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. S

    Why Does EMF Cancel Out When a Magnet Moves Constantly Inside a Solenoid?

    What will happen when I push a magnets into a solenoid with constant speed throughout? I understand that when the magnet leaves and enters an induced emf will occur, but in the middle no emf will occur. Why is this so? I thought that the magnetic flux linkage changes as it moves in the solenoid?
  2. T

    Why velocity affects electromagnetic induction?

    I understand that electromagnetic induction is determined because of a moving electric charge in a magnetic field, but why is the motion necessary? Why is it that motion causes electromagnetic induction and it isn't possible without motion?
  3. X

    Electromagnetic induction problem

    Homework Statement http://dc10.arabsh.com/i/03594/qn9gr42q192z.png What is the direction of current in ring 2 if : a) ring 2 moves towards ring 1 b) ring 2 moves away ring 1 The Attempt at a Solution I used Fleming right hand rule but I'm not sure if it is true, a) the...
  4. J

    Exploring Electromagnetic Induction in Coils: The Impact of Magnet Placement

    Homework Statement When we place a magnet in a long coil of wire the emf will be maximum when the magnet is at either end. What would happen when the magnet lies in the middle of the coil (i.e: the same amount of flux is interacting with the coil at all times). Would we have an induced EMF...
  5. E

    Electromagnetic Induction Question

    Can someone please tell me why the magnetic field makes the electrons flow round the coil in a generator? Does the force of the magnetic field have to go in the same direction as the coil?
  6. J

    Why Does EMF Change as a Magnet Passes Through a Coil?

    Homework Statement If I take a magnet and drop it though coil then the graph would have an increasing voltage until a maximum and then a reducing emf (until 0) and then a further reducing emf until a minimum and then an increasing emf again graph looks like this...
  7. C

    Electromagnetic induction torque-transferring slipper

    consider first , an induction motor... a rotating magnetic field is applied to an electrically conductive rotor, and the eddy currents induced will oppose the change in magnetic field experienced by the rotor, hence the rotor gets torque in an induction motor the rotating magnetic field is...
  8. A

    What Happens when a Bar Magnet Approaches a Conducting Loop?

    Fig.35 shows a light and flexible conducting loop X freely hung on a smooth horizontal rail. A bar magnet PQ approaches the loop from the right. Which one of the following descriptions about this process is correct? A If P is a N-pole, the loop will be repelled to the left and its area...
  9. G

    What is Electromagnetic Induction and How Does it Work?

    Hi everyone, So I feel sort of stupid posting what you'll probably find is a very elementary question but physics really isn't my best subject and I'm completely stumped. Thanks so much! Oh, and there's also the possibility that this question is just really badly worded. Homework Statement...
  10. P

    Does a Falling Wire Near a Magnet Experience a Magnetic Force?

    Suppose a single wire (in a horizontal position) falls toward a pole of a magnet. Does the wire slow down? A diagram is attached.
  11. P

    Electromagnetic Induction in the Earths Field

    Hi all, brand new to these forums but help you can give me some guidance with some summer exam revision! Heres a fairly simple one I can't see through for some reason, using EMF = B.u.l etc: 1. A copper disc, 250mm in diameter, is reotated at 300 rpm about a horizontal axis through its centre...
  12. M

    Help with Basic Homework, about electromagnetic induction

    Ok, so my class has spent about a day on the topic of electromagnetic induction and I really you help on this subject because tomorrow i have a quiz. I don't need you to explain it in a super detailed way but in a fashion where the teacher will realize that i actually understand these topics...
  13. B

    Can electromagnetic induction occur in a single straight wire?

    we have studied electromagnetic induction that takes place in coils, solenoids, or wires forming geometrical shape, but my question is can electromagnetic induction occur in a single straight wire by changing B the magnetic field that crosses the wire? would there be electromagnetic flux and...
  14. R

    Electromagnetic Induction, How to find direction of induced current?

    Homework Statement I have a few homework questions that ask for the direction of induced current for ex a loop of wire. I can't figure out how to find it .
  15. C

    Electromagnetic induction silly question

    I was thinking at electromagnetic induction in two parallel wires...I searched some websites about this and i found out that acording to Lenz's law :"An induced current is always in such a direction as to oppose the motion or change causing it". Acording to this an induced current is opposig the...
  16. M

    Recycled Electromagnetic Induction

    I'm not a physicist, in fact, I have absolutely no training in any related fields what so ever. I didn't even go to College. But in High School, some German guys came and took me out of class and gave me an IQ test, the results of which I was not allowed to know. However, I've come to invent...
  17. A

    Faraday's law of electromagnetic induction

    Homework Statement A flat circular coil with 139 turns, a radius of 5.74 x 10-2 m, and a resistance of 0.502 Ω is exposed to an external magnetic field that is directed perpendicular to the plane of the coil. The magnitude of the external magnetic field is changing at a rate of ΔB/Δt =...
  18. D

