What is the electrical term for the opposition to the flow of alternating current?

What is the electrical term for the opposition to the flow of alternating current?

• A. Resistance
• B. Impedance
• C. Reactance
• D. Conductance

Answer: (B)

When alternating current flows, the total opposition it meets is called impedance. That word captures both the resistive part, which dissipates energy as heat, and the reactive part, which stores and releases energy in magnetic and electric fields. Impedance is a complex quantity that depends on frequency and describes both how much the current is reduced (magnitude) and how the voltage and current relate in time (phase). It’s expressed as Z = R + jX, where R is resistance and X is net reactance (XL minus XC). The magnitude |Z| tells you how much the current is diminished, while the angle shows the phase difference between voltage and current. In a purely resistive circuit, impedance equals the resistance and there’s no phase difference. In circuits with inductors or capacitors, reactance changes with frequency and shifts the phase, but impedance still describes the overall opposition. The other terms don’t capture the full picture: resistance is just the opposition power dissipates, reactance is only the frequency-dependent part due to energy storage, and conductance is the reciprocal of resistance, not the total opposition to AC.

When alternating current flows, the total opposition it meets is called impedance. That word captures both the resistive part, which dissipates energy as heat, and the reactive part, which stores and releases energy in magnetic and electric fields. Impedance is a complex quantity that depends on frequency and describes both how much the current is reduced (magnitude) and how the voltage and current relate in time (phase). It’s expressed as Z = R + jX, where R is resistance and X is net reactance (XL minus XC). The magnitude |Z| tells you how much the current is diminished, while the angle shows the phase difference between voltage and current. In a purely resistive circuit, impedance equals the resistance and there’s no phase difference. In circuits with inductors or capacitors, reactance changes with frequency and shifts the phase, but impedance still describes the overall opposition. The other terms don’t capture the full picture: resistance is just the opposition power dissipates, reactance is only the frequency-dependent part due to energy storage, and conductance is the reciprocal of resistance, not the total opposition to AC.