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2
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1answer
29 views

Inductor potential difference direction

If you have increasing current going down an inductor, the inductor will produce a potential difference to produce a counter current in the opposite direction, or up. The lower potential is then on ...
1
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2answers
63 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 ...
1
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0answers
16 views

magnetic induction coupling [closed]

I would like to know if coil shape as illustrated by right hand drawing is more efficient to couple magnetic induction when magnet approaching. If the coil shape does have effect, how do I calculate?
1
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1answer
37 views

If a purely inductive circuit is started in presence of gravity, will the power source ever run out? [closed]

I have read that purely inductive circuits do no work. So if an Inductor with an AC source, coming from an inverter is set up, will the source of power ever run out due to work against gravity? This ...
0
votes
1answer
13 views

How much current travels transversely in a coil ?

Excuse the the cryptic q. I was just wondering, say in a guitar pickup or AC transformer, we have a coil of copper wire that is coiled around a magnetic core(s). Current is induced in the wire by the ...
1
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0answers
38 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 ...
0
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2answers
31 views

How is it possible to even develop any current in an inductor?

Potential difference across an inductor (ie p.d. between current exit point and current entry point) is given as $$V= -L\frac{di}{dt} -iR,$$ where $L$ is the inductance of inductor and $R$ is its ...
0
votes
1answer
12 views

Current induction on a volumic body

The Faraday's induction law states that the temporal variation of the magnetic flux induces an electromotive force, according to the following expression: $$\varepsilon^i=-\frac{d\theta^m}{dt}$$ I ...
0
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2answers
79 views

How do inductors store energy?

I know that in capacitors, when we create a potential difference between the two plates, and then cut off the current, the electrons stay there and this energy is stored. But what is the similar ...
1
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3answers
97 views

Please help me with this doubt from electromagnetic induction

If motional emf and induced emf are the same, how to explain the emf induced in a conducting rod moving with a velocity perpendicular to length of rod and magnetic field(magnetic field is ...
1
vote
1answer
42 views

What causes the induced EMF?

I read many different explanation but none of them is satisfying. There is two cases: 1. I move an iron rod in a magnetic field, between two bar magnet for example. To this case I read that when I ...
1
vote
1answer
25 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...
0
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0answers
51 views

Kinetic to Electric Energy

Not the best with understanding the formulas involved with the calculations but here is the gist: I want to use Faradays law to convert the kinetic energy from actions such as shaking to produce ...
-6
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1answer
33 views

I need proof for dW=eIdt [closed]

I need help to understand from where this equation is formed inorder to continue to study energy stored in an inductor.
0
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0answers
48 views

Calculating temperature in a steel rod/bar which is heated by induction?

I'd like to calculate what kind of temperatures I could achieve in a steel (or copper) bar/rod with the help of heat induction from a coil. Firstly, let's not take radiation or convection into ...
0
votes
0answers
25 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?
1
vote
0answers
23 views

Magnetic Forces and Junkyard Magnets: What's Going On? [duplicate]

In my electromagnetic theory class, I learned that magnetic forces do no work. This is easy to see when observing a cyclotron; the speed never changes, so the kinetic energy never changes and ...
3
votes
2answers
80 views

Kirchoff's rules and inductance

Can Kirchoff's loop rule be applied in a scenario involving an inductor? Kirchoff's loop rule states that the closed loop integral of E dot dl is equal to zero. But, in a situation with an inductor, a ...
0
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0answers
44 views

Point charge inside a electrically neutral cavity in conductor placed eccentrically, and effect of external electric field if switched on

bear with me, but i would like a definite answer, now, starting off the external charge density on the outer surface of sphere WILL be uniform by unique solution of Laplace equation and letting the ...
7
votes
1answer
264 views

Motion in a time-dependent uniform magnetic field

Suppose you have an infinite solenoid generating an uniform magnetic field inside. The field is oriented along the solenoid axis : unit vector $\vec{\bf n}$. The field intensity varies linearly with ...
1
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3answers
229 views

Derivation of transformer equations

I've learnt in high school that in an ideal transformer, $$\frac{V_s}{N_s} = \frac{V_p}{N_p}$$ I looked for derivation for this formula, and in every source I look, the argument goes thus: $$|V_p| = ...
1
vote
1answer
43 views

Conductive Rod in a Magnetic Field [closed]

I have a question about induction. Imagine a conductive object being moved in a magnetic field. What forces will it experience and how does the induced current in the object affect the motion, will ...
0
votes
1answer
90 views

How to draw + and - and $\nabla \times E$ on a circular wire?

Faraday's Law: $$\vec{\nabla}\times\vec{E}=-\frac{\partial\vec{B}}{\partial t}$$ Circulation of electric field: For time-varying magnetic field and a closed wire, How can we add + and - pole ...
0
votes
1answer
41 views

Induction: How does the electrons in the coil know in which way the magnetic field is moving?

It is well known that a coil will react to a moving external magnetic field in such a way, that the electrons inside it will start moving to produce an internal magnetic field, which counteracts the ...
12
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4answers
423 views

How does the emf “know” what the magnetic flux is?

I came across an example in my book where it has the changing flux from a solenoid passing through a larger ring at the end. Here's a picture: How does the large loop (or radius $r_1$) even ...
1
vote
2answers
85 views

Does voltage always cause current?

I'm wondering if the following statement is fully correct: Voltage causes current through a closed circuit, but through an inductor it is the change in current that causes a voltage. Obviously ...
2
votes
2answers
124 views

Can pulsating DC current be transformed?

