What is Magnetic flux: Definition and 366 Discussions

In physics, specifically electromagnetism, the magnetic flux through a surface is the surface integral of the normal component of the magnetic field B over that surface. It is usually denoted Φ or ΦB. The SI unit of magnetic flux is the weber (Wb; in derived units, volt–seconds), and the CGS unit is the maxwell. Magnetic flux is usually measured with a fluxmeter, which contains measuring coils and electronics, that evaluates the change of voltage in the measuring coils to calculate the measurement of magnetic flux.

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  1. Y

    How Do You Calculate Magnetic Field Magnitude for a Specific Flux?

    Homework Statement A horizontal rectangular surface has dimensions 3.10cm by 3.05cm and is in a uniform magnetic field that is directed at an angle of 34.5∘ above the horizontal. What must the magnitude of the magnetic field be in order to produce a flux of 4.5E-4 Wb through the surface...
  2. B

    Connection between coloumbs , ohms and magnetic flux density

    what is the connection between coloumbs , ohms and flux !
  3. 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...
  4. S

    Magnetic flux degaussing calculations.

    Hey guys. Ok so here goes. I want to know if there is a way to calculate the flux field degaussing effect of two magnets passing by each other in repelling configuration. Like south to south. Lets say I have two magnets of neodymium N52 grade. Rockwell C scale hardness of 46. Also let's...
  5. J

    BCS Theory Magnetic Flux Question

    In superconductors, electrons form Cooper pairs that move at the same speed. Also, magnetic flux becomes quantized. Can someone explain in layman's terms why and how the magnetic flux becomes quantized? Especially in contrast to the magnetic flux in a conductor. Does it have something to do with...
  6. A

    Magnetic Flux of a partially rotating loop

    Homework Statement r=0.10 m B=0.65 T Homework Equations ampere's law? The Attempt at a Solution
  7. A

    Magnetic Flux of a Wire Sliding on L-Shaped Rail

    A conducting wire slides with constant speed of 1 m/s on a bent L shaped metalic rail. The angke between the wire and the rail is 45 deg and it remains constant during the whole motion of the wire. Perpendicular to the plane of the rail acts a magnetic field B=0.2 T in the X direction (Into the...
  8. O

    Faraday's Law of Induction; Why is it the *enclosed* magnetic flux?

    Hello Reader, Basically in Faraday's law, a change of flux over time induces an EMF. I was wondering why is it the enclosed magnetic flux and NOT the magnetic flux through the conductor that we consider. More specifically, I understand that the flux through a rectangular surface would be...
  9. H

    Does the Curl Relationship Exist in Both Directions for Vector Fields?

    We are studying electrodynamics, more specifically magnetic potential. We are given B=∇xA I saw on a certain website here http://www.ittc.ku.edu/~jstiles/220/handouts/The%20Magnetic%20Vector%20Potential.pdf that A=∇xB So is it true in general that for a vector field, the curl...
  10. M

    Magnetic Flux and Induced EMF at South Pole

    Homework Statement The magnetic field strength at the South Pole is around 66μT, and magnetic field lines point out of the Earth perpendicular to the surface. The sled is a metal square of side 0.95 m (with non-conducting wooden slats in between). What is the magnetic flux through the sled...
  11. B

    Magnetic Flux through a Rectangular Loop Due to a Straight Wire

    Homework Statement A loop of wire in the shape of a rectangle of width w and length L and a long, straight wire carrying a current I lie on a tabletop as shown in the figure below. (a) Determine the magnetic flux through the loop due to the current I. (Use any variable stated above along...
  12. G

    Calculation of the magnetic field ring current and the magnetic flux t

    This work was motivated by the lack of open source analytic formulas for calculating the magnetic field of a current ring at any point in space As the result of the theoretical calculations, which are based on the law of "Bio Savart Laplace", the analytical formulas giving the ability to...
  13. M

    What is the magnetic flux through the desk?

