What is Lenz: Definition and 50 Discussions

Heinrich Friedrich Emil Lenz (; German: [lɛnts]; also Emil Khristianovich Lenz, Russian: Эмилий Христианович Ленц; 12 February 1804 – 10 February 1865), usually cited as Emil Lenz or Heinrich Lenz in some countries, was a Russian physicist of Baltic German descent who is most noted for formulating Lenz's law in electrodynamics in 1834.

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  1. bluesteels

    Simple question about Lenz' Law

    This the images of the figure. I am confused on why is the magnetic field for the top wired is out and the bottom is in. Is that the general rule?? Moreover what if the wired is point to the left instead of right is the magnetic field still out of the page.
  2. Frigus

    B How to apply Lenz' law if we don't know what to oppose?

    In this question I can't understand how the loop is opposing the change in flux, I can solve it by simply imagining a bar magnetic with south pole pointing outwards placed inside the plane of image but how do I know that it is the same case as that of bar magnet? What if their is a case in...
  3. Nicolas01

    Lenz law how to find dA/dT and O?

    Hello, I am new and I have a question about the lenz law. How I am suppose to find DA/dt and o in this problem? A= 9 but D(9)/dt is equal to 0 ? And I don't really know what is the angle o means in this formula. If I found the voltage i can find the current with I= eps/Req .
  4. H

    If a magnet does not feel the Lenz force, will there be a violation of energy?

    Consider the following, a magnet and a charge is attached to a platform, which is constrained to move only up and down direction. Now, if magnet is moved towards charge, due to changing magnetic field, an electric field will be created. This electric field will impart force on charge. since the...
  5. 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...
  6. thebosonbreaker

    B Understanding & Applying Lenz's Law: A Step-by-Step Guide

    I have been studying electromagnetic induction and have looked at the laws of Faraday and Lenz. Faraday's law makes perfect sense to me, but I can't seem to grasp Lenz's law. I have read about it and watched many yt videos, and the idea seems simple. But actually using it to predict e.g. the...
  7. U

    Calculation of Change in Magnetic Flux Linkage Across a Wire

    Homework Statement A straight wire of length 0.20m moves at a steady speed of 3.0m/s at right angles to a magnetic filed of flux density 0.10T. Use Faraday's law to determine the e.m.f. induced across the ends of a wire. Homework Equations E= Nd Φ/dt but N=1 so E= dΦ/dt The Attempt at a...
  8. S

    Lenz' law: North pole of bar magnet moves away from a coil

    Homework Statement You have a circular coil, and two metal plates a and b. The north pole of a bar magnet is moved away from the coil at a constant velocity(assume the bar magnet and the coil lies along the x axis). On which plate will the excess positive charge appear? Homework EquationsThe...
  9. S

    Lenz' Law - request for formula (for 2 given cases)

    Homework Statement Assume a uniform hollow cylindrical copper tube with the following parameters: Inner radius = R0 Outer Radius = R1 Length = L1 (Length > Outer Radius) Mass = M1 Now assume a cylindrical permanent magnet with the parameters: Length = L0 (L0 < L1) Mass = M0 Magnetic...
  10. G

    Self inductance of a superconductor

    Hi. Superconductors can be made hover above or even below magnets. As far as I know, this can be interpreted as an extreme form of Lenz's law: Eddy currents on the surface of the superconductor create an opposing force that is able to cancel gravity since the currents aren't affected by...
  11. G

    Thomson's jumping ring: Why net repulsion?

    Hi. According to Lenz's law, a conducting ring responds to an increasing external magnetic field with a repelling field and to a decreasing external magnetic field with an attracting one. Thomson's experiment uses an AC coil, so its field strength changes between increasing and decreasing a...
  12. F

    Exploring the Effects of Lenz' Law and Magnetic Flux: Is Ferromagnetism the Key?

