Impedansläran

Impedansläran, also known as impedance analysis, is a branch of electrical engineering that deals with the study of the behavior of electrical circuits when subjected to sinusoidal voltage and current. It is an extension of Ohm's law, which relates voltage, current, and resistance in direct current (DC) circuits. In AC circuits, however, the relationship between voltage and current is more complex due to the presence of reactance, which is the opposition to the flow of alternating current caused by inductance or capacitance.

In impedansläran, the total opposition to the flow of current in an AC circuit is represented by a complex quantity called impedance (Z). Impedance is a frequency-dependent property and is expressed in ohms. It is the vector sum of resistance (R) and reactance (X), where reactance can be inductive (XL) or capacitive (XC). The phase angle between voltage and current is also an important parameter in impedance analysis.

Impedance can be calculated using the formula Z = R + jX, where j is the imaginary unit. The magnitude of impedance is given by |Z| = sqrt(R^2 + X^2), and the phase angle is given by θ = arctan(X/R). Impedance analysis is widely used in the design and analysis of AC circuits, including filters, amplifiers, and power systems. It is also used in the study of transmission lines and antennas.