What is Electromagnetic induction: Definition and 252 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. Pushoam

    Faraday's law of electromagnetic induction -- Motional EMF

    There is magnetic field in B = B ##\hat z## in a region from x=0 to x=l. There is a metal rectangular wire loop with length l and width w in x- y plane with coordinates of four corners as (0,0),(0,w),(l,0),(l,w). This loop is moved with velocity v=v##\hat x##. Now according to Faraday's law...
  2. D

    Electromagnetic Induction repulsion

    Homework Statement http://imgur.com/a/7CUcU What happens when you close W? What happens when you open W again at Q? If there is a ring of metal at Q, on the coil. Homework Equations There is no relevant equations in this case. The Attempt at a Solution North will be on top and south on the...
  3. P

    Electromagnetic induction in current loops

    would be really grateful if someone could help throw some light on this - its probably really simple but I am typing myself up in loops! I have a piece of wire which is placed in an external AC magnetic field which is varying sinusoidally. The wire is folded to make two rings of radii r1 and r2...
  4. Toby_phys

    The slowing down of a Farady disc

    Homework Statement A homopolar generator consists of a metal disc of radius ##a## and a central axle which has radius ##a/4##. The disc has resistivity ##\rho## and thickness ##t##. It is rotated in a uniform magnetic field ##B## about an axis through the centre, which is parallel to ##B## and...
  5. F

    Calculating Magnetic Flux Change in Moving Coil Experiment

    Homework Statement We have a coil with cross-sectional area of 2.4m^2. Magnetic flux density is of 0.29T Number of turns are 1. Initially the coil is parallel to magnetic field lines. (Coil's normal vector is perpendicular to field vector) Calculate the change in magnetic flux when coil is...
  6. Xubi

    What is the curl of the electric field produced by changing magnetic flux?

    Homework Statement My book says that the electric field produced by changing magnetic flux is nonconservative in nature but it doesn't give any explanation. Homework EquationsThe Attempt at a Solution
  7. Xubi

    Exploring Electromagnetic Induction: A Rotating Ring in a Magnetic Field

    Homework Statement A ring of mass m, radius R having charge q uniformly distributed over it and free to rotate about its own axis is placed in a region having a magnetic field B parallel to its axis. If the magnetic field is suddenly switched off, the angular velocity acquired by the ring...
  8. C

    Flux through rim created by moving circuit and induced EMF

    In Purcell- Electricty and Magnetism book, in the chapter on electromagnetic induction, I found the following explanation regarding the magnetic flux through a circuit of area ##S##. Consider the circuit in figure, moving in a time ##dt## in a magnetic field ##B##, constant in time (but not...
  9. A

    B Why can't induced EMF in a straight conductor produce a current?

    I just read in my textbook that it is impossible to harness electricity from the induced emf if the velocity of a conductor is parallel to its straight length. Let me elucidate further: a magnetic field goes into the page and a straight conductor is moved straight down or up (perpendicular to...
  10. hackhard

    Graphite electromagnetic induction

    since graphite conducts. if spiral shape is drawn with pencil on the wall (thick , dark lines) will a voltage difference appear between inner and outer end of the spiral when a varying magnetic field is switched on, normal to wall
  11. mikemartinlfs

    Electromagnetic Induction (Long straight wire above circulua

    Homework Statement A circular loop of wire is placed next to a long straight wire. The current I in the long straight wire is increasing. What direction is the current that's induced in the circular loop? Homework Equations The Attempt at a Solution I'm aware that the answer is clockwise...
  12. P

    Induced Magnetic Moment (vector) vs. Induced EMF (scalar)

    When I induce magnetic flux through a closed loop, I should expect the lines of flux produced by current in that loop to oppose the change of flux through that loop. But what happens when that loop, say a rectangular loop, is curved into the shape of the letter J (like a candy cane) and my flux...
  13. Narayanan KR

    Can capacitors receive EM energy?

