Questions tagged [induction]

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Do magnets attract magnetic materials by inducing magnetism in them?

Here are 2 concise excerpts from a book I have been reading:- 1.A permanent magnet produces its own magnetic field. An induced magnet is a material that becomes a magnet when it is placed in a ...
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110 views

Induction equation in a rotating frame

In his book, Tom Cravens refers to the induction equation (perfectly conducting limit) in a rotating frame, the Sun. See link below: https://books.google.com/books?id=xw50iZep-McC&pg=PA222&...
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557 views

Would there be EMF induced in our body due to electromagnetic radiations?

The experiments of innovative Faraday and Joseph Henry in USA, conducted around 1830, demonstrated conclusively that electric currents were induced in closed coils when subjected to changing magnetic ...
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How to calculate induced emf of moving rod?

I have the following exercise: A copper rod with length L is moving on two frictionless conducting rails, in a distance a from an very long straight conductor. The rods resistance: R. Ignore any self ...
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42 views

Effect of greater coils on induced current in a solenoid

Simple case:- A bar magnet is inserted into a solenoid with 'n' turns at velocity 'v'. The current is measured using an ammeter that is part of the complete circuit of the solenoid. My question is ...
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474 views

Measurement of electrostatic induction

How is it with the electrostatic induction measurement? Everywhere you can read about the effect of electrostatic induction but I still can't found any detailed explanations or quantitative ...
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119 views

What would happen if a magnet was pushed towards a copper tube in space?

So the question was inspired by one of curious comments on youtube. What exactly would happen if you pushed a strong neodymium magnet towards the copper tube (aiming for the opening in an effort to ...
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522 views

Torque on a charged ring

I have been studying electromagnetic induction. As I understand, a magnetic field will exert a force on a moving charge. What I would like to know is whether a changing magnetic field will exert a ...
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79 views

Two Jumping Rings Go Higher than One. Why?

When I do the Thomson's jumping ring demo with one aluminum ring it rises up in the air to some height. When I place two identical rings on top of each other and repeat the demo, both rings rise ...
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44 views

Electromagnetic Induction, specifically induced voltage

Why is it that if a conductor 'cuts through' (what does this mean?) a magnetic field that a potential difference is produced? I read this recently in a textbook...
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1answer
69 views

How to induce charge in glass bubble particles ?

I am trying to induce charge ( + or - ) in the glass bubble particles ( manufacturer 3M 25-32 micrometer) . Can anyone tell me how to effectively charge them. I have tried placing these particles in a ...
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1answer
3k views

Back motor effect of loaded generators?

The back motor effect (see Counter-electromotive force) is the counter torque which opposes the rotational motion of the coils in a generator when the generator is under load. The back motor effect ...
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How to calculate the energy transfer between working coil and working piece and dissipated energy of working piece in induction heating?

For who don't know how does induction heating work, a short description can be found here. However, my question is about physics. Assume I have a coil inductor calculated carefully 50 uH as below: ...
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Induced current created by a magnet falling in a copper tube?

One of the educational demos often shown in schools is to drop a high strength neodymium magnet down a length of copper tube. It takes a considerable time to exit the tube because as it falls it ...
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If you toss a handful of confetti onto a comb, why does some of it stick and some of it fly away?

My guess is some paper pieces happen to be charged with the opposite charge compared to the comb, so they are attracted, but once they touch the comb, their charge is neutralized. But the comb is ...
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568 views

Attraction and repulsion of electron spin ups and electron spin downs

Alright, we know that copper is a diamagnetic material, which has paired electrons. These paired electrons have different spin. I'm specifically interested in what is going on with the electrons in a ...
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Faradays Law: How Does Curl E Change Over Time In a Coil?

I think I am currently making a mistake regarding my interpretation of Faraday's Law. $\vec{\nabla}\times\vec{E}=-\frac{\partial\vec{B}}{\partial t}$ Assuming we have an electric field $\vec{E}$ in ...
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What is the physics behind the vibrating feeling you get when you touched an inducted metal surface?

When I was last working on the highway, I stopped to help a motorist parked under high tension power lines. I'm driving a large Ford Transit van, fairly box shaped. My van was parked 90 degrees (...
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38 views

Conductor in motion in a magnetic field

I have the following exercise: there is a square conductor of a given side L and resistance R. The conductor is surrounded by a magnetic field B (90° with the y-axis) and it depends from z: B(z) = K*z,...
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Ed Leedskalnin's “Perpetual Motion Holder” (PMH)

Edward Leedskalnin (Coral Castle) describes a perpetual motion holder in his writings. I've built one and pretty much know how it works (I think). It is NOT a perpetual motion device by any means, ...
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What are the exact properties of a superconducting coil?

I've seen plenty of experiments involving a cylinder-shaped superconductor and a floating magnet. I haven't seen many, if any experimentation on the properties of coils. For example: Can we measure ...
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Induced emf in a circular conducting wheel

Consider a conducting wheel with $N \in \mathbb{N}$ spokes which is completely in a homogenous magnetic field $\vec{B}$ perpendicular to the wheel plane.        &...
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970 views

Absolute permittivity and permeability of free space

I'm reading about the propagation of EM waves in vacuum. We define the wave equation using two constants: $\epsilon_0$ and $\mu_0$. Of course they are absolute permittivity and absolute permeability ...
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682 views

Finding the terminal velocity of a magnet dropped in a solenoid

We have to find proportionality of the terminal velocity with the factors of the system: Plot: a small dipole(mass $m$) with dipole moment $\mu$ is dropped in a long solenoid (radius $r$, ...
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How to calculate the limits for volume and mass for induction heating samples?

