Why does the neutral line get charged, so that the neon tube of the electroscope glows
The fundamentals of neon tube lighting
The neon tube lights due to voltage present in the charged body under test rather than current passing through the circuit being tested (the charged body under test).
In actuality, the charged body being tested and the electric pen have a similar interaction.
The safety resistor, the human body, and the tip of the electric pen establish a conduit for the voltage to flow back to the ground when the measured point has a voltage to the ground (higher than 0 volts), and the current passing through the neon tube causes the neon tube to glow.
Only when a sufficiently big current flows will the neon tube begin to emit light. The neon tube cannot be made to generate light if the potential difference (voltage) between the measured spot and ground is non-zero but not excessively high. Obviously, the neon tube light's power source is A safe current for the human body is very modest.
As a result, when the electric pen produces light, it is actually testing voltage rather than current. Whether current is flowing via the measurement site is irrelevant.
In order for the electric pen drive to light up, there must be a voltage applied to ground.
Why does the electric pen not light up when it touches the zero line when the circuit is functioning normally?
Although it seems clear, it is not.
Since the neutral line is connected to the transformer's "neutral point" when the circuit is functioning correctly, the neutral line's voltage (potential) to the ground is zero, and since the electric pen tests the voltage, it does not produce light.
But for now, the neutral wire's current and the live wire's current are identical. It's even quite big!
This means that the voltage of the neutral line to ground, rather than the fact that there is no power on the neutral wire, is to blame. because of the hypothetical 0
Why is the voltage on the neutral line 0?
The zero line voltage is 0, which is not accurate in practice, but is theoretically 0, which is always greater than 0v in practice.
In the home power supply circuit, it is usually two-phase (single-phase electricity), which are connected to the power supply transformer through the transmission line, and the power supply transformer is three-phase alternating current. "Neutral", then all the neutrals of the power supply lines are connected from the neutral.
Because of the "neutral point" theory, when the three-phase circuit is balanced, that is, when the loads of the three-phase circuits are exactly the same, the ground potential of this neutral point is 0. This is only theoretical, in fact, the three-phase electrical load It cannot be absolutely equal. Therefore, the ground potential of the "neutral point" is always greater than 0, which means that the ground potential on the neutral line of all household lighting transmission lines is always greater than 0.
Then why is the zero line voltage not 0, and the neon tube of the electroscope does not emit light? It is because the (to ground) voltage on this zero line is very small in normal circuits, and it passes through the safety resistance of the electroscope and After the resistance of the human body, the current is extremely weak, and it is not enough to drive the neon tube to emit light.
