# Questions tagged [induction]

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350 questions
10k views

### Does any object placed in an electric field change the electric field?

Lets say I have a point charge of magnitude $+q$, All around it I would have a symmetric radial electric field. Now if I place a neutral object lets say a sphere (doesn't matter insulating or ...
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### Separating the convective and the inductive electric field

My question is basically this, if I am only able to measure the total electric field and the magnetic field at a few discrete points in space and time, is it possible to separate the convective and ...
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### Work done by Lorentz Force in case of motional emf

In the classical example of the slidewire generator where the rod slides on a U-shaped conductor in a magnetic field, we get a charge separation due to the Lorentz force. The way the induced emf is ...
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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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### How exactly does WiTricity's wireless power transfer using resonance work?

The WiTricity group has made a lot of buzz but no internet article explains the exact method that they are using. Does any one know how it works?
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### 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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### Current induced from a magnet moving through a solenoid?

If we had a magnet we move it towards a solenoid a half sine wave current is induced when we make it move back, the other half is induced, inducing an AC current in the solenoid. What if the magnet ...
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### What is the area in Faraday's law if we have only a piece of metal moving in a magnetic field?

If a piece of metal of length $l$ is moving with a speed $v$ in a region where there is a uniform magnetic field $B$ perpendicular to it, there will be a potential difference across its terminals ...
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### Does changing the electric / magnetic field cause self-reinforcing induction of the other?

I understand that changing electric field produces magnetic field and changing magnetic field produces electric field. Are these produced magnetic and electric field produced due to one defined to be ...
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### AC through a pure inductor

I've studied the AC circuit for an ideal inductor in many physics books. After deriving the final equation for current the integration constant $C$ is assumed to be $0$ by giving inadequate reasons. ...
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### Flux increase due to velocity?

I have a book question I'm trying to understand: The first bit is easy enough. The second part I was confused so I checked the solution: B is into the page. The flux increases as the bar moves to ...
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### 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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### Measuring voltage drop from induced current

I'm having trouble connecting voltage drops and induced current. Imagine you have a triangular loop make up off three resistors. You place this loop in a constantly changing magnetic field. This ...
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### induction for massive objects

We know that when two charged bodies are kept near one another, they attract the charges and induce some charge near the surface. This happens even when only lne body is charged as the charges are ...
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### Magnetic induction in Relativity

As we know magnetic phenomenon is a mere relativistic effect.My question is how to explain the magnetic induction in a relativistic manner?
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### Non-conservative electric fields due to changing magnetic flux?

What I read in several places, tells me that, the fact Coulomb's Law follows inverse-square law and gives a force which is radial, implies that a static electric field must be conservative.(In short, ...
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### current induced in magnetic field

"If a wire loop is completely in magnetic field no current is induced as voltage induced is balanced by an equal and opposite voltage. " My guess for this statement is that the loop wire must be ...
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### Explaining Lenz's Law without conservation of energy

I was often told by my professor, using the following example, to demonstrate the relationship of conservation of energy and Lenz's Law. If you push a conductor into a constant magnetic field. By ...
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### Cause of electromagnetic induction?

The rate of change of magnetic flux through a surface (open) is related with the line integral over the closed loop binding the selected surface by one of the Maxwell's equation. But that means even ...
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### Understanding the basics of electromagnetic induction

Suppose two rings are kept facing each other and that one ring have some current which increases constantly. Will the other ring be attracted or repelled? Does this also depend on how they are kept?
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### Is the standard explanation for the ring launcher incomplete?

Related: Faraday's law in a ring The ring launcher is a standard introductory physics demonstration that I assume almost everyone has seen (if not, YouTube it). The explanation of why the ring is ...
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### Why Is Current $\propto$ Number of Loops?

When an additional loop is added to a generator the magnetic flux through the loops does not change yet the current increases. This seems counter-intuitive and has been described as 'non-conservative.'...
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### Can you make ice red hot?

This video clip allegedly shows an otherwise unspecified ice cube that turns red hot (and burns) due to induction heating. Can somebody explain how this works?
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### Direction of the induced electric field

Assuming there is a time varying magnetic field (B), how to determine the direction of the induced electric field due to B. and to which parameters does it depend? P.S. determining the electric field ...
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### 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 ...
3k views

### Charging by induction (and grounding)?

The very familiar phenomenon of charging by induction includes bringing a charged object near an uncharged sphere to induce a separation of charges in it and then grounding the charge (same as the ...
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### What is wrong with this form of the Maxwell-Faraday equation?