    Why is it that the induced emf opposes the change in magnetic flux? Is it to follow the law of conservation of energy?
  13. M

    Faraday's and Lenz law - Experiment with AC coil and Cu ring

    Hi, can someone explain me the next experiment: If I have an AC coil on iron stick, and if I put Cu ring on that stick concentric with AC coil, when I turn coil power supply, the ring will levitate on some height. My question is: Powered AC coil produces an AC magnetic field. If I put a...
  14. Narayanan KR

    A motor design to defy Lenz' law?

    1. The two rotors (purple, green) are electricaly isolated but mechanically fit to rotate along same axis 2. The motor action on the left side rotor will move the armature set, this will produce currents in right side rotor that will pass via a variable load. 3. do you see the magnetic fields...
  15. M

    Help with magnetic induction and finding induced current

    Homework Statement I have attached a picture that details the problem. This is my practice test and I have no clue what I am doing wrong. Essentially a loop of wire is moving in constant velocity into a magnetic field. The magnetic field lines are pointing into the page. The problem is...
  16. NihalRi

    Find the induced EMF and Lenz' law

    Homework Statement There is a magnetic field directed inside/ towards the screen. There is also a single rectangular coil parallel to the screen where one of the sides are movable. The magnetc field increases, what happens to this movable side of the coil. This is my description of the...
  17. kostoglotov

    Does Increasing Current Add Resistance in an Inductor?

    I understand why slowing the current, causing a decrease in the flux, momentarily increases the current (stabilizing). I can use the right hand rule and Lenz's law to picture what is happening in that case. But why does increasing the current add resistance? The induced magnetic field is...
  18. L

    Will a Magnet and Copper Tube Hourglass Be Accurate Due to Lenz's Law?

    I had the idea of making an hourglass timepiece employing lenz's law using a magnet and copper tube (or copper bars for visibility). Any idea how accurate my hourglass will be? I know Lenz's law is effected by temperature (not sure by how much). If I drop a small magnet drop through a small...
  19. kostoglotov

    Lenz's Law applied to a non-circuit conductor?

    I was reading through my College Physics text, and it talked about how NASA once swung a 20km long conductor through the Earth's magnetic field and setup a 3500V potential difference along the wire. I understand that there's no conventional current in that wire, it's not a circuit. But for a...
  20. L

    Lenz's Law Q: Clockwise or Counterclockwise?

    Homework Statement A long, straight wire lies on a table and carries a current I. As the drawing shows, a small circular loop of wire is pushed across the top of the table from position 1 to position 2. Determine the direction of the induced current, clockwise or counterclockwise, as the loop...
  21. T

    About Lorentz force and Lenz' law

    Hello Physics forum, I have come here seeking for some experienced help about a doubt that to some extent is not letting me advance on my studies of electromagnetism. Basically is about the magnetic (B) field, and more specifically, about the force at each point of the vector field (The lorentz...
  22. N

    Inductors' voltage direction and Lenz Law

    In the attached figure, a de-energizing RL circuit is drawn (left switch is opened while right switch is closed). In the drawing the voltage induced in the inductor is put to be negative so that the math works out. However, that would be against Lenz's law, wouldn't it? The inductor should be...
  23. M

    Archived Lenz' Law Scenarios for two wires with varying distance between them

    Homework Statement For each of the following scenarios, predict the direction of the induced current ( c-to-d; d-to-c; NO INDUCED CURRENT) in the second set of coils, N2. 1. The current, I1, direction ‘a-to-b’, is increasing rapidly. The coils remain stationary. 2. The...
  24. J

    Understanding Lenz Law: Impact on Current Direction in a Magnetic Field

    So say you have a square loop of wire which has a current of some positive value going clockwise and it enters a magnetic field going into the board. Now since lenz law states that the induced emf will make a current going counterclockwise (to oppose changing mag flux) then what is the new...
  25. B

    Understanding Lenz' Law as it applies to a magnet falling in a tube

    Hi All! This is my first question/post here, so I will try to make it work! Homework Statement Ok, so the question is simple-ish. Homework Equations Faradays Law (ε=-NΔΘ/ΔT) The Attempt at a Solution Now, I understand the concept that as the magnet is falling towards the coil, the coil...
  26. U

