What is Faradays law: Definition and 30 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. Narayanan KR

    Orientation of Electric Fields in a Bucking Coil Setup

  2. boysenbeary

    Find maximum current in a coil using oscilloscopes and Faraday's Law?

    The experiment consists of a large field coil (connected to a current source) surrounding a coplanar and coaxial small detector coil in the center of the field coil connected to the oscilloscope. 1. Matching Current v. Time Graphs to Oscilloscope Graphs Example of one pair of graphs (I'll...
  3. Zack K

    How exactly do inductors work in an LC circuit?

    I understand Faraday's law and about induced electric fields created by a changing magnetic fields, etc. But what causes the current to oscillate in an LC circuit, with no battery? If you picture that there is current going into an inductor, and that current is decreasing over time, then you...
  4. Zack K

    Current induced on a coil by a changing magnetic flux in another coil

    I will first calculate the magnetic flux of the coil in motion. $$\frac {d\phi}{dt} = -\frac {dB_{loop}}{dt}A = -\frac{d}{dt}(\frac{\mu_o}{4\pi}\frac {2\pi NR^2I}{(R^2+z^2)^{\frac{3}{2}}})A$$differentiating in terms of ##z##, we get $$\frac {d\phi}{dt} =(\frac{\mu_o}{4\pi}\frac {6\pi^2...
  5. L

    How do I apply Maxwell's equations?

    For example, if I have a magnetic field perpendicular to some surface and I change this magnetic field with constant speed, how do I calculate the Electric field at any point on this surface, since ∫E⋅ds=k, where k is some constant, could be done with many different vector fields.
  6. PhotonSSBM

    Justifying Ampere's Law and Faradays Law with an experiment

    Homework Statement Given Ampere's Law and Faraday's Law (in differential or integral form fwiw) explain why it is easier to design an experiment to show that a changing magnetic field creates an electric field than it is to show a changing electric field creates a magnetic field. Justify your...
  7. 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...
  8. O

    What causes EMF induced in Faradays law when only B changes

    I am having trouble with deducing the origin of Maxwell's Laws, especially Faraday's Law. Obviously some of the laws has to be originated by experiments and the rest should be mere deductions. I would guess that Lorentz force law is the empirical information where we just named some terms as...
  9. TheJfactors

    Induced EMF due to changing current in straight wire

    I see a lot of problems on constant current inducing a current in another wire due to its associated magnetic field, but not so much a single wire's induced electric field. If the current along an infinitely long wire is flowing out of the page and inducing a counter-clockwise spinning magnetic...
  10. W

    Equation for the EMF generated by a spinning magnet?

    I have found an equation which gives the EMF generated in a coil when a magnet is spun near it, the equation is given as: E = FNAω × 10-8 volts. Where F is the field of the sample perpendicular to the axis of roation, N is the number of turns, A is the effective area of the coil and ω is the...
  11. DivergentSpectrum

    Conceptual difficulty with faradays law

    As i understand, the induced current in a wire equals -d(∫∫B⋅dS)/dt What is S? I know it has to be an open surface for the flux integral to be non-zero, but over what surface do i do the integral?
  12. T

    Flaw in the integral form of faradays law with large loops

    The situation is as such. you have a magnetic passing through a loop(loop 1)of wire as some time t, say you also have a larger loop of say one light year in radius surrounding loop 1, call this loop 2. at some time t the magnetic field is shut off. when this happens would loop 2 instantaneously...
  13. J

    Area perpendicular to a magnetic field from Faradays Law

    Hello Everyone, I have a question concerning the "Area perpendicular to the magnetic field". If the field was produced by a permanent magnet, would the "Area perpendicular to the magnetic field" be the same size as the Area of the permanent magnet?
  14. A

    How Does Faraday's Law Explain EMF Induction Outside a Solenoid?

    Today we did an experiment with a solenoid through which we varied the current. Around this solenoid, was a different circuit (not coupled to the coil-circuit) where we measured the potential across a resistor. By varying the current my teacher showed how the potential over the resistor would...
  15. H

    Explaining Faraday's Law: Why ε=2∅/Δt?

