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Magnetic field generated by wires with magnetic cores

Describe the magnetic field generated by alternating current as it passes through a wire's special core of tiny, metal-coated, cylindrical rare earth magnets? Examples of real-world consequences of ...
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2answers
47 views

A question about induced fields

This is something that I just realized bothers me, after thinking about it too much. Faradays law tells us a changing magnetic field creates a circulating electric field. This electric field has a ...
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2answers
103 views

Why can't mutual inductance create perpetual electricity?

Consider the following image. When the battery is connected then current starts flowing through the primary cicuit and magnetic flux changes through the coil, this causes electricity to be induced ...
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2answers
209 views

Why is there no induced electric field in the experiment (Faraday's Law)

Below are three circuit diagrams for each of Faraday's experiments that allowed Faraday to come up with Faraday's Law. In Griffiths' Introduction to Electrodynamics Griffiths states (on page 302 of ...
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0answers
31 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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2answers
152 views

Does the induced Electric field develop instantly or lags by $\frac rc$?

Consider a loop of radius $r_0=3 \times 10^8$ cm. A thin bar magnet is passed through its center. This implies that the magnetic flux through the loop will change. Now according to Faraday's law a non ...
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1answer
256 views

How does a magnetic field produce an electromotive force?

As I keep reading through texts and online, I keep getting conflicting views when in magnetic fields and electromotive forces are involved. From what I can see, the emf is the work done per unit ...
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1answer
119 views

Measured voltage on coil

I have a simple circuit of coil with inductance L $$u_c(t)= -L\frac{di}{dt}$$ and AC source with output voltage $u_s$ What is actually measured by the voltmeter ($u_c$, $u_s$ or $u_s - u_c$)? If ...
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3answers
317 views

Does a moving magnetic field produce an electric field?

Consider a conducting rod of length $L$ moving with speed $v$ in a magnetic field of intensity $B$. Let all the three parameters be perpendicular to each other. Moving charges in a magnetic field ...
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1answer
321 views

Magnetic fields in transformers and back emf?

i am having some trouble with understanding the magnetic fields inside transformers and how they relate to back emf. My first query is: is the magnetic field produced inside the soft iron core ...
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1answer
152 views

magnetic field of a rotating ring magnet

Can the magnetic field of a rotating ring magnet induce current in a conductor? Is there a flux linkage between magnetic field of a rotating ring magnet and a conductor?
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4answers
310 views

Can current be induced in a superconductor?

Moving a magnet close to a conductor induces a current. If it consists of a superconducting material with resistance $R=0$, then my textbook says: Then the induced current will continue to flow ...
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0answers
25 views

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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1answer
83 views

Magnetic field between two concentric inductors

Suppose we have two inductors with $n_1$ and $n_2$ turns, of radii $R_1$ and $R_2$ $(R_1 > R_2)$ respectively and length $l$. They are aligned concentrically and the smaller inductor is wholly ...
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0answers
63 views

Weird phenomenon on aluminum laptop casing [duplicate]

A couple of days ago I observed a phenomenon which I'm not sure I understand correctly. My brother-in-law has recently bought an ASUS gaming laptop in an aluminum casing. When the power supply is ...
7
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1answer
7k views

Does a positive or negative charge attract a neutral object?

Three objects are brought close to each other, two at a time. When objects A and B are brought together, they attract. When objects B and C are brought together, they repel. From this, we conclude ...
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1answer
54 views

Relativistic Induced Magnetic Field in particle's frame

Suppose there is a constant magnetic field: $\vec{\mathbf{B}} = B \hat{z}$. A charged particle orbits that magnetic field perpendicular to the magnetic field, and induces a magnetic field in the ...
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1answer
156 views

Induced electric field due to a moving wire

An infinite wire carrying a constant current $I$ in the $\hat{z}$ direction is moving in the $y$ direction at a constant speed $v$. Find the electric field, in the quasistatic approximation, at the ...
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1answer
133 views

Skin effect and the eddy currents

I am trying to understand the skin effect, there is a bit in Wikipedia article I don't understand; "...The change in the magnetic field, in turn, creates an electric field which opposes the change ...
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3answers
417 views

How are the Lorentz force, Maxwell's third law and Faraday's law of induction clasically related?

Faraday's law of induction can be used in any situation where the magnetic flux is changing through a closed conducting loop. While giving the correct answer, it seems to me that for the following ...
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1answer
93 views

A falling steel beam - Maximum induced voltage [closed]

I'd appreciate it if someone could explain how to answer this question: A 2 m long steel beam is falling from a height of 12,5 m. During the fall, the beam is oriented in an east-west direction. ...
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1answer
50 views

If we rub glass particles with paper , will there be any charge induction in glass particles?