    Faraday Lenz lab - My calculations are Way off and I'm not sure why

    The purpose of the lab was to measure, and also calculate, the induced current in a disconnected coil, due to a second coil connected to a power supply. Involved magnetic fields and electric fields (I think. For the purposes of this lab, the magnetic permittivity is 1.26*10-6, the number...
  27. L

    Calculate the direction of the current using Lenz Law/Other

    Important: Imagine that there is a wire connecting the two magnetic poles, (+,-) so there is an induced current and not only an ems. Homework Statement Hello there! I'm wondering if I can use both of these methods to calculate the direction of the current. The first one is Lenz...
  28. M

    Squared Quantum Runge Lenz Vector

    Homework Statement \mathbf{A} = \frac{1}{2}\left(\hbar\mathbf{L} \times \mathbf{p} \right) - \frac{1}{2}\left(\mathbf{p} \times \hbar\mathbf{L} \right) + Ze^2m \frac{\mathbf{r}}{r} Derive \mathbf{A}^2 = \left(\mathbf{p}^2 - 2m\frac{Ze^2}{r} \right)\left(\hbar^2 \mathbf{L^2} +...
  29. T

    Lenz' Law copper tube thickness question

    For the classic Lenz law demonstration using a neo. magnet dropped down a copper pipe, is the magnetic force generated correlated to the thickness of the copper pipe? Ergo, will the magnet go slower down a thick copper pipe vs. a standard size plumber pipe?
  30. S

    Is the Lenz Effect in a superconducting magnet strong enough to stop a bullet?

    After watching a fascinating youtube video demonstrating the Lenz Effect using a 1.5T MRI machine and an aluminum block, I was wondering if it would stop a bullet fired along the axis of the machine. If so, would there be any defensive military application?
  31. E

    Lenz Law copper tube problem modification

    Homework Statement If we drop a bar magnet down a copper tube, it will travel down very slowly. If we now cut vertical slits in the copper tube, will the magnet travel down faster or slower as compared to the original problem? Homework Equations \int \vec E \cdot d \vec l = -\frac{d...
  32. P

    Ideal Transformers and Lenz Law

    Hi, Can somebody answer this question? The induced magnetic field of the secondary coil opposes the magnetic field of the primary. Therefore there is a lower magnetic field on the primary - lower impedance and a lower voltage drop. This results in an increased primary current which will...
  33. N

    Understanding Lenz Law: How Current Flows in Close Proximity Coils

    Homework Statement Figure shows two coils placed close to each other . When the key is pressed so that a current starts building up in one the coils (a) a current flows along CBA in the loop (b) a current flows along ABC in the loop (c) No current flows through the loop (d) An...
  34. E

    Faraday Lenz law are just getting me more confused

    I am sick of searching and being confused more and more specially about lenz law... THere are many demonstrations and many law.. Can someone list atleast the most important one...
  35. S

    Lenz law wire and expanding loop

    Lenz law problem wire and expanding loop Homework Statement The loop has current radius R the red bar moves at velocity V. The distance the wire is from the loop is d and the top of the loop is length l Find the induced emf and the direction of the current in the loop. Homework Equations...
  36. G

    Exploring the Reversal of Lenz Law: What Would Happen?

    Question about Lenz Law. When a magnet is moved towards a coil, it produces a current in the coil. The current flows in the coil in the direction which produces an "induced" magnetic field that pushes away the motion of the approaching magnet. Faster the magnet approaches, bigger the current...
  37. C

    Lenz' Law, induced current in a ring falling

    Homework Statement A ring falls through a horseshoe magnet. Before reaching the magnet, is the current induced in the ring clockwise or counterclockwise? What about after the ring has passed through the magnet? The answers are clockwise before the ring passes through, and...
  38. Y

    Discussion of Faradays and Lenz law.

