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0
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1answer
18 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 ...
9
votes
2answers
997 views

Are capacitors and inductors mirror images of each other?

I'm reading through my E&M textbook (Physics for Scientists and Engineers 3rd edition, Knight) and watching as many lectures on YouTube (Shankar, Pomerantz, Lewin, etc) to prepare for next ...
1
vote
2answers
34 views

Sign of induced EMF and other elements in AC circuit

I am having problems to determine the direction of the induced EMF in AC circuits. For example, we have an inductor of inductance $L$. The induced EMF is given by: $$ \epsilon = - L \frac{di}{dt} $$ ...
0
votes
1answer
405 views

Why do we always consider the area of inner solenoid while calculating the mutual inductance of two coaxial solenoids?

While we know that flux linked to an area is the dot product of the area vector of the loop(and not the actual area encountering the field lines) and the magnetic field linked to it, why then do we ...
2
votes
4answers
701 views

If induced voltage (back-emf) is equal and opposite to applied voltage, what drives the current?

Suppose we have a circuit with a voltage source, a switch open and an inductor all in series. If we close the switch, the potential difference of the voltage source is instantaneously applied to the ...
0
votes
0answers
29 views

For a straight circular wire, what is the relationship between the self inductance and frequency?

Due to the skin effect, the AC inductance of a straight wire will decrease as frequency increases. Is there any formula that can describe this relationship?
2
votes
1answer
44 views

Problem with differential equation RLC circuit serie [closed]

I am trying solve the differential equation of RLC's circuit in serie, I have: $C=4\ F, L= 1\ H$, $R=5\ \Omega$, and $V_e=20\ V$. $1)$ first I got the equation, it is: $i''+5i'+\frac{1}{4}i=0$, what ...
3
votes
2answers
43 views

Kirchoff's rules and inductance

Can Kirchoff's loop rule be applied in a scenario involving an inductor? Kirchoff's loop rule states that the closed loop integral of E dot dl is equal to zero. But, in a situation with an inductor, a ...
3
votes
1answer
31 views

Is there an electric field within a superconducting inductor?

I have learned that the magnitude of the EMF (potential difference) between the terminals of an inductor is equal to L*di/dt. Does this imply that an electric field does indeed exist in an ideal ...
7
votes
3answers
2k 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?
1
vote
2answers
1k views

Self induction in transformer

Wont self induction ruin the working of a transformer ? While increasing voltage (AC) in the primary coil, wont there happen a self induction in the primary coil itself ? $E_0 = -L \frac{dI}{dt} $ ...
0
votes
1answer
60 views

In an RLC series circuit on resonance, how can the voltages over the capacitor and the inductor be larger than the source voltage?

Consider an RLC circuit in series, of the form If the source drives the circuit in AC at the resonance frequency $\omega =1/\sqrt{LC}$, the peak-to-peak voltages on the capacitor and the inductor, ...
1
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2answers
42 views
-2
votes
1answer
47 views

Do you know the principle which says that connecting two sources of similar kind produces a waste and destruction? [closed]

There is a great article, called commutation cells, which states that you cannot transfer kinetic energy from one container to another immediately, bypassing the potential energy storage. Otherwise, ...
1
vote
1answer
43 views

Self induction in a circular coil

There's a formula for self inductance : $$ L=\frac{n\Phi}{i}$$ where n is the number of loops. But the book also says self inductance is directly proportional to $ n^2 $ I totally agree with the ...
0
votes
1answer
70 views

Is the number of turns in a loop part of the magnetic flux?

In all both my physics textbooks, the number of loops $N$ is left out of the equation for magnetic flux $\phi_B = \int_s \vec B \cdotp\hat n dA$ and only when calculating the Emf induced by an ...
2
votes
1answer
63 views

Visualising current in the LCR circuit

I just went through the theory of the serial LCR circuit. There current and voltage are 90 degrees out of phase with each other. Now I was trying to imagine an animation with just dots. And I ...
0
votes
1answer
12 views

Phase angle of a circuit

Above is the problem at hand. I know how to calculate the angular frequency and total impedance of the circuit given the information provided. However, I'm not really sure what the question is ...
4
votes
3answers
692 views

Why do Capacitor Inductor circuits Oscillate instead of reaching equilibrium?

When the capacitor is fully charged there is a potential difference between its poles and that creates a current. This current would create a magnetic field that is changing in the Inductor (because ...
1
vote
1answer
263 views

Significance of Time constants in LR and RC circuits [closed]

What is the significance of a time constant in a circuit? Is there any use of knowing the time at which the charge in a capacitor is 1-1/e times its total charge? What is special about the capacitor ...
0
votes
1answer
1k 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 ...
0
votes
0answers
44 views

Physical intuition behind the fact that current in an inductor lags behind the emf/voltage by $\frac{\pi}{2}$ in an AC circuit

What exactly is the reason that current through an inductor in an AC circuit acquires maximum value after quarter a time period ($\frac{T}{4}$) of the emf getting the max value?
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vote
0answers
66 views

Calculation of transformer coupling coefficient [closed]

We know that the mutual inductance $M$ of a transformer is related to the inductances of the two coils via $$M^2=k L_1 L_2$$ where $L_1$ and $L_2$ are the coil self inductances and $k$ is called the ...
2
votes
3answers
814 views

Is there inductance to a DC circuit?