What is wrong with this form of the Maxwell-Faraday equation? $$\oint \vec{E}\ \partial \vec l= \bigcirc \hspace{-1.4em} \int \hspace{-.6em} \int \frac{\partial \vec B}{\partial t}$$ "Line integral ...
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### Induced voltage of a conductor in a magnetic field

A book which I referenced for Electrical Machinery states that the voltage induced in a conductor inside a magnetic field is given by $$\mathcal{E}=(\mathbf{v} \times \mathbf{B})\cdot \mathbf{l}$$ ...
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### 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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### Faraday Effect, Satellites, and Electromagnetic Atmosphere [duplicate]

If I launched a Satellite into orbit and dropped a silver wire caged in carbon fiber with aerodynamic wings (for support), would the Faraday effect of the wire traveling through earth's ...
591 views

### How does a force on electrons produce a force on a metal plate

In a paper from Cadwell Magnetic damping: Analysis of an eddy current brake using an airtrack about eddy current brakes the author explains the effect qualitatively as follows: When a ...
254 views

### Electric current streamlines in induction cooking vessel

I am looking for a plot of the typical streamlines of the electric induced currents ("eddy currents") in a induction cooking vessel. How can one theoretically predict the streamlines? How is it ...
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### measuring electromagnetic induction

There is a famous law which says that a potential difference is produced across a conductor when it is exposed to a varying MF. But, how do you measure it to prove? It is quite practical. ...
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### 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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### Magnetic induction in solenoid

I found an equation in theory about magnetic induction in a solenoid: $B_s=\mu_0 I n$. It should be magnetic induction for infinite length solenoid. I wonder if this is anyhow useful. Where can this ...
634 views

### Faraday's law in a ring

What role does the induced emf in Faraday's law play in generating current in a ring in which the magnetic flux is changing ?
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### What is the maximum power available from a magnetic field?

I just want to validate something I inferred from studying Griffiths (1999). The instantaneous magnetic field $\vec{b}(t)$ at a distance $r$ from a long infinite conductor carrying a current $i(t)$ ...
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### Is it possible to get energy from electrical wire using induction?

Pardon me if this is a stupid question but my physics courses are from a long long time ago and I was a teenager back then. ;) Electricity in a wire generates electromagnetism, right? Would it be ...
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### What will happen if we place salt water on a induction cooker?

As we know that induction cooker works on the principal of induction of current in a conducting plate. So I just wanted to know what will happen if we place salt water in a plastic container on the ...
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### Electrostatic induction

Is this a correct definition of electrostatic induction, The production of opposite charges on a neutral body when a charged body is brought near to it? I think it's not the production but ...
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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 ...
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### Induction cooker + superconductive pot [closed]

What will happen if I put a super-conductive object on an induction cooker, and turn the cooker on?
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### Why doe we not get a shock on induction cooker?

In induction cooking, eddy currents in cook-pot cause heat to be produced. But why do we not get a shock? Also, why is it that current is converted to heat while it has a good conductor(say, steel) ...
922 views

### What would result in a transformer that has its secondary wires disconnected from any circuit?

I am studying magnetism and I am curious as to what happens in a transformer that has its secondary output wires connected through a circuit versus one that doesn't. My main questions (in the case of ...
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### Basic magnet through a copper coil experiment - What if poles were rotated 90 degress

I was wondering what voltage or current, if any, would be produced if the basic magnet through a copper coil experiment had the poles rotated 90 degrees so north and south faced the top/bottom of the ...
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### Does special relativity unify the two phenomena at the base of Faraday's flux law (was Feynman wrong in this case)?

Consider Faraday's flux law for the EMF generated in a conductor loop: $$\varepsilon = - \frac{d \phi}{dt},$$ where $\varepsilon$ is the EMF, and $\phi$ is the magnetic flux through the loop. ...
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### What is the current through the lamp?

We have the following circuit: A neon lamp and a inductor are connected in parallel to a battery of 1.5 $V$. The inductor has a 1000 loops, a length of $5.0 cm$, an area of $12cm^2$ and a ...
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### locality vs non-locality

Suppose we have a circular loop of wire, and we put a long perfect solenoid inside it which is connected to an AC voltage source so that the magnetic field inside it starts to vary by time, does this ...
Imagine we have an induction coil which is strong enough to heat a sheet of metal. We can put a sheet of ferromagnetic metal close to the coil at distance $h_1$, and it gets heated to temperature $t_1$...