Which material does not allow electrical current to flow through it?

• A. Conductor
• B. Load
• C. GFCI
• D. Insulator

Answer: (D)

Current flows more easily through materials with low resistance. An insulator has high resistance, so its electrons are not free to move, and under normal conditions only negligible leakage occurs. This is why insulators like rubber or plastic are used to coat wires and protect people from shocks. A conductor, in contrast, has low resistance and readily lets current pass. A load is a device that uses electrical energy, not a property of a material. A GFCI is a safety device that interrupts current if it detects a fault, not a material that simply conducts or insulates. So the material that does not allow electrical current to flow through it is an insulator.