For proper functioning, what is necessary for an overcurrent protection device to operate effectively?

An overcurrent protection device, such as a circuit breaker or fuse, must be properly rated for the circuit it protects to function effectively. This rating includes both the current rating and the voltage rating, which ensures that the device can handle the electrical load without tripping under normal conditions but will trip in the event of an overload or short circuit.

If the device is under-rated, it may trip frequently during normal operation, leading to unnecessary interruptions. Conversely, if it is over-rated, it may fail to trip in a fault condition, which can cause damage to the circuit and create fire hazards. Thus, ensuring the device matches the specific requirements of the circuit is crucial for safety and reliable operation.

In contrast, proximity to the power source, the necessity of manual resets after tripping, and universality across applications do not guarantee the effective functioning of the device like proper rating does.