Final answer:
Knife switches rated for high currents and voltages are used as circuit breakers or disconnect switches to interrupt the flow of electricity and ensure safety in industrial applications and power distribution systems.
Step-by-step explanation:
Knife switches rated for more than 1200A at 250V or less, and at over 600A at 251 to 600V, should be used only as circuit breakers or disconnect switches. These switches are designed to interrupt the flow of electricity when needed, ensuring safety and preventing damage to electrical equipment. They are commonly used in industrial applications and power distribution systems.