An electric current passing through the human body can cause two types of damage – electric shock and electric injury.
Electric shock is more dangerous, it affects the entire body. Death occurs from paralysis of the heart or breathing.
Electric injuries are called shock by the external parts of the body, that is, various burns, etc. The electric shock can be mixed in nature and depends on the magnitude of the current, the type of effect, and the physical and mental state of a person.
Alternating current industrial frequency person begins to feel at 0.6-15mA. Current 12-15mA causes severe pain in the fingers and hands. A person can withstand such a state for no more than 5-10 seconds and can independently tear off hands from electrodes. A current of 20-25mA causes very severe pain, while the hands are paralyzed, breathing is difficult, a person cannot detach from the electrodes independently. At a current of 50-80 mA respiratory paralysis occurs, and at a current of 90-100 mA, paralysis of the heart and death.
To direct current, the human body is less sensitive. A person begins to feel its impact at a current of 12-15 mA. Current 20-25mA can cause a slight contraction of the arm muscles. At a current of 90-110 mA respiratory paralysis occurs. The most dangerous is alternating current with a frequency of 50-60 Hz.
With increasing frequency, currents begin to spread across the skin, causing severe burns, but not leading to electrical shock. The amount of current that passes through the human body depends on the resistance of the body and the applied voltage. The strongest layer has the strongest resistance; there are no nerves and blood vessels in it. When dry skin resistance can reach 40000-100000 Ohms.
The stratum corneum has a negligible thickness from 0.05 to 0.2 mm and instantly penetrates at a voltage of 250V. Damage to the stratum corneum reduces the resistance of the human body to 800-1000 ohms.
Also the degree of damage from an electric current depends on the way in which the electric current propagates. The most dangerous ways are hand-foot, hand-hand, when the current passes through the heart.
The physical and mental state of a person with an electric shock is also of great importance. Excessive sweating, overwork, nervous agitation, intoxication lead to a decrease in the resistance of the human body.
Everyone working with electrical radio equipment must understand that the human body does not affect voltage, but current. Under adverse circumstances, even a voltage of 30-40 V can be life threatening.