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By the way, it's my very first post here =D

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- Thread starter jrmiranda
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By the way, it's my very first post here =D

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Averagesupernova

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analogdesign

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Averagesupernova

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But why impedance oscillates? I understand how resistance is affected, but following this logic, capacitance and inductance should also increase with distance, but they don't, they vary sinusoidally.

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Averagesupernova

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I think you have some things confused. I don't understand what you mean by impedance oscillates. Nor do I understand what you mean by saying that capacitance and inductance vary sinusoidally. Capacitance is fixed. So is inductance. The reactance presented by each will vary with frequency but that is pretty much a linear relationship.But why impedance oscillates? I understand how resistance is affected, but following this logic, capacitance and inductance should also increase with distance, but they don't, they vary sinusoidally.

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Baluncore

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This OP is like “what happens when an irresistible force acts on an immovable mountain”. Either the circuit should not be modelled as “lumped constants”, or the frequency of interest should not be so “high”.I was wondering, athigh frequencycircuits, when thelumped circuitmodelmust be used, why does impedance depends on the position in the wire?

If the dimension or shape of the circuit is important in determining performance, then the lumped circuit is not applicable and transmission line theory must be used. Impedance does not oscillate. Circuits may oscillate.

Impedance comes in two parts, resistance and reactance. Z = R + jX.

If the circuit is specified by lumped constants then the circuit may appear to be “resonant at some particular frequency”.

At a resonant frequency, a circuit has zero reactance. That resonant frequency is when X = XC + XL = zero.

If the resistance component, R, of the circuit impedance is positive then it will be damped resonance.

If the resistance component of the circuit impedance is negative then the circuit has gain and so may oscillate at some frequency.

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