    Mindblowing electromagnetic induction

    Hi, I been practicing for my physics compettiotion as I stumbled upon a difficult problem.I couldn't do I for days so I turned to internet in hope someone can help me. The idea is as following: You have a frame made of wire and its area is S it rotates with a angular speed of W, in a magnetic...
  19. A

    A basic question on Electromagnetic Induction

    Homework Statement There is a circular loop in the horizontal plane and a bar magnet (with its north pole downwards) Is falling down along the axis of the loop... Now is the acceleration of the bar magnet less than,greater than or equal to g? Homework Equations The Attempt at a...
  20. kontejnjer

    Electromagnetic induction problem

    Homework Statement A circular loop with resistance 0.5 \Omega per meter of length is placed in a homogeneous magnetic field of induction B=2 Teslas. The magnetic field is perpendicular with the surface of the loop, as shown in the picture (image1). The radius of the loop is increasing...
  21. D

    Electromagnetic Induction - rod on two parallel tracks, force varies

    Homework Statement Two infinite parallel wires, having the cross sectional area 'a' and resistivity 'k' are connected at a junction point 'P'. A slide wire of negligible resistance and having mass 'm5 and length l can slide between the parallel wires, without any frictional resistance. If...
  22. S

    Question for electromagnetic induction

    Homework Statement a conducting rod of length 1 m is rotated with an angular frequency of 400/s about an axis normal to the rod passing through one of its ends .the other end of the rod is in contact with a circular metallic ring. a constant magnetc field of 0.5T parallel to the axis exists...
  23. S

    Question for electromagnetic induction

    a conducting rod of length 1 m is rotated with an angular frequency of 400/s about an axis normal to the rod passing through one of its ends .the other end of the rod is in contact with a circular metallic ring. a constant magnetc field of 0.5T parallel to the axis exists in the region.find the...
  24. D

    Calculating EMF in Electromagnetic Induction Devices

    Hi there, I'm currently working on a personal project, not really a homework question and didn't get an answer there so trying this forum. The idea is for a device that harnesses vertical motion via electromagnetic induction for the purpose of energy harvesting. I have built a prototype to...
  25. D

    Electromagnetic induction for energy harvesting

    Hi there, I'm currently working on a project that harnesses vertical motion via electromagnetic induction for the purpose of energy harvesting. I have built a prototype to confirm it's operation but haven't been able to figure out how to do the emf calculations. The device consists of a...
  26. A

    Why does a loop contract in area to minimize flux linkage?

    Homework Statement http://img269.imageshack.us/img269/8792/screenshot20100816at003.png Uploaded with ImageShack.us Homework Equations The Attempt at a Solution The answer says that the loop will reduce in area to minimize the flux linkage, but why? using Fleming's left hand...
  27. C

    Help with understanding electromagnetic induction

    When a charge is in motion, it produces a magnetic field. If the charge is in an external magnetic field, a magnetic force is induced on the charge. This I understand. When a conductor is moving relative to a magnetic field, there is an induced current in the conductor. This I don't get. If...
  28. T

    Understanding Magnetic Flux and Eddy Currents in Electromagnetic Induction

    How is magnetic flux different from magnetic field? Or rather how are they related to each other ? My thought is say there is a magnetic field acting along the x-axis direction, a conductor is allowed to fall through the magnectic field and now there is a change in magnetic field, hence...
  29. B

    Why does electromagnetic induction occur?

    I understand what electromagnetic induction is and its applications. However, I don't understand why this occurs- is there an explanation for why a changing magnetic flux induces an electric current? Thanks
  30. G

    Does Eddy Current Braking Violate the Conservation of Energy?

    Hey, I have one question about the eddy current brake, or electromagnetic induction at all. For instance, slowing a roller coaster from let me say 40m/s to 10m/s in 20m by a eddy current brake(THIS IS NO HOMEWORK!). What is about the conservation of energy in this case. can you say that E kin +...
  31. Y

    Electromagnetic Induction Multiple Choice

    Please go to the following link to see the multiple choice questions I am talking about (if I post the image directly into the thread, I shall immediately receive a warning about the size not being suitable for this forum): http://farm3.static.flickr.com/2731/4475421401_345855f17e_b.jpg...
  32. I

    A-level Physics - Faradays Law and Electromagnetic Induction

    Homework Statement The problem can be found http://www.drewett-gray.co.uk/alevel/ff&e/papers/ffe_04_Jun.pdf" (page 10 and 11) Question 4 part B i and ii Mark Scheme if needed http://www.drewett-gray.co.uk/alevel/ff&e/papers/FFE_04_Jun_MS.pdf" Homework Equations Faradays law: The induced...
  33. D

    Physical limitations of electromagnetic induction

    Hello. I am making a small induction motor and have been wondering about it's limits. I have googled a lot and can't find a helpful answer. Is there a maximum length of coil that a magnetic flux of specific strength can excite ? Thank you, Gary.
  34. L

    Why Does the Galvanometer Deflect When a Switch in a Coil Circuit is Operated?

    Homework Statement So in my textbook, they talk about have 2 coils; a primary coil that is connected in series with a battery and a switch, and a secondary coil in which is connected to a galvanometer. Now it says that when the switch in the primary circuit is closed, the meter in the...
  35. R

    How Does Electromagnetic Induction Affect the Magnetic Field in a Square Loop?

