Impedance

Those Impedance Z, also a.c. resistance, is (complex) Quotient from that Alternating voltage U and that Alternating current strength I.

<math>

\underline Z = {\underline U \more over \underline I} </math>

Impedance has the unit Ohm. The a.c. resistance sits down together from a real part, that Active resistance R and an imaginary part, that Resistance X. In Polar coordinates one needs amount and phase. The amount of impedance becomes as Apparent impedance Z designated, the phase with <math> \varphi</math>.

<math>

\underline Z = R + \mathrm{i}X </math>

<math>

\underline Z = Z \ e^{\mathrm{i} \varphi} </math>

The reciprocal value that Impedance is those Admittance Y (complex conductance).
High frequency-Cables becomes (design-caused) knowing impedance as Characteristic impedance designated. It amounts to with coaxial cables 50 ohms up to 100 ohms and with symmetrical (150 ohms up to 300 ohms Zweidraht)Leitungen
Loudspeaker have strongly periodical complex impedances - it is indicated however the middle real part (z. B. 4 ohms or 8 ohms)

Antennas one calls the feed impedance also fusspunktwiderstand, it should with the frequency, for those the antenna is intended, its and with the impedance of the cable agree material (z. B. 60 ohms or 240 ohms)

Source impedance one High-frequency transmitter should agree as good as possible with the cable and antenna impedance, there it otherwise too Reflections at the ends of the cable comes, those the transmitter to damage or destroy can.
On the other hand source impedance one must NF amplifier very many smaller than that the loudspeaker its, in order to dampen their periodic resonances.
Material one and imaginary Mismatchings can be repaired by four-wire networks. Transformers can do that, Capacities, Inductances, sucked. ?Filter or pieces of line of suitable impedance and length its.

- word origin, Synonymous one and translations

See also

| Active resistance | Resistance | Input impedance | Output resistance | Admittance | Break-even factor | Phase shift | acoustic impedance | Wave impedance | Adjustment | Terminal resistance | Source resistance | Impedance buffer | Ohm's law | Load resistance | Internal resistance | External load | Over match | Impedance spectroscopy |