    This started in the MIT professor's thread. But this part is concentrated on Faradays and Lenz law in constant magnetic flux loop and transformer that is very interesting and not quite relate to the MIT professor discussion. I want to bring this out and continue discussion about the Faraday's...
  39. B

    How do Lenz's Law and the right hand rule work together in electromagnetism?

    I am having trouble understanding how the right hand rule works with lenz's law. Please explain
  40. D

    Lenz Law in a single-phase pulsed induction generator

    Hello. I have made a little generator which is running quite efficiently but i would like to see if i can squeeze one or two percent more out of it. My physics knowledge is very poor and i wonder if anyone could tell me how Lenz's Law is affecting the device. I will describe it then attach...
  41. M

    Using centripetal force to fight lenz?

    hello to all, first post on this side of the web, maybe some of you folks can give me an opinion on something I've been running in my head ok, so this stemmed from thinking about how to overcome lenz law with gravity i thought of a magnet on the end of a lever, with a free standing...
  42. D

    What is the induced current in a moving frame near a changing current wire?

    in the following question i am given an infinite straight wire with a current changing according to i=2t, next to the wire is a conducting square with a side of a=5cm at t=0 the square is at a distance of b=5cm from the wire and the frame is moving away from the frame at v=2m/s, the frame has a...
  43. C

    The way Lenz force can accelerate a magnet

    Hello. I have problems with the Faraday and Lenz laws. Not problems with their definitions (they are OK), but with the usual assumptions and relation with conservation of energy: The definition of these two laws states: - Faraday law: The induced electromotive force or EMF in any closed...
  44. S

    Lenz Law: Which Capacitor Plate Becomes Positive?

    A circuit contains a resistor and an uncharged capacitor. Pointing into the plane of the circuit is a uniform magnetic field (B). If the magnetic field increases in magnitude with time, which plate of the capacitor (top or bottom) becomes positively charged? I don't understand how the...
  45. I

    Does Lenz's Law Apply When Inserting an Iron Rod in a Solenoid?

    1. suppose a long solenoid is connected to a DC source and after a long time steady state has reached. And suddenly an iron rod is inserted in the solenoid along its axis. Obviously, self inductance of the solenoid will increase by some factor. [One can assume some resistance of of the solenoid...
  46. D

    Lenz's Law & Magnet Dropping into Coils: Does Velocity Decelerate?

    So... am I understanding this right? Does Lenz's law suggest that the velocity of a magnet dropping (gravity) into a tube of coils will decelerate as it passes? By decelerate, I mean actually not accelerate as quickly as it would without coils around it. I am an idiot. Thanks in advance.
  47. S

    Why is the induced current zero when a magnet is inside a stationary coil?

    Basic question about Faraday's law? Hi guys, Ok I have a small problem with faraday's law. Taking the example of a north pole of a magnet coming close to a solenoid. My question is when the magnet is inside the coil and is stationary why is the induced current zero. Wouldn't the magnetic field...
  48. N

    The Faraday disc (unipolar generator) and Lenz' law

    Homework Statement Hi all. I can't seem to understand how to apply Lenz' law to a disc rotating in a magnetic field that is perpendicular to the discs plane (see first page on PDF): http://www.pa.uky.edu/~latimer/phy232s08/lectures/phy232l31_4.pdf I can see that using the right-hand...
  49. M

    The limitations of Lenz law?

    What are the limitations of Lenz law? If there where none, you could just move a magnet through a coil and keep moving it away, thus creating the worlds most powerful magnet. This seems highly unlikely. When moving a magnet towards the coil, the external magnet field induces a current in the...
  50. BobG

    What is the original purpose of the Laplace-Runge Lenz vector?

    What was the original purpose of the Laplace Runge Lenz vector? I understand the components (comparing centrifugal force to gravitational force) and, more importantly, that if you multiply the LRL by the reciprical of the geocentric gravitational constant (or helio..., etc), you get a vector...
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