everyone, I have a EE problem that I need to sort out for alternating voltage. I have to find out the maximum flux density. B_max= integral from 150 degrees to 30 degrees (u/(2NA) dt is my problem. I have a hard time to integrate this since I am to integrate with time and not degrees or...
  4. 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?
  5. 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...
  6. Shreya

    Flux density and Divergence of Electric field

    I think Flux density is flux/Volume. Or is it flux/ Area Please be kind to help
  7. J Silva

    Is the magnetic flux density B constant?

    Summary:: Is the magnetic flux density B constant? Is the magnetic flux constant? I am working on a project design for Uni and I am stuck. In a magnetic circuit is either the magnetic flux or the magnetic flux density B constant? This magnetic circuit has all different cross section areas and...
  8. GhostLoveScore

    Calculating flux density of radio telescope

    Hello I've made a small program that does FFT, Fast Fourier Transform on a signal from radio receiver (RTL SDR), and parabolic antenna. Of course, the output is amplitude depending on frequency. I want to use it to detect and measure 1420MHz radiation from space. But I'm not sure on what's the...
  9. Y

    How does the saturation flux density affect magnetic field strength?

    So I'm confused what the Saturation Flux Density is referring to. Defintion says it is when you no longer get an increase in H-field when increasing external B-field. So, does the satuation flux mean the core can only create fields UP TO that saturation flux, or that it can make a stronger...
  10. AN630078

    Solar Panels and Solar Radiation Flux Density Help - Very Confused

    Question 1; a) P=E/t E=5.796*10^7 J energy produced per day during the summer However, I am not certain how to calculate the time period, since although this concerns the energy produced per day, the sun does not shine for the entire duration of this 24 hour period. Also, I am unsure of the...
  11. A

    Magnetic field lines and magnetic flux density

    I'm trying to understand the relationship between the "number" of field lines passing through a region and the magnetic force in this region.I understand that the drawings are of course conceptual: we cannot draw "all" the field lines (although can be visualized with iron fillings).Also the...
  12. S

    Calculating the flux density between two magnets

    This is for an experiment to deflect a 28 SWG wire between two magnets, 3cm apart, by passing a current through it (example attached). The force on the wire is obviously F = BIL, but the wire will be passing at 1.5cm from each magnet so there will be some significant fall off of B and I can't...
  13. The forgetful one

    Magnetic flux density of a relativistic electron

    q = 1.602e-19C mass_electron = 1.098e27 c = 3e8 Omega(Mag_flux_den) = 5GHz Lorentz factor = 100 synchrotron radiation at frequency v = 5GHz Mag_flux_den = (Omega(Mag_flux_den) * c * Mass_electron * Lorentz factor) / mass_electron Mag_flux_den = (5000 x 3e8 x 1.098e27 x 100 ) / 1.602e-19 =...
  14. AndrewC

    Magnetic field intensity, flux density and magnetization of coax cable

    Inner conductor radius = 1cm outer conductor radius = 10cm region between conductors has conductivity = 0 & 𝜇r = 100 𝜇r = 1 for inner and outer conductor Io = 1A(-az) 𝑱(𝑟) = (10^4)(𝑒^-(r/a)^2)(az) Problem has cylindrical symmetry, use cylindrical coordinate system. Find the total current...
  15. Boltzman Oscillation

    Engineering How can I find this formula for the magnetic flux density? (EMagn)

    I drew an illustration to make this easier: Point P is where I wish to find the magnetic flux density H. Given the Biot-Savart formula: $$d\textbf{H} = \frac{I}{4\pi}\frac{d\textbf{l}\times\textbf{R}}{R^2}$$ I can let $$d\textbf{l} = \hat{z}dz$$ and $$\hat{z}dz\times\textbf{R} =...
  16. adamaero

    Getting less total B-field from two infinitely long parallel wires

    I got 4.7*sin(377t) micro-Tesla for each wire, but where are they getting the total B-field equaling 0.78 micro-Tesla? Is it some hidden trigonometry?
  17. F

    I Computing a value of radius for a typical white dwarf

    I try to get a correct result for the radius of a standard white dwark (roughly 10000 km). I just want the order of magnitude , i.e with the common values of a solar mass into Earth radius sphere. From http://www.astro.umontreal.ca/~bergeron/CoolingModels/Synthetic_Calibration.pdf page 1223...
  18. R

    X-ray Flux density and a differential equation for photon scattering

    Homework Statement Consider interactions of a X-ray beam at a depth, x, within a material. The flux density is: density flux = $$\frac{I}{A}$$ where I is the intensity of the beam that cross a unit area A at right angles to the beam. Let dx be a small slice at the depth x and let dI(x) be the...
  19. C

    How many Amp turns around the Earth for this flux density?

