What is Lenz's law: Definition and 137 Discussions
Lenz's law, named after the physicist Emil Lenz (pronounced ) who formulated it in 1834, states that the direction of the electric current which is induced in a conductor by a changing magnetic field is such that the magnetic field created by the induced current opposes changes in the initial magnetic field.
It is a qualitative law that specifies the direction of induced current, but states nothing about its magnitude. Lenz's law predicts the direction of many effects in electromagnetism, such as the direction of voltage induced in an inductor or wire loop by a changing current, or the drag force of eddy currents exerted on moving objects in a magnetic field.
Lenz's law may be seen as analogous to Newton's third law in classical mechanics.
Right. I know if you drop a strong magnet down a copper tube (or conductive but non magnetic tube) it falls slowly as it 'sees' a changing magnetic field and thus induces a current in the tube and this induced current causes its own magnetic field to be induced and acts a resistive force to the...
Heinrich Lenz postulated in 1834 the following law;
"An induced current is always in such a direction as to oppose the motion or change causing it"
I have checked many undergrad/grad-level textbooks for a derivation, but they all just state Lenz's Law without derivation as if it were a...
Homework Statement
http://dl.getdropbox.com/u/119186/Picture%20lenz.png
Homework Equations
Don't need any!
The Attempt at a Solution
I know that the first one is A. Loop 1 induces a magnetic field into the Loop2, then using right hand rule you get that it has to be clockwise...
Homework Statement
http://img38.imageshack.us/img38/7309/coil.png
When the switch in the circuit is closed a current is established in the coil and the metal ring jumps upward, Why? Describe what would happen to the ring if the battery polarity were reversed?
Homework Equations...
Homework Statement
http://www.freeimagehosting.net/uploads/2a25794363.jpg
What is the direction of the magnetic field due to the induced current when the following changes are made to the initial field?
a. The field is switched off.
b. The field strength is doubled.
c. The direction of the...
Hi, really quick question.
Is there a relationship between the Meissner effect (in superconductors) and Lenz's law.
Also, can the Meissner effect alone explain why a magnet can levitate over a superconductor, or do I need to learn about flux trapping (which isn't required by my syllabus).
Homework Statement
At a certain place, Earth's magnetic field has magnitude B = 0.590 gauss and is inclined downward at an angle of 77.5° to the horizontal. A flat horizontal circular coil of wire with a radius of 10.0 cm has 1000 turns and a total resistance of 55.5 . It is connected in...
I teach high school physics and I would like to get maximum mileage out of my Lenz's law experiment/demonstration.
I am going to get the students to drop magnets down a long copper tube to calculate the magnetic force using distance, time etc and making a direct calculation using Fnet=...
Homework Statement
Two coils are suspended around a central axis as shown in the figure below. One coil is connected to a resistor with ends labeled a and b. The other coil is connected to a battery E The coils are moving relative to each other as indicated by the velocity vectors v. Use...
Homework Statement
Two conducting loops carry equal currents I in the same direction as shown in the figure. If the current in the upper loop suddenly drops to zero, what will happen to the current in the lower loop according to Lenz’s law?
(a) The current in the lower loop will decrease...
Homework Statement
A copper bar is moved to the right while its axis is maintained in a direction perpendicular to a magnetic field as shown in Figure P31.28d (image d, bottom right). If the top of the bar becomes positive relative to the bottom, what is the direction of the magnetic field...
Homework Statement
Use Lenz's law to determine whether the induced current in the resistor R is from A to B or from B to A in the following configurations:
(1) a magnet with south side pointing down is entering a coil attached to a resistor with A coming before B if you go clockwise
(2) a...
Hey there, I've been searching online for a quite a decent amount of time trying to wrap my head around this concept.
We've been asked to research the link between Lenz's law and DC motors, and for some reason I was given the impression that back emf was a positive to DC motors.
After...
Homework Statement
The figures below show two different situations where a current may be induced in a loop according to Faraday's Law, with the direction given by Lenz' Law. The magnetic field is shown by the x's in Fig. 2. Select ALL correct answers (i.e. B, AC, BCD) for the current in the...
Homework Statement
A small metel ring, as illustrated by the picture, is dropped into a region of constant magnetic field.
For regions 1, 2 and 3, determine
(a) whether the induced current is clockwise, counterclockwise, or zero
(b) whether the magnetic force on the ring upward...
All right, I was just wandering about something. First, when we have a electric generator, than the rotor in it will rotate easily until current is drawn from it, correct? In other words, counter torque won't be produced until current is drawn. If this isn't true, than just stop reading the...
hi!
