What is impedance?

What is impedance?

• A. Opposition to an alternating current
• B. Resistance in a direct current circuit
• C. Capacitance in a circuit
• D. Inductance in a circuit

Answer: (A)

Impedance is the opposition a circuit presents to the flow of alternating current. In AC circuits, voltage and current can be out of step because energy is being stored and released by reactive elements like capacitors and inductors. Impedance combines the resistive part, which simply dissipates energy as heat, with the reactive part, which stores and releases energy and causes phase shifts. The overall impedance has a magnitude and a phase angle, and when there are no reactive elements, impedance reduces to just resistance. If the circuit contains only capacitors or only inductors, the impedance is purely reactive and is associated with a 90-degree phase shift. Hence, the description “opposition to an alternating current” directly captures what impedance measures in AC circuits.

Impedance is the opposition a circuit presents to the flow of alternating current. In AC circuits, voltage and current can be out of step because energy is being stored and released by reactive elements like capacitors and inductors. Impedance combines the resistive part, which simply dissipates energy as heat, with the reactive part, which stores and releases energy and causes phase shifts. The overall impedance has a magnitude and a phase angle, and when there are no reactive elements, impedance reduces to just resistance. If the circuit contains only capacitors or only inductors, the impedance is purely reactive and is associated with a 90-degree phase shift. Hence, the description “opposition to an alternating current” directly captures what impedance measures in AC circuits.