Understanding 230V AC in Outlets: Phase, Neutral, and Debating Electrical Current Flow

Hello, one thing is bothering me, how is it with electricity in the socket? I know, of course, that 230V alternating current flows in the socket, but why only in one hole, when we put a test tube, it will light up? My brother is arguing with me that the plus is only in the left hole and the minus is in the right and that it does not change because it is a holy thing because he has connected many times himself. I don't want to listen to my explanations that the sign of the current changes every 50 times per second. Could someone explain to me how it is with this phase and neutral in the socket?
There was a similar topic on the forum before, but I would like to ask for a deeper explanation so that I could prove to my brother.

The test tube shines where the phase wire is connected. When we apply to the neutral wire, the test tube does not glow. Apart from whether it will light up in the left or right, it depends only on how the wires will be connected, however, the principle has been adopted that the phase in the left, neutral in the right. Moreover, the plus and minus are in direct current.

The voltage in the socket is alternating, but the N terminal in the socket is always at 0 V (theoretically) to the ground potential. Therefore, it is commonly referred to as "zero". It can be imagined that the N conductor is somewhere (in the power plant, transformer station) connected to "earth". On the other hand, L or "phase" has an alternating voltage of +325 V and -325 V with respect to zero, N, ground. The value of 325 V is the peak value of sinusoidal voltage with an RMS value of 230 V. Due to the fact that N is 0 V in relation to the person holding the voltage tester - the neon lamp does not light. L, on the other hand, has a variable voltage that causes the current to flow through the body of the person holding the voltage tester and causes the neon tube in the tester to glow. You do not define plus or minus in the socket, only the phase and neutral wires. +/- changes there 50 times per second. As for proving my brother - I don't know if it makes sense.

It's easy. With alternating current, there is no such thing as plus and minus.
Why does the test tube glow in one hole and not in the other - this is also simple - the hole in which the test tube does not glow has - in a nutshell - the ground potential (e.g. neutral) on which you are standing. The second hole has a "phase", i.e. the potential is alternately higher and lower than the neutral (i.e. yes - the sign changes).

The greatest philosophy is to always understand how it is that the earth is somehow connected to an electric wire - it is extremely hard to imagine, but it is simple - the earth just has its conductivity.

Added after 1 [minutes]:

pawlik118 wrote:

As for proving my brother - I don't know if it makes sense.

It depends - whether the brother is older or younger. The older one is not worth it, because you can get in the head for being right

ThePatrolPL wrote:

Could someone explain to me how it is with this phase and neutral in the socket?

Understand that your body is permanently attached to the N and PE terminal in the socket, i.e. to one hole and pin if present.

By touching the second hole, the one that is not attached to your body, you close the circuit and KILL you.