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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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Why do phasor derivations related to LCR circuits consider $V_c = I * X_c$ even if voltage and current are out of phase?

In a capacitor, the current leads by $\pi/2$. But even then derivations of of total voltage in LCR circuits using phasor diagrams assume that $V_{inst.} = I_{inst.} * X_c$ Where $V_{inst.}$ is the ...
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Adding a capacitor in parallel improves power factor of an inductive circuit?

I know that to reduce power loss during transmission, we require a power factor as close to one as possible. This can be done by making $Z$ tend to $R$ which can be done by increasing $X_c$ such that ...
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Why isn't there any current in the Primary if Secondary circuit is opened in a Transformer?

Assume an ideal transformer, with no load/resistor attached on the Secondary (Open Circuit), it is said that the Primary would act as if it is an open circuit too, thus no current flows through the ...
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LC-circuit and the current

A capacitor and a coil are charged in the LC circuit. When the circuit switch is closed, the current starts to flow. In theory the oscillations and the current do not deteriorate, but why in reality ...
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Differential equations for the LC circuit

On wikipedia one can find that the DE for an LC circuit is given by $$\ddot I+\frac{1}{LC}I=0$$In one of my papers however I found the equation $$\ddot Q+\frac{1}{LC}Q=0$$ and I've been confused by ...
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How can there will be current in purely inductive circuit? [closed]

In a purely inductive circiut there are two emf's one is applied and other is induced applied emf and induced emf are equal and opposite, then how can there will be current in a purely inductive ...
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Does it make any sense to ask for mutual inductance between a wire and a coil?

I have been asked to work out the mutual inductance coefficient between a circular spire of $N=1$ turns and radius $R$ and an infinite wire contained in the plane in which the spire lies. This, ...
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Dissipation of energy in inductors

Please explain the dissipation of energy in a circuit containing a resistance and inductor after the switched in the circuit is opened.I mean how do you explain that the energy that is across inductor ...
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Can we define rms current for pure inductive and capacitive ac circuit?

For a purely inductive and capacitive ac(sinusoidally varying) circuit, average power dissipated across a capacitor or an inductor is zero. Then does that mean RMS current is zero?
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Can an Opposing Current Create another Opposing Current?

In Inductors when current increases it's magnetic field induces a voltage which causes an opposing current that slows down the rise of the current that initially creates it, but can this opposing ...
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47 views

Electrons in an Inductor

What basically happens to the electrons, does the magnetic field produced by the electron moving in the inductor affect itself. what are the forces involved? Please elucidate the mathematics. The ...
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34 views

Why do we ignore the negative sign of self induction while considering inductors in an AC circuit?

I have been taught that the back EMF in a coil as per Lenz's law is $$ e =-L \frac{di}{dt} $$ Then why is that during circuit analysis of AC circuits, we consider the e across inductors to be $$ ...
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What do the magnetic fields lines produced by a solenoid made out of another solenoid look like?

Suppose we take a solenoid: I was wondering what the magnetic field pattern would look like if the black current-carrying wire in the depicted solenoid was replaced by a solenoid. In other words, ...
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What does 'Oppose a Change in Current' really mean from Lenz Law?

We all know what Lenz Law is, but I have a bit of trouble conceptualizing the phrase above. Does 'Oppose a Change in Current' means it will take more time for the current to increase to its maximum ...
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43 views

Electromagnetic Force vs Magnetic Force

I am confused between these two types of forces, what makes them different? For example, a moving ferromagnetic object in a solenoid that moves because of a magnetic field created. Which field would ...
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rotating capacitor question

Imagine a simple setup. I have a copper disc and another copper element held close to the disc at one of it's sides, this element is stationary but the disc is rotating, the part between the disc and ...
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60 views

Why do we not have devices like inductors or capacitors to hold gravitational field? [closed]

I know that a capacitor can store electric field and an inductor can store magnetic field. So is there a way that gravitational field field can be stored in any such device. Also we do not have a law ...
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Now what will happen in this circuit?

Consider a circuit as shown in this figure below- Assuming switch S1 is closed such that current flows in loop ABCDE for a long time and steady state is reached. Now, my question is simple, suppose (...
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Why is the integration constant in a purely inductive AC circuit assumed to be zero?

While studying about AC circuits, I came across the usual differential equation of an AC circuit (in which the voltage across the source is a sinusoidal function of time) containing an inductor only. ...
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Why is the inductance of ionized air similar to inductance of wire?

Why is inductance of wire which is about 1 microHenry per meter similar to the inductance of air broken down by lightning (where the high voltage of a lightning strike breaks air down and it becomes a ...
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86 views

Why don't transformers have capacitors?

I recently learnt about how resonance in an LC (inductor capacitor) circuit could increase the efficiency of the circuit, for application in something like Resonant Inductive Power Transfer. Excuse ...
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70 views

Current as a function of time RL-circuit [closed]

The switch, S, in the circuit has been open for a long time. At t=0 it suddenly closes. Calculate the current through the inductor, $I_L$, as a function of time. Resistance in the inductor can be ...
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Dot convention inductors in series: what is going on

So I'm really confused with mutual inductors and dot convention. If your answer is going to be a link to any website I can assure I read them all and that only left me more confused. So here are my ...
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61 views

Inductance in Superconductors

This is a picture I got from a question in this website, it seems totally fine, but if you try looking it gain, is the heater placed in the wrong position? Because as I know current takes the path of ...
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39 views

Overdamped RLC circuit

I have a series RLC circuit with an equation: $$\frac{d^2I}{dt} + 2\alpha \frac{dI}{dt} + \omega_0^2 I = 0$$ (No outside sources affecting the circuit, only some $I_0$ was in the circuit at the ...
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Is induced EMF proportional to the square of the number of turns of a solenoid?

