All Questions
Tagged with electromagnetism inductance
44
questions
58
votes
7
answers
21k
views
Cyclist's electrical tingling under power lines
It's been happening to me for years. I finally decided to ask users who are better with "practical physics" when I was told that my experience – that I am going to describe momentarily – prove that I ...
- 180k
21
votes
4
answers
41k
views
Derivation of self-inductance of a long wire
Currently I am stuck, trying to derive the self-inductance of a long wire. According to literature it should be
$$L=\frac{\mu_r\mu_0l}{8\pi}$$
and in literature its derived by looking at the energy ...
- 1,573
18
votes
3
answers
11k
views
Faraday's law - does the induced current's magnetic field affect the change in flux?
I've had this conceptual problem with Faraday's law and inductance for a while now.
Take the example of a simple current loop with increasing area in a constant field (as in this answer). So Faraday'...
- 533
10
votes
4
answers
4k
views
Where does the extra energy come from in an LC circuit?
In an LC circuit, or an LC tank, the capacitor discharges in one direction
through an inductor and then the inductor seems to carry energy in the form of a magnetic field , to charge the capacitor ...
- 607
3
votes
1
answer
3k
views
Magnetic Flux conservation
My teacher said that after switch is shifted (after very long time), $\phi_i = \phi_f$ $\implies i_oL = i3L \implies i = \dfrac{i_o}{3} $ where $i_o$ is $\dfrac{\varepsilon}{R}$
So the initial ...
- 375
1
vote
3
answers
319
views
Significance of sliding switch in a LR circuit
The following image and statement are from my textbook Concepts of Physics on the chapter "Electromagnetic Induction", topic 38.6 "Growth and decay of current in an LR circuit", ...
- 5,306
1
vote
2
answers
2k
views
What is the magnetic flux density "outside" the solenoid when AC current is passing through it?
I know that there are well defined equations explaining the magnetic flux density in the solenoid.
However what about magnetic field outside the solenoid?
How is the magnetic flux density related ...
- 111
1
vote
1
answer
823
views
Differential equation in RL-circuit
I am self-studying electromagnetism right now (by reading University Physics 13th edition) and for some reason I always want to understand things in a crystalclear way and in depth. Now look at this ...
0
votes
2
answers
453
views
The direction of induced electric field around a changing current wire
I saw in my textbook that the induced electric field around a changing current wire is parallel to the direction of the current, for example:
Why is that?
Thanks!
10
votes
5
answers
10k
views
Magnetostatic energy density -- derivation without introducing inductance?
I was looking for a derivation of the expression for the energy density at any point in a static magnetic field. I do know that it is
$$u_B=\dfrac {1}{2 \mu_0}\left|\mathbf{B}\right|^2,$$
I was just ...
- 625
1
vote
1
answer
834
views
Is a unit coupling coefficient for mutual inductance (so $M=\sqrt{L_1L_2}$) compatible with different self-inductances $L_1\neq L_2$?
We considered mutual inductance in my lectures and the definition $M=k\sqrt{L_1L_2}$ where the coupling constant $k$ can vary between 0 and 1. When covering transformers, my lecture notes "assume that ...
- 3,997
1
vote
2
answers
144
views
Inductor with ac supply
When an ac source is connected with an inductor we have a continuous change in voltage and current across the inductor.
According to farady and lenz law we will get an equal and opposite voltage ...
- 1,441
1
vote
2
answers
405
views
How to calculate flux in a helical wire?
We have a wire going around in a helix (just like an inductor) and a constant magnetic field exists along its axis throughout the space.
How do we calculate the flux through it? I can't understand ...
- 1,270
1
vote
1
answer
2k
views
Does the direction of magnetic field in a solenoid point from north to south anywhere? [closed]
Is there any case where the direction of magnetic field inside a solenoid points from its North Pole to its south?
