What is a knife switch primarily used for?

A knife switch is primarily used to make and break electrical circuits. This type of switch consists of a metal blade that pivots on a hinge and can be moved into contact with fixed terminals, allowing for the manual connection or disconnection of the electrical current in a circuit. When the blade is in the "on" position, it completes the circuit, allowing current to flow, while moving it to the "off" position interrupts the circuit, stopping the current flow.

The design of the knife switch makes it particularly suited for applications where a clear visual indication of the switch status is needed, as well as for scenarios where a robust connection is required. They are often used in applications such as disconnect switches for power sources, allowing operators to safely turn off equipment or isolate circuits for maintenance work.

Other options pertain to different functions. For instance, modifying circuit resistance refers to variable resistors or rheostats, while allowing multiple circuit paths relates to parallel circuits. Overload protection is typically managed by circuit breakers or fuses designed to automatically interrupt current flow in the event of an overcurrent situation. These functions are not the primary role of a knife switch, reinforcing the validity of the chosen answer.