All Questions
Tagged with electromagnetism inductance
384
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What happens to the charges in an inductor when you induce a voltage?
Say you have two inductors, and - very much like a transformer - you connect the first one to a voltage source, then place the other one close to it, so that there will be an emf induced by the change ...
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Motion of a magnet inside a solenoid
I have a homework problem where a bar magnet is placed halfway inside a horizontal solenoid. A cut away shows that the magnet's north pole points to the left of the page and the south pole is outside ...
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2
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Cannot catch a minus sign mistake when deriving the ODE for an LC circuit
It's probably a very basic question but I just cannot wrap my mind around it. I'll just try to derive the differential equation for an LC circuit:
According to the law of induction, in a solenoid we ...
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What does an induced emf do to a loop of varying current?
I know that the magnetic flux through a loop in space is proportional to the current such that $\Phi=LI$. Therefore a change in magnetic flux will produce an emf, so $\mathscr{E}=-L\dfrac{dI}{dt}$. ...
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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 ...
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Inductors with different directions connected in series
I know that inductors oppose the change of the current. So for two inductors with different direction in series (one in clockwise and the other in counterclockwise), the equivalent inductor is $L_{eq} ...
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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 ...
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1
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194
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Self-inductance of a finite solenoid
Where did the $l$ in the denominator come from? I am talking about the $l$ in muNI/2l[...]?
I can't match LHS and RHS.
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How to calculate the Force (in Newtons) produced by a solenoid?
How would I calculate the force on an object (in Newtons) that is under the influence of an electromagnetic field produced from a solenoid? I know it would involve using the equation $B=(μNI)/L$ to ...
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Voltage drop across an ideal inductor
I was afraid to type the title of the question though there are lot of answers to similar questions. I spent half a day going reading these questions and trying to understand the answers posted and ...
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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 ...
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Disagreement between theoretical and experimental inductance of a coil
I have a coil of 20 AWG enameled copper magnet wire with approximately 270 turns: 9 layers of 30 turns. The coil is tightly packed with an overall height of about 30 mm, an overall outer diameter of ...
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Why $di/dt$ in inductor circuit reduces gradually after closing the switch?
When we close circuit having an inductor, an induced emf is generated across the inductor which opposes change in current through the circuit. This back emf depends on rate of change of current $di/dt$...
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Current sensitivity in transformer scheme with SQUID
I've tried to determine the maximum current sensitivity in this transformer scheme but I'm not sure if my solution is valid. I need to find the relation between the current in the input transformer ...
- 207k
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Kinetic Inductance and Magnetic Flux
Superconductors (SCs) are known to have kinetic inductance which is the manifestation of the inertial mass of superfluid. In this link, the concept is explained as follows:
When a current flows the ...
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Telegraphers' equations for lossy transmission line when $R$, $L$, $G$, and $C$ are frequency dependent
The telegraphers' equations are commonly written as
$$\frac{{\partial v(z,t)}}{{\partial z}} + R\space i(z,t) + L\frac{{\partial i(z,t)}}{{\partial t}} = 0$$
$$\frac{{\partial i(z,t)}}{{\partial z}} + ...
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How Are Electromagnetic Waves Produced?
How EM waves are produced say by a capacitor of an LC circuit here if $E$ is increasing in upward direction?
My thoughts
Thought 1:-
If E is increasing E flux is increasing thus B field must be ...
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3
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Can an inductor increase circuit current?
Suppose there is a simple circuit with a resistor, battery and inductor. The question that came to me is, by opening the circuit breaker, can the inductor be used to oppose and slow down the circuit ...
- 207k
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1
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Back EMF in electromagnetic coil
I am trying to quantify the back EMF generated while actuating an electromagnetic coil, this would be included in a general calculation to estimate the coil output under a variety of conditions. My ...
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2
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Calculating magnetic field strength for a very small electromagnet
I am trying to calculate the magnetic field (in tesla/gauss) of an electromagnet that is very small and has very few windings. For example 12 windings over 0.003 meters. I know this is not going to ...
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Equation relating the current carried by a solenoid to the force experienced by a magnetic dipole?
I am trying to find an equation or a series of equations that relates the current I carried by a solenoid of length L with turns N to the force F experienced by a magnetic dipole of strength M that ...
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Fundamental physical concept behind inductance of a long wire above a ground plane
Please explain the underlying physics concept behind the inductance of a long wire above an infinite ideal ground plane. Sometimes the image method is used and sometimes the coupled magnetic flux ...
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250
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Current through a capacitor in AC Circuits
I'm a little confused on the equation for the instantaneous current through a capacitor in AC circuits.
My textbook has it as:
$$i_C = \omega CV \ cos(\omega t + \pi/2) = -\omega CV \ sin(\omega t)$$
...
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Calculating the internal inductance of a long wire without the concept of flux linkage
I did read the following questions: "Flux linkage inside of a conductor", "Derivation of self-inductance of a long wire" and "Trouble understanding fractional flux linkage"
The answers to them are ...
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Thought experiment: EM fields and coils
Hello Physics Exchange,
I have been thinking a lot lately about EM fields. I thought about something the other day and wanted to check with the experts if my intuition is correct or not. I know this ...
