Questions tagged [electromagnetic-induction]

This tag is for questions regarding to electromagnetic induction, a process in which a conductor is put in a particular position and magnetic field keeps varying or magnetic field is stationary and a conductor is moving. Electromagnetic Induction was first discovered way back in the 1830’s by Michael Faraday.

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34 views

Do magnetic fields really travel with $c$ velocity in space?

I was thinking about a situation- In space there is our setup, a wood piece of mass $m$ and two coils $C_1$ and $C_2$ and a battery with a switch connected to C2. C2 also has m mass. C2 is placed say ...
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What is the right version of Faraday's Law of Induction for a moving integration contour?

In Electrodynamics the law of induction for a moving integration contour (not necessarily a conducting wire) is, according to my books, e.g. Jackson, Classical Electrodynamics $\oint_C \vec E' \cdot ...
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Motional emf through a non-uniform field

Suppose we have a rod of length L (in the upwards direction - y) moving to the right with velocity v. The magnetic field is into the plane of the page. If the field were constant the induced emf would ...
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Motional EMF vs Faraday’s Law contradiction

We can generalize the concept of motional emf for a conductor with any shape, moving in any magnetic field, uniform or not (assuming that the magnetic field at S each point does not vary with time). ...
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Why Faraday's law works with coils?

I always wondering why faraday's law works with coils Faraday's law only works with closed loops An the coil could be open. So the coil here doesn't form a closed loop so that we can apply faraday's ...
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I need help with this physics question on magnetism [closed]

This is for an AP physics 1 assignment and I really don't get the whole right-hand rule thing especially the specific way you need to put your right hand in order to tell the current, force, and ...
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How to generate electric current without a permanent magnet

The question is pretty simple: Can we build a device that coverts mechanical work in electric current1 without employing a permanent magnet and without access to any external source of current? The ...
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Is Magnetic force different in different frames?

Suppose a charged particle moves with a velocity $v$ near a wire carrying an electric current. So, a magnetic force acts on it. If the same particle is seen from a frame moving with velocity $v$ in ...
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How does a clamp meter only measure current on the wires inside clamp and not outside?

I think the title says it all, but I'll try to explain better: I know a clamp meter measures current by the current induced (if AC) or the magnetic field created (if DC). But how does the measurement ...
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How would a wire “detect” a change in magnetic flux inside an area it doesn't touch?

The law of induction says: $$ \mathcal{E} = -\frac{d\Phi_B}{dt} $$ In the case of a uniform field perpendicular to the area it is equal to: $$ -\frac{d(BA)}{dt} = -\bigg(\frac{dB}{dt}A + B\frac{dA}{dt}...
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What is the physical significance of negative sign in Faraday's law of induction?

People say that negative sign has something to do with Lenz's law. I understood that negative sign is used to get correct sign of emf according to definition of emf. But how we can relate negative ...
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Faraday's Law - When do we know when it is a motional EMF or an induced electric field?

So from what I know, Faraday's law states that when there is a change in magnetic flux, an EMF is induced. This can be explained with motional EMF where when the magnet moves towards the conducting ...
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Self-inductance of a given Setup

I am asked to prove that the self inductance of the system is given by I used Ampere's Law to find the magnetic field between the strips: The magnetic field due to the second strip would be the same ...
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How we get sense of direction from faraday's law while it as a whole is scalar?

I'm referring to Maxwell's third equation If we assume direction of existing magnetic field i.e. M.F due to magnet as positive then if I look at Right hand side of equation which is $\frac{-d∅}{dt}$ ...
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Does the magnetic force has anything to do with induced EMF in Faraday's law?

So according to faraday's law, when there is a change in magnetic flux, there is an induced EMF. My understanding: In the reference frame of the magnet, the charge is moving, hence there is a current. ...
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How does a change in magnetic field produce a curling electric field?

