What is Magnetic induction: Definition and 81 Discussions

Electromagnetic or magnetic induction is the production of an electromotive force across an electrical conductor in a changing magnetic field.
Michael Faraday is generally credited with the discovery of induction in 1831, and James Clerk Maxwell mathematically described it as Faraday's law of induction. Lenz's law describes the direction of the induced field. Faraday's law was later generalized to become the Maxwell–Faraday equation, one of the four Maxwell equations in his theory of electromagnetism.
Electromagnetic induction has found many applications, including electrical components such as inductors and transformers, and devices such as electric motors and generators.

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  1. L

    Find the magnetic induction vector

    I can find the magnetic induction vector of the first conductor at a given point using the formula (its 6,667*10^-7 Tl) but I don’t understand what needs to be done with the second conductor. I have come across similar problems in which, however, the distance from the second conductor to the...
  2. Lotto

    How to calculate magnetic induction just beyond the end of the magnet?

    I know I should use a limit $$B=\lim_{r\to l}{\frac{\mu}{4\pi}\cdot \frac{4rml}{{\left({r}^2-l^2\right)}^2}},$$,but in Wolfram I get a weird solution. https://www.wolframalpha.com/input?i2d=true&i=Limit[Divide[4rl,Power[\(40)Power[r,2]-Power[l,2]\(41),2]],r->l] What is the solution? It...
  3. F

    Question about a simple model for for back EMF

    Summary:: I've found an exercise about sparks caused by back emf. The exercise is based on a mathematical model of the current flowing in the circuit around the time when the switch is closed. I'm wondering to what extend that model is realistic The exercise I'm referring to proposes this...
  4. P

    Calculating Magnetic Induction of Moving Planar Condensator

    Summary:: A planar condensator with the distance between the plates d, is moving with velocity V. The charge fidderence is U. Find the magnetic induction B, between the plates during the motion I have solved this problem, but I am not sure about the solution, can anyone, please, tell me if I...
  5. Quarinteen

    EM fields and magnetic induction from an experiment

    If you take copper wire and wrap it tightly around a bolt will that alone create and hold a magnetic field? I add an image for clarification
  6. phys194

    EM: Separation of variables to find magnetic induction

    Consider the static field configuration shown in the image. There are three layers: 0 = vacuum, 1 = magneto-optic fluid and 2 = covering shell. Each of these layers have their own permittivity and permeability (ε_i,μ_i) (isotrope). A uniform electric field H_0 = H_0/sqrt(2) * (e_x + e_y) is...
  7. S

    Verify Magnetic Induction Homework: 50A Copper Wire 0.5*10-2m

    Homework Statement A current of 50A flows through a copper wire of diameter 0.5 * 10-2m. The magnetic induction on its surface will be: A)4*102T B)4*10-2 C) 4*10-3 D)none of these Homework EquationsThe Attempt at a Solution I just want to verify my solution, as the answer keys are currently...
  8. Abhimessi10

    Motion of a charged particle in magnetic field

    Homework Statement A particle of charge -q and mass m enterd magnetic field B at A with speed v1 at an angle alpha and leaves the field at C with v2 at angle beta.Then, a)alpha=beta b)v1=v2 c)particle remains in the field for time t=(2m(pi-alpha))/qB d)All of these Please see image below...
  9. P

    B GoalRef Technology Basics: Low Frequency Magnetic Fields & Coils

    Hi, I am interested in the basics of goalref technology however there is not many material out there. What i want to know is why does the magnetic fields have to be low frequency? and how does it detect if the ball has fully crossed the line? And lastly what is the purpose of the coils...
  10. I

    Magnetic field created by a current carrying wire

    Hi, I studied the Maxwell laws and the Biot Savart law and I found something I cannot answer. If you have a finite wire carrying current (let say 5m long) and you want to determine the magnetic induction vector due to it at some point that has distance r from the wire, you have 2 options I...
  11. F