    Someone is asking me how much current in a loop of wire the diameter of the Earth to make the same level of magnetism the Earth has? I hope I am asking this correctly. TIA Clark
  20. W

    The magnetic flux density at point P between parallel wires

    Homework Statement In the picture at points A and B are two thin parallel wires, where traveling currents are 15 A and 32 A to opposite directions. The distance between wires is 5.3 cm. Point's P distances from A and B are the same. Calculate the magnetic flux density at point P. Homework...
  21. Physics Dad

    Astrophysics Problem - Effects of cloud on flux density

    Hi, I am attempting the following question: 1. Homework Statement If the extinction in the infrared K-band (filter central wavelength = 2.13 micrometres) is 10 times less than it is in the optical V-band (filter central wavelength = 550 nanometres), what affect would a cloud of Av = 3 have on...
  22. T

    Temperature and magnetic flux density

    Hello all; I am new in this forum, currently in High School. For some time now, I have been looking online for a relationship between temperature and magnetic flux density of a ferromagnet; below the Curie point. However, I can't seem to find any relationship or formula. Do any of you know...
  23. G

    I How does flux density scale with redshift?

    I'm not sure I understand how to correctly scale flux density with redshift. That is, if I observe say 10 Jy at my observing frequency coming from a source at z = 0.3, how can I estimate the flux density I would expect from the same source at z=2? From what I understand, the final scaling is...
  24. Z

    The Effect of Temperature on Magnetism

    Hey guys, recently I have conducted an experiment investigating the effect of temperature (K) against magnetism (mT). I have found two formulas and understand that they are for both linear and non linear relationships but why does the function change from linear?
  25. C

    Is a flux density of 227.6 T realistic for a 5cm bar magnet?

    Flux density of a magnet is about how many T? In an experiment, I obtained the number 227.6 T. Is this a sensible value for a small (5cm long) bar magnet? Thank you~
  26. E

    Determining between direct evaluation or vector theorems

    So the main thing I'm wondering is given a question how do we determine whether to use one of the fundamentals theorems of vector calculus or just directly evaluate the integral, and if usage of one of the theorems is required how do we determine which one to use in the situation? Examples are...
  27. N

    Wavelengths, Flux Density, Irradiance from a temperature measurement

    Homework Statement In my experimental setup I have a purpose built small aluminium tube that has a black layer on the inside to mimic a blackbody. The tube is heated so the inside emits as a blackbody. A separate temperature sensor attached to the tube gives the temperature of the tube. I...
  28. G

    Weber & Flux Density: Learn How 1 Wb = 10^8 Lines of Magnetic Flux

    Hi, Eqn B = phi/A For flux density so 1T = 1Wb/m^2 Often wondered about a Weber and found on a site that 1 Wb is 1 x 10^8 lines of magnetic flux! Does this sound right that an exact amount of flux lines represents 1weber? I always thought that the concept of webers was a relative idea and not...
  29. B

    Flux Density, B, of a Cylindrical Magent

    Hi, I'm trying to calculate the flux density of a magnet, I can get all but one of the values needed to calculate it. Does anyone know how/where to get the z(distance from a pole face on the symmetrical axis) value?
  30. 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...
  31. texasnano

    A Does increasing photon flux density increase attenuation?

    follow up from responses in old thread. https://www.physicsforums.com/threads/why-does-attenuation-coefficient-decrease-with-increased-energy.569981/ I have seen in my experiment using a saline media ( some oxygen bubbles) that an increase in Incident PFD is showing an slight increase in the...
  32. E

    How Is Scattered Flux Density Measured from a Ruby Laser in the Atmosphere?

    Homework Statement [/B] An unpolarized ruby laser operated at 0.7 μm is projected vertically into a clear sky to investigate the density of the atmosphere. A detector located 10 km from the base of the laser is used to receive the flux density scattered from the laser beam by air molecules...
  33. T

    Find magnetic flux density B circulation in closed contour

    Homework Statement Find magnetic flux density B circulation in closed contour. The countour consists of square with a perimeter of 4b. It includes a square conductor with a perimeter of 4a. A homogenic current flows through a conductor with a current density of j. Homework Equations...
  34. TheSodesa

    Magnitude of a component of a triple star

    Homework Statement The apparent total magnitude of a triple star is ##m_0 = 0,0##. The apparent magnitudes of two of its components are ##m_1 = 1,0## and ##m_2 = 2,0##. What is the apparent magnitude of the third component? Answer: 0,9 Homework Equations Since according to Norman Pogson...
  35. moenste

