Why do fewer Hertz cause more tension?

Practical help

Electric current hazards

1 Physiological effect
2 Thermal effect
3 Chemical effect
4 More information


1Physiological effect

If a current flows through the human body, e.g. B. when touching a live conductor, the muscles cramp if the current coming from the outside is much larger than the body's own current in the nerve tracts. The injured person is then unable to let go of the point of contact. If alternating current flows through the human heart, it tries to follow the faster and stronger impulses from outside. It therefore works much faster. This leads to arrhythmias of the heart, i. that is, the heart works irregularly. Ventricular fibrillation with subsequent failure of the heart and subsequent cardiac arrest are also possible. The lack of oxygen causes damage to the brain cells after a short time and leads to death in the further course.

EKG - normal

EKG - ventricular fibrillation

The decisive factor for the consequences of an electrical accident is the strength of the current that flows through the body when live parts are touched. We know from experience that a current of 50 mA can cause death if the current flows through the heart.

Current strengths of 50 mA or more are life-threatening! The risk increases with higher amperage and longer exposure time.

The current flowing through the body depends on the voltage and resistance of the body. This body resistance is made up of the internal resistance of the body and the contact resistances at the point of entry and exit of the current.

The contact resistances depend on external conditions. Dry skin and dry clothes have great resistance. In the case of moisture, e.g. B. sweat or a wet floor, the transition resistance is low. The contact resistance also becomes smaller, the larger the contact area and the higher the contact pressure.

Important:

  • AC voltages over 50 V are life-threatening.
  • DC voltages over 120 V are life-threatening.
  • Alternating current with a frequency of 50 Hz is more dangerous than direct current because it can trigger ventricular fibrillation more easily.

2Thermal effect

The thermal effect of the electric current leads to burns at the entry and exit points when the current is high. This is where the so-called electricity brands are created. In the case of arcs, parts of the body can become charred (4th degree burns). Severe burns can overload the kidneys and possibly even death.


3Chemical effect

Due to the chemical effect of the current, the blood can be electrolytically decomposed, especially if it is exposed to it for a longer period of time. This leads to severe symptoms of intoxication. Such secondary diseases can only appear after a few days.


4additional Information

Immediate action in the event of an electrical accident