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. K

    How can I find the number of turns in a solenoid winding?

    A 30mH solenoid inductor is wound on a form 0.4 m in length and 0.1 m in diameter. A coil is tightly wound around the solenoid at its center. the coil resistance is 5.0 ohms. The mutual inductance of the coil and solenoid is 60μH. At a given instant, the current in the solenoid is 0.3A and is...
  2. 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...
  3. E

    Transformers - Variation in Current, EMF and Magnetic FLux

    This question about the variation of the aforementioned quantities in a transformer. Now according to me and my knowledge of electricity this is how I feel it should play out : If the input current were a sine curve that varies with time then : Input voltage = cosine curve i.e. it is...
  4. 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...
  5. T

    What Is the Magnetic Flux through a Loop in a Solenoid?

    Homework Statement A wire circle of radius 0.050 m is embedded in a solenoid of length 0.20 m with 1000 turns that carries a current of 0.50 A. If a vector that is normal to the plane of the circle makes a 40° angle with the axis of the solenoid, what is the magnetic flux through the loop...
  6. D

    Magnetic flux through coiled wire

    Homework Statement A circular coil has 25 turns and a radius of 5 cm. It is at the equator, where the earth’s magnetic field is 0.7G north. Find the magnetic flux through the coil when its plane is (a) horizontal, (b) vertical with its axis pointing north, (c) vertical with its axis pointing...
  7. V

    Differences between Electromagnetic flux and magnetic flux

    May I know that are there any different between the electromagnetic flux and magnetic flux? Are there any electromagnetic flux in a permanent magnet machine? What kind of flux will go through the permanent magnet machine's stator cores with copper wires on it? I am really sorry to ask so many...
  8. T

    Magnetic Flux through solenoid question

    Homework Statement "A solenoid is wound with 400 turns on a form 4cm in diameter and 50 cm long. The windings carry a current that produces a magnetic field, of magnitude 1.5mT, at the center of the solenoid. The magnetic flux through the solenoid is closest to? Homework Equations...
  9. L

    Flux Linkage - what, where, why?

    Hi, we have been doing lots of work recently on magnets. we have learned about the ideas of flux, and using them to describe induction and how transformers work etc. i feel that i understand quite well about these ideas, but now i have come across this idea of 'flux linkage'. i do not...
  10. I

    Fundamental and basic physics questions on flux lines

    Ok, Please correct me if I'm wrong; Flux lines are a sort of mathematical visualisation of magnetic fields, they do not exist. As such, there still exists a magnetic field between flux lines (?), just in calculations we use flux lines because they are simpler (?). In voltage transformers...
  11. L

    Surface Integral, flux. Boundary and orientation

    In solving a flux integral over a flat surface, inclined above the xy-plane, does the boundary of the surface influence the flux only through the integral limits? (and not through its normal vector) Let's say that there is an elliptic surface inclined above the xy-plane. The orientation is...
  12. F

    Calculating Electric Flux Through a Cone

    Homework Statement A cone is resting on a tabletop as shown in the figure with its face horizontal. A uniform electric field of magnitude 4550 N/C points vertically upward. How much electric flux passes through the sloping side surface area of the cone? Homework Equations flux = ∫...
  13. J

    How Does an External Charge Affect Flux Through a Cube's Face?

    A charge q is kept at the centre O of cube of length L(ABCDEF). Another charge q is kept at a distacne L from the centre O. Find the flux through face ABCD Well the flux through whole of the cube will remain unchanged that is q/ε. But now since we have another charge q outisde the cube we...
  14. S

    Magnetic Flux and Induced Voltage Interesing question

    Homework Statement assuming that friction is negligible and tthat electromagnetic forces are constant, (when they occur) calculate the speed of the cart at point 5w this is part IV of a question, so in the other parts and in the given, i found out that: mass of the cart=0.5kg number of...
  15. C

    How Does Rotating Magnetic Flux Arise from Perpendicular Alternating Fluxes?

    Homework Statement Sketch phasors for two alternating fluxes with a 90 degree phase difference. If the two fluxes are directed at right angles, show that the resultant flux rotates. Homework Equations perhpas N\Phi=BANcosθ although I don't think it's necessary The Attempt at a...
  16. A

    Flux through a box? And divergence as a limit?

    Let F=(7z+8)i+2zj+(2z+7)k, and let the point P=(abc), where a, b and c are constants. In this problem we will calculate div F in two different ways, first by using the geometric definition and second by using partial derivatives. (a) Consider a (three-dimensional) box with four of its corners...
  17. A

    Change of flux in an L-R circuit

    Homework Statement Homework Equations afaik, flux in inductor = Li. at t=0, current through L is 0. so change of flux = LΔi = L(i-0)=Li The Attempt at a Solution at t=∞, i through cap. is 0. so, i get the following equations: 5(i1+i2)=20 5(i1+i2)+ 5i2=10 i get...
  18. P