    Dynamos and transformers have inductor coils reacting with changing magnetic fields and importing energy into the circuit in form of induced current 1. What about the counterpart of above principle in case of capacitors? 2. Will capacitors interact with...
  14. Aafia

    What is induced magnetic field?

    What is emf in the coil? As far as I know about emf is that it is potential difference between two terminals of a source but what if it is induced in coil by changing flux linkage. What exactly happen when emf is induced?
  15. S

    What is the value of induced magnetic field?

    Homework Statement Two coencenteric metalic shell has inner radius $r_1$ outer radius $r_2$. We place along axis infinity wire has $\lambda$ charge in per unit length. The inner region of metalic shells inserted with relative permabilitty coefficent $\epsilon$. This system rotates with $\omega$...
  16. Icy98

    Understanding EMF and Charge Separation in a Changing Magnetic Field

    Homework Statement When there is a changing magnetic flux, emf is induced in the solenoid. The solenoid is made up of circular loops of wire. My first question is, since emd is induced in the solenoid, is there a site of higher voltage and another site of lower voltage? My second question is...
  17. H

    Electromagnetic induction question, coils and magnets

    Say you have a coil connected in a closed circuit. You then move a magnet inside of the coil and it remains stationary inside of the coil. Is the magnet, even though it is stationary, still inducing an emf in the coil or is it not? I'm guessing it doesn't induce an emf in the coil because...
  18. Neha98

    When Does the Rate of Change of Magnetic Flux Equal Zero?

    When does the rate of change of magnetic flux in linkage with a coil rotating in a uniform magnetic field equal zero?
  19. Omega0

    Why Does a Second Solenoid Feel a Strong Induction in Electromagnetic Induction?

    Hi, I have a trivial question about electrodynamics. If you have a very long coil, a long solenoid. Keep the current constant and you will have no \vec{B} outside (magnetostatics). Let's write down the Maxwell equations: \begin{matrix} \nabla\cdot\vec{B} &= &0 \\ \nabla\times\vec{E} &=...
  20. Karan Punjabi

    Why Doesn't Current Flow Continuously When Magnetic Flux is Permanently Changed?

    Guys, I have read Lenz's law and Faraday's law. My question is when the current is overall trying to keep the magnetic flux constant as that in initial time then if I permanently change the flux then why the current is not flowing through the conductor continuously to keep initial flux constant...
  21. Biker

    How does a magnetic field induce an electric current?

    Trying to understand how a magnetic field induces an electric current Suppose you have a wire in the magnetic field like this: If you move the wire with a velocity of V to the left. Then the magnetic field should exert a force on the wire which ultimately on the charges in the wire. According...
  22. Narayanan KR

    A motor design to defy Lenz' law?

    1. The two rotors (purple, green) are electricaly isolated but mechanically fit to rotate along same axis 2. The motor action on the left side rotor will move the armature set, this will produce currents in right side rotor that will pass via a variable load. 3. do you see the magnetic fields...
  23. Narayanan KR

    I Strange Magnus Force in a Whirlpool

    1. Imagine a big river with water flowing constant velocity , assume there is a whirlpool at center as shown in the figure. 2. Because of the magnus force the whirlpool should move towards left or right towards river bank depending on the spin, but it does't happens it just stays fine in its...
  24. W

    Help using electromagnetic induction

    Homework Statement I am attempting to create a generator using electromagnetic induction. I am using a push pull system to move a bar magnet through a coil to create current. But I am unsure of the dimensions to build it with and when I attempt to use the equation I get stuck. I am looking for...
  25. alexandria

    Effects of Reversing Magnet Motion on Induced Current and Magnetic Field

    Homework Statement Homework Equations no equations required 3. The Attempt at a Solution so here are my answers, can some please verify if these are correct. Thanks in advance :) a) i have no idea if I am labelling the poles correctly, or if the induced current is in the right direction ...
  26. E

