Questions tagged [inductance]

The property of an electrical conductor through which a change in current through it induces an electromotive force in both the conductor itself as well as in any nearby conductors by mutual inductance. Also use more broadly for electromagnetic phenomena in solenoids.

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Finding the Magnetic Field within a solenoid

So, I have to find the magnetic field within a solenoid such that the field at a point(on axis) is half than that it would be at the centre. Length of the solenoid is 20cm and the current through it ...
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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!
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Physics behind "nuisance trips" in a ground-fault circuit interrupter (GFCI) outlet due to switching off an inductive load elsewhere in circuit

I am working on rewiring my old house. All of the second-floor lights, switches, and outlets are on a single circuit from the breaker. I recently installed ceiling fans in the bedrooms with wall ...
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How long do inductors take to change voltage?

I'm an EE designing a power converter, and this question has been nagging at me for years, so I wanna ask people who know more fundamental stuff than I do. Also, I don't have a physics degree, so ...
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Can someone please clear this doubt regarding Lenz's Law?

In Lenz's Law or Faraday's Law of Electromagnetic Induction, whenever there is a change in magnetic flux in a solenoid due to an external magnetic field like an approaching magnet there is an EMF ...
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Wave equation derivation in a transmission line

$$ V(x, t) = L\Delta x\frac{\partial I}{\partial t}(x, t) + \frac{1}{C \Delta x}\int{I_c(x, t) \; dt} \tag{1} $$ $$ V(x + \Delta x, t) =\frac{1}{C \Delta x} \int {I_c(x, t) \; dt} \tag{2} $$ $$ I(x) = ...
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Why is the product of the $L$ and $C$ matrices for coupled transmission lines diagonal?

Background - transmission line $\newcommand{\ket}[1]{\left \lvert #1 \right \rangle}$ A transmission line can be modeled as an infinite sequence of inductors and capacitors: ...
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"Wind turbine" Motor balance equations [closed]

I have this model of a wind turbine with written balance equations. I don't really understand the equation in the second line, I would really appreciate it if you could tell me what it means exactly.
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In a LR circuit, Why do the current rate of increase decreases with time? [closed]

In a LR circuit, the current rate of increase decreases with time until it reaches zero eventually and that is when the current become steady. My question is why the current rate of increase decreases ...
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Deforming LC circuit into dipole antenna

I once learned in school, and as far as I know this is also a common thing in many introductory physics books, that a parallel LC circuit can be "bent open" into a dipole antenna, like this: ...
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Signal Speed in Coaxial Cable

I want to calculate the signal propagation speed in a real life coaxial cable. I have the data sheet which tells me its impedance and capacitance per unit length. For long parallel wires carrying ...
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Pressing force of a solenoid

If a current is passed through bundle of loosely coiled, insulated wire the space between the wires rapidly contracts, crushing it down into a disk. How can this crushing force be calculated? I know ...
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AC current generated from electromagnetic induced EMF is not sinusoidal. What is wrong?

I tried to induce an EMF by rotating a coil between two magnets, like so: I expected the output voltage to be a sinusoidal curve, but for some reason it dips back down at the peaks. I tried changing ...
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What Exactly is Axis of A Solenoid? How does placing a soft Iron Core Along The Axis increase its Strength of Magnetic Field?

I have trouble understanding what is meant by axis of solenoid. According to textbooks placing a soft iron core "along the axis of solenoid" increases the strength of the magnetic field of ...
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Magnetic Field Lines in a Circular Solenoid

We know about magnetic field lines in a circular loop and a solenoid. While studying them, I thought about how the magnetic field lines would be in a solenoid made circular by bending, forming ...
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How to find the voltage across a resistor in a RCL circuit? [closed]

In the circuit below I am trying to find an expression for the voltage across $R2$. I have found an expression for the voltage across R1 which I have confirmed with a simulation, but I can't get it ...
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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 ...
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No decay of current in $RLC$ circuits?

They are teaching alternating current in school. The book states that in an $RLC$ circuit, the instantaneous current is given as $$i(t)=\frac{v_m}{\sqrt{R^2+(X_C-X_L)^2}}\sin(\omega t+\phi)$$ where $\...
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Pure inductor with no resistive battery [closed]

In case of pure inductor with dc source E= Ldi/dt . Is it mean that all work done by battery is stored in form of magnetic field energy?
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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 ...
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Frequency response of ferrite filter

Why ferrite material only passes low frequency and blocks high frequency. I mean what's going inside this material which is leading to show such frequency characteristics?
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Inductance - a better analogy than the fact that it is similar to inertia

This question is to get a feel and good definition for what inductance actually is. I have read about the analogy where inductance can be compared to inertia-that the flux through an inductor resists ...
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Magnetic force exerted on an air core inductor

I'm trying to work out a weird case of the magnetic force exerted on a current-carrying loop, and could use some help understanding things. suppose you have an air core inductor / coil, which, when a ...
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Does $F = BIL$ apply for solenoids too?

I've been meaning to find an equation for the ("magnetic") force inside of a solenoid . I found an equation on Wikipedia, $$ F = \frac{B^2A}{2\mu_{0}}. $$ however I am not sure if it is ...
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Capacitor vs Inductor - who wins?

