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. 2

    Back emf in a single loop of wire?

    I have been thinking about coils of wire carrying alternatingcurrent. From what I understand, a back emf is induced in the coil because there is a changing magnetic field around each individual loop of wire, and therefore there is a changing flux through each loop because the changing field...
  2. 2

    Do back force and back emf come together?

    i have heard it said that back force occurs in generators and back emf occurs in motors, however I was considering a motor and I thought that it seems to me that as the coil is rotating and it has the changing flux linkage, and thus a back end is induced in it by Lenz's law, this reduces the...
  3. J

    Electromagnetic induction of a closed circular wire

    Homework Statement (See image) a closed circular wire A lies in the plane of the wire B in the circuit. Deduce the direction. Of the induced current in A when (A) the switch is closed (B) the switch is opened (C) the wire A is raised out of the plane of the paper. Homework EquationsThe...
  4. A

    Electromagnetic induction of two wires

    I have two wires in parallel at a distance r apart. They are unequal in length. The current carrying primary generates a magnetic field B at distance r. What is the area related to the secondary through which B passes? Is it correct to assume the thickness times the length of the secondary? All...
  5. Jackson Lee

    A question about electromagnetic induction

    Hey, guys, I encountered this and confused about it. "In a perfect conductor, an arbitrarily large current can be induced, and the resulting magnetic field exactly cancels the applied field." But I suppose, according to Faraday's law,the magnitude of emf is the rate of change of magnetic flux...
  6. Z

    Elastic Potential Energy to Aid Electromagnetic Induction

    Matter can neither be created nor destroyed...but potential energy can be converted into a different kind of energy. Let's say we have a spring with a mass connected to it. This mass is a magnet, and the apparatus is inside a copper coil. It's a horizontal magnet with friction minimized at the...
  7. C

    Electromagnetic Induction and a coil of wire

    The magnetic field that is oriented perpendicularly through a 9.2 cm diameter coil of wire drops from 6.4 T to 6.1 T in 0.076 seconds. What is the emf induced in the coil? Trying to answer this. My question is, if they are perpendicular then does that mean that cos90 makes phi = BAcos theta...
  8. A

    A question about electromagnetic induction

    Hi guys I just want to know why changing magnetic flux in a coil induces emf? Thanks in advance.
  9. M

    Electromagnetic induction confusion

    I was just thinking about the "changing magnetic field through a loop induces an EMF" and thought of a conceptual question I'm having trouble with. So, imagine you have an open surface where there's a changing magnetic flux that you know (say its a plane of magnetic field coming toward you...
  10. Ackbach

    MHB Electromagnetic Induction: Problem 30.85 in Halliday and Resnick and Walker

    $\newcommand{\uvec}[1]{\boldsymbol{\hat{\textbf{#1}}}}$ There is a uniform magnetic field $\mathbf{B}$ directed along the axis, and confined to a cylindrical volume of radius $R$. The magnitude of $\mathbf{B}$ is decreasing at a constant rate of $10$ mT/s. In unit-vector notation, what is the...
  11. C

    Exercise of Electromagnetic Induction

    Homework Statement Homework Equations That is my solution: The Attempt at a Solution i solve my problem without ø=30°, I confused what this angle was used to do?
  12. F

    Calculating Power Dissipation in a Thin Conducting Disc with Induced Currents

    Homework Statement Thin conducting disc, radius a, thickness b and resistivity p (assumed to be large enough induced currents produce no magnetic field). There is a uniform B field B0sin(wt) parallel to its axis. I first had to find the electric field a distance r from the disc axis in the...
  13. D

    Electromagnetic induction (production of emf)

    Homework Statement the ans is C for this question. i really have no idea , van someone explain please? Homework Equations The Attempt at a Solution
  14. D

    Electromagnetic induction graph of E versus I

    Homework Statement for this question, i only know that E=-L dI/dt... the ans is C , can anyone explain how to get C? Homework Equations The Attempt at a Solution
  15. P

    Electromagnetic Induction Problem

    Homework Statement A 425 mA conventional current is induced in a 48.0cm wire moved through a magnetic field. A 11.5 Ω resistor is connected to the wire as shown in the diagram below. If the magnetic force acting on the wire is 323 mN, then determine the direction and magnitude of the velocity...
  16. W

    Sound Wave, Microphone and Electromagnetic Induction

    Dear all, I have encountered an issue in understanding how microphone works and I hope you guys can assist. There are two scenarios involved. In the first scenario, there is tuning fork and a microphone. The microphone contains a small disc attached to a magnet and a fixed coil. (Please...
  17. V

    Electromagnetic induction and conductor

    Hello everyone, One very basic thing about this phenomenon is not very clear to me. If a conductor moves in a region of uniform magnetic field, would it have an EMF induced across it? I'm confused because as per Faraday's law, a change in flux through the conductor is necessary for EMF to be...
  18. U

    Which case generates emf by electromagnetic induction

    1. a. coil is moved up and down in the same direction of flux. b. coil is rotated around an axis that is parallel to the flux. c. coil is rotated to the direction of the flux like a dynamo. 2. Electromagnetic inductions laws. 3. I'm really having a hard time...
  19. E

    Torque due to electromagnetic induction

    Homework Statement A circular coil of radius r carries a current I. A magnetic induction B acts at right angles to a diameter of the coil. Show that the current experiences a torque T about the diameter given by T=Iπr^{2}Bsinω, where ω is the angle between the normal to the plane of the coil...
  20. Roodles01

    How Does the Source of EMF Change with Movement in a Magnet and Coil System?

