Which statement describes a superconducting material's resistance?

Which statement describes a superconducting material's resistance?

• A. It has zero resistance
• B. It becomes a conductor at high temperature
• C. It stores energy
• D. It blocks current

Answer: (A)

When a material becomes superconducting, its electrical resistance drops to zero as long as it stays below a certain critical temperature. In this state, electrons pair up into Cooper pairs and move through the lattice without scattering, so no energy is lost as heat when a current flows. That lack of dissipation is what makes superconductors unique: a current can circulate indefinitely without needing an external power source. This is different from a normal conductor, which always has some resistance, or from a device that stores energy (like a capacitor) or one that blocks current (an insulator or a very high-resistance material). Also, the idea that a superconductor becomes a conductor only at high temperature is incorrect—it's the opposite: superconductivity occurs at low temperatures specific to each material and is lost above that critical temperature.

When a material becomes superconducting, its electrical resistance drops to zero as long as it stays below a certain critical temperature. In this state, electrons pair up into Cooper pairs and move through the lattice without scattering, so no energy is lost as heat when a current flows. That lack of dissipation is what makes superconductors unique: a current can circulate indefinitely without needing an external power source.

This is different from a normal conductor, which always has some resistance, or from a device that stores energy (like a capacitor) or one that blocks current (an insulator or a very high-resistance material). Also, the idea that a superconductor becomes a conductor only at high temperature is incorrect—it's the opposite: superconductivity occurs at low temperatures specific to each material and is lost above that critical temperature.