    EMF induced in a coil encircling an ideal solenoid

    Homework Statement A current I(t)= (0,160 A s^{-3}) t^3 flows through an ideal solenoid with a turns density n = 9,00 \cdot 10^{-3} m^{-1} and a cross sectional area A_s=2,00\cdot 10^{-4} m^2 A single loop of wire has the same axis as the solenoid, but its radius is larger. That is: the loop...
  12. T

    Simple Question about the direction of magnetic induction

    Homework Statement There is a magnetic field B=0.02 Tesla and its direction is toward the plane (perpendicular to plane, shown by X X X X X - I'm not sure how to say this direction in English,sorry). we have a copper wire (uniform bar) perpendicular to magnetic field from south to north. we...
  13. D

    Calculating magnetic induction in a triangle

    Homework Statement Three very long parallel conductors situated in the air make a direct-symmetrical 3-Phase system. The conductors pass through the A B C points of the triangle of side ##a##. The currents in the conductor form a direct-symmetrical 3-Phase system. Effective values of currents...
  14. A

    Magnetic/electromagnetic induction

    Suppose there is a coil around a C-shaped iron core with a dipole magnet in the gap as shown in the dynamo below. As the magnet is spinning, in order to oppose the force, a changing pole is produced in the iron. (Eg. As N-pole approaches the iron core, a north pole is induced to oppose the...
  15. B

    Jackson problem 5.4: Magnetic induction in a current-free region

    Homework Statement Homework EquationsThe Attempt at a Solution I think that is taylor series expansion, How that can be expanded right that? even b0, b1 ... is not a differential term. The solution just use b(z) = Bz(0,z)
  16. B

    Simple calculation about Magnetic induction

    Homework Statement Homework EquationsThe Attempt at a Solution Why does the second term become zero??
  17. S

    I Hall Effect & Magnetic Induction Explained

    Can someone explain in detail if halls effect is magnetic induction?
  18. B

    Question about Magnetic induction of circular loop

    Homework Statement Homework EquationsThe Attempt at a Solution This is what i did about (a) but i don't know how to approach (b), it doesn't have x,y components, only Bz component.
  19. Clara Chung

    Question about magnetic induction.

    Homework Statement Homework EquationsThe Attempt at a Solution For cii), the answer is: Yes. When the rod moves down, it moves across the horizontal field, cutting field lines. A current will be induced to oppose the motion. The magnetic force due to the motion is vertically upward. But I...
  20. moenste

    What is the current induced in a wire loop placed in a changing magnetic field?

    Homework Statement A closed wire loop in the form of a square of side 4 cm is placed with its plane perpendicular to a uniform magnetic field, which is increasing at the rate of 0.3 T s-1. The loop has negligible inductance, and a resistance of 2 * 10-3 Ω. Calculate the current induced in the...
  21. Biker

    Magnetic induction: Lenz's law

    Homework Statement After you close the switch, There will be an induced current in the resistance R, Choose one of the following: Direction of current ... magnitude of current A to B ... decreasing A to B ... increasing B to A decreasing B to A... Increasing Homework Equations Faraday's law...
  22. M

    How Electromotive Force is Produced by Electric Generator?

    at 5:42 - What is Electromotive Force? Why does it make electrons move (make electric current) in one direction?
  23. M

    How electrons get deflected in magnetic field while moving?

    I don't understand why electron moves this way... e.g. A light object (crampled paper) going down until gets hit by the wind will go parallel (at least a few seconds) to the wind direction ... why not with electron?
  24. M

    What Causes Electrons to Move Directionally in a Wire within a Magnetic Field?