Actually am learning Lenz's law but am just getting confused.i know that the change of a magnetic field around a solenoid creates electricity. meaning that when we move the north pole of the magnet towards the end of the solenoid, the galvnometer deflects in one direction and when we move...
There is something on Lenz's law about induced current and the magnetic field that I don't quite understand. "Apply Lenz's law that when the magnet is brought near the coil, the magnet's magnetic field through the coil increases, and therefore the flux increases."
Here, why the magnet's...
Homework Statement
A wire is bent into three circular segments each of radius r=9.2 cm. each segment is a quadrant of circle, ab lying in the xy plane, bc, in the yz plane, and ca lying in the zx plane. If a uniform magnetic field points in the positive x direction, what is in volts the...
[SOLVED] Induced emf: Faraday's Law and Lenz's Law Question
The plane of a conductive loop with an area of 0.020 m^2 is perpendicular to a uniform magnetic field of 0.30 T. If the field drops to zero in 0.0045 s, what is the magnitude of the average emf induced in the loop...
Homework Statement
15. According to Lenz's law, the direction of an induced current in a conductor due to a change in the magnetic field near the conductor will be that which tends to produce which of the following effects?
a. Enhance the effect which produces it
b...
Homework Statement
A loop rests in the xy plane. The z axis is normal to the plane and positive upward. The direction of the changing flux is indicated by the arrow on the z axis. The diagram that correctly shows the direction of the resultant induced current in the loop is
a...
I'm reviewing for a midterm and I'm stuggling with this question because I'm not sure what equation would be appropirate. I believe that it is Lenz's Law, but I need some suggestions as to what equation to use.
Question:
To monitor the breathing of a hospital patient, a thin belt is girded...
For Lenz’s Law, most examples involve the north pole of a bar magnet passing through first in a wire coil, or solenoid.
If the bar magnet’s north pole moves toward the loop or solenoid, the magnet’s magnetic field lines move from the south pole to north pole? The current in solenoid is then...
i am having so much difficulty understanding lenz's law.
i don't know what it means and how to use it.
will someone please give me a good explanation for it because my book SUCKS and I'm having a very hard time understanding this hard(and stupid) topic so please help me.
Homework Statement Review the following drawing.
The semicircular piece of wire rotates through half a revolution in the direction shown, starting from the position indicated in the drawing. Which end of the resistor, the left or the right end, is positive?
a. neither -- there is no...
I'm stuck with Lenz's law, and questions involcing magnet/electromagnet theory
such as:
The diagram shows a bar magnet falling through an aluminum pipe. Electric currents are induced in the pipe immediately above and below the falling magnet. In which direction do these currents flow...
I only understand Len'z law for a current induced in a single loop... however I don't for in a coil... What does the relative poisition of the manetic poles of the magnet and the coil respectively has to do with the direction of the current?
Hi everyone.
At the moment I am doing motors and generators in physics, in particular Lenz's Law.
I understand most of the stuff, but I am really just stuck on 2 questions. If you could help me, I would really be appreciative (explanations, not just answers preferable).
Q1) A flexible metal...
Two loops, A and B, are aligned parallel to each other. There is a current in loop A, which induces a current in loop B. How does the current in loop A change with time?
By Lenz's Law, the current in loop B creates a magnetic field which opposes the change in magnetic flux which created it...
if someone could help me with understanding the basics of Lenz's law and Motional emf i'd really appreciate it. I'm having some trouble applying it to questions that were assigned.
For the situation shown in the figure below, the magnetic field changes with time according to the expression B = 2.07t^3 - 3.95t^2 + .808 and r2 = 2R = 4.96 cm.
Figure: http://east.ilrn.com/books/sepsp06t/pse6e.31.32p.e.jpg
(a) Calculate the magnitude of the force exerted on an electron...
The homopolar generator, also called the Faraday disk, is a low-voltage, high-current electric generator. It consists of a rotating conducting disk with one stationary brush (a sliding electrical contact) at its axle and another at a point on its circumference, as shown in the figure below...
Hi, I'm just doing my A-level physics revision and there's something I'm a bit unsure about. Lenz's law states that an induced EMF will always act to appose the change that is causing the EMF in the first place. However, if we take the example of a magnet falling through a coil that is part of...
Please look for flaws in my reasoning, any help would be appreciated.
Question:
HRW CH31 #28P(if you have the book handy)
A long rectangular conducting loop of width L, resistance R, and mass m, is hung in a horizontal, uniform magnetic field B that is directed into the page and exists only...