- 187
0
votes
0
answers
111
views
How to find the canonical equations of the RLC circuit
First, I consider the LC circuit with an ion in the capacitor, which is like this:
The current $I$ can be derived easily by using Shockly-Ramo theorem
\begin{equation}
I = -\frac{qp}{dM} + C\dot{U} \...
- 68
11
votes
3
answers
9k
views
When mutual inductance is occurring between two coils, is self inductance always occurring in each individual coil?
When a coil connected to an AC generator creates an EMF in another nearby coil (mutual inductance), is self inductance simultaneously occurring in both coils?
- 545
10
votes
3
answers
3k
views
Does a thermal inductor exist?
There is an analogy between electric and thermal circuits.
A voltage difference is equivalent to a thermal difference.
$$\Delta V \equiv \Delta T$$
Electric charge $q$ is equivalent to heat $Q$.
...
- 281
6
votes
2
answers
1k
views
Why is all of the energy from a battery stored on an inductor but only 50% on a capacitor?
I am learning about inductors and capacitors and we derived the energy stored on a capacitor to be 50% of that delivered by the battery. We did this considering a circuit of a capacitor connected to a ...
- 3,997
4
votes
5
answers
2k
views
Isn't the inductor equation negative?
The inductor "resists" change in current. So say you measure the voltage across the inductor from point A to point B - the current is flowing in from A towards B. Now say the current is increasing. ...
- 2,009
4
votes
2
answers
6k
views
Magnetic moment of an iron-core solenoid
I'm currently developing a Simulink model for the attitude control system (ACS) of an undergrad-developed CubeSat. The ACS uses magnetorquers for attitude actuation.
The magnetorquers are iron-nickel ...
- 93
4
votes
2
answers
3k
views
Why does the current increase in an LC circuit while the capacitor is being discharged?
From the maths governing an LC circuit (eg. $E_B=\frac{LI^2}{2}$) we can deduce, that the current through the inductor will have a maximum value, when there's no energy stored in the capacitor, or ...
- 773
4
votes
1
answer
48k
views
Magnetic field due to a coil of N turns and a solenoid [duplicate]
I have learnt that the formula for calculating the magnetic field at the centre of a current-carrying coil of $N$ turns is:- $$ B = \frac {\mu N I}{2r}$$
(where $r=$ radius of the loop,
$I=$ current ...
- 197
3
votes
2
answers
246
views
Using Faraday's law twice
I have trouble understanding Faraday's law when there is an induced current which in turn induces another current in the same circuit. I shall illustrate my confusion with an homework problem and I ...
- 963
3
votes
3
answers
1k
views
Kirchhoff law and Inductors
I am struggling with using Kirchhoff's rule in circuits with Inductors. Looks like if you have an inductor, we have Electric field (E) that is created using a time varying magnetic field and that E is ...
- 1,481
2
votes
2
answers
5k
views
How to get the magnetic field strength in space near a solenoid
I am trying to find the magnetic field strength along the axis of a solenoid.
If I know the strength of the field at the center of the solenoid, and I know the distance from the center of the ...
- 1,340
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
2
votes
1
answer
153
views
Quantization of a waveguide: he only has one of the two E.O.M in his Lagrangian. How can the quantization be correct?
I am following this reference, appendinx C and D, around page 61
The goal is to quantize electric of current of propagating wave in a waveguide.
Classical E.O.M:
We model a waveguide by a ...
- 1,450
2
votes
1
answer
7k
views
Transformers - Why more coils in second coil causes more voltage [duplicate]
I am learning about magnetic induction and transformers.
I have coil1 which uses AC to create an oscillating magnetic field.
I have ...
- 153
2
votes
3
answers
534
views
Why can't the current in a solenoid be changed rapidly?
Why can't the current in a solenoid be changed instananeously? My reasoning is since the current in a solenoid is given by a integral:
$$I(t) = \frac{1}{L} \int_{t_0} ^{t_f} V_Ldt$$
then if $t_f = t_i ...
- 548
2
votes
1
answer
1k
views
How do I show for an ideal transformer $M^2=L_1L_2$?
I've been stuck on this problem for about an hour.
