The minimum current that can cause people to feel is called the perceived current, which is 1mA for ac and 5mA for dc.The maximum current that a person can get rid of by himself after being electrocuted is called "getting rid of current". The ac current is 10mA and the dc current is 50mA.The current that endangers life in a short period of time is called lethal current. For example, 100mA current passing through the human body for 1s can be enough to kill people. In the case of protection against electric shock, the current allowed by the human body can be considered at 30mA.

Human body's response to electric current:

8~10mA hand has difficulty getting rid of the electrode, and has hyperalgesia (finger joints).

20~25mA hands were quickly paralyzed, unable to get rid of the electrode automatically, and breathing was difficult.

50~80mA dyspnea, atrial fibrillation.

Respiratory paralysis of 90~100mA. Three seconds later, the heart begins to paralyze and stops beating.

(1) body resistance:

The body resistance is mainly the skin resistance, 0.05 ~ 0.2 mm thick skin cutin layer of the resistance being very high, dry skin, the body resistance is about 6 ~ 10 k Ω, even as high as 100 k Ω;But the corneous layer is easy to be destroyed, get rid of the cutin layer of skin resistance of about 800 ~ 1200 Ω;The resistance of the internal organization of about 500 ~ 800 Ω.

(2) shock voltage:

The higher the voltage, the more dangerous it is, and more than 10mA of current passing through the body can be dangerous.Therefore, to make through the body of the current is less than 10 ma, calculate by 1200 Ω if human body resistance, according to the ohm's law: U = 0.01 x 1200 = 12 v = IR.If the voltage is less than 12V, the shock voltage is less than 12V, the current is less than 10mA, the human body is safe.Our country regulations: especially wet, easy to conduct electricity, 12V is the safe voltage.If the air is dry and conditions are good, 24V or 36V voltage can be used.In general, 12V, 24V and 36V are the three levels of safe voltage.

(3) electric shock time: the longer the electric shock, the more serious the consequences.The relationship between shock current and time is expressed as: milliamperes of current times duration, expressed as mA·s.Our country stipulates that 50mA·s is the safe value.Beyond this value, it will cause harm to the human body.

(4) electrocution site and health condition: when electrocution current flows through respiratory organs and nerve center, it will cause great harm;When it flows through the heart, it is more harmful;When flowing through the brain, it causes an immediate coma.Patients with heart disease, endocrine disorders, lung disease and mental illness are more at risk in the same situation.

So why every household installed a small circuit breaker (leakage action current is generally 30mA), but also in the electric water heater (or other electrical appliances may occur leakage) on a leakage protection plug?This is because the leakage action current of the ordinary household leakage protection plug is 6mA or 10mA;It is more sensitive and safer than small short circuiter with leakage action current of 30mA.It is especially effective and safe for children and the elderly.