IEVref: | 131-12-43 | ID: | |

Language: | en | Status: backup | |

Term: | impedance | ||

Synonym1: | complex impedance [Preferred] | ||

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Symbol: | $\underset{\_}{Z}$ | ||

Definition: | for a passive linear two-terminal element or two-terminal circuit with terminals A and B under sinusoidal conditions, quotient of the phasor $\underset{\_}{U}}_{\mathrm{AB}$ representing the voltage (131-11-56) between the terminals by the phasor $\underset{\_}{I}$ representing the electric current in the element or circuit $\underset{\_}{Z}=\frac{{\underset{\_}{U}}_{\text{A}\text{B}}}{\underset{\_}{I}}$ where the sinusoidal voltage $u}_{\text{A}\text{B}}={v}_{\text{A}}-{v}_{\text{B}$ represented by the phasor $\underset{\_}{U}}_{\mathrm{AB}$ is the difference of the electric potentials $v}_{\text{B}$ at A and $v}_{\text{B}$ at B, and where the sinusoidal electric current represented by the phasor $\underset{\_}{I}$ is taken positive if its direction is from A to B and negative if its direction is from B to A Note 1 to entry: The impedance of an element or circuit is the inverse of its admittance. It is equal to $\underset{\_}{Z}=R+\mathrm{j}X=Z{\mathrm{e}}^{\mathrm{j}\phi}$, where Note 2 to entry: With a suitable qualifier, the word impedance is used to form composite terms designating quantities of the same kind as impedance, e.g.: transfer impedance, characteristic impedance. Note 3 to entry: The coherent SI unit of impedance is ohm, Ω. | ||

Publication date: | 2013-08 | ||

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$\underset{\_}{Z}=\frac{{\underset{\_}{U}}_{\text{A}\text{B}}}{\underset{\_}{I}}$

where the sinusoidal voltage $u}_{\text{A}\text{B}}={v}_{\text{A}}-{v}_{\text{B}$ represented by the phasor $\underset{\_}{U}}_{\mathrm{AB}$ is the difference of the electric potentials $v}_{\text{B}$ at A and $v}_{\text{B}$ at B, and where the sinusoidal electric current represented by the phasor $\underset{\_}{I}$ is taken positive if its direction is from A to B and negative if its direction is from B to A

Note 1 to entry: The impedance of an element or circuit is the inverse of its admittance. It is equal to $\underset{\_}{Z}=R+\mathrm{j}X=Z{\mathrm{e}}^{\mathrm{j}\phi}$, where *R* is resistance to alternating current, *X* is reactance, *Z* is apparent impedance, and *φ* is displacement angle.

Note 2 to entry: With a suitable qualifier, the word impedance is used to form composite terms designating quantities of the same kind as impedance, e.g.: transfer impedance, characteristic impedance.

Note 3 to entry: The coherent SI unit of impedance is ohm, Ω.

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