A substance that conducts electricity and allows electrons to move freely.

• A. Insulators
• B. Conductors
• C. Semiconductors
• D. Resistors

Answer: (B)

Electric current flows when charged particles can move through a material. A substance that conducts electricity does so because its electrons can move freely within the material, especially in metals where many electrons are not bound to a single atom. This mobile electron "sea" lets charges drift under an applied electric field, producing current with relatively low resistance. Insulators trap their electrons tightly, so little current passes through. Semiconductors have conductivities that sit between conductors and insulators and can be changed by conditions like temperature or impurities. Resistors are components designed to limit current, not materials that inherently conduct. So the substance that conducts electricity and allows electrons to move freely is a conductor.