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In electrical engineering, impedance is the opposition to alternating current presented by the combined effect of resistance and reactance in a circuit. [1]Quantitatively, the impedance of a two-terminal circuit element is the ratio of the complex representation of the sinusoidal voltage between its terminals, to the complex representation of the current flowing through it. [2]
The input impedance of an infinite line is equal to the characteristic impedance since the transmitted wave is never reflected back from the end. Equivalently: The characteristic impedance of a line is that impedance which, when terminating an arbitrary length of line at its output, produces an input impedance of equal value. This is so because ...
In electrical engineering, the parallel operator can be used to calculate the total impedance of various serial and parallel electrical circuits. [nb 2] There is a duality between the usual (series) sum and the parallel sum. [7] [8]
Dual Miller theorem actually expresses the fact that connecting a second current source producing proportional current = in parallel with the main input source and the impedance element changes the current flowing through it, the voltage and accordingly, the circuit impedance seen from the side of the input source.
The total resistance is the sum of the individual resistances, as expressed by the following equation: R total = R artery + R arterioles + R capillaries. The largest proportion of resistance in this series is contributed by the arterioles. [3] Parallel resistance is illustrated by the circulatory system.
Equivalent unbalanced and balanced networks. The impedance of the series elements in the balanced version is half the corresponding impedance of the unbalanced version. Fig. 3. To be balanced, a network must have the same impedance in each "leg" of the circuit. A 3-terminal network can also be used as a 2-port.
The output impedance is a measure of the source's propensity to drop in voltage when the load draws current, the source network being the portion of the network that transmits and the load network being the portion of the network that consumes. Because of this the output impedance is sometimes referred to as the source impedance or internal ...
On the other hand, it might merely change the form into one in which the components can be reduced in a later operation. For instance, one might transform a voltage generator into a current generator using Norton's theorem in order to be able to later combine the internal resistance of the generator with a parallel impedance load.