The question asks what practical output is observed when connecting the input of a NOT gate to a logic low (0). To answer this, let's analyze the behavior of a NOT gate.

1. Understanding the NOT Gate: The NOT gate, also known as an inverter, is a basic digital logic gate that inverts the input signal. If the input is logic low (0), the output will be the opposite, which is logic high (1). Conversely, if the input is logic high (1), the output will be logic low (0).
2. Input-Output Relation: When the input of a NOT gate is connected to logic low (0), the expected behavior, according to its function, is to provide the opposite, which is a logic high (1) as output.
3. Evaluating Options:
   • Option 1: Logic low (0) - This would only occur if the NOT gate was malfunctioning.
   • Option 2: No Change - This is incorrect as the NOT gate should produce opposite output.
   • Option 3: Undefined - A NOT gate with a valid input does not result in an undefined output for digital logic.
   • Option 4: Logic high (1) - This is the correct behavior of a NOT gate when input is logic low (0).

Conclusion: The correct answer is the inventive behavior of the NOT gate which outputs a logic high (1) when input is a logic low (0). Thus, the practical output observed should be Logic high (1).