In an ideal transformer, the same flux passes through all turns of the primary and of the secondary . Show that in this case $M^2=L_1L_2$, where $...
- 5,371
2
votes
2
answers
1k
views
Magnetic flux inside solenoid
Suppose that I have a small coil that is moved at a steady rate into a solenoid. The solenoid already has a current passing through (basically, it is an electromagnet). The small coil starts beyond ...
- 21
2
votes
1
answer
989
views
Does a magnetized sphere contain energy
I believe this question is similar to "does a permanent magnet contain energy", which I understand to be no, but I just want to be sure. Say we have uniformly magnetized sphere with magnetization $M_0\...
- 612
2
votes
4
answers
250
views
Inductor connected to an AC source
Consider an inductor connected to an AC source, $V=V_0\sin\omega t$.
Let the the switch in the circuit be closed at $t=0$. Then by Kirchoff's voltage law,
$$
V-L\frac{dI}{dt}=0
$$
where $I$ is the ...
- 23
2
votes
3
answers
644
views
How is EMF still induced in an incomplete/open circuit?
I understand that current can't flow through a coil if it is not complete, but surely this means that if a magnet is dropped through the coil, no EMF would be induced either, since work is done when a ...
- 31
1
vote
3
answers
19k
views
Why in a solenoid, do the magnetic field lines resemble that of a bar magnet?
Each loop in the solenoid will have its own magnetic field wrapped around it. In that case it won't resemble the magnetic lines formed by a bar magnet...; but we see that it is the same. Why is that?
- 494
1
vote
2
answers
1k
views
How can we derive the polarity of the induced voltage in an inductor?
As we know, the voltage-current relation of a two-terminal constant-inductance inductor is:
$v_L(t) = L \, \dfrac{\mathrm di_L(t)}{\mathrm dt} \tag 1$
I've managed to prove that equation without ...
- 344
1
vote
1
answer
1k
views
Why is the magnetic flux proportional to the current (Inductance)?
I'm trying to understand the reasoning behing this formula, or how to get there, if possible, using Maxwell's equations:
$$\Phi_i = L_i I_i + M_{ij} I_j$$
From the wikipedia page of inductance I got ...
- 121
1
vote
2
answers
137
views
Why does electrical impedance have as many parameters as it has?
The impedance of a circuit is written:
$$ Z(R,L,C,f) = R + j ( 2 \pi f L - \frac{1}{2 \pi f C} ). $$
What is the line of thinking that frequency, resistance, capacitance, and inductance are the only ...
- 161
1
vote
2
answers
820
views
Contradiction using amperes law to calculate magnetic field $B$
I am trying to study the influence on the magnetic field B generated by a solenoid in two different cases
the solenoid is wound around an open iron core
the solenoid is wound around a closed iron ...
- 19
1
vote
1
answer
126
views
How to demonstrate the inductance of an inductor?
I have some troubles to demonstrate this formula. Actually my problem is about how the length of the coil is integrated in the formula... I could understand, that the electromotive force $V_L$ is ...
- 177
0
votes
1
answer
3k
views
How to determine the polarities of inductor?
How to determine the polarities of inductor?
I know it is determined from Lenz law but most of the time i get a wrong answer,can anyone demonstrate how it is got, through an example?
- 399
0
votes
3
answers
1k
views
Current in an AC circuit with only an inductor
In an AC circuit with only an inductor, we have a current that lags behind the EMF. So, at time 0 we have zero emf and max current. But in realty, how is this possible? How can we have a current ...
- 329
0
votes
1
answer
471
views
Mutual inductance circuit analysis
given the following circuit, I need to find $ I_1(t) $ and $ I_2(t) $
(forgive my microsoft paint skills ;) )
I've come up with a solution, and I wish to check with you if it is current or, ...
- 113
0
votes
1
answer
133
views
Phase difference
Is there a phase difference between the magnetic field and the current producing this field?
I have simulation results for three-phase transformer at different frequencies. The spectrum of the ...
- 1