What property describes a material's opposition to the flow of electric current?

• A. Resistance
• B. Capacitance
• C. Inductance
• D. Conductance

Answer: (A)

Opposition to the flow of electric current in a material is described by resistance. In a conductor, electrons collide with atoms as they move, which impedes their motion and converts some electrical energy into heat. This resistance sets how much current you get for a given voltage, described by Ohm’s law: I = V/R. Materials or geometries that make it hard for electrons to move—long, thin wires, or substances with high resistivity—have higher resistance.

Capacitance, by contrast, relates to storing electric charge in an electric field between conductors. Inductance is about opposing changes in current due to magnetic fields created by current flowing in a circuit. Conductance is the reciprocal of resistance and represents how easily current can flow. So the property that specifically describes opposition to current flow is resistance.