Flux Definition and 1000 Threads

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. T

    Zero-Divergence of Rate of Change of Magnetic Flux

    Let's introduce a time-varying scalar field ρ(x,y,z,t) [charge density] and vector field J(x,y,z,t) [current density] Assuming the system follows Maxwell's equations, what must both fields satisfy such that ##∇⋅(\frac{∂B}{∂t})=0## ?
  2. 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...
  3. D

    I Calculating Flux through shape on irregular plane in 3-Space

    I'm not sure if I should be posting here of all places but it's worth a shot. I just had my unit test and there was a pretty weird problem on it where there was a circle of radius r in 3space on the plane of ax+by+cz=d and you were given the circle's center (C1,C2,C3). To be clear, I was given...
  4. CAH

    How is emf constant of flux linkage is increasing?

    how is this true? I get that it's the rate of change of flux, and if you have a graph of flux linkage against time, the gradient with a constant gradient then emf is constant since it IS the gradient... But how? If the flux linkage is increasing, why doesn't the emf?
  5. P

    A Formula for calculating neutron flux?

    I have a liquid scintillator, the electronics system, and a beam of neutrons from a reactor. How do I calculate the neutron flux? Cold anybody give me a formula or equation? Not this equation: phi = n X v, where phi - flux, n = number of neutrons per cm3, v = velocity of the neutrons, because I...
  6. 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...
  7. J

    Transformer Flux and Exciting Current

    Can anyone explain in a transformer, how could a non-sinusoidal wave of exciting current produces a sinusoidal wave of flux?
  8. P

    Understanding the change of flux and it's consequences

    So I was busy trying to imagine the ways in which lenz's Law would work physically. So I imagined a loop through which a magnet is brought and after that the magnet is pulled out of the loop a current is induced in order to keep up the magnetic field. So in this case the flux would go down which...
  9. D

    Understanding Magnetic Flux: Integrals vs. Simplified Equations

    Homework Statement So I understand that the magnetic flux is equal to the integral of (B dotted with dA) (new to the site don't know how to use math symbols). My question is, how come in some problems, is it ok to just say the magnetic flux is equal to the magnetic field times the area, while...
  10. 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...
  11. gsmtiger18

    Line charge creating induced emf and displacement current

    Homework Statement A long, straight wire has a line charge, λ, that varies in time according to: λ = λ0 exp(-βt). A square wire loop of dimension a is located adjacent to the wire at a distance of a from the wire. Calculate expressions for the displacement current at the center of the wire loop...
  12. L

    Overall Electric flux of a rigid body

    When we looked at some closed surface, we defined the overall electric flux of that surface as the sum of all infinitesimal fluxes of all the infinitesimal surfaces that make the quoted closed surface. Does that change if we do not have a closed surface, but a rigid body such as, let's say, a...
  13. Chaos

    Electric flux on non-orientable surfaces

    How to define and calculate electric flux on mobius strip or klein bottle?These surfaces are non-orientable, so I feel confused about that. Thanks for discussion and help.[emoji4]
  14. 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...
  15. M

    Calculate photon flux at a distance from the source

    Homework Statement A 100W sodium lamp(lambda=589nm) radiates energy uniformly in all directions. (A) At what distance from the lamp will a totally absorbing screen absorb photons at the rate of 1.00 photon/cm2.s? (B) What is the photon flux on a small screen 2m from the lamp? Homework...
  16. I

    Electric flux inside a conductor

    Hello, If we have a solid conductor with all of its charge on its surface, and we then enclose some its charge with a gaussian surface that goes inside the solid conductor, will the part of the gaussian surface within the conductor have any electric flux? My textbook says it will have zero...
  17. T

    Do harmonics cause stray flux losses in transformers?

    I read here: http://static.schneider-electric.us/docs/Motor%20Control/AC%20Drives/8803PD9402.pdf that harmonics cause stray flux losses in transformers, how is this so? Thanks
  18. T

    Flux in magnetic core according to special relativity

    Hi, So say you have a magnetic flux in a closed magnetic path circuit (like a TX core). Well I mean we draw arrows and stuff to indicate how the magnetic flux travels, but after watching this: I'm having trouble understanding why there is any flux moving through at all. Can someone please help...
  19. A

    What is the Photon Flux for a 100 MHz Signal Traveling 4 Light Years Away?

