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1. Principles and generalities of electrochemical impedance
An impedance is a quantity defined for a linear system. After explaining the notion of transfer function, of which impedance is a special case, we'll see how this concept can be extrapolated to a non-linear system such as an electrochemical interface.
1.1 Linear systems, transfer functions and impedances
In sinusoidal operation, the relationship between the current flowing through a circuit and the voltage applied to its terminals can be expressed by the ratio Z between the rms values of voltage and current, and the phase shift ϕ between the rotating vectors which, at each instant, represent voltage V and current I. These quantities can be given the meaning of modulus and phase of a vector Z representable as a complex number R + jX. If the circuit is linear,...
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Principles and generalities of electrochemical impedance