    What exactly is happening to the electrons inside the wire while it is moving quickly downwards within the Magnetic field? Why do electrons move in one direction if the wire is being push down? I don't care what direction electrons move... I want to know WHY they move in one direction?
  25. F

    Magnetic induction/ goal ref technology

    Hi, I am interested in the basics of "goal ref technology", but I was not able to find a lot of material. Just one very brief wikipedia page and some paragraphs at the http://www.iis.fraunhofer.de/en/ff/kom/proj/goalref.html#. Does this work a bit like the anti shoplifting RFID tags? As far...
  26. D

    The size and direction of magnetic induction and force

    Homework Statement Hello, I have this problem: Four long straight parallel wires are placed in vacuum according to the picture, the distance between each wire is a = 20 cm. Through each wire flows electric current I = 20 A in the specified direction. What is the size and direction of magnetic...
  27. M

    Magnetic Induction: Homework Help

    Homework Statement Homework Equations I am not really good at this topic, but I think you would need both the right hand rules (one that involves finding direction of current via magnetic field as well as the one for finding magnetic force) The Attempt at a Solution So I drew out magnetic...
  28. M

    Help with magnetic induction and finding induced current

    Homework Statement I have attached a picture that details the problem. This is my practice test and I have no clue what I am doing wrong. Essentially a loop of wire is moving in constant velocity into a magnetic field. The magnetic field lines are pointing into the page. The problem is...
  29. Z

    How Is Magnetic Induction Calculated in a Triangle of Parallel Wires?

    Homework Statement Three parallel wires are put in the angles of an equilateral triangle with sides 14 cm. The values of the currents are 10A,10A, 20A and the first and third are in different directions. Find the magnetic induction in the center of the triangle Homework Equations B=I*μ0/2*pi*d...
  30. Z

    Find the induction of the magnetic field at the point O

    Homework Statement In a wire passes the current I=21A. A part of the wire is bent to form three consecutive sides of a square with sides 40 cm. Find the induction of the magnetic field in the point O which is the center of the square. Homework Equations B=I*μ0*/2*pi*d The Attempt at a Solution...
  31. Titan97

    Calculating Induced EMF in a Circular Region with Decreasing Magnetic Field

    Homework Statement In the below figure, magnetic field is decreasing at a rate of 1.5T/s in a circular region of radius 2m. EMF developed in the rod will be? Homework Equations $$V_{\text{induced}}=-A\frac{\mathrm{d}B}{\mathrm{d}t}$$ The Attempt at a Solution I tried using induced electric...
  32. UncertaintyAjay

    Current Growth due to Magnetic Induction

    What factors affect the rate of growth of current when an emf is induced in a coil?
  33. M

    Magnetic Induction in Two Different Media

    From Faraday's law of induction we know if we have a coil with ac current it will create ac current to other coil placed within magnetic field. My question is if one coil is in water and another coil is in air how I can calculate the induced emf?
  34. K

    Magnetic Induction on Wireless Earbuds

    I was thinking about buying these new wireless earbuds called DASH. They are made by a kickstarter company Bragi. They recently told us that in order to connect both earbuds together and also connect it to a device using bluetooth they needed to use magnetic induction. I was wondering what that...
  35. C

    Finding the Magnetic Field in a System with Intersecting Current-Carrying Pieces

    Homework Statement In the system shown in the picture, there's a current whose constant density is J=0,5A/mm^2. System contains two pieces as shown in the picture, in the area where two pieces intersect, there's no current. If R=1mm and a=1,25mm (a - distance between centers of the circles)...
  36. A

    A circular loop over a magnetic field directed outwards

    Homework Statement There is a counterclockwise current I in a circular loop of wire situated in an external magnetic field directed out of the page as shown. The effect of the forces that act on this current is to make the loop Select one: a. expand in size X b. contract in size c...
  37. D

    Homework Help on Kirchoff's Laws and Magnetic Induction

    Homework Statement I am stuck on 2 and 3. I attached all the problems and variable and unknownsHomework Equations I attached my work for 1, 2, and 3. I'm not sure if it is right though. [/B]The Attempt at a Solution Can someone check my work for problems 1, 2, 3 and 4? The equations...
  38. M

    How Do Faraday's Law and the EMF = BLv Equation Relate?

