What should you know about the effect of electric current on the human body?
Electricitypassing through the human body can cause two types of damage — electric shock and electrical injury.
More dangerous electric shock as it affects the whole body. Death occurs from paralysis of the heart or respiration, and sometimes from both at the same time.
Electrical injury called electric shock to external parts of the body; this is burns, metallization of the skin, etc. Electric shock is usually of a mixed nature and depends on the magnitude and type of current flowing through the human body, the duration of its impact, the paths through which the current passes, as well as on the physical and mental state of a man at the moment of defeat.
AC power frequency one begins to feel at 0.6 — 15 mA. 12-15 mA current causes severe pain in fingers and hands. A person endures this state for 5-10 s and can independently tear the hands from the electrodes. A current of 20 — 25 mA causes very severe pain, the hands are paralyzed, breathing becomes difficult, a person cannot free himself from the electrodes.At a current of 50 — 80 mA, respiratory paralysis occurs, and at 90-100 mA — cardiac paralysis and death.
The human body is less sensitive to direct current... Its impact is felt at 12-15 mA. 20 — 25 mA current causes a slight muscle contraction of the hands. Respiratory paralysis occurs only at a current of 90-110 mA. The most dangerous — alternating current with a frequency of 50 — 60 Hz. As the frequency increases, currents begin to spread over the surface of the skin, causing severe burns, but not leading to electric shock.
The amount of current flowing through the human body depends on the resistance of the body and the applied voltage. The greatest resistance to the current is provided by the upper stratum corneum, devoid of nerves and blood vessels. Dry intact skin, the resistance of the human body to electric current is 40,000 — 100,000 ohms.
The stratum corneum has a negligible thickness (0.05 - 0.2 mm) and under a voltage of 250 V it instantly breaks through. Damage to the stratum corneum reduces the resistance of the human body to 800 — 1000 ohms. Resistance also decreases with increasing exposure time to current. Therefore, it is very important to quickly eliminate contact of the victim with live parts.
The outcome of the defeat also largely depends on the path of the current in the human body. The most dangerous paths are arm-leg and arm-arm, when most of the current goes through the heart.
On the size of the resistance and therefore on the result of the defeat electric shock greatly influences the physical and mental state of a person... Increased sweating of the skin, fatigue, nervousness, excitement, intoxication lead to a sharp decrease in the resistance of the human body (up to 800 - 1000 Ohms).Therefore, even relatively small voltages can cause electric shock.
It must be remembered that the human body is not affected by the voltage, but by the magnitude of the current. Under adverse conditions, even low voltage (30 — 40 V) can be life-threatening. If the resistance of the human body is 700 ohms, then a voltage of 35 V will be dangerous.