What type of electrical component consists of conductive surfaces separated by an insulator?

The fundamental physical construction of a capacitor is two conductive surfaces (often called plates) separated by an insulating material. This insulator is formally known as a dielectric. Because the plates are separated by this insulator, direct current cannot flow through, allowing an electrical charge to build up on the surfaces instead. Other options are incorrect based on their physical makeup and function. A resistor is made of materials that simply impede current flow, and a potentiometer is just a variable resistor. An oscillator is not a basic component at all, but rather an entire circuit designed to generate a repeating electronic signal.