So according to Faraday's law, when there is a change in magnetic flux, an EMF is induced. The reason why an EMF is induced is because there is an electric field produced. So my question is, how ...
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What factor(s) can induce the charges to the conductor as in this isolated situation?

The 2 conductors exists. The actual diagram(not this diagram) depicts conductor with clay form but I depicted it as sphere form since I thought that sphere form can also be congruent of clay form. $$ ...
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Why is there no conduction current $i_C$ through a surface between capacitor plates?

The image is from Young and Freedman's University Physics with Modern Physics, Chapter 29 (Electromagnetic Induction). The image shows a parallel plate capacitor being charged where the current ...
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Formula for The Voltage of a Coil

I've seen 2 different formulas being used for the voltage of a coil in a circuit. The first one is $$U_L=L\cdot\dot{I}$$ and the second one is $$U_L=-L\cdot\dot{I}$$ The first formula was used in a ...
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Is an increase in inductive current caused due to an increase in magnetic field?

I'm studying Inductive current in high school. I learned the Faraday law, and that the voltage produced is equal to the delta of magnetic field flux over time. So, I was curious about this topic and ...
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EMF generated by moving square

I have been studying electromagnetic induction and I have trouble understanding some things. Say we have a square wire going through a magnetic field like in the picture (height is "h" and ...
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Why is force due to induced electric field not considered in the case of eddy currents?

In case of eddy current, I have noticed that we only consider the influence of magnetic force (due to induced current) on the conductor. But what if the conductor has charge? Will the force due to the ...
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Why does flux remain constant on changing the inductance?

I got the above question when I came across the following problem. A current $I_0$=1.9A flows in a long closed solenoid. The wire it is wound of is in a superconducting state. Find the current ...
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How many electrons in a ferromagnetic material, per atom, have their spins pointing in the same direction?

Is there a list or chart somewhere that states, approximately, how many outer electrons per atom in a particular ferromagnetic material are aligned? Are there, say, five electrons in an FeO2 magnet's ...
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Electromagnetic induction - Two circular loops

I have tried to do this exercise but I don't know if it's correct: Two small circular loops of area A1 and A2, parallel and initially coaxial, are separated by a distance x. A current I passes through ...
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How to mathematically show that magnetic field in Helmholtz coil is homogeneous

From the title of the question you have probably already figured out what my question is... How to mathematically show that magnetic field in Helmholtz coil is homogeneous? I know that magnetic field ...
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Alternator rotate in reversed direction: does the induce emf violate the Lenz's law?

There is a question in my textbook: Below show the structure of a bicycle alternator: And the output terminal is connected to CRO to show the induced emf. When the magnet is set to rotated in one ...
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90 views

What would happen if we remove the battery from a DC motor?

The construction of a DC motor and an AC generator is nearly the same, the only difference is that a dc motor has battery while the ac generator doesn't have the battery. If we remove the battery, won'...
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What are the applications of a magnet being dropped down a non-magnetic metal pipe and why does BAcosθ apply to coils when most of it is empty space?

You know those experiments you do in school to demonstrate Lenz's law, where a magnet is dropped through a copper or aluminium tube and it takes very long to fall? Are there any applications where ...
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Is the induced electric field generated due to the separation of charges in a moving wire in a magnetic field non-conservative?

As the title suggests, whenever there is a moving wire in a magnetic field of constant magnitude, an induced voltage is produced. Now, due to the separation of charges, which is a result of the ...
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Does a straight, current-carrying wire always repel a permanent magnet? Regardless of the permanent magnet's orientation?