The idea behind the question is to determine which one of the two - capacitor or inductor will drive the current in the circuit when connected in a specific way. Say I have a circuit in which I have ...
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Microscopically (Classically), How does Current keep Increasing with Decreasing Electrostatic Field inside of Capacitor in a $R(L)C$ circuit?

Assuming the capactior is intially charged with voltage $V$, then detached from the voltage source I know mathematically by using: $$C\frac{dV_c}{dt}+\frac{V}{R}=0$$ I can get an expression of the ...
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Derving circuit equations for $RLC$ circuit such that order does not matter [closed]

Can we derive the circuit equations for an $RLC$ circuit from first principles in a way that makes it clear that the order of circuit elements doesn't matter? I understand conceptually why the order ...
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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 ...
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Is the magnetic field outside a solenoid almost null for AC current?

Despite an answer to this thread, I'm not so sure the magnetic flux outside an infinite ideal solenoid is null whenever the current is AC. I've seen no real proof of that, and the Biot-Savart law ...
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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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What effects do inductors have on circuits?

The above diagram is a simple circuit containing an inductor. According to the right hand grip rule, it can be deduced that the magnetic field is to the right. But the magnetic field produced by the ...
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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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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}...
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Does a Mobius resistor have zero inductance? How would you calculate the inductance?

Wikipedia describes a Möbius resistor as follows, and the Patent for this device gives a similar description. A Möbius resistor is an electrical component made up of two conductive surfaces separated ...
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Doubt regarding the calculation of EMF due to self-inductance and mutual inductance

When finding the EMF induced in an inductor due to both self-inductance and mutual inductance, the EMFs due to both of these contributions are summed. However, I have doubts regarding their summation. ...
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Inductance in case of volume and surface currents [closed]

Is inductance always just defined as the constant relating flux directly to current? Is it true even for surface and volume currents?
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Does the EMF induced in an inductor due to mutual inductance equal the total EMF?

For an inductor in a circuit without a power source, does the induced emf found by using the mutual inductance value include self inductance, or is the self induced emf considered separately? From ...
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The current in an $LR$ circuit [closed]

I am trying to understand $LR$ circuits better. I am under the impression that inductors are resistant to change in current. So, the premise here is that the circuit was switched to side 1 for a long ...
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How to derive the formula for total impedance, $Z$, in an $RLC$ circuit? [closed]

Where this is an AC circuit, how can we derive the below formula for impedance, $Z$? $R = $ resistance, $X_{L} = $ inductive reactance, and $X_{c} = $ capacitive reactance.
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Inductance of a coated cylinder

Say we have an infinite cylinder, through which a current of intensity $I$ flows. Say this cylinder is coated with a conductive material, of negligible thickness, through which a current of the same ...
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Emf induced by a solenoid

Could someone please clear my confusion regarding this concept and point out what is wrong with my argument: Say we have a simple circuit as shown in the image: Why is the potential difference ...
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Why does this derivation not work for showing $M_{12}= M_{21}$ for mutual inductance?

If we assume two inductors behave like the centers of ideal solenoids then the induced emf in inductor 2 due to inductor 1 will be found by $-N_2 \frac{d \phi_{21}}{dt}$. But the induced emf is also ...
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Do self-inductance and mutual inductance have the same value for a given inductor?

My textbook states that the inductance of an inductor depends only on the geometry of the inductor. Moreover, the formulas used to calculate self-inductance and mutual inductance are the same. So, is ...
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Self-Inductance of a coil: What is the logical reason to not just write $\Phi = L * I$ but we also add the factor $N$ to the left side?

What is the reason to not just write $\Phi = L\cdot I$ but we also add the factor $N$ to the left side? ($N\cdot\Phi = L\cdot I$) $\Phi$ is in Webers here, and is the induced magnetic flux. $L$ is the ...
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Kirchoff analysis in faraday law for RL circuit

Faraday law state that $$\epsilon_L=\oint \vec{E} \cdot d\vec{l}=-\frac{d\phi}{dt}=-L\frac{dI}{dt}.$$ So by kirchoff's analysis, isn't the equation would be like $$\oint \vec{E}\cdot d\vec{l}=0-IR+\...
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Are we always allowed to treat an inductor as a battery with the same voltage?

When there is an induced emf, Kirchhoff's Loop Rule no longer is true, because electric fields are nonconservative when there is an induced current, as stated by Faraday's Law: However, I have seen ...
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What position axially within a solenoid gives the maximum magnetic force?

Assuming an infinitely long shaft, which is held stationary at a given position in the coil, where should interface Y be positioned along length x such that the plunger experiences the maximum force ...
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Apparent contradiction in Ampere law for a solenoid

This picture in Wikipedia is supposed to explain the solenoid formula for the magnetic field $$B l= \mu_0 N I$$ (assuming steady currents). But this would be true if one consider only the part of the ...
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How to model a circuit with resonant inductive coupling?

I need to model (write the equations for) a circuit with resonant inductive coupling, such as the one in the picture below. The picture is taken from the Wikipedia article on Resonant inductive ...
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What goes on in an AC circuit when the power delivered to the inductor is negative?

The instantaneous power delivered to a resistor by an alternating voltage source $v(t)=V_0\sin\omega t$, is always nonnegative. But the instantaneous power delivered to an inductor by $v(t)=V_0\sin\...

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