Basic electrical quantity recall: In circuit theory, resistance is measured in which unit?

Introduction / Context:
Fundamental SI units underpin all electrical engineering calculations. Resistance quantifies opposition to current flow and is central to Ohm’s law and power dissipation analysis.

Given Data / Assumptions:

• Quantity: electrical resistance.
• Relevant relationships: V = I * R and P = I^2 * R = V^2 / R.
• We need the correct SI unit name.

Concept / Approach:
Recall that resistance is measured in ohms, symbol Ω, named after Georg Ohm. Other listed units measure different physical quantities and therefore are distractors by design.

Step-by-Step Solution:

Verification / Alternative check:
Dimensional analysis: From V = I * R, R = V / I, so the ohm equals volt per ampere, consistent with SI derivation. No other option matches V/A.

Why Other Options Are Wrong:

• henries: unit of inductance (H).
• hertz: unit of frequency (Hz).
• watts: unit of power (W).

Common Pitfalls:

• Confusing symbol Ω (ohm) with W (watt) when handwriting.
• Assuming 'ohm' is only a symbol; the pluralized word 'ohms' is standard in text.

Final Answer:
ohms