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

    Induction heater with high Q factor

    Consider Parallel LC Resonance Induction heater. The material to be heated is from copper (it has relative magnetic permeability 1 and does not change with different temperatures) and is placed inside Inductor coil and there is Air gap between the coil perimeter and the material. Like this...
  2. A

    Flux linked with circular coil vs solenoid

    $$E_{max}=N^2πr^2Bω=N×0.603V$$ $$<E_{avg.}>=<N^2πr^2Bω\sin⁡(ωt)>=E_{max.}<sin⁡(ωt)>=0$$ $$I_{max.}=N×0.0603A$$ Average Power loss=$$\frac{<(E_{ind}^2)>}{R}=N^2×0.018W$$ The correct solutions are : ##0.603## ,##0## ,##0.0603##, ##0.018## Why am I gettting an extra N? Is the emf of thin circular...
  3. M

    Electromagnetic induction (Faraday's law)

    I used the formulas above and got the right answer: ##\phi=4\pi t## ##\Phi_B=0.128\cos 4\pi t## ##\epsilon=1.61\sin 4\pi t## ##\epsilon_\text{max}=1.61\ V## But I still have a question: Faraday's law requires a closed loop, whereas the semi-circular loop I used was open on one side.
  4. J

    Best way to measure magnetic waves for electromagnetic induction

    Hi all, Looking to measure some magnetic waves being generated at an electric coil. Freq is between 0-20kHz and magnitude is pretty small <1T. Any have suggestions for the best tool to measure and log data of this magnetic waveform? Googling around, I found meters like this: [Possible spam...
  5. Manuel12

    Magnets with Halbach array in an AC generator

    As a project, I am demonstrating electromagnetic induction by making an AC generator. The magnets I currently have access to are very strong neodymimium countersunk magnets, but I noticed that they utilise a Halbach array. I am aware that this means the magnet has alternating N-S poles spaced...
  6. P

    Induced EMF due to motion of a wire perpendicular to a magnetic field

    This question appeared in a university entrance exam.Basically, if magnetic flux passing through a surface of a loop changes over time ,only then e.m.f will be induced to that loop.But here only a straight line is used and there's no chance of forming any area.So by definition there's no chance...
  7. L

    Conducting rod in equilibrium due to magnetic force

    I am having problems understanding point (b) so I would like to know if my reasoning in that part is correct and/or how to think about that part because I don't see how to justify the assumption ##v_y=0\ m/s##. Thanks. I set up the ##xyz## coordinates system in the usual way with ##xy## in the...
  8. billyt_

    Experimental investigation of Faraday's Law of Induction

    Looking at how the induced EMF is proportional to the rate of change of magnetic flux, intuitively it seems that if I increase the velocity of the magnet through the solenoid, i.e. drop it from a higher height, the EMF should increase as well. However, I am unsure if this is true and can't seem...
  9. J

    Can Resistance Determine the Torque in a Solenoid Pendulum System?

    The flux enclosed by the loop consisting of the solenoid, wires and conducting rod at an angle θ is Φ = blBsinθ, then using small angle approximations and differentiating the induced emf can be found. I know that there must be some torque opposing the motion but am unsure how to proceed.
  10. patric44

    I What is the origin of Lorenz force?

    hi guys one of my friends asked me about the origin of the electromagnetic induction, I know somehow that its related to the Lorenz force as the electrons in the conduction band of say the coil interact with the magnetic field ,which results in separation of electrons and positive ions which...
  11. Narayanan KR

    A Question on Skin Effect and Eddy Currents

    When you try to create time varying magnetic fields in solid metals, there is severe heating due to eddy currents, when you increase the frequency, just like in NDT(non destructive testing) the magnetic field is pushed away from the core to the periphery due to eddy currents opposing the field...
  12. Narayanan KR

    Interesting Links Between Faraday's EM Induction and EPR

    Imagine a magnet moving up and down so that its flux 'B' cuts the copper rod to produce an alternating emf, suppose if the movement is fast enough such that its frequency equals to the electron spin resonance frequency given by F = B x 2.8 Mhz per gauss, neglecting skin effect, more copper...
  13. B

    Waveform of Classic Electromagnetic Induction

    Hi guys, Can someone please provide graphical representation (waveform) of emf induced in coil due to a bar magnet spinning perpendicular to axis of coil. Thanks, SB
  14. Narayanan KR

    An Interesting Question on Faraday's Law of Electromagnetic Induction

    On examining Maxwell's third equation which is about time varying magnetic fields (Faraday's electromagnetic induction) we find that time varying magnetic fields produce loops of electric fields in space irrespective of whether a coil is present or not, if any coil is present then these loops of...
  15. L

    Maximum Induced Voltage of an AC Generator

    I would like to ask a question about the induced voltage of an AC generator. So, according to a graph I found on Google, the maximum induced voltage is reached when the loop is parallel to the loop. (The graph shown below.) Then I was wondering, what if the loop is initially (when it is at 0...
  16. Mr_Allod

    Electromagnetic Induction of a Disk

    Hello I'm having trouble finding the right way to apply Faraday's law to this question. I've found the flux through the disc: ##\phi = \vec A \cdot \vec B = B_{0} \sin{\omega t} \left( \frac D 2 \right)^2 \pi ## and the EMF: ##\varepsilon = - \frac {d \phi} {dt} = -B_{0} \omega \cos{\omega t}...
  17. C

    Is there a difference between Faraday’s induction experiments?