Several people have told me that a current-carrying wire usually (or always) repels a nearby permanent magnet.... Most recently, I saw this Veritasium video on YouTube: 'How Special Relativity Makes ...
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Energy Transformations in a Motor

I'm confused about how the energy transformations in a motor work. I'm not comprehending how the electrical potential energy within the circuit is transformed to rotational kinetic energy of the coil, ...
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Moving charges in magnetic field

With homopolar generators, I understand that a current flows from the centre of the disk to the rim. And then using Fleming's left hand rule this creates a force which opposes the motion of rotation ...
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Self-sustaining Homopolar generator

I have been having some confusion with homopolar generators. My lecturer saying that these homopolar generators can be electrically self sustaining and I don't understand how. I get that a current ...
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Faraday's law of induction applied onto a magnetic film

Situation: Consider an infinite magnetically active film with the film normal in the z-direction and thickness $h$. The dynamic magnetization inside the film is $\mathbf{m}=(0,m_y,0)e^{i\omega t}$. ...
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60 views

Faraday's law conditions

Does Faraday's law only apply when there is a changing B field or change in area for a closed loop? Thanks
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Induced voltage as a difference of potentials on a ring

If you put a ring (Picture 1) of wire into changing magnetic field, the process called magnetic induction creates induced voltage. Voltage is by definition (Definition 2) the difference in electric ...
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Are induced electric fields parallel or perpendicular to a conductor?

Suppose you have a conductor embedded in a resistor at a 45 degree angle to the (x,y) coordinate axis, and you apply a time-varying, plane-wave magnetic field in the y direction (see Figure 1). As per ...
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Forms of energy in a closed circuit with a coil

I am a bit confused. When i move a magnet through a coil thats in a closed circuit, what does my kinetic energy convert to? I assume I will create a magnetic field, and that magnetic field will create ...
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Why is there no EMF induced or flux change of the left ring zero? [closed]

I tried by dividing the system into three parts, and flux is increasing for the left most and right most part and decreasing for middle, but am not able to arrange this in form of a battery, any help ...
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249 views

Why does alternator become easier to turn if you disconnect a transformer from it?

An experiment shown in class showed an alternator connected to a transformer. When you disconnected the transformer, the alternator become easier to move. My thoughts are that when the current induced ...
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Will a stationary charge be affected by changing magnetic field?

We know that changing magnetic fields ($dB/dt \neq 0$) produce electric fields in circular loops. So if we keep a stationary charge in the changing magnetic field, will it experience any force due to ...
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What does reactive power translate to in terms of torque?

Say I'm trying to connect an AC generator to a circuit containing an inductor and a resistor, powered by a steam turbine. I understand that because of the resistor, I'll be dissipating energy and ...
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How does magnetic hysteresis (ie. the B-H curve) transform the input-output of a guitar pickup or speaker?

I understand that magnetically dependent equipment like a guitar pickup or speaker are affected by magnetic hysteresis. Here is an article discussing the effect on speakers for example. That article ...
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Squared Field Derivative Model of Eddy Current Losses in Inductor

For a project that I am working on I would like to calculate the expected eddy current losses that occur in a rod shaped inductor. In order to do so I was referring to the following paper. The paper ...
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Finding how to calculate the speed of a magnetic train through a coil in a simple DIY Hyperloop model

before I start, let me just say that I am terrible at physics, and this question might have some inaccurate vocabulary. I apologize for that. I am currently working on a physics model (both ...
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Magnetic levitation using Eddy currents

I was watching Walter Lewin's lectures; https://www.youtube.com/watch?v=rLZLa-fyt1w&list=PLyQSN7X0ro2314mKyUiOILaOC2hk6Pc3j&index=20 He talks about magnetic levitation in the following way: ...
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Misunderstanding the right hand screw rule for magnetic fields

I have learned that the right hand screw rule works for your thumb being in the direction of conventional current (positive to negative potential) but also that the right hand screw rule is used for a ...
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Loss of energy when permanent magnet falls trough coil?

Is there a loss of mechanical energy when a permanent magnet falls trough a coil? Given a magnet with mass m and a coil with N windings. The coil is placed vertically so the magnet can fall trough. ...
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How does a copper ring levitates above a AC supply primary coil?

Doesn't AC current gives decreasing current and so decreasing magnetic fields or flux. This should then attract the copper ring above primary coil. When magnitude of current increases in AC then due ...

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