    Flux of a vector field through warped sphere

    Homework Statement Consider the surface S with the graph z = 1-x^{2}-y^{2} with z≥0, and also the unit disc in the xy plane. Give this surface an outer normal. Compute: \int\int_{S}\vec{F}\bulletd\vec{S} where \vec{F}(x,y,z) = (2x,2y,z)Homework Equations \int\int_{S}\vec{F}\bulletd\vec{S} =...
  19. N

    The proton flux in Solar System in keV range

    Dear Forum Users, I am looking for a database of proton fluxes. I have found already the SOHO database: http://umtof.umd.edu/pm/ but I need also the database for energy range of 1keV to 100 keV range. Does someone could send me some hints where to search? nykon
  20. A

    Flux lines in diametrically magnetized cylinder

    Hey everyone, First I'd like to say my thanks to the community for all the information I managed to glean while lurking on the forum and doing my schoolwork over the last year or so. It's been an invaluable resource to me! Now, on to my question. (I see that it says not to post homework...
  21. _maxim_

    Hall Effect Magnetic Flux Sensor in very Strong Magnetic Fields

    Dear PFs I am facing a problem with finding a good Hall-effect magnetic flux sensor which should be fixed in the top of a probe working in a very intense magnetic field. The probe must be aligned to a certain degree with respect to the direction of the main field. The requested alignement...
  22. N

    How Do You Convert Proton Flux from 1/(cm^2 s sr) to 1/(cm^2 s)?

    Dear forum users, I have a quite simple question. I have got a flux of protons measured in 1/(cm^2 s sr), I would like to have it in 1/(cm^2 s). nykon
  23. P

    How do I relate flux equation to transformers?

    http://imgur.com/VsDrQ,dJ2iv#1 So according to the picture, I found the transformer voltage equation and current equation to be the following: Precondition: i1 is current in left loop i2 is current in 2nd loop Transformer Voltage Eq: V1/N1 = 4i2/N2 Current Eq: Ni(i1) =...
  24. T

    Finding the electric flux through a sphere

    Homework Statement A sphere of radius R is placed in a uniform electric field of E=233 N/C i. Find the electric flux into and out of the sphere. Homework Equations I understand that Gauss's Law is shown as... ∫E dot dA = Q/epsilon not The Attempt at a Solution Well, since...
  25. T

    Changing electric flux caused by a resistor

    I'm learning the basics about electromagnetism, including that a changing electric flux through an open surface causes a magnetic field. Obviously a capacitor causes this, but doesn't a resistor like a light bulb (whose resistance varies with temperature and therefore time) also cause this?
  26. C

    Temperature of a star via its flux

    Homework Statement What is the temperature of a star if the flux at 450 nm is measured to be 1.3 times the flux at 650 nm Homework Equations To determine monochromatic flux I use: 2πhv3/c2 ex-1 x= hv/kT The Attempt at a Solution So basically I plug in the...
  27. S

    Flux through sphere NOT centred at origin

    Homework Statement Let's say the sphere has a radius of 3 and is centred at (3, 0, 3). Is there a way to implement spherical cooridnates, or is it essentially impossible for this situation to not get messy? I have searched everywhere as to how I can evaluate this, but to no avail. Any help is...
  28. X

    Astrophysics: Finding flux of a star given magnitude

    Homework Statement The faintest stars a naked eye can see under the ideal conditions are of m = 6 magnitude. Diameter of a maximally dilated pupil is d = 9mm. Calculate the magnitude of the faintest star a person can see if observing through binoculars (d = 5cm), a large backyard...
  29. K

    How Does Side Length Influence Electric Flux Through a Cube?

    A point charge 6.50 nC is at the center of a cube with sides of length 0.260 m. PART A: What is the electric flux through the surface of the cube? PART B: What is the electric flux through one of the six faces of the cube? ATTEMPT: A) Total flux enclosed by the cube = Q / eo...
  30. K

    Simple electric flux through tetrahedron problem

    A tetrahedron has an equilateral triangle base with 20-cm-long edges and three equilateral triangle sides. The base is parallel to the ground and a vertical uniform electric field of strength 200 N/C passes upward through the object. (a) What is the electric flux through the base? (b) What is...
  31. M

    Flux for an Infinite charge line through a cylinder

    Homework Statement An infinite line of charge with charge density λ1 = 2.9 μC/cm is aligned with the y-axis as shown. a = 7.9 cm. h = 8.8 cm. λ2 = -8.7 μC/cm. Another infinite line of charge with charge density λ2 = -8.7 μC/cm parallel to the y-axis is now added at x = 3.95 cm as shown...
  32. S

    Finding Flux of $\vec{F}$ Outward Across Sphere

    Homework Statement Find the flux of \vec{F}=(x, y, z) outward across the sphere x^2+y^2+z^2=a^2. I am able to get it to this point: \int\int_Cadxdy and I then convert it to polar coordinates, and integrate rdr from 0 to a, and theta from zero to 2pi. However, this does not give me the...
  33. R

    Flux, Capacitance, Difference Potential, and Volt

    I have a question about electricity and magnetism. My teacher went through these chapters in 3 days, and I am completely confused. Can some body please explain what exactly is flux, capacitance, difference potential, and voltage? And can you also explain to my what the number stands for when...
  34. K

    Electric flux changing forumla variables

    A point charge Q at the center of a sphere of radius R produces an electric flux of (flux symbol) coming out of the sphere. If the charge remains the same but the radius of the sphere is doubled, the electric flux coming out of it will be? LINK TO ORIGINAL PROBLEM: http://i.imgur.com/e8Tmt.png...
  35. K

    Problem with understanding the definition of magnetic flux.

