Faraday's law Definition and 268 Threads

Faraday's law of induction (briefly, Faraday's law) is a basic law of electromagnetism predicting how a magnetic field will interact with an electric circuit to produce an electromotive force (EMF)—a phenomenon known as electromagnetic induction. It is the fundamental operating principle of transformers, inductors, and many types of electrical motors, generators and solenoids.The Maxwell–Faraday equation (listed as one of Maxwell's equations) describes the fact that a spatially varying (and also possibly time-varying, depending on how a magnetic field varies in time) electric field always accompanies a time-varying magnetic field, while Faraday's law states that there is EMF (electromotive force, defined as electromagnetic work done on a unit charge when it has traveled one round of a conductive loop) on the conductive loop when the magnetic flux through the surface enclosed by the loop varies in time.
Faraday's law had been discovered and one aspect of it (transformer EMF) was formulated as the Maxwell–Faraday equation later. The equation of Faraday's law can be derived by the Maxwell–Faraday equation (describing transformer EMF) and the Lorentz force (describing motional EMF). The integral form of the Maxwell–Faraday equation describes only the transformer EMF, while the equation of Faraday's law describes both the transformer EMF and the motional EMF.

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  1. K

    Solve Faraday's Law: Find Current in Circular Wire

    The drawing shows a copper wire (negligible resistance) bent in a circular shape with a radius of .5 m. The radial section BC is fixed in place, while the copper bar AC sweeps around at an angular speed of 15 rad/s. The bar makes electrical contact with the wire at all times. The wire and bar...
  2. P

    How Does Faraday's Law Explain Induced Current in a Changing Magnetic Field?

    I was wondering about the following problem: You are looking down on a single coil in a constant magnetic field B = 0.9 T which points directly into of the screen. The dimensions of the coil go from a = 6 cm and b = 15 cm, to a* = 20 cm and b* = 19 cm in t=0.028 seconds. If the coil has...
  3. C

    Power loss in transmission lines (Electromagnetic Induction and Faraday's Law)

    Show that the power loss in transmission lines, PL, is given by PL = (PT)^2 X R/(V^2), where PT is the power trasmitted to the user, V is the delivered voltage, and R is the resistance to the power lines. I don't even know where to start. I am so confused by this chapter, I don't know what...
  4. V

    Magnetic induction, Faraday's law and the likes

    Recently I started "studying" electromagnetic induction (O.K. that might be a bit of an overstatement, but I am interested in it, so it's just as well) and I came to the following important "discoveries": - one of the Maxwell's equations states (Faraday's law if my memory serves me correct)...
  5. I

    Integration of V(t) using faraday's law

    Ok the question is with a U-shaped conductor and a bar that slides across. There is a battery and a switch, the switch is open for a long time then closed at t=0. I am supposed to find the velocity as a function of time. I am mostly having trouble with the integration, i know the answer but i...
  6. F

    Electromagnetic induction and Faraday's Law

    I need to be enlightened on this. If a magnet with north pole facing towards a coil of wire is pushed in does it induce a current clockwise, or counterclockwise? If you push the coil in towards the magnet will it induce current in the opposite direction? How can I use the right hand rule with...
  7. M

    Faraday's law of electomagnetic induction

    A piece of copper wire is formed into a single circular loop of radius 13 cm. A magnetic field is oriented parallel to the normal to the loop, and it increases from 0 to 0.60 T in a time of 0.45 s. The wire has a resistance per unit length of 3.3 x 10-2 ohm/m. What is the average electrical...
  8. C

    Does Faraday's Law Indicate Charge Separation in a Loop?

    So I'm studying for my physics final, and I ran across a problem that is giving me a bit of trouble. http://cyclotron.tamu.edu/dhy/sample_final_exam.pdf the question is 3b. I'm thinking that the wire loop will have no induced current in it since there isn't a change in flux when you...
  9. Eye_in_the_Sky

    How Is Faraday's Law Applied in Time-Varying Loops?

    Faraday's law of induction is emf = - (d/dt) ∫S B∙da . When the closed loop (serving as the boundary of the surface S) is independent of time, the above relation is equivalent to the Maxwell equation curl E = - ∂B/∂t . However, when the closed loop C (i.e. the boundary of S) is...
  10. R

    Faraday's Law of Induction: Calculating Induced emf in a Moving Square Loop

    Induced emf around a closed path in a time-varying magnetic field. A magnetic field is given in the xz-plane by B=Bo*cos(pi)(x-Uot)ay Wb/M^2. Consider a rigid square loop situated in the xz-plane with its vertices at (x,0,1), (x,0,2),(x+1,0,2) and (x+1,0,1). 1.What is the expression for the...
  11. A

    Electromagnetic Induction and Faraday's Law

    The generator of a car idling at 950 rpm produces 12.4 V. What will the output be at a rotation speed of 2500 rpm assuming nothing else changes? I'm guessing that is easier and I'm looking to make it harder. I can't find anything in my textbook involving rpm. I'm thinkin to use this...
  12. L

    Physical Explanation of Faraday's Law

    So we were going through Faraday's Law today in class: \int\vec{E}\cdot d\vec{l} = -\frac{d}{dt}\int\vec{B}\cdot d\vec{A} Mathematically I'm fine with it, however, is there any good physical way to explain it, it seems very odd that if you had a field such as: \vec{B} = B_0cos(\omega...
  13. F

    Faraday's Law of Electromagnetic Induction

    A constant magnetic field passes through a single rectangular loop whose dimensions are 0.348 m x 0.593 m. The magnetic field has a magnitude of 2.26 T and is inclined at an angle of 66.0° with respect to the normal to the plane of the loop. (a) If the magnetic field decreases to zero in a time...
  14. R

    How Is Average EMF Calculated in a Rotating Coil?

    A closely wound, retangular coil of 80 turns has dimensions of .25m x .4 m. The plane of the coil is rotated, in .06 sec from a position where it makes an angle of 37 degrees with a magnetic field of 1.1T to a position perpendicular to the field. What is the average emf induced in the coil...
  15. D

    Faraday's law and loop of wire of resistance

    Hello there, I'm new to this place, I thought these forums looked like a wonderful source of knowledge, so purhaps some of you could be so kind as to help with the following problem...? (here's hoping I'm in the right forum for a start...) sorry about the length of it, but i did draw a...
  16. G

    Faraday's Law and magnetic flux

    Why is it that a changing magnetic flux through a surface should induce an emf? I know that the emf is from a non-conservative electric field, but how exactly was this field generated? (if that is the correct expression for it)
  17. P

    Faraday's Law of Induction Question

    I can't seem to wrap my head around this question. Any help would be great. A coil consists of 20 turns, with a 10cm radius (all turns are uniform). It rotates uniformly around the z-axis at an angular speed of: w=20 rad/s A uniform magnetic field passes along the x-axis with a magnitude...
  18. D

    Understanding Faraday's Law of Induction

    I'm having trouble with the following problem: A bar of mass m, length d, and resistance R slides without friction on parallel rails. A battery that maintains a constant emf E is connected between the rails, and a constant magnetic field B is directed perpendicular to the plane of the page...
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