Hay una máquina que se encenderá al medir la electricidad con un bolígrafo probador eléctrico, pero no se encenderá cuando la toque con la mano y el cuerpo no la sienta. ¿Hay algún problema con la máquina? ¿Es peligroso seguir usándolo?
The neon lamp of the test pen can be lit with a voltage of several tens of volts, and the lower the current, the weaker the brightness. For the human body under normal conditions, the safe voltage is 36 volts. The neon light is on, indicating that the current flows through the human body and into the "earth", and when the hand touches it, it goes out, indicating that a small part of the current flows through the neon light and the hand through the human body (the current is too weak to light up), and most of the current flows from another branch. The touched hand flows through the human body (the resistance of this path is much smaller, which is equivalent to bypassing the path of the neon lamp), but the current is so small that it still cannot cause harm to the human body, so it cannot be detected. There are two possible reasons for the small current: 1. The voltage is low (such as 30 volts), and the current obtained by dividing it by the body resistance (such as 1500 ohms) is 20 mA, but 20 mA is very sensible, so this Probably not too big. However, if your hands are dry and your shoes are insulating, the current may be as small as 2 mA or 0.2 mA (which is imperceptible at this point). 2. The power is not stable. It belongs to the nature of accumulation. It is similar to the charging and storage of capacitors. Once the electricity is discharged immediately after contact, the voltage drops to an impossibly perceptible current value. The machine in this state is unsafe, and the grounding circuit of the peripheral power supply should be checked, and then the machine itself.
