Why are fuses used in electrical installations?

Fuses are critical components used in electrical installations primarily for their role in protecting circuits. They function as safety devices that prevent damage to electrical systems and reduce the risk of fire hazards. When the current flowing through the circuit exceeds a predetermined level—typically due to an overload or a short circuit—the fuse will "blow" or break the connection. This interruption stops the flow of electricity, thereby safeguarding not just the circuit but also the devices connected to it from potential damage caused by excessive heat or current.

In addition to protection, the other options do not accurately reflect the primary purpose of fuses. Enhancing circuit efficiency, while desirable, is not a function of fuses; rather, they are about safety. Similarly, fuses do not convert voltage levels, as voltage conversion is the role of transformers. Finally, while fuses do limit current in the sense that they will break the circuit if the current goes too high, they do not regulate or control current flow like other devices such as rheostats or variable resistors. Thus, option B clearly outlines the essential function of fuses within electrical installations.