    Calculate the magnetic flux density

    Homework Statement The magnetic flux density in the vicinity of a large air-cored electromagnet is determined by measuring the induced flow of charge in a small coil as the current in the electromagnet is switched on -- see the diagram below. Calculate the magnetic flux density at the...
  36. moenste

    Magnetic flux density between two wires

    Homework Statement Two identical wires R and S lie parallel in a horizontal plane, their axes being 0.10 m apart. A current of 10 A flows in R in the opposite direction to a current of 30 A in S. Neglecting the effect of the Earth's magnetic flux density calculate the magnitude and state the...
  37. moenste

    Flux density expressions at solenoid centre

    Homework Statement A long air-cored solenoid has two windings wound on top of each other. Each has N turns per metre and resistance R. Deduce expressions for the flux density at the centre of the selenoid when the windings are connected (a) in series, and (b) in parallel, to a battery of EMF E...
  38. moenste

    Point between two wires at which the flux density is zero

    Homework Statement A long wire (X) carrying a current of 30 A is placed parallel to, and 3.0 cm away from, a similar wire (Y) carrying a current of 6.0 A. What is the flux density midway between the wires: (a) when the currents are in the same direction, (b) when they are in opposite...
  39. entity314

    Flux Density in Mutual Induction Solenoid with Core

    For a standard solenoid, I've found that B=μnI where μ = permeability of the core (4π×10^-7 for free space) n = number of coils I = current Firstly, is the permeability of soft iron 0.08, as I found? Primarily, however, I'm wanting to know if this still applies for a mutual induction apparatus...
  40. D

    I What is Reluctance in a Magnetic Circuit?

    Electrical resistance is due to electrons colliding with the atoms of the conductor. In a magnetic circuit reluctance is analogous to resistance in an electric circuit. Just as resistance impedes the flow of electrons in an electric circuit, reluctance impedes the flux in a magnetic circuit but...
  41. E

    Calculating flux density in an air gap

    I am trying to calculate the flux density of an air gap in an electromagnet. I am following this page that calculates the flux density in a C core with an air gap. My confusion is that I am using 50Hz AC instead of DC I have control over the voltage amplitude since I would be using a variac to...
  42. A

    Question about magnetic flux density B

    Magnetic flux density B is a vector quantity and thus represents a force. However most texts state that the magnetic force is perpendicular to the direction of B, which is tangential to the magnetic field line at any give point. I assume that this magnetic force refers to the Lorentz force. So...
  43. Fernando Valadares

    Electric flux density of oscillating electric charge

    Homework Statement The electric flux density in free space produced by an oscillating electric charge placed at the origin is given by \vec{D}=\hat{r}\frac{10^{-9}}{4\pi r^2}cos(wt-\beta r), \ \ where \ \beta=w \sqrt{\mu_0 \epsilon_0} Find the time-average charge that produces this electric...
  44. engnrshyckh

    Surface Charge Density of Coaxial Cylinder with Canceling Electric Fields

    a long straight wire has fixed -ve charge density of 39nC/m. the wire is enclosed by thin wall non conducting coaxial cylinder of radius 1.7m. the shall has positive charge density and its Field is such as that it will cancel the field due to wire. what will be the surface charge density of...
  45. D

    Magnetic Flux Density Direction

    Would the direction of the Magnetic Flux Density vector B at the south side be towards the south pole like this? and is the direction for B correct for the other side? One more thing, how can magnetic flux density be a vector and have a direction when its sort of a density, I mean its over an...
  46. R

    Simulator for Radiometry:Radiosity/Radiant Flux density?

    Hey All, I was wondering if anyone knows of any good simulation software packages that can do quantitative radiometry. I'm thinking COMSOL may have a radiometry suite, but I'm not very familiar with the software or package offerings. Basically, I'm trying to optimize the placement of hundreds...
  47. Nile Anderson

    How does one calculate the flux density B at end of solenoid?

    Homework Statement I came across a recent problem that asked me to calculate the flux density at the end of a solenoid. I was given the current 3 A , the number of turns per unit length , 12 cm-1 and the using the permeability of free space as 4π × 10^-7 Homework Equations The equation I used...
  48. 3

    Calculating magnetic flux density using Biot-Savart law.

    Hello, all. I have been working on the following problem and was wondering if someone could check my work and provide some valuable input: Here is my work: What do you guys think about my approach to this problem?
  49. 3

    Charge passing through a magnetic field of uniform magnetic flux density

    My reasoning: The magnetic force on charge q is Fm = qv x B B does not change |v|. Therefore, |Fm| is constant at time t > 0 and Fm is always perpendicular to the direction of movement of charge q. Fm behaves as a centripetal force, and thus the charge moves along the circumference of a...