If we rub glass particles with paper , will there be any charge induction in glass particles ? I know if you rub with silk they do get charged, but i want to know specifically for glass and paper.
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2answers
192 views

Currents induced by rotation of a coil about magnetic field lines

If the coil on the left is rotated about the magnetic field lines, will there be an induced current? I know that the flux concerns only the component of the magnetic field perpendicular to the ...
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1answer
235 views

Density of charge induced on a hollow sphere due to eccentric charge inside

Suppose we have a lone hollow metal sphere with net charge equal to $0$. If we were to put a point charge $Q$ inside of the sphere and move it, let's say, away from the sphere center at some distance ...
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1answer
38 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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2answers
113 views

Force on a loop with induced current

Consider an infinitely long ideal solenoid with current $I$, radius $a$, turns per unit length $n$. Put a closed conducting loop around it (radius $b > a$), on a common axis through their centers. ...
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1answer
187 views

Constant current in inductor

When I brought the dc voltage from $25 V$ to $0 V$ . A constant flow of electrons I could see in the inductor. Why is this phenomenon happening ? When a constant voltage was supplied the inductor ...
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2answers
33 views

Lagging in induction coils

In an induction coil, When I supply a constant DC voltage of $10 V$ the current goes increasing with time. Why is this phenomenon taking place in an inductor ? How much is the lag between the ...
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2answers
461 views

Self induction in transformer

Wont self induction ruin the working of a transformer ? While increasing voltage (AC) in the primary coil, wont there happen a self induction in the primary coil itself ? $E_0 = -L \frac{dI}{dt} $ ...
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1answer
35 views

When mutual inductance are occurring between two coils, why the two coils have the same mutual inductance?

I learned that $$\epsilon_1 = -M_{12}\frac{di_2}{dt}$$ $$\epsilon_2 = -M_{21}\frac{di_1}{dt}$$ And the book tells us directly that $M_{12} = M_{21}$ without a reason. Is there a mathematical proof ...
2
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0answers
101 views

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 ...
2
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2answers
489 views

Why do old transformers make sounds, but new ones don't?

What I think is that maybe insulation is gradually removed between plates, and eddy currents start passing from one plate to another and this produces sound. Am I right?
3
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4answers
610 views

Faraday's paradox

I have studied that Faraday's law of induction and motional emf are two different lines of thinking but are essentially same. But then, how can Faraday's paradox be explained by Faraday's law of ...
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2answers
70 views

Is there any theoretical reason behind multiplying by $N$ when using Faraday's law of induction?

It is a well known fact that whenever we want to calculate the emf in a solenoid we usually multiply the changing flux for one loop times $N$, which is the number of turns in the solenoid. But why is ...
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1answer
100 views

Can we induce e.m.f. with magnetic field without any change in flux

An e.m.f. is developed when there is a change in flux. Can we induce e.m.f. without any change in flux? Is it against Faraday's law?
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1answer
129 views

Calculating the induced emf without knowing the change in magnetic flux [closed]

A conducting rod of length $\ell$ moves on two horizontal frictionless rails, as in Figure P20.30. A constant force of magnitude 1.00 N moves the bar at a uniform speed of 2.00 m/s through a ...
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0answers
86 views

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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1answer
64 views

Why can intramedullary rod heat with MRI?

It is said, that steel rod inside body, like funeral nail, can heat while magnetic resonance imaging (MRI). But why? Isn't MRI scanner use constant magnetic field? If the heating effect is caused by ...
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0answers
116 views

Electrical field of the coil

Take the case of two coils, first one connected to alternating current supply, and the second one connected to load. First coil creates magnetic field, and electric field is reduced by anti-emf ...
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0answers
34 views

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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4answers
845 views

Application of Kirchhoff's laws in circuits with inductors

As we know,the Kirchhoff circuit laws are applicable for conservative electric fields. Now it is applicable for circuits where inductors are present but the field there is not conservative. So how ...
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1answer
81 views

Direction of EMF

I was reading electromagnetic induction and came across EMF.Now in my text book as the theory has been developed ,they have many a times talked about direction of EMF. But they have not clearly ...
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4answers
211 views

Why uncharged particles do not feel the Lorentz force? [closed]

Why uncharged particles do not feel the Lorentz force? Please do not answer with the formula $ \vec F = q\left( \vec E + \vec v \times \vec B \right) $. Edit after an answer which is an circular ...
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2answers
137 views

Is the electron magnetic moment responsible for the Lorentz force?

My question about the sum of the electrons' magnetic moments in a wire(What is the sum of the electrons' magnetic moments in a wire?) had an answer which disappeared later. The answer was - if I ...
2
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1answer
104 views

What is the sum of the electrons' magnetic moments in a wire?

Electrons have magnetic dipole moment. This magnetic moment will be influenced in an electric field in case the electron get moved non-parallel to the current. The magnetic moments will be more or ...
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1answer
79 views

Direction of compass needle nearby an electric wire

Let through a straight wire flow an electric current. Using a compass needle how the needles tip will be directed to the wire? What happens when we switch the current direction and approach the needle ...
0
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1answer
103 views

Asymmetry in magnetic field direction of an electric wire

The simplest magnetic field is that of an infinitely long wire with uniform current. It does enjoy radial symmetry about the wire and has the variation as 1/r. To find the direction of the resulting ...
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1answer
96 views

Can non-conductive materials can be grounded by a wire?

Suppose that I comb my hair. The plastic comb would become negatively charged and would attract small paper pieces. But if I touch the comb in bare hand and in bare foot standing on the ground, or if ...
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1answer
466 views

Some general questions about static electricity ( ex : Combing the hair ) [closed]

We know , static electricity is built up when i comb my dry hair. what type of charge is gathered in comb & what type of charge in hair ? ( i.e. + or - charge ) why would charges would gather ...
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2answers
77 views

What physical forces allows for electromagnetic induction

In electromagnetic induction, what force is actually doing the work? what physical force actually drives the electrons around the circuit? Let's say we have a coil and an increasing magnetic field ...