    Homework Statement Probably a silly question, but I can't figure it out. Why is magnetic flux defined as magnetic field strength per unit area if it is found by multiplying the strength of magnetic field B by area A rather than dividing by area A? Thanks for any responses :)
  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. DryRun

    Calculate Outward Flux Through a Sphere

    Homework Statement http://s1.ipicture.ru/uploads/20120121/YUmpPl4N.jpg The attempt at a solution First of all, taking a look at the wording in the problem itself. I am not sure if the unit normal vector is supposed to be outward or inward. There is the "outward flux" but the "inside the...
  38. S

    Electric Field & Flux, A loop & Charge

    Hey everyone. Having a bit of trouble with a 4-part question. So I thought I'd post here, if someone could check the first 3 parts and perhaps help me with the last part, I'd really appreciate any feedback! Thank you so much! :) Homework Statement a) A circular loop is held to the left of a...
  39. M

    Calculating Electric Flux of Displacement Vector w/ Cylindrical Co-ords

    Using cylindrical co-ordinates (r, theta, z), calculate the electric flux phi=integral D . dS when the displacement vector D is given by: D=10ezcos(theta)/r2 . kr + z2sin(theta)/r2 . Kz and the surface S is part of a cylinder of radius a=0.3, defined by 0 is less than or equal to z which is...
  40. DryRun

    Flux Calculation for Vertical Cylinder with Top Cut Off

    Homework Statement http://s1.ipicture.ru/uploads/20120119/gW4x6Mxi.jpg The attempt at a solution I drew the graph. It's a vertical cylinder, with its axis along the z-axis, with the top cut off by the plane z=3 but the cylinder goes down to infinity. The radius of the cylinder is 1...
  41. phosgene

    Derive an expression for the flux through a sphere

    Homework Statement Three charges with values + 20 μC, -10 μC and -10 μC are placed at the corners of a 0.10m square, as shown. c) Consider a sphere of radius 0.3m which totally encloses all three charges. Using Gauss's law derive an expression for the flux through this surface. Homework...
  42. L

    Rotating magnet inside coil = flux change?

    Apparently, that's how a lot of car speedometers work... but I don't understand how a rotating magnet inside a coil (or any conductive material, really) can induce a current in the coil. I can understand how pushing a magnet in and out through a coil can induce current, because Flux = Area...
  43. 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
  44. E

    Gauss Law and Flux for variable charge density in a sphere

    Gauss Law and Flux for variable charge density in a sphere Homework Statement The charge density within a sphere varies as a constant, a, times its radius, r. Find an expression for the direction and magnitude of the electric flux, D, within the sphereHomework Equations Gauss' Law sphere...
  45. S

    How to find flux through certain sides of a surface with divergence theorem.

    Homework Statement Given a vector field \textbf{F} and a composite (with this I mean cuboids, cylinders, etc. and not spheres for example) surface S, how do I calculate the flux through only some of the sides of S? I am interested in a general way to do this, but right now I am struggling with...
  46. P

    Exploring Gauss' Law of Flux & Newton's Shell Method for Hollow Spheres

    While I do see how this makes sense using Newton’s Shell method, I don’t see how Gauss’ Law of Flux for a closed surface proves the same thing. Both Gauss’ Law of Flux and Newton’s Shell method make perfect sense to me in showing that when dealing with a point outside the hollow conducting...
  47. T

    Magnetic flux through a closed surface

    This is always zero, right? What if you construct a closed surface which only encompasses one of the poles of a magnet? Surely there would then be a non-zero flux as the inside of the surface would constitute a source (or sink) of magnetic field lines. I'm new to electromagnetism, so any...
  48. B

    Magnetic flux through a coil. Field generated by a straight conductor.

    Hi! I'm stuck on a problem concerning the magnetic field produced by a long straight conductor: A triangular piece of conductor (N=1) rests in the vicinity of a long straight conductor with a current I=50A. What is the magnetic flux through the triangle if a=1cm? (See attached file). My...
  49. Z

    Which equation should I use to calculate flux for a point charge in a sphere?

    Calculate the flux, due to a point charge of 100 nC at the origin, that penetrates a sphere of radius 0.01 m centred at the origin. Would anyone know which equation I should be using for this problem? Thank you.
  50. J

    Calculate the flux across a surface using the definition of flux

    Find the flux of F= <XY,YZ,XZ> across the surface S of the cube {lXl≤1, lYl≤1,lZl≤1} using the given definition of flux. The first part of this problem asked me to solve using the diveregence theorem, which I did with a result of 0. I've been racking my brain on this part, seems the trickiest...
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