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2
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Maximum Impedance for LCR series circuit
Impedance of an LCR series circuit can be maximum when either Inductive Reactance or Capacitive Reactance is maximum at an instant of time.
Max Capacitive Reactance is at minimum frequency, and max ...
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Why doesn't current flow stop in LC oscillation?
Why doesn't current flow stop in a LC circuit? It is supposed to stop when the magnitude of emf developed across capacitor is the same as the inductor, right?
- 12.1k
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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 ...
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35
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What does "90 degrees ahead of phase" mean in inductance problems?
I've been working on this homework problem and I have determined that the induced EMF on the right coil is sin(x-90). However, I do not understand what "ahead of phase means." When I graph ...
- 207k
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What is the $B$-field on the axis of a finite Iron-Core Solenoid, a Given Distance Beyond The Tip?
I am building a solenoid electromagnet with a core of known permeability $\mu$. The core needs to stick out slightly beyond the ends of the coils. Let's assume that the magnet is oriented with its ...
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Ewing's Molecular Theory of Magnetism & Induction Cookers
This question regards Ewing's molecular theory of magnetism.
I.) Ewing's molecular theory of magnetism describes every magnetic substance as being a collection of dipoles that are initially in a state ...
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Coilgun projectile force calculation
Please excuse me if I am completely wrong because I am a 9th grader but I hopefully am able to explain briefly about my problem. I was trying to create a function to calculate the Force of an iron ...
- 12.1k
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3
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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 ...
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415
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Why is the flux not zero here (Faraday's law)?
I've recently been reading the Griffiths Electrodynamics book, and came across this problem (7.17, 4th edition) and its solution:
I don't have any objections for the solution to part a). I have, ...
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29
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Is AC voltage across transformer pi shifted?
Suppose the voltage in the primary coil in a capacitor be
Vprimary = Vosin(wt)
According to my understanding, as the (AC) current in the circuit increases, the Magnetic flux across the secondary ...
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3
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720
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Magnetic field strength just outside of a solenoid
From my understanding, the magnetic field inside a solenoid is constant, so at points C and D, the magnetic field strength is the same. Magnetic field strength outside solenoid is minimal and is ...
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Current and Magnetic Poles of a Solenoid (Diagram) & Right Hand Thumb Rule
Well, my doubt's pretty elementary.
Firstly I wanted to confirm whether both the cases, as illustrated in the picture, are correct. I've darkened the part of each coil that faces us. Using the clock-...
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Determining the condcutivity of a material by method of contactless resistance caused by putting a sample rod in the inductor of an RLC circuit
I'm doing an experiment where I'm trying to determine the conductivity of a material by putting a sample rod in the center of a coil which is a part of an RLC circuit with an AC generator.
I was told ...
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1
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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 ...
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1
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Does parasitic capacitance contribute to the magnetic flux?
When modeling a real inductor, typically the equivalent circuit is the following one:
Source
A series resistance and parallel capacitor is added.
This model works very well to explain the following ...
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5
answers
109
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Magnetic field in a capacitor in a $LC$ circuit
Consider a simple $LC$ circuit in which the charge on the capacitor varies sinusoidally. Current flows in this circuit, changing the charge on the capacitor and hence changing the electric field ...
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How to find magnetic permeability of a mixed core?
Inserting a ferromagnetic rod into the core of an inductor increases its inductance. If the change in inductance is known, the following equation can be used (or so I assume) to find the relative ...
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1
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How to calculate impedance in a wire moving through a magnetic field?
I'm trying to build a homemade rail accelerator. I understand that the force on a wire is proportional to the cross product of the magnetic field vector and the current vector. I asked my professor ...
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3
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Does the unit "volt-seconds" have any interesting interpretation?
I was contemplating the units of capacitance and inductance in electrical circuit theory and noticed something that bugs me. Although there are many equivalent ways to write the farad (seconds per ohm,...
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Electric Field in an Infinite Alternating Current Solenoid
Reading Wangsness's Magnetic Fields book I stumbled upon an explanation I can't understand. It goes like this: There's an alternating current solenoid with radius $a$. We know the magnetic induction ...
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Mathematical expression for self-inductance constant $L$?
Is there a mathematical expression for what the value of $L$ (self-inductance constant) is for a given geometry? I've tried to come up with something, but I don't know if it's right or not...
$$\phi_B=...
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If we change the direction of the connections in a step-down transformer, will it become a step-up transformer?
If we change the direction of the connections in a step-down transformer, will it become a step-up transformer?
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How can Current Flow through the Inductor in the AC Circuit? [duplicate]
It's said that if the inductor is connected to the alternating voltage source, alternating current will be created in the circuit. Changing magnetic flux through the inductor will induce a voltage as ...
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Why are partial derivatives of Energy and Co-Energy with respect to x opposite numbers?
In a system where the flux linkage $\lambda = \lambda(x, i)$ is a function of dispalcement $x$ and current $i$.
Its energy is defined as
$$
W = \int_{0}^{\lambda} i(\lambda', x)d\lambda'.
$$
Its co-...
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2
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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 ...
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