May I ask when the neon tube low-voltage electroscope pen is testing the DC power supply, does the positive end or the negative end light up, or both ends light up? Why?
Answer When the neon bulb of the test pen is energized, only the end connected to the negative polarity will light up. When measuring alternating current, the two poles of the neon bulb are alternately positive and negative, so the two poles light up at the same time.
When the electroscope pen is connected to direct current, only one pole of the neon bulb lights up, the bright pole is connected to the negative pole of the power supply, and the non-lit pole is connected to the positive pole of the power supply.
The end connected to the negative polarity is bright, but the end connected to the positive polarity is not bright because the direction of movement of the electrons is opposite to the direction of the current, and the electrons flow from the negative pole to the positive pole, so the negative pole lights up. The neutral point of the TT system or TN system power supply is grounded. When a person stands on the ground and holds an electroscope pen to measure the power supply, a potential difference is generated at both ends of the neon bulb and it will light up. If the direct current is not grounded, it will not light up when measured with a test pen, but it will light up when the neon tube is connected between the direct current power supply.
The electroscope can also measure whether the ungrounded direct current is grounded, and judge whether it is positive or negative. The method is: a person stands on the ground and uses the electroscope to test the direct current. There is a grounding phenomenon. The test end of the electroscope pen lights up, indicating that the positive electrode is grounded; the hand-held end lights up, indicating that the negative electrode is grounded.