Since pulsating DC current is changing, why doesn't it induce a changing magnetic flux in the transformer core? Is it able to induce a transformed current in the secondary coil?
0
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0answers
19 views

Does inductors oppose the same change in current that it itself produces in case of DC Current?

We know that the inductor is a solenoid. In that solenoid, due to self induction it produces its own emf. That causes a change in the initial current. To counter this change the inductor produces ...
1
vote
1answer
58 views

Self induction in a circular coil

There's a formula for self inductance : $$ L=\frac{n\Phi}{i}$$ where n is the number of loops. But the book also says self inductance is directly proportional to $ n^2 $ I totally agree with the ...
3
votes
3answers
495 views

How to find the direction of an eddy current?

Suppose there is a magnetic field going from left to right. Suppose a thin sheet of metal conductor (e.g. a 1m*1m square) is dropped through the magnetic field such that the plane of the conductor is ...
0
votes
3answers
110 views

Why does AC induction motor rotate the same way?

Suppose an aluminium disc is suspended where it can freely rotate. A magnet is placed above (not touching) the aluminium disc and made to spun. This obvious causes a changing magnetic field. By ...
0
votes
0answers
28 views

Induced emf around plane wing tips- varying magnetic field(revised)

I understand that a solenoid wire with an induced magnetic field can be subjected to a varying magnetic field. My question is if you can you have a varying magnetic field around the wing tips of an ...
0
votes
1answer
213 views

Induced emf vs Potential difference

Let a square conductor frame length l, resistance R,be pulled out with a constant velocity v from a magnetic field B perpendicular to plane of the frame .Then an emf e=Blv is produced across the ...
1
vote
0answers
78 views

Calculation of transformer coupling coefficient [closed]

We know that the mutual inductance $M$ of a transformer is related to the inductances of the two coils via $$M^2=k L_1 L_2$$ where $L_1$ and $L_2$ are the coil self inductances and $k$ is called the ...
2
votes
2answers
103 views

Why is an $LC$ oscillator lossless, but $C V^2 / 2$ energy is lost to a capacitor connected to an ideal voltage source?

It is mathematically proven that in an $LC$ oscillation that all the energy gets transferred from the inductor to the capacitor and vice versa. There is no energy loss as there is no load in the ...
1
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0answers
70 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 ...
2
votes
1answer
67 views

EMF produced when a square wire is pulled from the corners [closed]

The shown diagram is of a square conducting frame being pulled from the corners. The velocity of A and B is given as $u$. Each side has length $a$. I was trying to find the induced emf at the instant ...
1
vote
1answer
83 views

Charging identical spheres using induction

Suppose I can induce a charge Q in a conducting sphere by the traditional induction method, then why is it that the charges would be equally shared if I put this sphere in contact with another ...
2
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2answers
118 views

Why is Kirchhoff's second law commonly used for circuits involving inductivity?

I have often seen in introductory literature, e.g. for the activation process of a circuit with a power source which delivers the voltage $U$, current $I$, resistance $R$ and an inductivity $L$, that ...
0
votes
0answers
22 views

What state is needed to model AC 3 phase induction motor?

Suppose I have a regular 3 phase 50hz AC squirrel cage motor of known design. If I wanted to make a model of this motor, would I need to know more than: Angle of rotor Angular velocity of rotor ...
3
votes
2answers
185 views

Why in electrostatics is $dV=-E.dr$ but in electromagnetic induction, $EMF=+E.dS$?

In electrostatics we learned that $$dV=-E.dr$$. I understood the derivation which was used to derive this. Now when I have come to Electromagnetic Induction,I see that when there is a time varying ...
0
votes
1answer
32 views

Does resonant inductive coupling work in the presence of a strong magnetic field?

Does resonant inductive coupling work in the presence of a strong magnetic field? I am unsure because resonant inductive coupling uses magnetic fields to transmit power wirelessly and a strong ...
2
votes
1answer
48 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: ...
0
votes
1answer
307 views

Inductor's back-emf vs voltage drop across resistor

In almost all physics books I've seen it says that the back-emf generated across inductor causes the delay in current (current is shifted 90 degrees with respect to the voltage across inductor). I ...
1
vote
1answer
77 views

Eddy Currents – Tubes with slits

When a magnet falls down a tube, eddy currents form and flow around the tube, perpendicular to the direction in which the magnet falls. However, when there is a vertical slit in the tube, are ...
0
votes
0answers
20 views

Can the movement of gas induce a current in a coil?

I'm trying to determine if I can generate a current by passing a gas over/through a coil or over plates. I understand that I may need special gasses and/or special coils/plates to achieve this.
0
votes
1answer
70 views

What happens if I have a square conducting wire being permeated by a magnetic field and the field suddenly disappears?

Suppose there is a square conducting wire in a magnetic field. The two vertical branches will have the same emf, and the two horizontal branches will have 0 emf, resulting in a net emf of zero and ...
2
votes
3answers
162 views

Zero current induced in a loop

Consider the following two cases, Case 1 – A coil moving through a constant magnetic field Case 2 – A conductor moving through a constant magnetic field Now, in Case 1 (a coil moving through a ...
2
votes
2answers
264 views

Is light moving because of self induction? [duplicate]

Light is made by an electric field wave and a magnetic field wave. Induction laws state that a variation in the electric field creates a magnetic field and vice versa. Therefore can it be said that ...
0
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0answers
63 views

Approximate of self-inductance of a square wire coil

Imagine you have a square coil of wires with n turns. In order to calculate the self-inductance coefficient I should know the magnetic field. Is it acceptable to consider the 4 sides as infinitely ...