What physical quantity is used to describe the opposition that a material presents to the flow of electric current?

The physical quantity that describes the opposition to the flow of electric current in a material is resistance. Resistance is a fundamental concept in electrical circuits and is measured in ohms (Ω). It quantifies how much a material impedes the movement of electrons, which constitutes electric current.

When a voltage is applied across a conductor, it creates an electric field that encourages electron movement. However, the material of the conductor itself resists this flow to varying extents depending on its properties, such as its temperature, length, and cross-sectional area. The greater the resistance, the less current will flow at a given voltage according to Ohm's Law, which states that current (I) is equal to voltage (V) divided by resistance (R).

Voltage refers to the potential difference that pushes the electrons through the circuit, while power relates to the rate at which electrical energy is transferred or converted, calculated as the product of voltage and current. Capacitance measures a material's ability to store electric charge, which is a different concept altogether. Thus, resistance is the appropriate term that directly corresponds to the opposition faced by electric current in a conductor.