    EDIT! Hmmm, sorry. What is the difference between the origin of the emf in a small current loop when; a) a magnet is stationary & the coil moves, b) the coil is stationary & the magnet moves This was the original message, now realized to be incorrect. A current is generated when a...
  21. A

    Conceptual difficulty with Electromagnetic induction

    Hi all, I have a conceptual difficulty with the idea of induction of a current in a wire due to a changing magnetic field. Initially I was very comfortable with the idea. Upon seeing the typical setup of a square wire being rotated in a region of uniform magnetic field, I was happy to accept...
  22. S

    Electrons in electromagnetic induction

    Hello, when a coil rotates in a magnetic field an AC is produced at the ends of the coil but do that electrons come from the coil wire ? If yes, shouldn't the coil run out of electrons after some time ? thank you
  23. E

    Energy transfer in electromagnetic induction

    Consider a magnet moving towards a coil. We know that the motion of the magnet will induce a current in the coil and the direction of this induced current is to oppose the motion of the magnet. Now does the magnet experience resistance to its motion immediately as soon as it starts...
  24. A

    Electromagnetic induction between 2 coils problem.

    We know that 1)a change in current and voltage in a coil may result in induction in other stationary coil..this induction is directly related to frequency..ie The higher the frequency the more intense the induction effect. 2)we also know that there is no induction in case of DC current flow...
  25. E

    Im so confused about electromagnetic induction. Need help please?

    I first thought that electromagnetic induction disobeyed the law of conservation of energy since there is another current created by another current by changing it (AC). but then there is Lenz law that says when you have yourself an current and also a changing magnetic flux, there will be an...
  26. K

    Electromagnetic induction with two coils and an iron heart

    Homework Statement Two coils are place on an iron heart, like in the picture. The top Coil is connected to a galvanometer, the second could be connected to a power source. Homework Equations Will an electric current flow through the top coil when: a) connecting and then...
  27. D

    How to prove Fardays' law of electromagnetic induction

    Homework Statement Here is a question which frequently occurs on on our school test: "Prove Faraday's law of electromagnetic induction on the basis of principle of conservation of energy" I do not really know how to begin.Thanks!
  28. S

    Describing Electromagnetic Induction of a Guitar Pickup

    First Post! So I was curious about how I could relate my new found knowledge of electromagnetic inductance on guitar pickups and I came across this on the internet: http://www.sciencebuddies.org/science-fair-projects/project_ideas/Music_p004.shtml#background Which says, "All of these...
  29. P

    Electromagnetic Induction (EMI)

    A non conducting ring of mass m and radius R has a charge Q uniformly distributed over its circumference. This ring is placed on a rough horizontal surface such that the plane of the ring is parallel to the surface. A vertical magnetic field B=B0t2 τ is switched on. After 2 second from switching...
  30. S

    Electromagnetic induction on iron core question

    Homework Statement An iron core with a solenoid coiled around it is in a circuit with a switch and a dc current supply. In front of it, there is a iron ring tied to the ceiling such that it faces the solenoid without touching the circuit. When the switch is turned on what is observed and...
  31. O

    Electromagnetic induction problem

    Homework Statement http://imageshack.us/photo/my-images/194/55132039.png/ http://imageshack.us/photo/my-images/194/55132039.png/ How much curret flows trough circuit ABCD when the center of the circuit (O) is distance r from the straight wire? I think these are the relevant equations...
  32. S

    Electromagnetic induction near a generator

    Hi , i am a high school student ( class 10 ) and after reading about electromagnetic induction iwas thinking about what if u place a wire coil connected to a circuit in the magnetic field / near a generator ? Because electricity is turned of for a fraction of a second there will be great...
  33. E

    Electromagnetic induction question

    Hello I am new to this forum and wanted to ask a question on em induction. I know if a current passes through a wire a magnetic field around the wire is produced and can be amplified by having a coil of wire. If that is then placed in a magnetic field (like between a north and south pole...
  34. C

    Bit of confusion with coils and electromagnetic induction

    Apparently for emf to be induced in a coil, the magnetic field (or part of it) has to act along the normal to the coil face. So does this mean that the coil moves side-ways through the magnetic field? where instead of moving through its length (its longer side), it moves through the coil face...
  35. throneoo

