# Video: Defining Impedance

What is the technical equivalent of impedance in an AC circuit?

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### Video Transcript

What is the technical equivalent of impedance in an AC circuit?

We know that this term speaks to the capacity of a circuit to resist the flow of current. Impedance, represented with the letter capital π, has two primary components to it. One is the resistance, capital π, of the circuit, measured in ohms, and the other is called the inductive reactance, π sub πΏ.

In an AC circuit, thereβs a 90-degree phase difference between the inductive reactance and resistance, meaning that impedance, π, is not equal to their linear sum, but rather to their combination according to the Pythagorean theorem.

Written as an equation, we can say that impedance is equal to the square root of π squared plus π sub πΏ squared. We can say then that impedance is the sum, understanding it to be a vector sum, of resistance and inductive reactance. Thatβs the technical equivalent of impedance in an AC circuit.