    Understanding Electromagnetic Induction and Toppling of a Conducting Ring

    Homework Statement A uniform conducting ring of mass π kg and radius 1 m is kept on a smooth horizontal table. A uniform but time varying magnetic field ##\vec{B} = (\hat{i} + t^2\hat{j} ) T## is present in the region (where t is in sec and the positive y-axis is in vertically upward direction...
  27. F

    Electromagnetic induction in a U shaped conductor

    Homework Statement [/B] A 0.393 m long metal bar is pulled to the left by an applied force F. The bar rides on a parallel metal rails connected through a 42.9 ohm resistor as shown in the figure. So the apparatus makes a complete circuit. You can ignore the resistance of the bars and the rails...
  28. Rmehtany

    Understanding Lenz's Law and the Right Hand Rule in Electromagnetic Induction

    Homework Statement Homework Equations Not really? I just used the right hand rule and Lenz's law The Attempt at a Solution By the right hand rule, outside of loop 1, the magnetic field is out of the page. However, increasing resistance means that field is weakening. We know by Lenz's law...
  29. erashish14

    Electromagnetic Induction Help Requested

    Hi Experts, I'm doing an experiment of Electromagnetic Induction (producing current by changing magnetic field i.e. by circulating magnetic wheel of N52 Neodymium Magnets around copper coil), but what i found when the speed of wheel is HIGH, the Output Current is LOW (in range of .02...
  30. E

    Electromagnetic induction graph

    Homework Statement A small bar magnet is being slowly inserted with constant velocity inside a solenoid as shown in figure. Which graph best represents the relationship between emf induced with time Homework Equations ε = -dφ/dt φ = B.A The Attempt at a Solution Since the magnet is brought...
  31. A

    Electromagnetic induction by a rotating sphere

    Homework Statement http://physics.columbia.edu/files/physics/content/Quals2010Sec2.pdf Problem 1 Consider a rigid, ideally conducting sphere of radius R, with total charge zero. The sphere rotates with angular velocity Ω, ΩR<<c. Suppose a dipole magnetic field threads the sphere. the dipole is...
  32. F

    Can anyone explain this anomaly?

    Homework Statement Hi, so during an experiment, I spun a magnet inside a coil of wire in order to induce an emf, and measure the input power and output power. One of the things I found was that the slower the magnet spun (ie the smaller the input voltage to the motor) the larger the induced...
  33. R

    Electromagnetic Induction concept understanding

    Homework Statement Using a galvanometer and a coil, we thrust a magnet with a defined north and south pole into the coil and the galvanometer measured the induced current created. Now, depending on how the coil flow(front to back or vice versa) the galvanometer measured an induced current...
  34. M

    Electromagnetic Induction in a moving DC circuit

    Consider a closed electric circuit consisting of a conducting straight rod connected to a DC voltage source switched on. In steady state the current flowing through the conductor creates a steady magnetic field around it with magnetic flux lines that can be represented as concentric circles...
  35. A

    Understanding Electromagnetic Induction: Flux and Induced e.m.f.

    I'm studying electromagnetic induction and I'm trying to understand a couple of things: Why is the flux greatest when the angle between the conductor and magnetic field is 90 degrees? How does the induced e.m.f oppose the change which induces it? My thoughts: The flux is greatest when the angle...
  36. Y

    Electromagnetic Induction in a disc

    Homework Statement Please see the attached file.Homework Equations $$\frac{dΦ}{dt} = ε$$The Attempt at a Solution The only way I see is to apply some conservation of energy. But I don't know how. The potential energy is being converted to rotational energy. But how do I find the potential energy?
  37. S

    Electromagnetic Induction capacitor

    Consider the arrangements shown in figure in which the north pole of a magnet is moved away from a thick conducting loop containing capacitor. Then excess positive charge will arrive on : (Plate B = answer) Am i correct in marking the side facing the magnet as south pole? ( because of Lenz...
  38. Zahid Iftikhar

    Why is EMF generated by changing magnetic flux?

