All Questions
38
questions
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12
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Self-induction in a permanent magnet
when a permanent magnet is moved in a coil, an emf is induced in the coil. so is an emf also induced in the magnet itself? and if not then why not. and if I replace this permanent magnet with a ...
- 117
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0
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50
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What logic is being used in Bleaney & Bleaney to prove the reciprocity theorem for mutual inductance?
I'm currently reading Bleaney & Bleaney 3rd Ed. On pg 136 they discuss the case of 2 coils. Their logic is as follows:
If a second coil is brought near to a coil carrying a current $I_1$, there ...
- 126
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votes
3
answers
69
views
Are there losses in an ideal transformer?
In a circuit with an AV power source $V$ and a zero-resistance ideal coil, the power from the source. $P_{in} = IV$ is equal to the rate of change in the magnetic energy $U_B$ stored in the coil. The ...
- 2,141
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votes
1
answer
24
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How different is the induced magnetic field of a coil with a solid rod core and a sheet-wrapped one? (Assuming both use the same material)
I'm doing research for a university project and looking for commercial references for Mu metal, I found out that in my country at P2B (particular to business) level, sheets are significantly easier to ...
- 1
1
vote
2
answers
149
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Intuition behind self-inductance
I'm having a little bit of a hard time understanding some concepts to do with self-inductance in class.
I understand mutual inductance. That's when a loop has some time-dependent current going through ...
- 187
2
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0
answers
65
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Variation of Permeability with DC magnetising Field
For any Powder core, as DC magnetising field increases, the initial permeability decreases known as "permeability roll off".
For example for an MPP core-
For MPP cores the initial ...
- 21
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22
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How does proximity of a grounded conductor effect an electric / inductive field (and practical application)
My apologies - I'm missing a couple years of learning to be able to ask this question well, to know the right terminology.
Suppose a grounded conductor, such as a 12mm copper water pipe.
The grounded ...
1
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0
answers
42
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Please clear up the following confusion about Faraday's law, electromotive force, magnetic inductance, and current
As the magnet moves from the outside, the magnetic flux that is linked to the circuit is [pi_0 sin(wt)].
We have listed a series of processes related to electromotive force, self-inductance L, and ...
1
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0
answers
45
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What is the flux linkage or inductance or induced voltage per unit length of the hollow tube conductor surrounding the inner conductor?
What is the flux linkage or inductance or induced voltage per unit length of the hollow tube conductor surrounding the inner conductor in some section due to the current in the inner thin conductor?
...
1
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2
answers
315
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Magnetic Field Produced by Solenoid
I was reading about solenoids and came to know that the magnetic field strength of a solenoid is greatly increased by
Increasing the number of turns in the solenoid coil (directly proportional to ...
- 229
1
vote
1
answer
164
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Calculating Induced EMF in Wireless LED Circuit
I have built the following circuit to power a wireless LED and my calculations and measurements do not give the same values. I am measuring a voltage nearly 6 times larger than I would expect in my ...
- 113
1
vote
2
answers
224
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Doubling the length of a solenoid doubles its inductance. Two identical solenoids in series have up to four times the inductance due to M. Why?
The inductance of a long solenoid with $N_o$ turns and a length $l_o$ is
$$L_o=\pi r^2 \mu_0\frac{N_o^2}{l_o}$$
If I now make a new solenoid, $L_{new}$, with double the length of the original ($l_{new}...
- 1,581
0
votes
1
answer
188
views
Is self-inductance dependent on geometry? Is $\Phi$ net flux or just flux due to cirucit?
Self-inductance of a circuit is defined as $L=\frac{\Phi}{I}.$ But it is not clear what $\Phi$ (read phi) is. Is it net magnetic flux or flux due to the magnetic field created due to current in the ...
- 480
1
vote
1
answer
140
views
Do transformers return current to source when magnetic field collapse at primary coil?
When we close the circut containing an inductor and a battery, the current starts flowing, which builds magnetic field around inductor, changing magnetic field produces its own current in opposite ...
