What term is the measure of opposition to current in a circuit when voltage is applied?

• A. Impedance
• B. Operating Instructions
• C. Installation
• D. Permit

Answer: (A)

Impedance describes opposition to current when voltage is applied. It captures how much the circuit resists the flow of electrical current, and in alternating current it combines resistance (the real part) and reactance (the imaginary part) into a single value, commonly written as Z. The current follows I = V / Z, so higher impedance means less current for the same voltage. In direct current, reactance drops out and impedance equals resistance, but the basic idea remains: impedance is the measure of opposition to current flow. The other terms are unrelated to electrical behavior and refer to procedures or permissions (operating instructions, installation, permit).