    Homework Statement It's in attachment Homework Equations E=hf. Where h= planks constant and f= frequency The Attempt at a Solution I know that the flux of a photon is (# of photons)/(sec m^2) I don't know the number of photos but I do know the frequency and power. E=(6.6261*10^(-34)) J•s *...
  20. A

    Calculate Area of Ring in Uniform Magnetic Field | Faraday's Law Problem

    Homework Statement In a uniform magnetic field with induction of 0.1 Teslas - a coil is located perpendicular to the lines of induction (I suppose it's something like a ring of wire, meaning N=1). Resistance = 2 Ohms. What is the area of the "ring" if when the field is switched on - it will...
  21. quaticle

    Finding electric flux through the circular cap of a sphere

    Homework Statement A sphere of radius R = 1.40 m surrounds a particle with charge Q = 42.0 μC located at its center as shown in the figure below. Find the electric flux through a circular cap of half-angle θ = 28.0°. Homework Equations Φ = ∫E⋅dA E = (kq)/r2 A = πa2 where a = rsin(θ) --> from...
  22. M

    Find an expression for magnetic flux and calculate

    Homework Statement Loop of wire with the following properties in a magnetic field B. Find an expression for the magnetic flux through the loop and evaluate the magnetic flux at t=25s. The magnetic field is uniform but changes strength at time (t) given by B(t) = B0 exp (kt)Resistance = 20ohms...
  23. M

    How do I compute electric flux through a half-cylinder

    Homework Statement In figure 1, take the half-cylinder's radius and length to be 3.4cm and 15cm respectively. If the electric field has magnitude 5.9 kN/C, find the flux through the half-cylinder. Hint: You don't need to do an integral! Why not? Homework EquationsThe Attempt at a Solution I...
  24. S

    Electromagnet which produces varying magnetic flux

    I want to make an electromagnet but it should Produce magnetic flux which changes with time. What material wire would be the best to make make windings?
  25. P

    Flux integral over ellipsoidal surface

    Homework Statement I am having trouble with part iii) of the following problem: Verify the divergence theorem for the function ##\vec{u} = (xy,- y^2, + z)## and the surface enclosed by the three parts: (i) ##z = 0, x^2+y^2 < 1##, (ii) ##x^2+y^2 = 1, 0 \le z \le 1## and (iii)...
  26. E

    A Question about Radiance, Solar Flux and Reflectance

    I stumbled upon this equation for a Lambertian uniform target: ##\rho^{*} = \frac{\pi L}{\mu_s E_s}##, where ##\rho^{*}## is the reflectance, ##L## is the measured radiance, ##E_s## is the solar flux at the top of the atmosphere, and ##\mu_s## is the cosine of the sun zenith angle...
  27. Z

    Is the coil the only viable shape for an electric engine ?

    Hi, I'm an hobbyist right now I'm into electric engines, simple engines for low voltage and low current applications; I have noticed that there are many variations about how and what an electric engine can do even considering only DC motors, but basically all the engines that I have examined up...
  28. gracy

    Flux through distorted surface

    There is a distorted surface and the source of the flux is inside the cube I have read that flux through it would be q/2ε0 I want to know Why?It is not my homework problem and I think it does not involve any calculation that's why I did not post it in homework section .There should be some...
  29. F

    A coil moves into a magnetic field

    Homework Statement A coil, made up of 1850 loops, is inserted in an electric circuit and has a resistance of 45,0Ω. The area of each loop is 4,70⋅10^(-4) m^(2). The coil moves from a region where there's no magnetic field, to a region where the magnetic field is present. The normal to the coil...
  30. B

    Flux Vectors of One E-: Force Vectors or Scalar Quantity?

    How many magnetic/electric flux vector one e- can produce? Only one or many? (Here I mean flux as force vectors and not a scalar quantity like in flux density.)
  31. T

    Calculating Magnetic Flux Needed for Ion Control

    Homework Statement A magnet is used to control negative ions and only allow those with a specific mass to pass through a narrow gap opening . The magnet will bend the ion beam in a quarter circle of radius 50 cm . In an experiment, a negative ion accelerated by a voltage of 3.0 kV. Which...
  32. M

    [Magnetic Flux and Lenz's Law] Is this picture correct?

    Is the arrow of the ammeter pointing in the correct direction? The induced current is going through the positive end of the ammeter and out of the negative end. Since current is traveling towards the positive end of the ammeter, shouldn't the ammeter point towards the negative direction?
  33. T

    What Happens to Flux in an Induction Motor When Short Circuited?

    Just a curiosity about what happens to the flux, when you short circuit an induction machine. Say there is an initial flux and you're rotating the shaft of an IM and then you short circuit the stator, so no doubt you'll get large currents in the stator, but those large currents, will they cause...
  34. T

    How does a Synchronous condenser shift the phase

    Hi, So when you over-excite the rotor of a synchronous motor, or under-excite the rotor of a synchronous generator, how is the flux actually changing the power factor of the armature to leading? (something to do with the magnitude of the armature reaction flux vector?) That is to ask: by what...
  35. S

    Will We Witness a Daytime Visible Supernova in the Near Future?