I'm evaluating the feasibility of using volumetric induction heating to quickly heat up steel molds. One thing I have come across is that induction heating really only works for surface heating or for ...
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Vector calculus and principle of reciprocity MRI

I'm studying the principle of reciprocity for the MRI. At some point during a calculation the book states that: $$\oint d\vec{l} \cdot \left[\int d^3r' \frac{\vec{\nabla'}\times\vec{M}(\vec{r}')}{\...
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Which coil configurations transfers the most magnetic flux?

So i'm working on a home project that involves magnetic coupling. I was wondering, of the two configurations described bellow, which one would should allow the secondary coil to receive the most ...
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533 views

Inductive loop: Rectangular vs circle shape

In the traffic field there are inductive loops that are installed under the road to detect cars. We cut asphalt and install 3-4 loop of wires like the following picture. The corners are cut ...
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169 views

Can magnets induce magnetism stronger then their own magnetism?

This might sound foolish but bear with me for the explanation. I came across a weird magnetic behaviour playing with coins on a mac. There are magnets in mac, two on the top corners of the screen and ...
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35 views

Uniform field through a disc

Let us say that we have a magnetic field of the form $B_0 \sin(\omega t) \hat e_z$ in all space. Now let us say we put a conducting disc within this field. I want to find the electric field within ...
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401 views

Calculating the amount of charges for an object that is electrostatically induced

Induction is one of the ways to get an object electrostatically charged. While positive charges accumulate on one side, negative charges accumulate on the other side for an object in an electric field....
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67 views

What happens to the emf generated due to a change in magnetic flux in a coil?

When we move a magnet into a coil of wire (open circuit) and then out of it, we create a emf across the ends of the coil and another emf in the opposite direction. My question is what would happen to ...
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142 views

Non-linearity of a guitar pickup

I basically understand induction and why a pickup generates a signal. (From: http://www.brighthubengineering.com/consumer-appliances-electronics/64277-the-physics-behind-the-electric-guitar/) What ...
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Explain the infinitude of magnetic flux about a finite length of wire

Ok so it is clear the flux caused by an inductor is limited. If I integrate about a flat spiral inductor I will find that the flux lines going up are a fixed quantity. Since every flux line going up ...
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382 views

Remotely changing superconductor levitation height?

I want to be able to modify the height of a quantum locked superconductor. My original plan was to levitate the superconductor over an electromagnet and modify the current to said magnet (increase the ...
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39 views

How might inducted current/ voltage in multiple coil layers connected in parallel behave?

This is a branch from this question. In the event that two or more layers are connected in parallel - would the energy created across each layer likely be significantly less? In the event of (say) ...
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344 views

Finding the induced EMF on a bar - Faraday's law

I have a couple of questions about the following problem: A conducting bar of length L moves with velocity v, in a rectangular region with a uniform and stationary magnetic field B_1. Near the bar, ...
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Would a $50\: \mathrm{Hz}$ spinning magnetic plate in front of a human generate harmful current?

We know that spinning magnetic plate will generate current inside any wire. so if we stand before 50Hz spinning magnetic plate, then, does that 50Hz spinning magnetic plate in front of us (human body )...
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211 views

Hertzian dipole in time varying electric field

Suppose we place a Hertzian dipole (short, ends loaded with capacitance) in a time varying electric field $\vec{E}\left(t\right)$, with magniture $E\left(t\right)$ and direction as shown in this ...
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92 views

Blocking electro-magnetic waves between two near field antennas

Its been a while since I studied physics, so pardon my ignorance. I have two near field antennas. The range of the antennas is about 2-3 cm. I am looking for a way where I can block and unblock the ...
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Violation of conservation of energy (seemingly) in process of electromagnetic induction

A bit long question but it's really bugging me a lot. Say we have a closed circular conducting loop at rest and initially a bar magnet rests along its axis with north side facing the loop. Now we ...
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56 views

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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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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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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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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44 views

EM Induction in non-uniformly conducting ohmic toroid, thought experiment

Assume that there's a conducting toroid with radius of revolution $R$ and an own radius of $D$ so that the cross section of the toroid is given by $\pi D^2$ Assume that there's a circular region of ...
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57 views

What is the range of the validity of the Maxwell-Faraday equation?

Similar to the question about the range of the validity of Coulomb's law, I am looking for references to literature that investigates the emirical bounds of the Maxwell-Faraday equation. However, it ...
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291 views

Efficiency of resonant inductive coupling as a function of distance

What is the relationship between the efficiency of energy transfer between resonant inductive coupling between two coils, and the distance between the coils?
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Eddy Currents in Metal Implants

Related: Why is stainless steel a poor conductor of electricity? I recently had a metal implant, and I'm psyching myself out- should I be considered at all with eddy currents in the implant? I feel ...
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What is the current induced in a straight wire when a magnetic field is turned from on to off?

Consider a straight wire which runs along the y-axis. A B-field exists which is uniform and only in the x-direction: $$\vec{B}=(B(t),0,0)$$ The B-field at time $t_0$ is 'switched off' in a ...