What type of circuit element opposes the flow of alternating current?

• A. Capacitance
• B. Voltage
• C. Impedance
• D. Resistance

Answer: (C)

The correct answer is impedance. Impedance is a comprehensive measure used in alternating current (AC) circuits that combines both resistance and reactance, which refers to the opposition to the flow of electric current. In an AC circuit, impedance accounts for the effects of not only resistance (the opposition to current flow in a purely resistive circuit) but also the reactance caused by capacitors and inductors.

When an AC voltage is applied, the capacitive and inductive elements introduce phase shifts between voltage and current, resulting in a combined effect quantified as impedance. This means that impedance determines how much current will flow in response to a given AC voltage, incorporating both the resistive aspects of the circuit and the effects of capacitance and inductance. Therefore, it accurately describes the total opposition encountered by AC, making it the most suitable answer to the question.

Resistance alone only pertains to the opposition from resistive elements and does not account for the phase relationships or reactive effects seen in AC circuits, while capacitance and voltage do not directly describe opposition to current flow.