    I have heard that some centuries ago a supernova happened which its light was visible in daytime.according to the observations will have a such supernova in the next few years?
  36. S

    Flux surface average for a tokamak

    I am trying to figure out the flux surface average of a 3D perturbation in a tokamak. For example what is the flux surface average of cos(m*theta+n*phi) at a given flux surface. (Theta and phi being poloidal and toroidal angles respectively?
  37. I

    Magnetic Flux Linkage: Rate of Change & Cutting

    Hi, this may be really easy but.. I understand that to have an induced e.m.f , we can either have a rate of change of magnetic flux linkage ( ac source ) or cutting of flux ( like a plate oscillating and cutting through a magnetic field produced by a solenoid ). However does cutting of flux...
  38. V

    Direction of current in a magnetic field when loop is square

    Homework Statement A flexible wire loop has a radius of r = 0.178 m and it is inside a uniform magnetic field of B = 0.332 T. The loop is grasped at points P and Q and stretched until its area is zero. It takes 0.146 s to close the loop. Homework Equations EMF = ∆Phi/∆t Phi = magnetic flux...
  39. P

    Heat flux through a composite wall

    1. State the problem A plane wall consisting of three different materials, each of constant thermal conductivity k. Assume steady-state temperature distribution. a) Comment on relative magnitudes of q(dot)''2 and q(dot)''3 and of q(dot)''3 and q(dot)''4. b) Comment on the relative...
  40. G

    Electromagnetism help: Find magnetic flux through a loop

    Homework Statement Very large conductor with DC current is in vacuum. Find magnetic flux through a loop. Given parameters: I,a,\alpha Homework Equations \Phi=\int_S B\mathrm dS - basic equation for magnetic flux B=\frac{\mu_0I}{2\pi x} - electromagnetic induction created by very long...
  41. 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...
  42. 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...
  43. Titan97

    Finding flux from electric field

    Homework Statement If ##\vec{E}=k\frac{x\hat i +y\hat j}{x^2+y^2}##, find flux through a sphere of radius R centered at origin. Homework Equations ##\int E.da=\int(\nabla\cdot E)\cdot da## The Attempt at a Solution I was able to solve this problem without finding divergence of electric field...
  44. G

    K Corrections: Explaining Fluxes in 250μm (Janskys)

    So I'm trying to k-correct some fluxes in 250μm (janskys) using the M82 template found here and the relevant equations found here (I also have the transmission filter function). The template is normalised to 5500 A and doesn't have a brightness so I fail to see how I can correct my observed...
  45. G

    Calculating heat flux (Q) without thermal conductivity (K)

    How to calculate K or Q without one or the other? For example, if the material is unknown (but cannot test density, or melting temperature) how would you test heat flux? Q=K(Th-Tc)/(x)
  46. D

    How Is Magnetic Flux Calculated Through a Square Loop Inside a Solenoid?

    Homework Statement A single-turn square loop of side L is centered on the axis of a long solenoid. In addition, the plane of the square loop is perpendicular to the axis of the solenoid. The solenoid has 1280 turns per meter and a diameter of 5.85 cm , and carries a current of 2.15 A . Find...
  47. SarahAlbert

    Flux Through Concentric Spheres with Varying Charge Density

    Homework Statement A sphere of radius a has its center at the origin and a charge density given by p=Ar^2 where A=constant. Another sphere of radius 2a is concentric with the first. Find the flux through the larger sphere. Homework Equations Flux=E*da The Attempt at a Solution According to...
  48. Kurtis McIntosh

    How Do You Calculate Net Electric Flux Through a Cube?

    Homework Statement Assume the magnitude of the electric field on each face of the cube of edge L = 1.07 m in the figure below is uniform and the directions of the fields on each face are as indicated. (Take E1 = 35.1 N/C and E2 = 25.3 N/C.) A.) Find the net electric flux through the cube. B.)...
  49. gracy

    Electric flux through the square

    Homework Statement A point charge of +6μC is placed at a distance 20 cm directly above the center of a square of side 40cm.The magnitude of the flux through the square is Homework Equations The Attempt at a Solution Now how to enclose the charge completely?The answer is with the help of 5...
  50. gracy

    The flux through the hemispherical surface

    Homework Statement The flux through the hemispherical surface in the figure shown below is Homework Equations The Attempt at a Solution But the above formula is for closed surface .But hemisphere is not a closed surface to make it closed surface we will need another hemisphere . then the...
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