When an input signal 1 is applied to a NOT gate, the output is ..................

Logic gates are the basic building blocks of digital circuits, and each type of gate follows a fixed rule for turning input signals into an output signal. A NOT gate is the simplest of these: it has only one input and one output.

A NOT gate performs logical inversion, meaning its output is always the opposite of its input. Since the input signal given is \(1\), the output must be \(0\). This can be summarised in a small truth table:

The output cannot be "either 0 and 1" at once, because a NOT gate produces exactly one definite output for a given input, never both simultaneously. Since a valid, single-value answer exists, "none of the above" is also incorrect.

Remember the NOT gate with a single rule: it always flips the input, 0 becomes 1, and 1 becomes 0.