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Questions tagged [electromagnetic-induction]

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Where does this form of the induction law come from?

I am currently studying a eddy current disk break and came across this promising paper (PDF, princeton.edu) from 1942. However, in the first formula a suspicious $4\pi$ appears before the current $U(...
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Simple explanation to the induction from the slowly changing $\vec B$ of a solenoid in the region of $0$ magnetic field

I would like to get some elementary intuition into the problem a solenoid fed with a time-dependent current, and the resulting current that such the solenoid field would induce in a loop completely ...
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1answer
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Induced current due to induced current

Say we have a square coil and a change in magnetic flux is created through the coil. Thus inducing a current in the coil whose magnetic field opposes this change inside the coil. If we assume(for ...
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1answer
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Relationship between Flux and Current in the primary coil of a transformer [closed]

I am not exactly too sure what is the right way to approach this question. However, I had two ways in mind. My first method was to use the fact that $\epsilon=-n\frac{\Delta\phi}{\Delta t}$, which ...
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Lenz's Law/Right Hand Grip Rule for Diamond Shaped Loop [duplicate]

A diamond-shaped loop of wire is pulled at a constant velocity through a region where the magnetic field is directed into the paper in the left half and is zero in the right half, as shown in the ...
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1answer
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Order of Magnitude for Photon Induction

What does magnetic induction look like when we imagine just one photon passing by? I'm imagining some sort of coil wrapped around the edge of a waveguide or something so that it picks up some of the ...
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1answer
31 views

How to induce large current in a flexible wire

I have not tested this method in the lab or anything, but based on what I know about electrodynamics I would say the following set up could work: I would take two straight flexible free-of-current ...
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Would the voltmeters give different readings in a circuit with induced current?

$\def\vE{{\vec{E}}}$ $\def\vD{{\vec{D}}}$ $\def\vB{{\vec{B}}}$ $\def\vJ{{\vec{J}}}$ $\def\vr{{\vec{r}}}$ $\def\vA{{\vec{A}}}$ $\def\vH{{\vec{H}}}$ $\def\ddt{\frac{d}{dt}}$ $\def\rot{\operatorname{rot}}...
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Lighting an Electric Bulb with Earth's Magnetic Field

Yesterday, I was solving some problems of Electromagnetic Induction. Suddenly a thought struck my mind. Earth has its own magnetic Field.If an aircraft of metallic body is flying in the air then ...
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1answer
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Flux of Electric field non-zero through a surface for light in free space?

Consider an electromagnetic wave propagating through free space.The Electric and magnetic components of the fields, vary as sinusoids. If I construct a sphere of radius $\lambda/4$ at any location; i ...
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How does back emf occur if a system can’t do work on itself? [closed]

If a coil is connected to a battery and the current starts up, the electrons have to be moving at a certain speed through the wire and therefore have a certain kinetic energy. But if they are moving ...
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Is Kirchoff's Voltage law valid in: 1) motional emf 2) induced emf

I am aware that induced electric field is non-conservative and therefore KVL is invalid. But incase of motional emf, there is no induced nonconservative electric field, just the lorenz force. So i ...
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How can one generate a magnetic field of a specific intensity(in terms of flux)?

Was wondering how to generate a static magnetic field of a fairly precise value(teslas) for my science class. It needs to be relatively precise. Thanks for the help you can offer.
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3answers
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Lenz's law and the motor effect

The picture shows the basic motor effect, which can be described with Fleming's left-hand rule. There are two cases of what could be happening however. Case 1: There is a force applied to a wire such ...
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2answers
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Why is the graph for the flux density of a copper ring, when a magnet falls through, not linear?

In an experiment where a magnet is falling through a wire, the flux density is presented by the top graph in the image. Why is the graph not a straight line like the one below it? I thought that if ...
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2answers
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In a transformer, why does Vp depend on the flux?

To obtain the emf in the secondary of a transformer as a function of $V_p$ (input voltage in the primary), we asume that $V_s=N_s\frac{d\phi}{dt}$ and that $V_p=N_p\frac{d\phi}{dt}$. What I don't ...
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1answer
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Two types of electric field

My textbook mentions that electric field produced by electric charge and that produced by changing magnetic field are different in nature. After searching from various sources I found that electric ...
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2answers
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Why is there no current induced when the coil is vertical in an AC generator?

In this picture, the movement of the coil inside an AC generator is shown. My question is when the angle is zero or like in the beginning, the coil is vertical to the magnetic field yet no emf is ...
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1answer
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Secondary current in a loosely coupled transformer

How does the secondary current depend on the resistive load placed on the secondary winding of a loosely coupled transformer, in which the primary winding is supplied with a linear current ramp ?
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Equipotential Surface in Non conservative electric field

Is there any equipotential surface in non conservative field or induced electric field produce due to change in magnetic field through a given area
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Question on the magnetic flux inducing current in the secondary winding of a transformer

In transformers, does all of the magnetic flux change make a current in the secondary winding? Or just a part of it, and other part of it will cause self induction?
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1answer
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Does the Vector Potential Coil and Transformer Violate Special Relativity?

"Vector Potential Coil and Transformer" by M. Diabo et al reports the induction of voltage by a time varying curl free vector potential. A refinement reported in "Vector-Potential Coil and ...
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Self inductance of a circular coil

I have read from my reference that the self inductance of a wire ring is derived in a non-trivial manner. I have copied an image off the result below, let me know if I should translate it to Latex. ...
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1answer
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Does the force on magnet depend on coil, when it is being moved relative to the coil?

I am new to electo-magnetism, so i prefer simple language, the problem is: When we move a magnet relative to a coil such that one of its face is towards or at the coil, an EMF is induced in the coil ...
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1answer
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Does it make any sense to ask for mutual inductance between a wire and a coil?

