Which device serves as an overcurrent protective device that contains a fusible member?

The device that serves as an overcurrent protective mechanism and contains a fusible member is a fuse. A fuse operates by using a thin strip of metal or a fusible link that melts when the current flowing through it exceeds a predetermined level. This melting interrupts the electrical circuit, thereby protecting the rest of the electrical system from potential damage due to overcurrent conditions, such as short circuits or overloads.

Fuses are widely used in various electrical systems to safeguard equipment and prevent fires or failures caused by excessive current. The design and function of a fuse are specifically geared towards providing this protection, which makes it essential in building utilities to ensure safety and reliability.

The other options listed do not fulfill the same function. A switch is simply a device used for controlling the flow of electricity in a circuit but does not offer overcurrent protection by itself. A thermostat regulates temperature and does not have a role in current protection. A safety valve is typically associated with the protection of pressurized systems, such as gas or steam, rather than electrical circuits. Hence, the fuse is uniquely suited for overcurrent protection, establishing its importance in electrical systems.