Inductor-Capacitor Circuit: E Field & Differential Equation

  • Thread starter atavistic
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In summary, the inductor capacitor circuit has an E field that is driving the current. There are two different ways to setup the differential equation for this circuit. One is using conservative assumptions and the other is using non-conservative assumptions.
  • #1
atavistic
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In an inductor capacitor circuit , what is the kind of E field driving the current? Conservative or non-conservative? And I really don't understand what is the correct way to setup the differential equation for it. This is why:

In high school level textbooks(Resnick Walker), they have applied loop rule.

In Griffith, he says [tex]\epsilon[/tex] = -L di/dt = Q/C

In MIT OCW , walter lewin says [tex]\int[/tex] E.dl = -Ldi/dt = Q/C

I think last two are the same but still can someone clear this.I mean going by what griffith says(hes the best) can someone tell me why is [tex]\epsilon[/tex] = -L di/dt . I know [tex]\epsilon[/tex] = [tex]\int[/tex]f.dl . How can I arrive using [tex]\int[/tex]f.dl that the [tex]\epsilon[/tex] in the circuit is -Ldi/dt. This thing has been bugging me a lot, please reply.

[tex]\epsilon[/tex] = EMF and [tex]\int[/tex] = closed loop integral.
 
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  • #2
atavistic said:
I know [tex]\epsilon[/tex] = [tex]\int[/tex]f.dl . How can I arrive using [tex]\int[/tex]f.dl that the [tex]\epsilon[/tex] in the circuit is -Ldi/dt. This thing has been bugging me a lot, please reply.

[tex]\epsilon[/tex] = EMF and [tex]\int[/tex] = closed loop integral.

The e.m.f is not the line integral of force but of the electric field. e.m.f is potential (work/charge) and not energy.

Another thing, it should be EMF=-L di/dt+Q/C (I mean, + rather than = between the last two terms).
It's just Kirchoff second rule: sum of the potential drops equals the EMF.
 
  • #3
yep, this is getting into my question. there's a pretty good elementary discussion in this
textbook "Electromagnetic Fields and Energy" by Haus and Melcher that gets into the
difference between electrostatics and magnetostartics into the area called {electro-or magneto}
quasistatics, and how to discriminate the difference between the two. I think the differences are
pretty important in the theory of electric machines: rotating magnetic fields and all that. My primary
interest is in modeling physical circuits by extracting lumped models from gemoetric descriptions.
I'll dig out that old textbook and do some reading, maybe we can compare notes?
 

Related to Inductor-Capacitor Circuit: E Field & Differential Equation

1. What is an inductor-capacitor (LC) circuit?

An LC circuit is a type of electronic circuit that consists of an inductor (L) and a capacitor (C) connected together. These components store energy in the form of electric and magnetic fields and can be used to filter or resonate specific frequencies.

2. How does an LC circuit work?

When an LC circuit is connected to a power source, the capacitor stores electrical energy in the form of an electric field, while the inductor stores energy in the form of a magnetic field. The two fields interact and exchange energy, causing the circuit to oscillate at a specific frequency.

3. What is the role of an inductor in an LC circuit?

An inductor is responsible for storing energy in the form of a magnetic field. It opposes changes in current and helps to maintain a constant flow of current through the circuit. It also plays a significant role in determining the resonant frequency of the circuit.

4. What is the role of a capacitor in an LC circuit?

A capacitor stores energy in the form of an electric field. It opposes changes in voltage and helps to maintain a constant voltage level in the circuit. It also plays a crucial role in determining the resonant frequency of the circuit.

5. What is the differential equation for an LC circuit?

The differential equation for an LC circuit is d^2q/dt^2 + (1/LC)q = 0, where q is the charge on the capacitor, t is time, L is the inductance, and C is the capacitance. This equation describes the behavior of the circuit and can be used to calculate the resonant frequency and other properties of the circuit.

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