How to judge the voltage between the lines of the voltage tester pen
There are two wires in the home circuit, one is the live wire and the other is the neutral wire, and the voltage between the two wires is 220V.
Under normal circumstances, the voltage between the neutral wire and the ground is zero (this is the origin of the name "neutral wire"), and the voltage between the live wire and the ground is 220V, which can make the test pen glow (this is the origin of the name "hot wire" ).
When the test pen is testing A, C, and D, the neon tubes all glow, indicating that there is voltage between these three places and the earth. That is to say, there is no voltage between C and D, so the light bulb is connected to the live wire, but it will not emit light.
