Electric current will directly harm the human body. Generally speaking, if the current passing through the human body exceeds 1 mA, there will be a feeling of numbness: When the current reaches tens of mA, it will be difficult for a person who is shocked to get rid of the power source alone: if the current exceeds 100 mA, May be life-threatening.

According to Ohm's law, the magnitude of the current through the human body is determined by the resistance of the human body and the power supply voltage of the contact. The resistance of the human body is related to many factors. When the skin is intact and dry, the resistance can reach 10-100 kilohms; when the skin is broken or sweating, the resistance of the human body can be reduced to below 1000 ohms. In addition, the larger the contact area between the skin and the charged object, the tighter the pressure and the lower the resistance. If the human body resistance is calculated at 1000 ohms, when the power supply voltage is 40 volts, the current flowing through the human body will be 40 milliamperes, which is already dangerous to the human body. Our country stipulates that hand-carrying lights (traveling lights) that are often moved should use 36 volts. When working in particularly humid places, use 24, 12 volts and other lower voltages. Such a low voltage is called a safety voltage.

The degree of danger of electric shock is related to the length of the electric shock and the way the current passes through the human body. It is generally believed that the product of the current passing through the human body and the duration of the electric shock is greater than 50 milliamperes·sec, which is very dangerous. The risk of electric current passing through the heart is high. Electric shock between the hands or from the left hand to the left foot may cause the current to pass through the heart. Therefore, when repairing live electrical equipment, in addition to using safety equipment. One-handed operation should be used as much as possible, in case of electric shock can reduce the risk.

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