What does the unit of resistance, ohm (Ω), measure?

The unit of resistance, ohm (Ω), specifically measures the opposition that a material presents to the flow of electric current. This concept is rooted in Ohm's Law, which states that the current through a conductor between two points is directly proportional to the voltage across the two points and inversely proportional to the resistance. In simple terms, when a voltage is applied to a circuit, the ohm value quantifies how much that circuit will resist the flow of electricity. Therefore, a higher resistance value indicates that the material will impede current flow more than a material with a lower resistance.

The other choices refer to different electrical concepts: energy supplied per unit time relates to power, potential difference pertains to voltage, and capacitance refers to a component's ability to store an electric charge. Each of these concepts plays a critical role in electrical theory, but they do not define what an ohm measures.