Which unit describes electrical resistance or impedance?

Which unit describes electrical resistance or impedance?

• A. Ohm
• B. Siemens
• C. Henry
• D. Farad

Answer: (A)

Electrical resistance and impedance are quantified in the ohm, the unit defined as volt per ampere. In DC circuits, resistance is the straightforward opposition to current, R = V/I, so its magnitude is measured in ohms. In AC circuits, impedance extends this idea to include reactance, forming a complex quantity Z = R + jX, whose magnitude is still expressed in ohms. The other units relate to different electrical properties: siemens is conductance (the reciprocal of resistance), henry is inductance, and farad is capacitance. So the unit that describes resistance or impedance is the ohm.

Electrical resistance and impedance are quantified in the ohm, the unit defined as volt per ampere. In DC circuits, resistance is the straightforward opposition to current, R = V/I, so its magnitude is measured in ohms. In AC circuits, impedance extends this idea to include reactance, forming a complex quantity Z = R + jX, whose magnitude is still expressed in ohms. The other units relate to different electrical properties: siemens is conductance (the reciprocal of resistance), henry is inductance, and farad is capacitance. So the unit that describes resistance or impedance is the ohm.