Which type of circuit breaker relies on liquid for its operation?

The correct answer is the oil circuit breaker. This type of circuit breaker utilizes oil as a medium for insulation and arc extinction. When a fault occurs, the electric arc that forms is extinguished by the oil, which cools and helps to isolate the fault, thereby protecting the electrical system. The oil also serves to insulate the conducting parts, preventing unwanted current flow.

In contrast, the other types of circuit breakers operate on different principles. Air circuit breakers use air as an insulating medium; vacuum circuit breakers operate within a sealed chamber where the electrical contacts are enclosed, allowing for the arc to be quenched in a vacuum; gas circuit breakers use a gas, typically sulfur hexafluoride (SF6), as the insulating medium. Each of these alternatives has its own unique operational methods, which distinguishes them from the oil circuit breaker.