What is impedance in an AC circuit?

Impedance is the total opposition offered by a circuit to the flow of alternating current.

In an AC circuit, the flow of current is not constant, but rather oscillates back and forth. Impedance is the measure of the total opposition that the circuit offers to this alternating current. It is a complex quantity that includes both resistance and reactance. Resistance is the opposition to the flow of current due to the material properties of the circuit, while reactance is the opposition due to the circuit's capacitance or inductance.

Impedance is measured in ohms and is represented by the symbol Z. It is calculated using the formula Z = R + jX, where R is the resistance, X is the reactance, and j is the imaginary unit. The magnitude of impedance is given by |Z| = √(R² + X²), while its phase angle is given by θ = tan⁻¹(X/R).

Impedance plays a crucial role in AC circuit analysis, as it determines the amount of current that will flow through the circuit. In a series circuit, the total impedance is the sum of the individual impedances, while in a parallel circuit, it is given by the reciprocal of the sum of the reciprocals of the individual impedances. Understanding impedance is essential for designing and analysing AC circuits, such as those used in power transmission and distribution.