    Hello to all. What form would the magnetic field (due to the square loop) take? My understanding is that the current is changing, so the magnetic field will be changing.
  36. A

    Electromagnetic Induction Help

    I'm having a hard time understanding basic electromagnetic induction through wire loops. I can usually find out the EMF, but then I have a hard time finding the current in the loops. General advice on the matter would be extremely helpful. Thanks.
  37. K

    Electromagnetic Induction and Magnetic Flux Question

    Homework Statement A loop of are 4 cm^2 has its plane parallel to the field lines of the magnetic field, B = 0.6T, as shown in the figure. The loopis pulled in the opposite direction of the field with a constant velocity of v = 6m/s Homework Equations ΦB = BAcos ε = −BLv V =...
  38. C

    Electromagnetic Induction in AC circuits

    A 9.7 Ω resistor, a 10.8 µF capacitor, and a 27.9 mH inductor are connected in series with a 120 V (rms) source with variable frequency. (a) At what frequency will the current be maximum? Hz (b) Find the maximum rms current. A (c) Suppose you now replace the 10.8 µF...
  39. K

    Electromagnetic induction and alternating currents

    Homework Statement A solenoid with an iron core inside it is connected in series with a resistance to a battery. What happens to the defelction in the ammeter connected in the circuit when the iron core is suddenly removed? Homework Equations Inductive reactance = wL Induced e.m.f. = -...
  40. S

    Electromagnetic Induction? HELP

    Electromagnetic Induction!? HELP ! Homework Statement 1. A single horizontal loop of wire is moving in a horizontal plane at a constant speed across a uniform vertical magnetic field that "fills" and surrounds the loop. The emf induced across its terminals will be ...?? the answer was "none...
  41. W

    Why negative sighn in faraday law of electromagnetic induction?

    pleasezzzzzz anyone can clear me on this point: why -ve sighn comes in faraday law of electro magnetic induction?what is it sighnificance?if in answer value of induce EMF become -ve than waht will be its direction.
  42. J

    Electromagnetic induction - which graph is correct?

    Homework Statement A 10 cm by 10 cm square coil with 3 turns moves into a magnetic field 30 cm wide and of strength 10.0 T to the right of the diagram at a speed of 0.10 m/s as shown. http://two.xthost.info/joeykeys/1.png Sketch a graph of the induced voltage versus time, starting time...
  43. E

    How can I generate practical electricity using a pendulum and a magnetic field?

    Assume I can maintain the oscillation of a pendulum. Can I generate a practical amount of electric current by letting the pendulum oscillate in a magnetic field? (practical amount in this case means enough electricity to do useful work). 1)Do I need a series of pendula in their respective...
  44. K

    Electromagnetic Induction vs. Electromagnetic Radiation

    So, I have a few questions regarding some of the laws of electromagnetism. While I was in school, one of my classes was Electrodynamics (as an ECE undergrad). We discussed how a current through a conductor creates both magnetic and electric fields (Maxwell's equations, among others, were...
  45. X

    Electromagnetic induction; bike dynamo

    Hi, I am trying to learn more about electromagnetic induction because I want to build a generator for a wind turbine. I am a bit confused about something, hopefully someone out there can help me! I recently opened a bike dynamo. It contains a permanent magnet that can rotate, and the...
  46. G

    Insane Electromagnetic Induction Question. Challenge your brains

    Insane Electromagnetic Induction Question. Challenge your brains! :D F=BIL, F=mg There is a B field acting on the rod so we resolve that. I tried to resolve the other force vectors according to: 1. Force acting on rod by gravity 2. Force acting on rod by electromagnetic (F=...
  47. M

    Electromagnetic induction Coil testing

    Whats the easiest way to test the max output of electricity induced in an air coil. I will wire it 3 phase delta. (or double delta) Will I need a resistive load attached for current flow? What should I use? How do I test? Use a multi tester? Is there math I can use to estimate the amount. I...
  48. K

    Induced emf in a falling wire aligned with Earth's magnetic field components

    Homework Statement Whether a length of metallic wire, if placed in the geographic (a) east-west, and (b) north-south directions, and dropped freely from a height, would have an induced emf or not. Homework Equations E= - d(phi)/dt, where phi = flux intercepted by wire The Attempt at...
  49. U

    Which Axes Should a Coil Rotate Around to Induce EMF?

    http://img30.imageshack.us/img30/7309/coil.png The figure shows a coil of wire in xy-plane with a magnetic field along y-axis. Around which of the three axis should the coil be rotated in order to generate emf and current in the coil? I think the answer is X and Z AXES because in these...
  50. U

    Why Is My Calculation of EMF in Electromagnetic Induction Incorrect?

    Electromagnetic Induction Problem : Help needed The flux density B in a region between the pole faces of a horse shoe magnet is 0.5T directed vertically downward. Find the emf induced in a straight wire 5cm long, perpendicular to B when it is moved in a direction at an angle of 60 degrees with...
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