Which statement about impedance is correct?

• A. It is measured in volts
• B. It is unrelated to inductance or capacitance
• C. It is expressed in ohms (Ω)
• D. It is the same as resistance

Answer: (C)

Impedance is the overall opposition a circuit offers to alternating current, coming from both the real resistance and the reactive effects of inductors and capacitors. Because those reactive parts depend on frequency, impedance changes with frequency and is measured in ohms. This means it’s not given in volts, and it isn’t unrelated to inductance or capacitance—those elements create the reactive part that shapes the impedance. It’s also not the same as resistance, since impedance includes both resistance (the real part) and reactance (the imaginary part) that can cause a phase shift between voltage and current. At DC, where reactances disappear, impedance reduces to just resistance, but in general the two are different.