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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]
Consider the circuit diagram of Anderson's bridge in the given figure. Let L 1 be the self-inductance and R 1 be the electrical resistance of the coil under consideration. Since the voltmeter is ideally assumed to have nearly infinite impedance, the currents in branches ab and bc and those in the branches de and ec are taken to be equal.
Stripline illustrating the incremental Wheeler inductance rule. The incremental inductance rule, attributed to Harold Alden Wheeler [1] by Gupta [2]: 101 and others [3]: 80 is a formula used to compute skin effect resistance and internal inductance in parallel transmission lines when the frequency is high enough that the skin effect is fully developed.
The table below lists formulas for the self-inductance of various simple shapes made of thin cylindrical conductors (wires). In general these are only accurate if the wire radius a {\displaystyle a} is much smaller than the dimensions of the shape, and if no ferromagnetic materials are nearby (no magnetic core ).
This formula for the increase in AC resistance is accurate only for an isolated wire. For nearby wires, e.g. in a cable or a coil, the AC resistance is also affected by proximity effect, which can cause an additional increase in the AC resistance.
The henry (symbol: H) is the unit of electrical inductance in the International System of Units (SI). [1] If a current of 1 ampere flowing through a coil produces flux linkage of 1 weber turn, that coil has a self-inductance of 1 henry. The unit is named after Joseph Henry (1797–1878), the American scientist who discovered electromagnetic induction independently of and at about the same ...
The winding resistance appears as a resistance in series with the inductor; it is referred to as DCR (DC resistance). This resistance dissipates some of the reactive energy. The quality factor (or Q ) of an inductor is the ratio of its inductive reactance to its resistance at a given frequency, and is a measure of its efficiency.
is the impedance of a loading coil and Z 0 {\displaystyle Z_{0}\!\,} is the characteristic impedance of the unloaded line. A more engineer friendly rule of thumb is that the approximate requirement for spacing loading coils is ten coils per wavelength of the maximum frequency being transmitted. [ 2 ]