- 129
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votes
2
answers
762
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How can I find the force of a solenoid with a moving plunger?
It seems like it should be a simple equation, until I realized that the core isn't magnetized until it is induced, then there is a dipole moment, and then as it moves the core of the solenoid ...
- 103
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votes
1
answer
96
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Forms of energy in a closed circuit with a coil
I am a bit confused. When i move a magnet through a coil thats in a closed circuit, what does my kinetic energy convert to?
I assume I will create a magnetic field, and that magnetic field will create ...
- 15
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0
answers
84
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How to simulate magnetic field of a toroidal solenoid?
I am trying to simulate the magnetic flux inside and outside of a classic toroidal solenoid. The simulation must be able to simulate a toroidal solenoid with several densely wound layers of copper ...
- 3
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votes
1
answer
26
views
Does electromagnetic induction moves the body or it just makes an induced current?
If I approched a magnet to a coil does it moves it by the effect of induced electric current so it repells away from the magnet or it just induces the current in the coil without the coil making a ...
1
vote
0
answers
97
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How to find inductance using $\phi=L I$ for distributed current case? [closed]
A current flows via two long coaxial cables.
Inductance is defined as
$\phi=L I$ but in this case where is the loop through which I should find the flux?
Is it even reasonable to define inductance ...
- 1,270
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0
answers
122
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Self-inductance, back EMF and energy stored in magnetic fields
First let's talk about self inductance. A current-carrying loop produces a magnetic field which in turn produces a flux through the loop. If this current is increased, the flux changes as the magnetic ...
- 453
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votes
1
answer
119
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What equation should I use to calculate inductance of a wire coil?
I've been working on a project recently which requires me to build an inductor, however in my research I found many different equations (with a range of variables used and giving very different ...
2
votes
1
answer
290
views
Mutual inductance - induced magnetic flux in the primary
Let there be two coils, L1 (with self inductance L1), and L2, with self inductance L2.
The first coil is connected to a sinusoidal supply, and the second one is connected to a resistor load, as shown ...
- 21
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votes
1
answer
75
views
Energy stored in an Inductor is used to move electrons
I was reading about the energy stored in an Inductor and first of all I had the question that is this actually stored? The inductor produces a magnetic field which exerts a force on electrons. Isn't ...
1
vote
3
answers
821
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Why does the current through an Inductor changes when the Inductor doesn't like the change of flux through it?
Consider the example shown above. Here we have connected an active inductor, in which the initial current is "I", to a resistance, with the help of a switch and close the switch at t=0. We ...
- 2,517
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votes
1
answer
108
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Understanding the physics of inductors
If an inductor "stores energy in a magnetic field", what does that mean exactly? It sounds like there's an invisible force field emanating from the coil or orbiting around the wire. As if electrons ...
- 179
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votes
1
answer
329
views
Why exactly does a current flow in an inductor oppose itself
So, I've understood that a current flow in an inductor produces
1) The original magnetic field along the direction of the curl E of the inductor.
2)Change in the magnetic field along the opposite ...
- 581
3
votes
0
answers
231
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flux threading through superconducting ring
I have been confused over the wording used in this paper describing RSFQ logic circuits: http://www.mukhanov.com/uploads/LikharevSemenov-RSFQReview_IEEETAS91.pdf
From page 6: " If such a single flux ...
- 101
1
vote
1
answer
330
views
Which method of calculating mutual inductance to use?
I am planning to make a wireless charging device for a school project using coupled induction. However, I have found a few different ways of calculating mutual inductance for coupled solenoids and ...
- 13
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votes
1
answer
57
views
Interaction between a current-driven coil and a second passive coil in the same space
Good evening,I have some doubts about mutual inductance. I hope that somebody will be willing to reply to my questions.
We have a coil L1 traversed by a current I1. If the current is stationary, L1 ...
1
vote
2
answers
621
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Paramagnetic material in a coil
If we hold the voltage constant, will (and how) the current through a coil change if we put a paramagnetic material in the coil ?
