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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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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1 answer
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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 answers
44 views

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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1 answer
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Which of these is the right way to interpret finding the current across a coil

If we have a coil which has a resistance of 100 ohms an induced emf of say 20V and this is connected to an AC power source of 100V and is in a series connection with another resistor of lets say 50 ...
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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 ...
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1 answer
53 views

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?
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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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1 answer
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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 ...
1 vote
2 answers
522 views

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 ...
1 vote
2 answers
4k views

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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2 answers
284 views

Resonance frequency with metal

I've made an experiment with resonance frequency of a LC circuit. One part was to place a metal (I think iron) in the middle of the induktivity of LC circuit. I measured a higher resonance frequncy as ...
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0 answers
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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 ...
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3 answers
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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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1 answer
259 views

Predicting voltages in RLC series circuits from AC source: differences in order?

Hoping this isn't too homework-like, but I'm missing some sort of concept here. Doing a lab, and I have to use previous data to predict the voltage across the 2nd and 3rd elements (e.g. order is LCR, ...
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2 answers
395 views

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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Which properties of a metal can be measured via an Inductor in an $RLC$ circuit?

I am trying to understand the properties of metals by using them as cores for an inductor in an $RLC$ circuit. Now the resistivity, saturation point, magnetic permeability electric permittivity all ...
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28 views

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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1 answer
363 views

Back emf in an Inductor with an A.C supply

If a pure inductor is supplied with an AC voltage we will always have AC current and time changing electric field in the circuit. That always changing electricfield will cause changing magnetic field ...
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1 answer
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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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1 answer
47 views

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}} + ...
2 votes
3 answers
620 views

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 ...
1 vote
1 answer
108 views

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-...
1 vote
2 answers
294 views

If inductive reactance increases with frequency why do tesla coils have coils?

So I was reading about the special properties of radio frequencies. Specifically I read this: "In contrast, RF current can be blocked by a coil of wire, or even a single turn or bend in a wire. This ...
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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 ...
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 ...
1 vote
3 answers
250 views

Understanding simple $LC$ circuits

I'm trying understand the physics of simple inductor-capacitor circuits such that there is just an inductor $L$ and a capacitor $C$ and a switch. Imagine first that the capacitor is fully charged and ...
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4 answers
1k views

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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1 answer
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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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2 answers
1k views

How to compute the charge as a function of time in a simple $CL$ circuit?

I am trying to compute $q(t)$ in a series circuit consisting of a capacitor of plate charges $q_0$ and $-q_0$ and an inductor. The switch is closed at time $t=0$. By Kirchoff's Law, $$\frac{q}{C}+L\...
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1 answer
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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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1 answer
205 views

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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Does the temperature of a transformer affect the relationship between the induced voltage and primary current?

I'm doing an experiment involving inductance between two coaxial solenoids of the same length where I measure the rms value of the alternating current through the outer solenoid and rms value of the ...
2 votes
1 answer
481 views

RL circuit with AC source transient

I have a simulation of RL circuit connected with an ac source. Any one can tell me please that why the peak of the current during the first positive half cycle is higher than the peak of current ...
2 votes
2 answers
1k views

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 ...
2 votes
1 answer
272 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 ...
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1 answer
3k views

Voltage drop across an inductor in a $RL$ circuit

for a circuit that has a resistor (resistance $R$), and a inductor (inductance $L$), that are connected in series to a source of AC electromotance. How do I find the voltage drop across the inductor ...
2 votes
5 answers
105 views

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 ...
1 vote
1 answer
256 views

Inductance of a toroidal electromagnet with a gap

Suppose we have a toroidal electromagnet of length $l$ and section $A\ll d^2$, with an air gap of width $h\ll d$ with a wire turned $N$ times around it. Suppose we also know that for a large interval ...
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1 answer
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Why actually at resonance the inductive and capacitive reactance cancel each other?

I am learning about series LC circuit that is in resonance. It says it is when the impedance offered is minimum due to the angular frequency being at a particular value(1/√LC).People say that they are ...
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2 answers
99 views

Why current does not instantly reach maximum value in an $LR$ circuit?

In an $LR$ circuit, I read that when an resistor $R$ and an Inductor $L$ are connected to an emf $E$ source in series, and the switch is switched on, the current flowing in the circuit does not ...
2 votes
2 answers
11k views

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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1 answer
381 views

Apply Kirchoff Law to an $LC$ circuit (no battery)

In the image above, I understand the current is moving clockise. I was attempting to apply Kirchoff Rule which for an RLC circuit is but I wanted to confirm that $V_s$ is zero in this scenario such ...
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4 answers
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Confused about sign of mutually induced EMF when applying KVL

Suppose I have several circuits with inductors like so: and I want to find the current $ i_1, i_2, i_3 $ in each circuit. I will use Faraday's law to find the induced EMF and then use Kirchhoff's ...
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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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Calculation of self-inductance of an arbitrary shape

I have been taught two methods for doing this however I do not understand one of them completely. I will try to explain what I don't understand with a few examples. Irodov 3.319: A long coaxial cable ...
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1 answer
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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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1 answer
238 views

Energy Stored In Superconductor

I have two questions regarding this topic: What is the equation to calculate the energy stored in a superconductor when you apply a current. I’ve been looking it up and have been getting ...
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3 answers
261 views

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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2 answers
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Reactance of an Inductor

The following video here derives an equation for the reactance of a capacitor. I am trying to derive the equation for reactance of an inductor. Given an AC voltage drop $V(t)=V_osin (\omega t)$ in ...
1 vote
1 answer
161 views

If two inductors with different inductances are connected in parallel to a dc circuit, will they have the same current in them at steady state?

Can the current division rule be applied to the inductors in steady state ? Wouldn't they have the same current in them if they are ideal ?

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