    Faraday first demonstrated his law of induction by showing that when he created a current in one wire coil it created a second current in a second coil. Another experiment showed the same effect. When he moved a magnet through a wire coil, it created a current in the coil. My question is this...
  18. K

    DIY Electromagnetic Induction Experiment

    So I was watching this video containing DIY experiments on electromagnetic induction . At minute 4:45, the dude pretty much creates a transformer without using an iron core. He runs 30-50 kHz AC in a coil (forming the primary circuit) and then brings another coil with its ends attached to a...
  19. nomadreid

    E-M fields mutual induction in E-M radiation

    In electromagnetic radiation, the electric field and the magnetic field mutually induce each other: but my impression is that it would be better to say that they are two aspects of the same wave, so that there is no time between them. However, an alternative would be that there would be that...
  20. J

    Electromagnetic induction in motors

    why does an electrical motor produce an induced back emf which is equal to V-It when terminal speed of electrica, fans or electric drills is reached
  21. Stephen Bulking

    Electromagnetic Induction exercise, is something wrong with these answers?

    1. |ε|=dΦ/dt B=μ0I×cos(0-cos180)/4πr =μ0I/2πr dΦ=BdS=μ0I×(vdtxdr)/2πr ΔΦ=(μ0I×(vdt)/2π)x∫dr/r=(μ0I×(vdt)/2π)xln(b/a) *the intergral goes from a to b |ε|=dΦ/dt=(μ0I×v×ln(b/a)/2π) i=ε/R=(μ0I×v×ln(b/a)/2πR) 2. dI/dt=-50 B=μ0NI/L ε=-dΦ/dt=-BdS/dt (*) =-NBS/dt (wait what?)...
  22. TateTheL

    Electromagnetic Induction -- Insane Idea

    Would you be able to transfer a "current" through rings of conductive and paramagnetic material? As in, have a current, which causes a magnetic field to pop up in the ring, which fluxes, and causes the next ring to have a current? I am curious because this is a research project for FLL. (There...
  23. I

    Electromagnetism EMF induction calculations

    A square conducting loop of side length a is in a non-uniform magnetic field. The loop occupies the first quadrant of the xy plane, i.e. the space between the origin (x, y) = (0,0) and the point (x,y) = (a, a). The magnetic field is in the +z direction. Develop an expression for the magnitude of...
  24. F

    Calculating Current in Moving Rods: Exploring the Blv Rule and Faraday's Law

    Homework Statement: The rod is moving on a second rod with speed of v in the magnetic field perpendicular to rod. I know its resistance per meter. I am expected to omit megnetic field created by the current and resistance at the point where rods touch each other and calculate current. I...
  25. U

    Current induced from a changing magnetic field

    This question is motivated by Problem 7.12 in Griffiths Electrodynamics book. I have not included it in the homework section, because I have already solved it correctly. However, I question whether my solution which agrees with the solution's manual is correct. Relevant Equations: $$\Phi =...
  26. Physics lover

    Amount of magnetic energy stored in a cylinder

    I first calculated Magnetic field at a distance x using Ampere's law.Then i took an element and wrote its inductance using L=Flux/Current. Then i integrated from a to b. But i arrived at nothing. Help.
  27. TOUHID11

    Calculate Induced EMF in Circular Loop: Cylindrical Coordinates

    In order to calculate for the curl of the induced electric field for a loop moving in a uniform magnetic field, and using the cylindrical coordinate system for a curl, it's my understanding that since the B field is in the 𝑧̂ direction, then so is the partial time derivative of B, and therefore...
  28. christang_1023

    Understand Faraday's Law and Lenz' Law

    Above is an example figure. 2. When a ring in a changing magnetic field is not complete (i.e. open circuit with a small gap), how to analyze the emf of the ring? According to the general form of Faraday's law, ## \oint \vec{E} \cdot d \vec{s} = -\frac{d \Phi}{dt} ##, I deduce that although it...
  29. N

    Challenging question about electromagnetic induction

    Homework Statement I have been stuck on this for weeks Homework Equations ∫E.dl = -dφ/dt The Attempt at a Solution Total EMF (V) = -dφ/dt (Where φ is the magnetic flux through the loop) ⇒V = -A(dB/dt) (Since Area remains constant) ⇒V = -Ax (x=dB/dt) ⇒V = -2xl^2 I do not know how to proceed.
  30. T

    Why Does a Voltmeter Show a Reading When an Iron Rod is Moved in Coil P?