    Homework Statement The total magnetic field intensity at the location of Edmonton was 57652 nT on March 20, 2012, when I first wrote this question. Now, on Feb. 19, 2013, it is 57569 nT. The magnetic inclination is +75 degrees (i.e., it points downward at an angle of 75 degrees with respect to...
  14. F

    Solving Magnetic Flux Through a Sphere in a Homogeneous Field

    Homework Statement In homogeneous magnetic field the magnetic flux density vector is B = (0, 5T)ez (ez is unit vector in z direction). There is a sphere of radius R = 2cm with its centre at the origin. Find the flux crossing that half of the sphere surface for which z larger or equal to 0...
  15. L

    Solving for Magnetic Flux in a Rotating Wire Loop

    1. A loop of wire has the shape shown in the drawing. The top part of the wire is bent into a semicircle of radius . The normal to the plane of the loop is parallel to a constant magnetic field of magnitude 0.75 T. What is the change in the magnetic flux that passes through the loop when...
  16. dennisk

    Separated paraLLEL COILS WITH MAGNETIC FLUX INTO ONE

    I have two parallel air coils attached to each other but separated by 3" of air. if I move a magnet past one coil it will induce a magnetic flux into it and that will create a voltage across it. Will that voltage transfer to the other coil thereby creating a magnetic pulse in the second coil...
  17. S

    Max Power from Coil in Magnetic Flux: Turns, Voltage, Current

    Am I understand correct that when an air coil pass through magnetic flux, it create current and emf? power = IV If turns increase, do I get more power? why? If power changes, then how to get out max power.
  18. M

    Are parallel flux lines necessary for C-EMF generation?

    A friend of mine told me that in order for Back-EMF to be generated, The flux lines has to be parallel. Is that true? This question is based on a electromagnet - magnet set up. The flux lines must be parallel? At least C-EMF can be generated but if the flux lines are perpendicular it will...
  19. O

    Calculating Magnetic Flux in 3D

    Hi everybody, first time poster here. I am working on calculating the force of magnets in a 3 dimensional space. I have found a formula for the magnetic flux density at a distance z from the magnet face at this link http://www.magneticsolutions.com.au/magnet-formula.html, under Flux density at...
  20. K

    Definitions for Magnetic flux and Faraday's Law

    I was wondering if my understanding on Magnetic flux and Faraday's law was correct or not, is this okay? Magnetic flux is the number of lines in a magnetic field (Φ) Magnetic field strength (B) is the number of magnetic field lines over a given area B = Φ/A Other names for magnetic field...
  21. I

    EMF induced via change in magnetic flux vs. velocity in magnetic field

    Homework Statement (See attached diagram)--Note this problem was taken from Barron's SAT Physics Practice Test 1 #58 As the loop rotates, the induced voltage will be maximum at... a) 0 degrees and 90 degrees b) 0 degrees and 180 degrees c) 90 degrees and 270 degrees d) 180 degrees and 270...
  22. M

    Magnitude of magnetic flux of a solenoid using Biot-Savart law

    Homework Statement A 10 cm long, 1 cm diameter solenoid contains 500 turns of wire. A current that varies as I = 5Sin(100πt) Amps flows through the solenoid wire. Calculate the magnitude of the magnetic flux at the centre of the solenoid as a function of time using equation (1). Compare this...
  23. 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...
  24. O

    Electric field, magnetic flux , potetial difference

    Homework Statement As shown in the figure below, potential difference V exists between two parallel plates(a,b) that have a small hole. Uniform electric field E and magnetic flux density B exist in the region above the plates, and are perpendicular to each other. The directionof E is parallel...
  25. T

    How does wireless power transfer produce magnetic flux?

