What is resistance?

• A. Opposition to flow
• B. The rate of flow of charge
• C. Pressure that pushes electricity
• D. The energy per unit charge

Answer: (A)

Resistance is the opposition that a material or component offers to the flow of electric current. It quantifies how hard it is for charges to move through a conductor. In circuits, for a given voltage, higher resistance means smaller current, since Ohm’s law says I = V/R. The resistance of a part of the circuit depends on what the part is made of, its dimensions (longer and thinner paths have more resistance), and temperature (most materials resist more as they heat up). When current flows through a resistor, energy is dissipated as heat, which is why resistors convert electrical energy into thermal energy.

The other statements describe different concepts: the rate of flow of charge is the current, the force that pushes charges is the voltage, and the energy per unit charge is the electric potential (voltage).