    Need help with an electromagnetic induction problem concerning two rods

    Homework Statement Two metal rods are placed on two parallel smooth conducting rails , under uniform B field lines . The metal rod on right-hand side is initially moving at a constant velocity of 3 m/s , while the other one is initially at rest . What would be the subsequent motions of the two...
  36. B

    Electromagnetic Induction Without Air Core

    Scientifically, it doesn't make sense why you can't just wind up wire without really much air in the middle. In order to get more wire closer to the magnetic flux, why wouldn't you just wind up the coil tighter? I keep seeing ferromagnetic or air cores. Why not a tightly would wire so more...
  37. A

    Electromagnetic induction question

    Homework Statement img341.imageshack.us/img341/1338/scanpic0001a.jpg This is the picture. Sorry i can't add a link cause i do not have 10 posts. The part that i don't understand is why the aluminium ring takes a longer time to fall when an alternating current is used The Attempt at a...
  38. T

    Future Space Travel referring to Electromagnetic Induction

    Homework Statement I have a question for homework which is. "Chemical rockets are unsuitable for travel beyond close planets. Describe a method of propulsion based on electromagnetic induction which could be used for long distance space travel beyond the nearest planets." Homework Equations...
  39. C

    Electromagnetic induction inside a field with a contraint

    1. A closed loop is held stationary in the magnetic field between the north and south poles of two permanent magnets held fixed. Can we hope to generate current in the loop by using very strong magnets? well, my doubt is: as magnetic field is a vector and since we have two pairs [one...
  40. Coffee_

    Solving the Paradox of Electromagnetic Induction

    Hello everyone, I have the following problem understanding electromagnetic induction. THis is not a homework question but it's a thought experiment I seem to not succeed in doing. Let's take the situation where you move a rectangle shaped plate with a speed perpendicular to a homogenous...
  41. T

    Explanation of Electromagnetic Induction

    I took a physics competition recently and found I missed 6 questions on electromagnetic induction and the like. I've always been shaky here, so I'm wondering if anyone can give me an online resource, or just explain to me exactly how it works (i.e., Lenz's law, etc., etc.)? I'm sorry for not...
  42. M

    Electromagnetic Induction of a permanent megnet

    Hello everyone, How are you doing? I have a doubt about electromagnetic induction, in three particular cases. I need to confirm that I have the right concepts, so I ask for your help. The main problem: Imagine that you have a permanent magnet, axially polarized and rotating on its...
  43. J

    Why Is EMF Induced Only in One Direction in a Moving Conductive Square?

    Homework Statement If I move a SQUARE conductive layer in a forward direction, with a magnetic field pointing vertically upward why is an EMF only induced in the left-right plane NOT the forward-backward plane??Homework Equations The Attempt at a Solution I would have thought that as BOTH...
  44. K

    What Is the Direction of Current in a Loop Near a Current-Carrying Wire?

    Homework Statement You are holding a conducting loop of copper and looking at its circle. Behind it is a long current-carrying wire carrying the current from left to right. As you pull the loop toward you, what is the direction of current flow if any? A)No way to tell B)Counter-clockwise...
  45. H

    What really causes electromagnetic induction/ the motor effect?

    When a conducting wire is subjected to a changing magnetic field, what causes the electrons in this wire to move? Conversely, why does the movement of current in the wire (with a non-'moving' magnetic field) cause the wire to move? I understand these phenomena macroscopically (and that they...
  46. S

    Electromagnetic Induction Lab. Magnet through a coil

    I apologize in advance if some of my answers don't quite make sense. I'm generally articulate, but not when it comes to physics I'm barely grasping. I did a lab and part of it was dropping a magnet through a coil, which produced a Voltage vs Time graph using LabPro. For trial 1 we had the N...
  47. P

    Calculating Average Induced EMF in a Rotating Coil

    Homework Statement A flat coil of wire has an area of 0.010 m2and contains 100 turns. Initially the coil is oriented so that the normal to its surface is parallel to a downward constant magnetic field of 0.2 T. The coil is then rotated clockwise through an angle of 30oin a time of 0.10 s...
  48. P

    Electromagnetic Induction and an electric generator

    Homework Statement An electric generator consists of n = 500 turns of wire formed into a rectangular loop with a length of 5 cm and width of 3 cm placed in a uniform magnetic field of 2.50 T. What is the maximum value of the emf produced when the loop is spun at f = 100 rpm about an axis...
  49. M

    Electromagnetic induction question, includes solenoids

    Homework Statement This isn't a homework problem but I am very curious. How much voltage can a magnetic, about the size of a fist, generate by passing through a solenoid with about 3 loops every centimeter with being pulled by a tension of 1000 N over a distance of 2 meters...
  50. S

    Electromagnetic induction open cuircuit and how to determine direction

    When a magnet is pushed into a solenoid an induced emf occurs. So if it is a closed circuit then an induced current will flow. But if it is an open circuit then an emf will still be induced but no current this time. So will any poles be formed to repel it? What do they mean by the current...
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