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0answers
21 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 ...
2
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3answers
67 views

How does an Inductor “store” energy?

It seems to me that an electromagnetic field is nothing more than a collection of photons, which as I've heard, extends through space infinitely. Why is it, then, that an inductor such as simple ...
0
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1answer
18 views

Average induction voltage

I've got a basic question on the method of computing the average induction voltage. Here is the task: A conductor loop with the area $A_1 = 50\text{cm}^2$ in a magnetic field with the flux density of ...
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1answer
19 views

currents in an isolated metal exposed to an alternating uniform electric field

For example, let's look at a metal sphere between a capacitor's (infinite) plates. Let's run an AC current through the capacitor, resulting in an oscillating electric field. The charges will move in ...
2
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2answers
137 views

Em induction, sliding rod with resistance?

Consider the digram below: This consists of a rod sliding with velocity $v$. I want to find the voltage developed between $A$ & $B$. To do this I drew this 'equivalence circuit': From this ...
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0answers
28 views

The affect of high frequency and high voltage AC on induction

I am designing an induction system to wirelessly transfer power a short distance. I was planning on using resonant inductive coupling to increase the efficiency. The Inductance of my coil is about ...
0
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1answer
20 views

Does displacement current occur in an inductor?

We have learned in school that displacement current comes about due to a change in electric field flux per time in a capacitor (Ampere-Maxwell Law). Does the same displacement current come about in an ...
0
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1answer
53 views

Pulling a bar through a magnetic field

This is a question on magnetic flux and induced voltage. I believe that this problem's answer key is incorrect, and I want to determine whether my opinion is sound. I also want to explore one ...
0
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3answers
56 views

Where is the energy stored in an inductor?

In an inductor, Most text books say that the $(1/2)Li^2$ is stored in the magnetic field. But is there another way to explain this? In a capacitor I understand that all the energy that the battery ...
0
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1answer
30 views

Faraday's electromagnetic induction

Does the emf increase when no of turns of the same wire increased? Consider a wire of length 'l' is coiled with an area of cross section 'A' is subjected to a change in magnetic flux. an emf will be ...
0
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1answer
43 views

Voltage Flows in an Inductor

Pretend that a current increases across the left end to the right end of this inductor. I want to understand why the left edge is at a higher potential. This is my logic that contradicts that ...
0
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0answers
46 views

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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2answers
92 views

Derivation of Faraday's law using Lorentz force?

For a stationary loop of wire with a time varying magnetic field $\vec{B}(t)$ through it. Is it possible to derive Faraday's law, using only the Lorentz force $$\vec{F}=q \vec v\times \vec B \tag ...
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3answers
77 views

Induction and electromagnetic fields

I've got a few questions on induction and electromagnetic fields. My current understanding of induction and electromagnetic fields is that, when electricity/current flows through a wire, it creates an ...
2
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2answers
95 views

Predicting Polarity of capacitor in the given diagram

I have to determine the polarity of the Capacitor in the given diagram. I Approached the problem as follows: When Magnet 1 moves with its North pole towards the coil, emf is induced in the coil as ...
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4answers
104 views

How eddy current brakes function

Take the following example: where a rectangular sheet of metal is entering a constant magnetic field at $v \dfrac{m}{s}$. Due to Faraday's law of induction + Lenz's law, we can state that an eddy ...
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1answer
39 views

Basic Conductor question

I have just taken a physics test in my high school in which one question posed that a positively charged rod is held near two uncharged spheres being held by silk filaments. Sphere 1 is held by a dry ...
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0answers
10 views

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 ...
1
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2answers
42 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 ...
0
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2answers
69 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 ...
2
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1answer
94 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
25 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 ...
3
votes
2answers
123 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
82 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 ...
0
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1answer
88 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 ...
0
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3answers
82 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 ...
0
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1answer
89 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 ...
0
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1answer
76 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?
4
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4answers
160 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 ...
2
votes
0answers
18 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 ...
1
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1answer
50 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
votes
1answer
3k 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 ...
2
votes
1answer
37 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 ...
1
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1answer
59 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 ...
1
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1answer
80 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 ...
0
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1answer
65 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. ...
0
votes
1answer
38 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
82 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 ...
1
vote
1answer
120 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 ...
1
vote
1answer
26 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 ...
1
vote
2answers
74 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. ...
0
votes
1answer
77 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 ...
0
votes
2answers
28 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 ...
0
votes
2answers
165 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} $ ...
0
votes
1answer
28 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
votes
0answers
57 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
votes
2answers
472 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?
4
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4answers
494 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 ...
0
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2answers
63 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 ...