When a DC circuit is carrying current, large amounts or small, is there induced-emf due to the inductance? Or is it only applied to AC circuits?
0
votes
2answers
239 views

Current in Inductor and Capacitor with DC voltage source? [closed]

A DC source in series with pure Inductor and pure Capacitor no Resistance. How the current will flow in this circuit? What I just know is that in the beginning Inductor will behave as an open circuit ...
3
votes
2answers
228 views

RLC circuit, turning off the voltage source

An RLC circuit (pictured above) is governed by two equations: \begin{align} -iR &= -L \frac{dj}{dt} = \frac{q}{C}+V(t) \\ \frac{dq}{dt} &= i+j \, . \end{align} $q$ satisfies the equation ...
0
votes
3answers
228 views

Rate of change of current in an Inductor

Considering an Inductor in a DC circuit: when the switch is first closed there is a change in current through the inductor, which induces an emf in the opposite direction (Lenz's Law). My question is ...
15
votes
2answers
416 views

Are there analogs to resistance, inductance, capacitance, and memristance connecting the weak force to electromagnetism?

A question was asked over at EE.SE recently which I tried to answer, but much of my answer was speculative. I'm hoping someone here can help my ignorance. In electronics design, there are four ...
0
votes
0answers
54 views

Resistor and conductor and inductor

What I am gonna to have if: -an inductor is in parallel with a capacitor and all that group is in parallel with a resistor. I know that a capacitor in parallel with an inductor is: ...
0
votes
1answer
239 views

Inductor's back-emf vs voltage drop across resistor

In almost all physics books I've seen it says that the back-emf generated across inductor causes the delay in current (current is shifted 90 degrees with respect to the voltage across inductor). I ...
4
votes
1answer
51 views

Mutual capacitance upper limit

I am having trouble making an analog for mutual capacitance from mutual inductance. In circuits with magnetic coupling, there is an upper limit established on mutual inductance due to energy ...
0
votes
0answers
47 views

Approximate of self-inductance of a square wire coil

Imagine you have a square coil of wires with n turns. In order to calculate the self-inductance coefficient I should know the magnetic field. Is it acceptable to consider the 4 sides as infinitely ...
1
vote
0answers
39 views

EMF and Distance

As a professional underground service locator, EMF and Inductance are at the very core of what we do. Very few of us truly understand the detailed physics behind what makes it possible for us to ...
0
votes
1answer
44 views

Coaxial waveguide - wave impedance

Determine the capacity $C$ per $m$, the inductance $L$ per m and the wave impedance $Z_0$ for a coaxial waveguide with inner radius $a$ and outer radius $b$. How large would $b$ have to be so ...
1
vote
1answer
85 views

Highly inductive circuits question in general

I've been reading about self-inductance in circuits in M. Purcell's Electricity and Magnetism and came across an interesting fact: "What happens if we open the switch after the current $I0$ has been ...
0
votes
3answers
139 views

Why do inductors maintain the exact same current?

As we know, a capacitor will maintain the same voltage across its poles even if it is disconnected from a battery source. For example, in this problem: http://www.unm.edu/~toolson/rc_circuit.gif ...
0
votes
0answers
60 views

Maximum current in LC Circuits

Two capacitors of capacitance $C$ and $3C$ are charged to potential difference $V_o$ and $2V_o$ respectively and connected to an inductor, all three in series. Now the switch S is closed. Find the ...
0
votes
1answer
38 views

Induced current in a loop due to varying flux

Suppose you have a loop of wire beside a infinite long wire carrying a current I. The current in the infinite wire is given by: $$I(t) = I_0(1-e^{(-\alpha t)})$$ Where $\alpha$ is a constant and $I_0$ ...
3
votes
1answer
184 views

Does an Inductor maintain it's energy?

Consider a simple LCR ac circuit; generally I (might) understand that the charge exchange between capacitor and inductor would induce a harmonic current flow, but I remain confused for two reasons: ...
0
votes
0answers
26 views

Image charges for currents?

I am struggling to get my head around a problem involving creating a transmission line using a wire of radius $a$ in a vacuum a distance $d$ above an infinite grounded plate ($d \gg a$). I wish to ...
1
vote
2answers
59 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 ...
2
votes
1answer
286 views

Would a strong diamagnetic material exhibit inductance?

Do metals with the property of strong diamagnetism also exhibit inductance? Would a fluctuating magnetic field induce a weaker current in a strongly diamagnetic metal as compared against a ...
0
votes
2answers
216 views

Magnetic field by a solenoid?

I am really not able to understand why is it that the current,while finding the magnetic field in the solenoid (ideal one), is not $I$ the current flowing throught the solenoid but $nI$, where $n$ is ...
4
votes
4answers
1k 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 ...
7
votes
3answers
5k 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 ...
0
votes
0answers
57 views

Mutual inductance versus self inductance of two parallel thin-film wires

I am considering the scenario of two long superconducting thin-film wires (thickness << width << length) running parallel to eachother. They carry a current density that is as usual peaked ...
0
votes
1answer
505 views

Why does the inductance of a coaxial cable not depend on the number $N$ of coils?

Suppose we have a long coaxial cable like in the following figure: I want to compute the self-inductance $L$ of the cable. As I understand, given a coil with $N$ closely winded turns, through which ...
1
vote
1answer
521 views

Non-conservative Electric Field

I was watching this video from Walter Lewin and while watching these two videos, I noticed there is a "contradiction" in what he is doing. All links direct you exactly to where he begins, so you don't ...
0
votes
1answer
24 views

Inductor in transformer

In an inductor, a current waveform 90 degrees out of phase with the voltage waveform creates a condition where power is alternately absorbed and returned to the circuit by the inductor. If the ...
0
votes
0answers
178 views

Internal inductance of the outer conductor of a coaxial cable

Suppose there is a coaxial cable with the inner conductor in $ r < a$, vacuum in $ a<r<b$, and the outer conductor in $b < r < c$, what is the internal inductance of the outer ...