In order for this question to be clear I must first give some context: Consider a 10cm long solenoid (solenoid A) of radius approximately 1cm with 400 turns. Let the current in $A$, $I_A$, ...
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220 views

Can Kirchhoff's Voltage Law be applied here?

First, consider a simple circuit comprising of an ideal battery of EMF: E and a single resistor of resistance R. Imagine that the switch is opened in the circuit. In the battery, some internal ...
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61 views

Current in circuit after joining two inductors with different currents through them [duplicate]

Let's take two inductors: one has its peak current (say, Io) flowing through itself and the other has no current through itself. Now if these two inductors are joined in series in a closed circuit, ...
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31 views

Energy and electromotive force in transformers

I just learnt the formula $ε_2=ε_1\frac{N_2}{N_1}$ in relation to transformers. While I understand the mathematics that were used to derive it, I am having difficulty understanding where the extra ...
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37 views

Integration in order to derive formulas for self-inductance

When deriving formulas for Self Inductance, I stumbled upon the following integration: $$\frac{V_o}{L}\int_0^tsinωtdt=\int_0^t\frac{dI}{dt}$$ The result logically is: $$-\frac{V_o}{ωL}cosωt +...
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134 views

Magnetic field of a solenoid

Why, when explaining the magnetic field of a solenoid, are the individual "quasi-rings" split up into two layers with opposite direction of current (see attached pictures; where the x-es and the dots ...
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155 views

How do we understand L C Oscillations (Inductor - Capacitor Circuit Oscillation) Intuitively?

How do we understand L C Oscillations (Inductor - Capacitor Circuit Oscillation) Intuitively? How to intuitively understand the Phase Lag and Imagine What is happening in the circuit exactly without ...
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Potential difference across the strips of an inductor [closed]

The voltage across the ends of an inductor is $L (di/dt)$. Applying the loop law $V = L(di/dt)$, so the voltage across the strips at a distance x measured from the "LEFT END" should be $V \frac xl$ ...
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27 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 ...
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What is the speed of rotation of the magnetic field of a solenoid or current-carrying WIRE

How does one find the speed of rotation of the magnetic field around a current-carrying wire? or How fast is it circulating around the wire? How does one identify the speed of rotation of the ...
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Can inductance be dependent on direction in plasmas?

Inductance is given by the ratio of magnetic flux to the current. For a given plasma at a particular density and temperature (which itself could be a tensor), one may define $$L = {\Phi(i) \over i},$$ ...
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224 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 ...
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Sudden removal of core of an electromagnet

Imagine we have an electromagnet with a soft iron core running 1 A producing a magnetic field strength of 1 T (relative permeability of the core is around 10,000), also assume the wires have ...
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90 views

Resistance of an inductor in direct current

In a multiple choice question a simple circuit of only a battery and an inductor the length of the inductor is doubled. The question is how does the velocity of the electrons change. Big spoiler alert:...
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130 views

voltage drop of LC filter in reverse

Two questions that are probably really simple to others. If we are to measure the voltage drop across the capacitor, the same way the circuit above is usually used as an LC filter, we would get the ...
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50 views

Are EMF and inductor in parallel or in series in a pure inductor circuit

How can we say whether the applied emf and the inductor in the the image are in parallel or in series? In some discussions I have seen people taking the applied emf and inductor to be in parallel and ...
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Inductances, open switch, arcing: What maintains the arc? EMF source or circuit inductance?

As we know, with an inductance in circuit, arcing will happen at switch contacts while opening the switch. The arc is created because of the circuit inductance. My question is - what will maintain ...
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51 views

Inductors problem

In figure, the switch is in the position 1 for a long time. Then the switch is shifted to position 2 at $t=0$. At this instant, the value of $i_1$ and $i_2$ is Well I'm confused over what will happen ...
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51 views

Is there a potential difference across an inductor [closed]

Walter Lewin in his lectures says but all books and online resources go against him. Who is correct?
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82 views

Light is a high frequency electromagnetic wave. Can an LC oscillation circuit emit visible light? [duplicate]

As we all know, light is a kind of high-frequency electromagnetic waves. Can LC oscillation circuit emit visible light?
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107 views

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 ?
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71 views

Computing the magnetic field inside an infinite solenoid

I want to compute the magnetic field inside an infinite solenoid. I know how to do this if we suppose that outside the solenoid, the magnetic field is equal to zero. But how do you do this if it ...
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1answer
120 views

Why is the magnitude of induced e.m.f more in an LR circuit at the removal of key?

One of the statements in my book:- "The magnitude of induced e.m.f in an LR circuit ( A circuit connect to a AC source having a resistor and a pure inductor in series) is more at the break of circuit ...
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106 views

Discharging a LC(R) Circuit

Reading through my lecure script I encountered this example which I don't quite understand: Given is the following Circuit: At time $t= 0$ the circuit is closed, before that the circuit was open, ...
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161 views

Magnetic field and electric field close to small signal audio

I have built a very compact tube amplifier. I have a 6VAC/3A supply powering the vacuum tube heaters. The 2 wires (positive & return current) are very close to the input. The input signal is very ...