    From what I learned, for an electric current to be induced in a wire, there must be a magnetic flux. On youtube, there are lots of videos showing wireless power transfer to a lightbulb or LED. However, the light is constant. How is the magnetic flux changing in such a setup?
  26. 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...
  27. M

    Magnetic Flux Quanta - Definition & Animation

    What is "Magnetic flux quanta"? is there any animation describing this subject?
  28. B

    Problems for magnetic flux 2nd

    Homework Statement Please let me know whether it's wrong for my attached solution. Homework Equations i = (d∅/dt)/R The Attempt at a Solution In part (d), does it calculate wrong?? In part (e), where has the dissipated energy? is it for heat energy?? Thanks!
  29. B

    Calculating Magnetic Flux: A Troubleshooting Guide

    Homework Statement Please let me know whether it's wrong for my attached solution. Homework Equations magnetic flux = BAcosθ The Attempt at a Solution I don't know how to calculate the part (c) as attached file, please advise!
  30. N

    Magnetic Flux inside a Transformer

    I have read that when the secondary of a transformer has current flow, it will reduce the magnetic flux in the core. This then reduces the back-emf on the primary, causing a increase in current to reestablish the magnetic flux to what it once was. What I want to know is when the secondary...
  31. Z

    Problem with calculating magnetic flux for a single coil of wire.

    Homework Statement This is more of a general question about magnetic flux in a uniform magnetic field, but I think this is the correct place to post it. I understand that magnetic flux through an area A is the product of the magnetic flux density B and the projection of area A onto a surface...
  32. A

    Why isn't the magnetic flux of a loop infinite?

    If B~1/r2, then if we have a simple loop, B near the inner edge of the loop will be infinite (or close to it). Why then, would our flux not be infinite? I also get infinity if I take ∫ ∇ X A *da =∫B*da =∫(closed)A*dl Since A ~1/r and r~0 at the limit of our surface integral. I know I am...
  33. D

    Question about changing magnetic flux

    Homework Statement A 200-loop coil of cross sectional area 8.5 cm2 lies in the plane of the page. An external magnetic field of 0.060 T is directed out of the plane of the page. The external field decreases to 0.020 T in 12 milliseconds. What is the magnitude of the change in the external...
  34. B

    Magnetic Flux Through Wire Loop

    Homework Statement A wire loop with radius R is located a distance d from a long straight wire carrying a current I. Find the flux through the loop. Homework Equations B = \muI/(4\pi) Magnetic Field above wire \phi=B*da*cos\vartheta The Attempt at a Solution Somehow you have to...
  35. M

    Factors that would increase magnetic flux through a coil?

    24. A square coil is perpendicular to a uniform magnetic field. Which one of the following would increase the magnetic flux through the coil? A. Decreasing the area of the coil. B. Increasing the number of loops in the coil. C. Removing the coil from the magnetic field. D. Increasing the...
  36. C

    Magnetic Flux Q&A: Can Length Contraction Alter Quanta?

    Can I alter the quanta of magnetic flux using length contraction of the source creating the B field. Like for example could I get half of the flux by moving relative to the B field. Or some other fraction of it. The unit of flux is like \frac{h}{2e}
  37. M

    When is the magnetic flux on a section of a closed surface equal to zero?

    Homework Statement When is the magnetic flux on a section of a closed surface equal to zero? A. When the magnetic field is in the direction opposite that of the section’s area vector. B. When the magnetic field is in the direction of the section’s area vector. C. When the magnetic field...
  38. M

    Which describes the magnetic flux through a section of a loop?

    Homework Statement Which describes the magnetic flux through a section of a loop? A. It is a vector that is directed outward through the section. B. It is a vector that is directed inward through the section. C It is a vector that is tangent to the section. D. It is a scalar...
  39. I

    Exploring Magnetic Flux Tubes: Current, Composition, and Buoyancy

    Does a magnetic flux tube always have a current flowing in it? Where is the current? Electrons on the surface and protons inside? Why are flux tubes magnetically buoyant? That is, why is there a difference in pressure inside and outside the tube. As far as these questions go, is...
  40. 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...
  41. T

    Magnetic Flux through 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...
  42. 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...
  43. 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...
  44. 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...
  45. 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...
  46. 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...
  47. _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...
  48. 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 :)
  49. 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
  50. 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...
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