I am a little bit confused why in AC single phase 2 wire source is merely classified the 1 wire as hot and other wire as neutral. The hot wire travels the current from the source to the load and going back the current to the source through the neutral wire. I know that in AC circuit, the signal or source is a sinusoidal, it has positive and negative cycle. Meaning the flow of current is back and forth, therefore at positive cycle the current flows from the hot wire to neutral wire and at negative cycle, the current flows from neutral to hot wire? So, each wire for a 1 phase 2 wire system is hot during cycle and neutral during - cycle. If my hypothesis is correct, My follow up concern is that, for example in residential wiring with 2 wire source ,why only the hot wire (1 wire) is protected with breaker and the neutral (other wire) is unbroken or not fused and grounded to earth if it is also become hot (during - cycle)? Also, if the neutral is grounded, does its dangerous because there is potential I.e instantaneous volts during negative cycle? Can you please help me to have clarification on these.. Tnx

What exactly is your question?

The neutral is the return conductor for a circuit, and is grounded so the voltage is at ground potential, but it is carrying the current flowing in the circuit.

Only the hot is protected for overload or short circuit. If a fuse was in the neutral conductor, and it opened before the fuse in the live conductor, in the event of a short circuit the device or short could still be live.