I have been asked to work out the mutual inductance coefficient between a circular spire of $N=1$ turns and radius $R$ and an infinite wire contained in the plane in which the spire lies. This, ...
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1answer
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How to calculate total charge going through a coil, when its rotated in a uniform magnetic field?

A conductive coil has N turns of loops with a radius r, and it has a resistance R. The coil is initially in an external homogenous magnetic field B, perpendicular to it. The direction of the magnetic ...
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How can a magnetic field exert a torque that causes a disc to rotate?

I'm confused about the premise of this homework problem: A thin, non-conducting horizontal disc lies in the $x$-$y$ plane. The disc has a mass $m$ and a total charge $q$ distributed uniformly over ...
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Mutual induction, how long does it last?

I understand the process of mutual induction and why it occurs, but i have a doubt. Imagine we have two circular coils. One is connected to a fem generator and the other isn't. Here it's what i've ...
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1answer
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Power transferred between two circular coils

[EDITED] I am interested in studying the physics behind wireless charging for autonomous vehicles. Therefore, I want to compute the mutual inductance between two coaxial circular coils. I have read ...
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1answer
28 views

Equation for: How does Thickness of Aluminum Pipe affect the velocity of the magnet falling through?

I need help in finding the equation for how the velocity of a magnet dropped through an aluminum foil pipe is affected when the thickness of the pipe is changed. Thank You.
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1answer
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Current induced by permanent magnet moving along toroid coil

(It's not really shown in the pictures, but please assume that the coils are included in a closed circuit in both configurations. Maybe they could serve as a tension source in their respective circuit ...
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Conducting wire covered by a paramagnetic dielectric

How does the conductance of a conducting wire change if it is covered by a paramagnetic material comparing to a diamagnetic one? I am interested in the DC or low frequencies response mainly. For me ...
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Can an Opposing Current Create another Opposing Current?

In Inductors when current increases it's magnetic field induces a voltage which causes an opposing current that slows down the rise of the current that initially creates it, but can this opposing ...
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1answer
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Self-induction and conservation of energy [closed]

back EMF when switch is open is greater than back EMF when it is on; is that opposes the law of conservation of energy?
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1answer
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Sliding rod in magnetic field with two loops

The circuit is concatenated with a constant flux $B$ and the rod slides with constant velocity $v$. Find the current through the rod. Before I always solved the problem without the resistor $R_2$ by ...
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1answer
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Why do we ignore the negative sign of self induction while considering inductors in an AC circuit?

I have been taught that the back EMF in a coil as per Lenz's law is $$ e =-L \frac{di}{dt} $$ Then why is that during circuit analysis of AC circuits, we consider the e across inductors to be $$ ...
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1answer
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Why is rate of decay of current in a coil greater than the rate of its growth?

In this experiment: Where neon lamp doesn’t light when the switch is closed because the voltage is much lower than that required to ionize the gas, but it only lights up momentarily when the switch ...
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Induction heating through a slightly magnetic material

Would be be possible to inductively heat a rod with with ~100 relative permeability enclosed in a tube with ~2 permeability? The gap between the rod and the interior surface of the tube is uniform ...
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1answer
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Can emf be induced by reducing the radius of a loop?

Faraday's law tells us, that the induced emf in a conducting loop, is equal to the change in magnetic flux per second through the area encircled by the loop. If we decrease the radius of the loop, ...
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1answer
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Influence of Lorentz force on Eddy Current

A magnetic field exerts a force on a moving charge called Magnetic Lorentz force. How does this force work in case of eddy currents? The following is an extract from Wikipedia: "Another way to ...
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Scientific reason behind electromagnetic induction [duplicate]

What actually happens inside a loop when placed in a changing magnetic field that EMF gets induced across it? And also if it is connected and the direction of the magnetic field is changed then ...
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2answers
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What does 'Oppose a Change in Current' really mean from Lenz Law?

We all know what Lenz Law is, but I have a bit of trouble conceptualizing the phrase above. Does 'Oppose a Change in Current' means it will take more time for the current to increase to its maximum ...
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1answer
33 views

Why EMF induced in the coil acts to oppose any change in the magnetic flux?

This might be an absurd question for some of you guys. According to Lenz's Law an induced current will create a magnetic field that induces another current in which it opposes the current causing it ...
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Average induced emf of a AC generator

In my physics textbook, it says if a simple generator made of one coil rotates 180° from the position the plan parallel to the magnetic field lines equal 0 if the rotation from position ...
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2answers
871 views

Why is there an induced EMF in a plastic ring?

If we were to pull a plastic ring across the boundary of a magnetic field, why does an emf form? If this was a metal ring I would fully understand because the electrons are free to move in a metal ...
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Conceptual question about Magnetism? [duplicate]

I am confused about Magnetic force whether it does work or NOT because i think that the battery does the word and the magnetic force only redirects the work done by battery into some displacement etc. ...
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0answers
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In motional emf why doesn't the magnetic field due to the current in the moving rod exert force on the rod?

When a metal rod moves in a magnetic field an emf is produced across its ends called motional emf. When a resistor is connected across it a current flows through it.Due to this current a magnetic ...
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rotating capacitor question

Imagine a simple setup. I have a copper disc and another copper element held close to the disc at one of it's sides, this element is stationary but the disc is rotating, the part between the disc and ...
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1answer
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Why do we need frequency of changing current for induced EMF?

I know that a constant current doesn't create induced emf, however, I do not know why a changing one does. Are there any ways to understand it briefly/easily, or is it just the way it is?
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Why are there two concave poles in an AC generator

If we suppose that the magnetic poles in the AC generator are regular rectangular bar magnets, then the field lines are supposed to be straight lines as in the photo below: And then the direction of ...