What type of current is more dangerous?

What type of current is more dangerous?

Typically, electricians, answering the question: "Why is AC more dangerous than DC" - joking: "Because DC current pushing a only once and the AC current 60 times per second." In fact, the answer is not as straightforward, although some truths in this joke there. For the man action of the DC or AC is dangerous, but the latter is considered to be 3-5 times more dangerous. The safe threshold value of the DC current - 50 mA, and the AC current - only 10 mA. At the same time the danger of alternating and direct current depends on the voltage. It is believed that at a voltage up to 400 V is more dangerous alternating current (60 Hz) than a direct current, but at the voltage about 500 V are both equally dangerous.
In fact, the impact of the current on the human body contains a lot of current factors, both internal (the resistance of the human body the changes by of the mood even) and external (it is important to not only the voltage but also the internal resistance of the generator, which determines the amperage). In addition, the resistance of the body depends on the frequency: power frequency current (60 Hz) is the most dangerous because it can cause disturbances of the heartbeat. As can be seen from Fig. 1, the most dangerous currents with a frequency of 20 - 100 Hz. At lower and higher frequencies the risk decreases. Thus, current with a frequency of 200 Hz, commonly used for power hand tools, and with a current frequency of 16 Hz, which is used in the industry in the United States, have approximately the same danger of 85 - 90% dangerous with current of frequency of 60 Hz. By the way, these data strongly contradict of the widespread misconception about the dangers of small currents with a frequency of 200 Hz.

Fig. 1. The dependence of shock hazard from the frequency of the applied voltage

However, with increasing frequency (1000 Hz), the danger is reduced, and frequencies above 70,000 Hz current is consider to be safe because of the so-called "skin effect" (current only flows through the human body surface area). That is why the Tesla, showing lightning, flying from his hand, was in complete safety: but he used a high-voltage, high-frequency generator of own design. And with a perfectly calm look he was passed through a voltage alternating current into millions of volts - lightning danced on the surface of his skin, but he remained unharmed. And when he was enveloped in electric discharges picked up of the filament lamps are not connected to the any wire, they obediently lit up in his hands. It seemed a real magic. Some people tried also repeat of the Tesla performance. For example one of them, Peter Terren decided to repeat the experiments Tesla, passing through a voltage of 500 kilovolts! The photo shows Peter Terry in the pose of the thinker. his whole body was wrapped in foil , and the head was protected by a helmet. Peter was alive and well.