    I am fixed to find out the reason what makes the charges get separated in conductor causing an emf leading to induced current. A very good reason exists for motional emf. It can be explained with the help of F=qvBsinΘ.
  39. R

    What could cause significant magnetic field shifts at home?

    Hi everyone. I have a question that I would be grateful to receive your insights on. In our bedroom, we have a LED strip running from a typical 12V transformer. We turn it off at night using the controller box, which is in between the LEDs and the transformer. The thing is, a couple of times...
  40. Mr Davis 97

    Is a battery needed for electromagnetic induction?

    I am just scraping the surface of electromagnetic induction, and I have some questions. First, let me illustrate what I know. I know that in a simple circuit with a battery and a switch, when the switch is turned on, a current flows which produces a magnetic field of strength in proportion to...
  41. H Smith 94

    NFC/RFID devices -- How do they transmit data?

    Hi all, I am designing an NFC device but am still a little unsure about the principles behind NFC/RFID. From what I understand: A primary coil constantly emits a 'carrier frequency' magnetic field. This field induces an e.m.f. on a passive secondary coil which is in a secondary circuit. The...
  42. Cookiey

    Induced Emf due to changing magnetic flux

    If we have a conducting loop, and a magnet (say North pole first) is pushed into it; that induces and emf and hence a current in the coil due to the changing magnetic flux, right? According to Lenz' law, the direction of the current is such that it opposes the change. So from the side the magnet...
  43. D

    MHB How Does Coil Orientation Affect Induced EMF in Electromagnetic Induction?

    hello guys! I am confused about determining the equation for the induced emf in a rectangular coil with n turns rotating in a uniform magnetic field. According to faraday's law of EMI the emf induced in a coil of wire is the rate of change of flux passing through it $E_{induced}...
  44. J

    Electromagnetic Induction Project Help

    Hi, trying to http://physics.stackexchange.com/questions/189766/teslas-egg-of-columbus# Tesla's egg of Columbus for a science project (). I have managed to cast a small rod of solid aluminium into a solid egg shaped piece of aluminium. I also have a large glass bowl that could sit inside an...
  45. PhysixChick

    Electromagnetic Induction - Concentric Circles

    Homework Statement A small circular metal ring of radius r is concentric with a large circular metal ring of radius 10r. Current in the outer ring flows counterclockwise due to an unpictured power supply. By adjusting the power supply, you can adjust I, the current in the large ring. The graph...
  46. B

    A.c. current and induced force

    when A current-carrying conductor is placed in A magnetic field due to the interference of both magnetic fields,the field is made variable so a force will be induced on the Conductor. so my question is, If an Ac current is passed through conductor it will have variable magnetic field will it...
  47. I

    Is there an electromagnetic transducer to melt ice?

    Hi I have a project to were I would like to melt ice from several feet away. Is there an electromagnetic transducer that I can operate to melt ice? What resonate frequency would I need to use? Any ideas? Thanks
  48. J

    Electromagnetic induction question

    I seem to have a fundamental misunderstanding of the principle here. in the previous part it was required to sketch the graph for the hall probe. I knew since the speed was constant the field was cut at a constant rate hence a straight line was needed. However I did not understand why it...
  49. R

    Electromagnetic induction of a wire in a complete circuit

    Say for you had a wire in a complete circuit inside a magnetic field (pointing inwards) perpendicular to the wire. You move the wire across (to the right) , cutting lines of flux, this induces a current in the wire. The induced current acts upwards using the dynamo rule (thumb is motion...
  50. C

    How Coulomb's Law relates to generators? (voltage)

    Homework Statement In science class, we are supposed to explain how a generator works and functions. However, we have to incorporate coulomb's law in our explanation. Homework Equations F=kQ1Q2/r^2<-- coulomb's law The Attempt at a Solution How I understood it was that a generator consists of...
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