A. When the test pen detects whether a conductor is a live wire or a neutral wire, the current through the test pen (that is, the current through the human body) I = the total voltage U applied across the test pen and the human body, divided by (/ is equivalent to Fractional line) to measure the total resistance R across the pen and the human body.
B. When measuring the live wire, in the lighting circuit, there is a voltage U=220V between the live wire and the ground. The resistance of the human body is generally very small, usually only a few hundred to several thousand ohms, while the resistance inside the electric pen is usually about several megohms. The current of the test pen (that is, the current passing through the human body) is very small, usually less than 1 mA. When such a small current passes through the human body, there is no harm to people, and when such a small current passes through the neon bubble of the test pen, the neon bubble will glow.
C. When measuring the zero line, U=0, I=0, that is, there is no current passing through the neon bulb of the test pen, and the neon bulb does not emit light of course. In this way, we can judge whether the live wire or the neutral wire is based on whether the neon bulb glows.
AC Voltage Tester Pen GD116A :
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