Which of the following terms describes a device used to prevent the passage of electrical current?

The term that correctly describes a device used to prevent the passage of electrical current is an insulator. Insulators are materials that resist the flow of electric current. They are essential in electrical systems because they help to contain and direct electricity where it is needed, preventing leaks or unintended connections. This is crucial for safety and functionality in electrical installations.

In contrast, a resistor is used to limit the flow of current but does not entirely prevent it; rather, it allows some current to pass while dissipating energy in the form of heat. Conductors, on the other hand, allow electricity to flow freely and are typically made of materials like copper or aluminum. A transformer is a device that modifies voltage levels in an electrical circuit, but it does not prevent the passage of current. Therefore, the correct answer clearly relates to a device specifically designed to stop electrical flow, which accurately describes an insulator.