Final answer:
When a good fuse or circuit breaker blows or trips in a malfunctioning circuit, it indicates that there is an excessive current flowing through the circuit, and the fuse or circuit breaker is designed to protect the circuit from damage in such situations.
Step-by-step explanation:
When a good fuse or circuit breaker in a malfunctioning circuit blows or trips, it indicates that there is an excessive current flowing through the circuit. The fuse or circuit breaker is designed to break the electrical connection when the current exceeds a certain limit, thus protecting the circuit from damage or fire hazards. For example, a fuse has a metal strip with a low melting point that breaks the connection when it overheats due to excessive current.