    Hi Could someone explain why ε=Δ∅/Δt becomes 2∅/Δt?? i don't see how the change in magnetic flux is 2∅.
  16. jegues

    EM Plane Wave + Faradays Law

    Homework Statement See figure attached. The file attach isn't working so here is a link to the problem statement, http://imgur.com/FhoIe The answer is given in a red box. Homework Equations The Attempt at a Solution The file attach isn't working so here is a link to my...
  17. jegues

    Various Faradays Law Questions

    Homework Statement See the figures attached for each of the individual problem statements. Homework Equations The Attempt at a Solution I'll start by explaining my concerns for each problem, P1) Did I plot the Iinduced waveform correctly? I'm having some trouble picturing...
  18. jegues

    Direction of Induced EMF (Faradays Law) Confusion

    Homework Statement See figure attached. Homework Equations The Attempt at a Solution If we attempt to solve part a) in this question we encounter several confusions. If we assume i(t) to be a positive current, the magnetic flux will flow through the core in a counter...
  19. A

    Faradays law in different units?

    This is maddening and i cannot find a concise explanation anywhere despite the simplicity of this question. I keep coming across faradays law expressed as \text{curl}\left(\mathbf{E}\right) = -\frac{1}{C^2} \frac{\partial\mathbf{B}}{\partial t} Im only used to working in SI units so all i...
  20. M

    How Is EMF Generated in a Coil Flipped in a Magnetic Field?

    A 25-turn circular coil of wire has diameter 1.00 m. It is placed with its axis along the direction of the Earth’s magnetic field of 50.0 /T, and then in 0.200 s it is flipped 180°. An average emf of what magnitude is generated in the coil? This is a question in my book and the answer was...
  21. teroenza

    Faradays Law, Calculate E field

    Homework Statement I have been asked to calculate the magnitude of the induced electric field using Faraday's law. I am unable to provide the picture that accompanies the problem and must describe it with words. A circle has a magnetic field (perpendicular to the circle) directed into the...
  22. 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...
  23. J

    Applying amperes law and faradays law to a solenoid and energy density

    This isn't really a homework problem, I just need to know how to do a problem similar to this one for the final and I don't want to fail, so I posted it here. A solenoid with n turns per unit length, length l and radius a (l>>a) has a current I(t)==Io sin(wt) [w is omega], where I and w are...
  24. E

    How Is the EMF Calculated in Faraday's Law of Electromagnetic Induction?

    Homework Statement Explain carefully the mathematics of Faraday's law of electromagnetic induction. Homework Equations EMF=(∆(BA)) / ∆t
  25. R

    Faradays Law - Induced Current

    Homework Statement A loop of wire is situation between a wire (Wire 1) that is perpendicular to the loop and another wire (Wire 2) that is parallel to the loop (the diagram has the loop and Wire 2 in the plane of the page, Wire 1 is running "through" the page). Is a current induced, and in...
  26. N

    Faradays law: magnetic coil question

    Homework Statement (The information is for several questions and i have posted one of them) Two coils magnetically coupled, Voltage of 240v, 50Hz applied to coil 1, current of 2A flows, second coil connected only to a high impedance rms voltmeter reading 100v find: The peak total flux...
  27. D

    Faradays law wattage/voltage question?

    faradays law,,, wattage/voltage question? hi, I am an industrial design major and am working on a project for a shoe. the shoe incorporates faraday's law of magnetic induction so that while you run, a magnet is going back and forth and powering a capacitor. my question is, how might i be able...
  28. S

    Another Faradays Law of Magnetic Induction

    A piece of copper wire is formed into a single circular loop of radius 12 cm. A magnetic field is oriented parallel to the normal to the loop, and it increases from 0 to 0.55 T in a time of 0.45 s. The wire has a resistance per unit length of 3.3*10^-2 ohms/m. What is the average electrical...
  29. M

    Dynamical Magnetism Faradays Law

    Problem: A fixed loop with Radius a and Resistance R is parrallel with the y-z plane. Another loop with radius r parallel to the y-z plane and a distance away from the other loop has a velocity v moving toward the other loop. What is the induced Voltage? Assuming (Told to assume this)...
  30. T

    How Fast Must a Magnetic Field Change to Induce a Specific Current?

    Ok, I need a lot of help on this one. A single conducting loop of wire has an area of 7.4*10^-2 m^2 and a resistance of 110 ohms. Perpendicular to the plane of the loop is a magnetic field of strength 0.18 T. At what rate (in T/s) must this field change if the induced current in the loop is...
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