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Questions tagged [electromagnetic-induction]

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What is the QM equivalent of induction?

And regarding electron correlations, reciprocally what QM ones are strictly due to classical induction and near field effects? Edit: thanks to whoever thinks necessary to downvote questions without ...
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Electrostatic induction with a zinc plate

As you can see in the images, in the first one I am using a plastic rod rubbed with my hair to attract the pieces of paper using induction. In the second one, I am using a pure zinc plate(extracted ...
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Can we generate electricity by using rotation of wheel of a bicycle? [closed]

Can we generate electricity by using rotation of wheel of a bicycle ?
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Electromagnet, why does not coil and metal repel each other

In an electromagnet, if the electric coil induces a magnetic field in the metal bar with the same polarity as the one in the coil, should not the bar and coil repel one another, "like poles repel"?
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Variation of Induced EMF in a cross bar of a ferris wheel

The question is as follows. A ferris wheel which consists of two parallel large wooden wheels is joined together with metal cross bars as shown in the figure,is erected so that the planes of wheels ...
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1answer
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current induced on an inductor modifying inducing magnetic field. Wouldn't that cause an infinite oscillating feedback?

Imagine a simple circuit with an inductor and resistor in series. Now pass thru a varying flux thru the inductor, a phi. The vary flux induces voltage on the ...
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Effects of opposing fields in coupled inductor

This is a duplicate question that I already made in the electrical engineering part of stack exchange. As I`m asking for the physics behind the effect I thought it might be worth to ask also here. ...
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1answer
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Magnetic flux density compard to other definition of flux

With regards to flux i have always assumed it was defined as $$(1) Something/m^2s$$ For instance $Luminosity/(4\pi r^2)$ Is an example of radiation flux. Why then is faradys law often cited as the ...
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Transformer Equation Confusion

I have read some posts on here which I think to revolve around my problem too but couldn't really understand the explanations. So basically, I have seen how the Transformer equation is derived: $\...
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Confusion regarding torque given by M×B

The magnetic torque acting on a loop of magnetic moment M placed in a magnetic field B, is given by τ=M×B. My question is, about which axis does this give the torque about? Is it the instantaneous ...
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Can you generate 3-phase AC power from linear motion?

If you have reciprocating linear motion (such as a piston moving up and down in a cylinder), is it possible to generate three-phase AC power from it without converting it into rotary motion first? I ...
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What is meant by “changing magnetic field”

At first I thought it was the consequence of an object moving from an area of high to low or low to high flux density, but that doesn’t help understand what is meant by “a changing magnetic field” ...
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Infinite Electricity from Photon Inside Closed Box with Magnet Attached in a Coil? (Thought-experiment)

Let's say I have a very large box with a magnet attached to the outside. Inside the box there is a perfect mirror on each side. I open my box and quickly shoot in one photon before shutting it. After ...
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Current sources and conservative electric fields

Suppose a current density ${\bf J}({\bf r},t)$, for which $\nabla \cdot {\bf J} =0$, is compactly supported on a 3D region $R_1$ in vacuum. In general it can produce a nonzero electric field ${\bf E}({...
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How does an alternator produce AC?

As an alternator’s coil moves, one side of the coil induces a voltage and thus a charge flow in one direction However, simultaneously the other side of the coil induces a voltage and charge flow in ...
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Does the state of curl of the $E$-Field at a point adjust itself instantaneously as soon as $B$ begins changing at a fixed rate, or is there delay? [duplicate]

Faraday’s Law () states that a time-changing magnetic field vector induces a curl of the Electric field around that point. However it does not specify how quickly the necessary spatial gradient is ...
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How can EM waves propagate indefinitely when they really are oscillations of electric and magnetic fields?

I can't claim that I've fully grasped the science behind EM waves, but as far as I understand, EM wave is basically oscillations of electric and magnetic fields kinda switching back'n'forth and ...
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Relationship between self induced EMF, inductance and current's rate of change

I'm kind of confused about the principles of self induction; Does change in current represent the change in the net current (battery's current + induced current) or just battery's current? among the ...
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1answer
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Can $F=qvB$ be applied to a solenoid and a parallel moving magnet?

If you take a scenario like this, Charge gathers at either end, and if you could somehow form a complete circuit without there being a canceling effect, there would be a current flowing. This makes ...
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Induced Electric Fields and Faraday's Law

I'm an undergraduate student and we just covered Faraday's law. However, I am still confused conceptually about a few things: Faraday's law states that $\oint_{\partial\Sigma} \vec{E} \cdot \vec{dl} =...
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Does back E.M.F. create a second back E.M.F. which creates a third back E.M.F. and so on? [duplicate]

Does back E.M.F. also generate a back E.M.F. of it's own? If so, why do I not hear this discussed? Is this because it has a very small effect, i.e. it lasts a small amount of time or it has a small ...
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In a D.C. motor, is the Lorentz force on the conductor directly proportional to the back E.M.F.?

In a D.C. motor, when there is a current in the conductor a magnetic force arises on the conductor. If there is no load on the D.C. motor the magnetic force will move the conductor. With the motion of ...
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1answer
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A changing magnetic field passes through a wire loop but the loop itself is not in the field. Is an EMF induced in the loop? [duplicate]

$$\nabla \times \vec{E} =-\frac{\partial{\vec{B}}}{\partial{t}}$$ Applying Stokes' theorem: $$\oint_{loop} \vec{E} \cdot d\vec{l}=\int_S -\frac{\partial{\vec{B}}}{\partial{t}} \cdot d\vec{S}$$ ...
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What is the difference between Charge By Induction using two conductors, two insulators, and one conductor + one insulator?

I know that when you're charging by induction, it doesn't require two objects to contact for that to happen. Let's say you have two Van de Graaff generators that are initially at neutral charge. Let's ...
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Description of the spiral path of an electron under the influence of a magnetic field

Moving charged particles in an external magnetic field (of course non-parallel to each other) get deflected into a spiral path. For a calculation of this phenomenon it is not sufficient to use the [...
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Motional EMF with a rod in a closed loop

Let me preface this by saying that while this is a problem which came from my college physics class, it was not a graded assignment, it was optional study material (and you can see from the photo I've ...
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Counter Torque in Electric Generator

I am going to use some sort of “dynamo” or electric generator component to generate electricity from the flowing drilling fluid. However, the effect of the magnet rotating within an electrical coil ...
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1answer
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magnetic flux and EMF - in an open circuit

Lets say I've got a rectangular conducting frame resting inside a changing uniform magnetic field. the magnetic flux (Φ) is: the vector of the magnetic field cross product the vector of the area of ...
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1answer
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A question regarding Faraday's integral law

This might be a quickly phrased question so I apologize if I've missed something trivial in my understanding. Faraday introduced the concept of fields to explain the phenomenon of action at a ...
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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
49 views

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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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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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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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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Could magnetic fields really be completely substituted by relativity and electric fields?

In many textbooks (especially those for undergraduate level), magnetic fields are described merely as a relativistic side product of electric fields when considering frames in motion relative to ...
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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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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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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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635 views

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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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?