    Alright, I need to put my question in the context of the probably ubiquitous example of a conductor rod moving perpendicularly over a magnetic field to generate an emf between the two sides of the rod. That emf is equal to BLv (magnetic field, length, velocity) according to my book(studying for...
  39. R

    Magnetic Induction (Non-uniform Current)

    Homework Statement long wire of radius R0 carries a current density j given by Find the magnetic induction B inside and outside the wire. Homework Equations Current density: ##J=\frac{I}{A}## Ampere's law: ##\oint B.dl = \mu_0 I_{enc}## The Attempt at a Solution For the magnetic field...
  40. B

    Magnetic Induction Through a Moving Wire

    Homework Statement A very long u-shape conducting wire is placed vertically in a constant magnetic field. The magnetic field is perpendicular to the plane of the wire. The strength of the magnetic field is B = 0.9 tesla. A conducting rod is placed on the wire, as shown in the picture. The...
  41. A

    Metal rod rotating in magnetic induction.

    Homework Statement A metal rod (1/sqrt(pi)) m long rotates about one of its ends in a plane perpendicular to magnetic induction of 5*10^-3 T. Calculate the number of revolutions made by the rod if EMF induced between the ends of the rod is 1.5 mV. I have been thinking about this problem for...
  42. P

    What are the Induced Poles in Coaxial Coils Facing a Moving Bar Magnet?

    Homework Statement A bar magnet is moved between 2 coaxial coils A and B as shown in the figure.The end planes of the two coaxial coils facing the magnet due to induction will behave? Homework Equations The Attempt at a Solution My solution: It will induce south pole in A and B...
  43. R

    Magnetic Induction and Magnetic Field

    Homework Statement I would appreciate some help with the following problem: http://img407.imageshack.us/img407/7647/questionb.jpg Homework Equations This is an equation derived from Biot-Savart law: B= \frac{\mu_0 I}{4 \pi s} \int^{\theta_2}_{\theta_1} cos \theta d \theta =...
  44. M

    Question about magnetic induction

    hi everyone iam happy to join physics forums i 'd like to ask a question about magnetic induction if i have a current carrying wire(connected to a battery=V) of length (L)& of intensity (I) & perpendicular to a uniform magnetic field(B) then a force act on it (F=LIB) so when it moves...if it...
  45. Telemachus

    Magnetic induction for a tesla flat spiral coil

    Hi there. I have a current I running throught a tesla spiral coil, and I have to compute the magnetic field at the center of it. The tesla coil has N turns, and an inner radius a, and outer radius b. This is the tesla spiral coil: The courrent enters through the outer cable, and goes out...
  46. X

    Magnetic Induction: EMF Function of Time

    Hi, I've been thinking about the shape of the voltage waveform induced by a magnet falling through a coil. I know (both intuitively and from empirical experience) that the voltage should become increasingly positive as the magnet approaches the coil, then it should decrease rapidly...
  47. D

    Can Magnetic Induction Be Used to Boost or Weaken Magnets Remotely?

    new guy here with a simple magnetic theory question. if i were to coil 10 turns of insulated wire around an 1/8" round x 1" long neodymium magnet, then wire it in parallel to a second magnet with 20 turns of the same gauge wire, what kind of change could i exspect in the second magnets field...
  48. A

    Magnetic Induction: Investigating Unmagnetized Pipe

    Hello, I wasn't really sure as to where to post this, since it kinda doesn't really fit in with the listed categories, but I have a question. I work at a chem lab that specializes in Non-Destructive testing, and I am also minoring in Non-Destructive testing in college. In the engineering...
  49. B

    Ratio magnetic induction between 2 solenoids

    We have 2 solenoids : S1 and S2 The coils are wind up as close as they can get and both have length L. They are both made from the same material and have the same length. They are both connected to a DV source. S2 has a wire with a double diameter The ratio between B1 and B2 then is? I...
  50. F

    Magnetic induction of infinite conducting sheet using Ampere's Law

    Homework Statement http://i.imgur.com/j3uzQ.png" to screenshot of question Homework Equations The "Integral Form" the question refers to is the http://upload.wikimedia.org/math/0/3/1/0311484f33c932135c09ab12ca8d1a29.png" The Attempt at a Solution The hint hasn't really helped me...