Certified Fire Investigator Practice Exam

Which of the following are two types of overcurrent protection devices?

1. Circuit Breakers and Resistors

2. Fuses and Circuit Breakers

3. Relays and Fuses

4. Transformers and Circuit Breakers

The correct answer is: Fuses and Circuit Breakers

The identification of fuses and circuit breakers as two types of overcurrent protection devices is based on their function in electrical systems. Both fuses and circuit breakers serve to protect circuits from excessive current, which can lead to overheating and potentially cause fires. Fuses are designed to automatically break the circuit when the current exceeds a predetermined level. They contain a filamental component that melts when too much current flows through, thereby interrupting the circuit and preventing further damage. Fuses must be replaced once they have operated. On the other hand, circuit breakers perform a similar function but can be reset after tripping. They contain mechanical or electronic components that detect excessive current and break the circuit, offering convenience and reusability. This ability to reset without needing replacement makes circuit breakers favorable in many applications. The other options contain devices that do not serve the primary function of overcurrent protection. Resistors, for example, are used to control current flow and voltage levels, while relays function as electrically operated switches. Transformers are designed to change voltage levels and do not provide overcurrent protection by themselves.