    Homework Statement Two coils P and Q are placed close to one another. P is connected to a power supply whereas Q is only connected to a voltmeter and no supply (see attached diagram). The current in coil P is constant. An iron rod is inserted into coil P. a) Explain why during the time that...
  31. L

    Electromagnetic Induction and Faraday's Law w/ Right Hand Rule

    Homework Statement Homework Equations Right Hand Rule The Attempt at a Solution I am not understanding why the force is left. I can only figure out that the current in the solenoid is moving clockwise because of the right hand rule. From there, I see that the induced current might be...
  32. J

    The direction of induced current and magnetic field produced

    Homework Statement The figure below shows a small circular loop of wire in the plane of a long, straight wire that carries a steady current I upward. If the loop is moved from distance x_2 to distance x_1 from the straight wire, what will be the direction of the induced current in the loop and...
  33. T

    Difference between Vav and Vrms

    Homework Statement [/B] I encountered this problem during my exam. A coil of 50 turns, each with area 0.02m2 is rotated in a uniform magnetic field of magnitude 0.4T. The coil is rotated at a frequency of 60Hz. Given the average power generated is 50W, what is the resistance of the...
  34. Y

    Why does Fleming's right hand rule apply for induced current

    I know that the right hand rule applies for induced currents, and the left hand rule is for motors, but why? It doesn't seem to connect with any other physics laws and is very counter-intuitive that the current will flow in one direction rather than the opposite direction if both are...
  35. EF17xx

    Electromagnetic induction emf question

    Homework Statement The correct answer is D Homework Equations The Attempt at a Solution The current is clockwise( in the first picture at least) due to right hand rule. The magnetic flux is changing, the direction of the induced emf depends on the direction of change (increase or...
  36. MermaidWonders

    MHB What is the current in a wire loop outside a solenoid with a changing current?

    A 2000-turn solenoid is 2.0 m long and 15 cm in diameter. The solenoid current is increasing at 1.0 kA/s. (a) Find the current in the 10-cm-diameter wire loop with resistance 5.0 $\varOmega$ lying inside the solenoid and perpendicular to the solenoid axis. (b) Repeat for a similarly-oriented...
  37. S

    I Phase differences in Transformers

    How is the phase difference between the current in the primary coil and induced e.m.f. in the secondary coil be 90*??
  38. Humbleness

    Electromagnetic Induction Problem (Very Introductory)

    Homework Statement Look at the following diagram: - copy the diagram and then label the poles for the induced magnetic field and the direction of the induced current - explain what would happen to the magnetic field and the current if the direction of motion of the magnet reversed - explain...
  39. V

    Doubt in electromagnetic induction

    Homework Statement suppose a coil is placed in a changing magnetic field and the circuit is not closed will the current induce in the coil Homework EquationsThe Attempt at a Solution What I thought was that the current flows only in a closed circuit because it needs a potential difference...
  40. LonelyElectron

    Electromagnetic induction questions

    Problem: Look at the following diagram: · Copy the diagram and then label the poles for the induced magnetic field and the direction of the induced current · Explain what would happen to the magnetic field and the current if the direction of motion of the magnet is reversed ·...
  41. S

    Oscillation related to electromagnetic induction

    Homework Statement A copper ring is suspended by a long, light rod pivoted at X so that it may swing as pendulum, as shown in the diagram below. An electromagnet is mounted so that the ring passes over it as it swings. The ring is set into oscillation with switch K open. What happens to the...
  42. Pushoam

    Angular momentum due to electromagnetic induction

    Homework Statement Homework EquationsThe Attempt at a Solution ## \frac { - d \phi }{dt} = V ## V denotes emf. The current is in ## \hat \phi ## direction. Magnetic force is along ## ~\hat s ## direction. Where ## ~\hat s ## is the radially outward direction in cylindrical...
  43. Pushoam

    What is the relationship between induced emf and induced electric field?

    Homework Statement Homework EquationsThe Attempt at a SolutionThe emf gets induced due to the changing flux. The flux through the rod remains 0. So, there is no induced emf. I don’t know how to calculate induced electric field. But as there is no induced emf, so there is no induced...
  44. T

    Why does electromagnetic induction occur

    Greeting I know the field of electromagnetism is not yet fully clarified but I wonder if there is an idea,theory Why does electromagnetic induction occur only when the conductor cuts the magnetic field lines.
  45. 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...